Silicon-carbon composite material with enhanced electrochemical properties

Abstract

Silicon-carbon composites and related methods are disclosed that overcome the challenge of providing amorphous nanometer-sized silicon entrained within a porous carbon. The materials and methods disclosed herein are better for various applications, including energy storage devices, such as lithium ion batteries, than other inferior materials and methods described in the prior art.

Description

background Technical Field

[0002] Embodiments of the present invention generally relate to silicon-carbon composite materials with enhanced electrochemical properties and performance, overcoming the challenge of providing amorphous nanoscale silicon encased within porous carbon. The silicon-carbon composite materials are produced by chemical vapor infiltration to impregnate amorphous nanoscale silicon into the pores of a porous scaffold. Suitable porous scaffolds include, but are not limited to, porous carbon scaffolds, such as carbon having pore volumes including micropores (less than 2 nm), mesopores (2 to 50 nm), and / or macropores (greater than 50 nm). Suitable precursors for carbon scaffolds 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. Silicon precursors include, but are not limited to, silicon-containing gases, such as silanes, higher 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 scaffold material is achieved by exposing the porous scaffold to a silicon-containing gas (e.g., silane) at elevated temperatures. The porous carbon scaffold can be particulate porous carbon.

[0003] A key achievement in this area is obtaining silicon in the desired form and shape, specifically amorphous nanoscale silicon. Another key achievement is realizing silicon impregnation into the pores of porous carbon. Yet another key achievement is the enhancement of the electrochemical properties of the silicon-carbon composite material. This enhancement includes an increase in the graphitic properties and / or electrical conductivity of the carbon scaffold, where the electrical conductivity includes electronic and / or ionic conductivity. Such silicon-carbon composite materials with enhanced electrochemical properties can be used as anode materials for energy storage devices (e.g., lithium-ion batteries). A method for preparing silicon-carbon composite materials with enhanced electrochemical properties is also disclosed herein.

[0004] Related technical descriptions

[0005] CVI is a method in which a gaseous substrate is reacted within a porous scaffold material. This method can be used to produce composite materials, such as silicon-carbon composites, where silicon-containing gases decompose within a porous carbon scaffold at high temperatures. While this method can be used to manufacture a variety of composite materials, particular attention is paid to silicon-carbon (Si-C) composites. Such Si-C composites have practical applications, such as as energy storage materials, for example, as anode materials in lithium-ion batteries (LIBs). LIBs have the potential to replace devices currently used in many applications, such as electric vehicles, consumer electronics, and grid storage. For example, current lead-acid automotive batteries are unsuitable 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 currently used lead-based systems due to their capacity and other considerations.

[0006] Therefore, there has been considerable interest in developing new LIB anode materials, particularly silicon, which has a 10-fold higher gravimetric capacity than conventional graphite. However, silicon exhibits large volumetric changes during cycling, leading to electrode degradation and instability in the solid electrolyte interphase (SEI). The most common approach to improvement is to reduce the silicon particle size, for example, by using D... V,50 <150nm, for example, D V,50 <100nm, for example, D V,50 <50nm, for example, D V,50 <20nm, for example, D V,50 <10nm, for example, D V,50 <5nm, for example, D V,50 <2nm, as discrete particles or within a matrix. To date, techniques for fabricating nanoscale silicon have involved high-temperature reduction of silicon oxide, coarse-grained 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.

[0007] It is known from scientific literature that non-graphitizable (hard) carbon is advantageous as an anode material for LIBs (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). This improved performance is due to the disordered nature of the graphene layers, which allows Li ions to embed on either side of the graphene plane, thus theoretically allowing for a doubling of the stoichiometric content of Li ions relative to crystalline graphite. Furthermore, unlike 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 embedding of Li ions. Despite possessing these desirable electrochemical properties, amorphous carbon has not yet been widely adopted in commercial Li-ion batteries, primarily due to its low free charge efficiency (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 in batteries to improve conductivity and reduce surface side reactions.

[0008] In recent years, amorphous carbon, as a material for LIB batteries, has attracted considerable attention as a coating for silicon anode materials. Such silicon-carbon core-shell structures not only have the potential to improve conductivity but also to buffer the expansion of silicon during lithiation, thereby stabilizing its cycle stability and minimizing problems related to particle fragmentation, 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). Problems associated with this strategy include the lack of suitable silicon starting materials for coating processes and the inherent lack of engineered void spaces within carbon-coated silicon core-shell composite particles to accommodate silicon expansion during lithiation. This inevitably leads to cyclic stability failure due to the destruction of the core-shell structure and the SEI layer (Beattie SD, Larcher D, Morcrette M, Simon B, Tarascon, JM. J Electrochem Soc 2008 155: A158-A163).

[0009] An alternative to the core-shell structure is a structure in which amorphous nanoscale silicon is uniformly distributed within the pores of a porous carbon scaffold. Porous carbon possesses desirable properties: (i) carbon porosity provides pore volume to accommodate the expansion of silicon during lithiation, thereby reducing net composite particle expansion at the electrode level; (ii) the disordered graphene network provides increased conductivity for silicon, enabling faster charge / discharge rates; and (iii) the nanoporous structure acts as a template for silicon synthesis, thus defining its size, distribution, and morphology.

[0010] To this end, the desired reverse hierarchical structure can be achieved using CVI, where silicon-containing gas can completely permeate nanoporous carbon and decompose into nanoscale silicon within it. The CVI method offers several advantages in terms of silicon structure. One advantage is that nanoporous carbon provides nucleation sites for silicon growth, while also defining the maximum particle shape and size. Confining silicon growth within the nanoporous structure reduces susceptibility to breakage or fragmentation and contact losses due to expansion. Furthermore, this structure promotes the nanoscale silicon to remain in an amorphous phase. This property provides high charge / discharge rates, especially when combined with the silicon-peripheral region within the conductive carbon scaffold. This system provides a high-rate solid-state lithium diffusion pathway capable of directly delivering lithium ions to the nanoscale silicon interface. Another benefit of providing silicon within the carbon scaffold via CVI is the suppression of undesirable Li crystallization. 15The formation of the Si4 phase. Another benefit is that the CVI method provides void space within the particles.

[0011] To quantify the percentage loading of silicon in the silicon-carbon composite, thermogravimetric analysis (TGA) can be used. For this purpose, the silicon composite is heated from 25°C to 1100°C, which, without being bound by theory, presupposes that all carbon is burned off and all silicon is oxidized to SiO2. Therefore, the silicon % constituting the silicon-carbon composite is calculated as follows:

[0012] %Si=100x[[M1100 x(28 / (28+(16x 2)))] / M°]

[0013] 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 50°C and 200°C when heated in air from about 25°C to about 1100°C, determined by thermogravimetric analysis.

[0014] To measure the relative amount of silicon impregnated into the pores of porous carbon, thermogravimetric analysis (TGA) can be used. TGA can be used to assess the fraction of silicon residing within the pores of porous carbon relative to the total silicon present (i.e., the sum of 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, reflecting the initial oxidation of silicon to SiO2; the sample then shows a mass loss as carbon is burned off; then the sample shows a mass increase, reflecting the continued conversion of silicon to SiO2, increasing to an asymptotic value near 1100°C, where silicon oxidation 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 carbon is completely burned off. Any other mass increase beyond this point corresponds to the oxidation of silicon to SiO2, and the total mass at which oxidation is complete is SiO2. Therefore, the percentage of unoxidized silicon after carbon burn-off, expressed as a proportion of the total silicon, can be determined using the following formula:

[0015] Z=1.875x[(M1100-M) / M1100]x 100

[0016] Where M1100 is the mass of the sample when oxidation is completed at 1100℃, and M is the minimum mass recorded when the sample is heated from 800℃ to 1100℃.

[0017] 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 silicon due to the diffusion of oxygen atoms through the oxide layer. Therefore, silicon residing within the carbon pores will oxidize at a lower temperature than silicon deposits on the particle surfaces, where a thinner coating is necessarily present. In this way, the calculation of Z is used to quantitatively assess the fraction of silicon not impregnated within the pores of the porous carbon scaffold.

[0018] The graphitic and amorphous properties of carbon can be studied using a variety of methods known in the art. Such methods include, but are not limited to, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman spectroscopy. The latter two methods have been shown to be suitable for quantification and to be correlated (Z. Zhang and Q. Wang, Crystals 2017, 7(1):5).

[0019] Regarding XRD, the graphitic properties of carbon materials can be assessed by monitoring the peak intensities at 2θ corresponding to each Miller index. Without being bound by theory, the diffraction lines of graphite are divided into groups, such as the 00l, hk0, and hk1 indices, primarily due to the strong anisotropy of the structure. One such group is 002, corresponding to the basal plane of graphite, located between 2θ and 26°; this peak is prominent in highly graphitic carbon materials. Carbon materials exhibiting less graphitic properties are characterized by very broad 00l lines (e.g., 002) and shifts (e.g., 2θ–23°), due to a smaller degree of layering and asymmetric hk lines (e.g., 10 corresponding to 2θ–43°).

[0020] Regarding Raman spectroscopy, this method can be used to evaluate the graphitic properties of carbon reported in this field (L. Bokobza J.-L. Bruneel and M. Couzi, Carbon 2015, 1:77-94). For this purpose, the D band (~1300-1400 cm⁻¹) can be monitored. -1 ) and G-band (~1550-1650cm) -1 The graphite properties of carbon materials are evaluated by the ratio of peak intensities of I to the peak intensities of 2π. D / I G It is a measure of the graphitic properties of carbon and is determined by direct peak intensity or by deconvolution. In the latter case, additional deconvolution peaks may include D4 (~1000–1200 cm⁻¹). -1 ) and D3 (~1450–1550cm) -1 Without being bound by theory, D4 and / or D3 bands exist in highly defective carbons, such as carbon black, and involve amorphous carbon and / or hydrocarbon and / or aliphatic portions bonded to the basic structural unit of graphite. Summary of the Invention

[0021] Silicon-carbon composite materials with enhanced electrochemical properties and performance, and related methods, are disclosed, overcoming the challenge of providing amorphous nanoscale silicon encased within porous carbon. The materials and methods disclosed herein are superior for a variety of applications, including energy storage devices such as lithium-ion batteries, compared to other inferior materials and methods described in the prior art. Attached Figure Description

[0022] Figure 1 The relationship between Z and average coulombic efficiency for various silicon-carbon composite materials.

[0023] Figure 2 Differential capacity versus voltage plot of silicon-carbon composite 3 using half-cells in the second cycle.

[0024] Figure 3 Differential capacity versus voltage plot for silicon-carbon composite 3 using half-cells from the 2nd to the 5th cycle.

[0025] Figure 4 dQ / dV versus V diagrams for various silicon-carbon composite materials.

[0026] Figure 5 Silicon-carbon composite 3 Calculation examples.

[0027] Figure 6 Z-pairs of various silicon-carbon composite materials picture.

[0028] Figure 7 Raman spectra of carbon scaffold sample 11 and carbon scaffold sample 15.

[0029] Figure 8 Raman spectra of carbon scaffold sample 12 and carbon scaffold sample 10.

[0030] Figure 9 Raman spectra of carbon scaffold sample 13 and carbon scaffold sample 14.

[0031] Figure 10 Surface area of ​​carbon scaffold samples before and after heat treatment at various temperatures. Detailed Implementation

[0032] In the following description, certain specific details are set forth to provide a thorough understanding of various embodiments. However, those skilled in the art will understand that the invention can 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 appended claims, the word “comprise” and its variations (e.g., “comprises” and “comprising”) should be interpreted in an open-ended, inclusive sense, i.e., as “including but not limited to”. Furthermore, the headings provided herein are for convenience only and do not constitute an explanation of the scope or meaning of the claimed invention.

[0033] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a specific feature, structure, or characteristic relating to that embodiment is included in at least one embodiment. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Additionally, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural indicators unless the context clearly specifies otherwise. It should also be noted that, unless the context clearly specifies otherwise, the term "or" generally takes on the meaning of including "and / or."

[0034] A. Porous support material

[0035] For the purposes of embodiments of the present invention, porous scaffolds into which silicon is to be impregnated can be used. Throughout this document, the porous scaffold can comprise a variety of materials. In some embodiments, the porous scaffold material primarily 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. Porosity can be introduced into carbon materials in various ways. For example, porosity 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 subsequent sections.

[0036] In other embodiments, the porous scaffold comprises a polymeric material. For this purpose, various polymers are contemplated for use in the 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, polygermanane, and polystanane. Other examples of inorganic polymers include, but are not limited to, hetero-chain polymers, such as polyborazylene, polysiloxanes (e.g., polydimethylsiloxane (PDMS), polymethylhydrosiloxane (PMHS), and polydiphenylsiloxane), polysilazanes (e.g., perhydropolysilazane (PHPS)), polyphosphazenes and poly(dichlorophosphazene), polyphosphates (salts), polythiazyl nitrides, 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), polyurea, poly(lactide), poly(glycolic acid) and combinations thereof, phenolic resins, polyamides, polyarylamides, polyethylene terephthalate, polychloroprene, polyacrylonitrile, polyaniline, polyimide, poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PDOT:PSS), and other substances known in the art. Organic polymers can be synthetic or of 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 caramelization of monosaccharides or oligosaccharides (e.g., fructose, glucose, sucrose, maltose, raffinose, etc.).

[0037] In some embodiments, the porous scaffold polymer material comprises a coordination polymer. Coordination polymers as used herein include, but are not limited to, metal-organic frameworks (MOFs). Techniques for generating MOFs and exemplary materials for 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 as used herein include, but are not limited to, Basolite. TM Materials and zeolite imidazole ester skeleton (ZIF).

[0038] With the envisioning of various polymers possessing the potential to provide porous substrates, various processing methods are envisioned in various embodiments to achieve the aforementioned porosity. In this regard, as is known in the art, there are many general methods for generating porosity in various materials, including, but not limited to, methods such as emulsification, micelle generation, vaporization, dissolution followed by solvent removal (e.g., freeze-drying), axial compaction and sintering, gravity sintering, powder rolling and sintering, isobaric compaction and sintering, metal sputtering, metal coating and sintering, metal injection molding and sintering, etc. Other methods for generating porous polymer materials are also envisioned, including the generation of porous gels, such as freeze-dried gels, aerogels, etc.

[0039] In some embodiments, the porous scaffold material comprises a porous ceramic material. In some embodiments, the porous scaffold material comprises a porous ceramic foam. As is known herein, general methods for generating porosity within ceramic materials are diverse, including, but not limited to, generating pores. General methods and materials suitable for constituting porous ceramics include, but are not limited to, porous alumina, porous zirconia-toughened alumina, porous partially stabilized zirconia, porous alumina, porous sintered silicon carbide, sintered silicon nitride, porous cordierite, porous zirconia, clay-bonded silicon carbide, etc.

[0040] In some embodiments, the porous scaffold comprises porous silica or other oxygen-containing silicon materials. The production of silica gels (including sol-gels) and other porous silica materials is known in the art.

[0041] In some embodiments, the porous material comprises a porous metal. Suitable metals in this regard 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 known in the art. In some embodiments, the porous support material comprises a porous metal foam. The types of metals and methods of their manufacture are known in the art. Such methods include, but are not limited to, casting (including foaming, infiltration, and low-foaming 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).

[0042] B. Porous carbon scaffold

[0043] 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. Patents Nos. 7,723,262, 8,293,818, 8,404,384, 8,654,507, 8,916,296, 9,269,502, and 10,590,277, and U.S. Patent Application No. 16 / 745,197, the entire disclosure of which is incorporated herein by reference for all purposes.

[0044] Therefore, in one embodiment, this disclosure provides a method for preparing any of the above-described carbon materials or polymer gels. Carbon materials can be synthesized by the pyrolysis of a single precursor, such as saccharides, including sucrose, fructose, glucose, dextrin, maltodextrin, starch, amylopectin, amylose, lignin, gum arabic, and other sugars known in the art, and combinations thereof. Alternatively, carbon materials can be synthesized by the pyrolysis of a composite resin, for example, using a polymer precursor (e.g., phenol, resorcinol, bisphenol A, urea, melamine, and other suitable compounds known in the art, and combinations thereof) with a crosslinking agent (e.g., formaldehyde, hexamethylenetetramine, furfural, and other crosslinking agents known in the art, and combinations thereof) in a suitable solvent (e.g., 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 be varied as known in the art.

[0045] In some embodiments, the method includes preparing a polymer gel involving a monomer precursor and a crosslinking agent, two existing polymers and a crosslinking agent, or a single polymer and a crosslinking agent, a condensation method, or a crosslinking method, followed by pyrolysis of the polymer gel. The polymer gel may be dried (e.g., freeze-dried) prior to pyrolysis; however, drying is not necessarily required.

[0046] The desired carbon properties can be derived from various polymer chemistry principles, as long as the polymerization reaction produces a resin / polymer with the desired carbon backbone. Different polymer families include linear phenolic resins, soluble phenolic resins, acrylates, styrene-based resins, urethanes, rubbers (chloroprene rubber, styrene-butadiene, etc.), nylon, etc. Any of these polymer resins can be prepared by a variety of methods, including sol-gel, emulsion / suspension, solid, and molten states, for the polymerization and crosslinking processes.

[0047] In some embodiments, an electrochemical modifier is incorporated into the polymer material. For example, an organic or carbon-containing polymer, such as RF, is copolymerized with the polymer containing the electrochemical modifier. In one embodiment, the polymer containing the electrochemical 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 others, they are phenyl groups; and in still others, the side chains include phenyl, pyrrolidone, acetate, vinyl, or siloxane segments. In some cases, the side chains include Group 14 elements (silicon, germanium, tin, or lead). In still others, the side chains include Group 13 elements (boron, aluminum, boron, gallium, indium). In still others, the side chains include Group 15 elements (nitrogen, phosphorus, arsenic). In still others, the side chains include Group 16 elements (oxygen, sulfur, selenium).

[0048] In another embodiment, the electrochemical modifier includes thiophene. In some cases, it is phenol-thiophene or silane-fluorene. In others, it is polythiophene or polysilane-fluorene. In some cases, silicon is replaced by germanium (germanium heterocyclopentadiene or germanium heterofluorene), tin (tin heterocyclopentadiene or tin heterofluorene), nitrogen (carbazole), or phosphorus (phosphapentadiene or phosphaphenene). In all cases, the heteroatom-containing material can be a small molecule, oligomer, or polymer. The phosphorus atom may or may not be bonded to oxygen.

[0049] In some embodiments, the reactants comprise phosphorus. In some other embodiments, phosphorus is in the form of phosphoric acid. In some other embodiments, phosphorus may be in the form of a salt, wherein the anion of the salt comprises one or more phosphate, phosphite, phosphine, hydrogen phosphate, dihydrogen phosphate, hexafluorophosphate, hypophosphite, polyphosphate, or pyrophosphate ions, or combinations thereof. In some other embodiments, phosphorus may be in the form of a salt, wherein the cation of the salt comprises one or more phosphonium ions. Any of the non-phosphate-containing anion or cation pairs from the above embodiments may be selected for use with 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.

[0050] In some embodiments, the catalyst comprises a basic volatile catalyst. For example, in one embodiment, the basic volatile catalyst comprises ammonium carbonate, ammonium bicarbonate, ammonium acetate, ammonium hydroxide, or combinations thereof. In other embodiments, the basic volatile catalyst is ammonium carbonate. In yet another embodiment, the basic volatile catalyst is ammonium acetate.

[0051] In other embodiments, the method includes mixing acids. In some 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 pressure that does not provide dissolution of one or more other polymer precursors.

[0052] The acid can be selected from many 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 1:99. In other embodiments, the acid is acetic acid, and the first solvent or the second solvent is water. In other embodiments, acidity is provided by adding a solid acid.

[0053] The total acid content in the mixture can vary to alter the properties of the final product. In some embodiments, the acid is present at about 1% to about 50% by weight of the mixture. In other embodiments, the acid is present at about 5% to about 25%. In still other embodiments, the acid is present at about 10% to about 20%, for example about 10%, about 15%, or about 20%.

[0054] In some embodiments, the polymer precursor components are blended together and subsequently held at a time and temperature sufficient to achieve polymerization. One or more of the polymer precursor components may have a particle size less than about 20 mm, for example less than 10 mm, for example less than 7 mm, for example less than 5 mm, for example less than 2 mm, for example less than 1 mm, for example less than 100 micrometers, for example less than 10 micrometers. In some embodiments, the particle size of one or more polymer precursor components is reduced during the blending process.

[0055] The blending of one or more polymer precursor components without solvents can be achieved by methods in the art, while simultaneously controlling process conditions (e.g., temperature). These methods include 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 carried out before, during, and / or after incubation at the reaction temperature (or a combination thereof).

[0056] The reaction parameters include aging the blended mixture at temperatures and times 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 or near the melting points of one or more polymer precursors. In some embodiments, suitable aging temperatures are from about room temperature to or near the glass transition temperatures of one or more polymer precursors. For example, in some embodiments, the solvent-free mixture is aged at temperatures 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 some embodiments, the solvent-free mixture is aged at temperatures from about 50°C to about 250°C.

[0057] The reaction duration is typically sufficient for the polymer precursor 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 outcome. Typical embodiments include aging periods of approximately 2 hours to approximately 48 hours, for example, in some embodiments, aging for approximately 12 hours, and in other embodiments, aging for approximately 4-8 hours (e.g., approximately 6 hours).

[0058] In some embodiments, an electrochemical modifier is incorporated during the polymerization process described above. For example, in some embodiments, the electrochemical modifier, in the form of metal particles, metal slurry, metal salt, metal oxide, or molten metal, may be dissolved or suspended in the mixture that produces the gel resin.

[0059] Exemplary electrochemical modifiers used to generate composite materials may fall into one or more chemical categories. In some embodiments, the electrochemical modifier 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.

[0060] In some embodiments, the electrochemical modifier comprises a metal, and exemplary substances include, but are not limited to, aluminum isopropoxide, manganese acetate, nickel acetate, ferric acetate, tin chloride, silicon chloride, and combinations thereof. In some embodiments, the electrochemical modifier is a phosphate (salt) compound, including but not limited to phytic acid, phosphoric acid, ammonium dihydrogen phosphate, and combinations thereof. In some embodiments, the electrochemical modifier comprises silicon, and exemplary substances include, but are not limited to, silicon powder, silicon nanotubes, polycrystalline silicon, nanocrystalline silicon, amorphous silicon, porous silicon, nanoscale silicon, silicon with nano-features, silicon with both nanoscale and nano-features, silicyne, and black silicon, and combinations thereof.

[0061] Electrochemical modifiers can be combined with various polymer systems using latent (or secondary) polymeric functional groups through physical mixing or chemical reactions. Examples of latent polymeric 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., sulfidation 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, spirocyclic compounds, etc.).

[0062] Electrochemical modifiers can also be added to polymer systems through 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 electrochemical modifiers, and co-precipitation of electrochemical modifiers and main polymer materials.

[0063] In some cases, electrochemical modifiers can be added via metal salt solids, solutions, or suspensions. The metal salt solids, solutions, or suspensions may contain acids and / or alcohols to improve the solubility of the metal salt. In another variation, the polymer gel (before or after an optional drying step) is contacted with a slurry containing the electrochemical modifier. In yet another variation, the polymer gel (before or after an optional drying step) is contacted with a metal or metal oxide sol containing the desired electrochemical modifier.

[0064] In addition to the electrochemical modifiers exemplified above, composite materials may contain one or more other forms of carbon (i.e., allotropes). In this regard, it has been found that incorporating 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) into the composite material is effective for optimizing the electrochemical properties of the composite. Various allotropes of carbon can be incorporated into the carbon material during 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 milling stage, or after milling. In some embodiments, a second carbon form is incorporated into the composite material by adding a second carbon form before or during polymer gel polymerization as described in more detail herein. The polymer gel containing the second carbon form is then treated according to the general techniques described herein to obtain a carbon material containing a second allotropy of carbon.

[0065] In a preferred embodiment, carbon is generated from a precursor having little or no solvent required for processing (solvent-free). The structure of polymer precursors suitable for use in low-solvent or substantially solvent-free reaction mixtures is not particularly limited, as long as the polymer precursor can react 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.

[0066] 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 or second polymer precursor is a carbonyl-containing compound and the remainder of the first 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 precursor is 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.

[0067] Polymer precursor materials suitable for reaction mixtures with low or substantially no solvents as disclosed herein include (a) alcohols, phenols, and other monohydroxy or polyhydroxy compounds, and (b) aldehydes, ketones, and combinations thereof. Representative alcohols herein include straight-chain and branched, saturated and unsaturated alcohols. Suitable phenols include polyhydroxybenzenes, such as dihydroxybenzenes or trihydroxybenzenes. Representative polyhydroxybenzenes include resorcinol (i.e., 1,3-dihydroxybenzene), catechol, hydroquinone, and phloroglucinol. Other suitable compounds in this regard are bisphenols, such as bisphenol A. Mixtures of two or more polyhydroxybenzenes may also be used. Phenols (monohydroxybenzenes) may also be used. Representative polyhydroxy compounds include sugars such as glucose, sucrose, fructose, chitin, and other polyols such as mannitol. In this paper, aldehydes include: straight-chain saturated aldehydes, such as formaldehyde, acetaldehyde, propanal, and butanal; straight-chain unsaturated aldehydes, such as ketene and other ketones, propenal, crotonal, and 3-butenal; branched-chain saturated and unsaturated aldehydes; and aromatic aldehydes, such as benzaldehyde, salicylaldehyde, and hydrogenated cinnamaldehyde. Suitable ketones include: straight-chain saturated ketones, such as acetone and 2-butanone; straight-chain unsaturated ketones, such as acrylone, 2-butenone, and 3-butenone; branched-chain saturated and unsaturated ketones; and aromatic ketones, such as methyl benzyl ketone and ethyl benzyl ketone. Polymer precursor materials can also be combinations of the precursors described above.

[0068] In some embodiments, in a low-solvent or substantially solvent-free reaction mixture, one polymer precursor is an alcohol-containing substance, and the other polymer precursor is a carbonyl-containing substance. The relative amounts of the alcohol-containing substance (e.g., alcohols, phenolic compounds, and monohydroxy or polyhydroxy compounds, or combinations thereof) reacting with the carbonyl-containing substance (e.g., aldehydes, ketones, or combinations thereof) can vary significantly. In some embodiments, the ratio of the alcohol-containing substance to the aldehyde-containing substance is chosen such that the total number of moles of reactive alcohol groups in the alcohol-containing substance is approximately the same as the total number of moles of reactive carbonyl groups in the aldehyde-containing substance. Similarly, the ratio of the alcohol-containing substance to the ketone-containing substance can be chosen such that the total number of moles of reactive alcohol groups in the alcohol-containing substance is approximately the same as the total number of moles of reactive carbonyl groups in the ketone-containing substance. The same approximately 1:1 molar ratio also applies when the carbonyl-containing substance comprises a combination of aldehydes and ketones.

[0069] In other embodiments, the polymer precursor in the 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 combinations thereof. Other embodiments include polymer precursors selected from isocyanates or other reactive carbonyl compounds (e.g., acyl halides).

[0070] Some embodiments of the disclosed method involve preparing low-solvent or solvent-free polymer gels (and carbon materials) containing electrochemical modifiers. Such electrochemical modifiers include, but are not limited to, nitrogen, silicon, and sulfur. In other embodiments, the electrochemical modifiers include fluorine, iron, tin, silicon, nickel, aluminum, zinc, or manganese. The electrochemical modifier may be included in any step of the preparation process. For example, in some cases, the electrochemical modifier is mixed with a mixture, a polymer phase, or a continuous phase.

[0071] The blending of one or more polymer precursor components without solvents can be achieved by methods in the art, while simultaneously controlling process conditions (e.g., temperature). These methods include 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 carried out before, during, and / or after incubation at the reaction temperature (or a combination thereof).

[0072] The reaction parameters include aging the blended mixture at temperatures and times 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 or near the melting points of one or more polymer precursors. In some embodiments, suitable aging temperatures are from about room temperature to or near the glass transition temperatures of one or more polymer precursors. For example, in some embodiments, the solvent-free mixture is aged at temperatures 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 some embodiments, the solvent-free mixture is aged at temperatures from about 50°C to about 250°C.

[0073] Porous carbon materials can be achieved via the pyrolysis of polymers from which the precursor materials described above are produced. In some embodiments, the porous carbon material comprises amorphous activated carbon produced by pyrolysis, physical or chemical activation, or a combination thereof, in a single or sequential process step.

[0074] The pyrolysis temperature and residence time can be varied; for example, the residence time can be varied 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, and 4 hours to 24 hours. The temperature can also be varied; for example, the pyrolysis temperature can be varied from 200°C to 300°C, 250°C 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, and 1150°C to 1250°C. In some embodiments, the pyrolysis temperature varies from 650°C to 1100°C. Pyrolysis can be carried out in an inert gas (e.g., nitrogen or argon).

[0075] In some embodiments, alternative gases are used to further achieve carbon activation. In some 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 activation temperature and residence time can be varied, for example, the residence time can be varied 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, and 4 hours to 24 hours. The temperature can be varied, for example, the pyrolysis temperature can be varied from 200°C to 300°C, 250°C 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, and 1150°C to 1250°C. In some implementations, the combined pyrolysis and activation temperature variations range from 650°C to 1100°C.

[0076] In some embodiments, combined pyrolysis and activation are performed to prepare porous carbon scaffolds. In such embodiments, the process gas can remain the same during the process, or the composition of the process gas can be varied during the process. In some embodiments, after appropriate temperature and time, an activating gas such as CO2, steam, or a combination thereof is added to the process gas to allow for the pyrolysis of the solid carbon precursor.

[0077] Suitable gases for carbon activation include, but are not limited to, carbon dioxide, carbon monoxide, water (steam), air, oxygen, and other combinations thereof. The activation temperature and residence time can be varied; for example, the residence time can be varied 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, and 4 hours to 24 hours. The temperature can be varied; for example, the pyrolysis temperature can be varied from 200°C to 300°C, 250°C 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, and 1150°C to 1250°C. In some embodiments, the activation temperature varies from 650°C to 1100°C.

[0078] Carbon particle size reduction can be performed before pyrolysis and / or after pyrolysis and / or after activation. Particle 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 particle size reduction methods are also envisioned, such as milling, ball milling, jet milling, water jet milling, and other methods known in the art.

[0079] Porous carbon scaffolds can be in the form of particles. Particle size and particle size distribution can be measured using various techniques known in the art and can be described based on fractional volume. In this respect, the Dv,50 of the carbon scaffold can be from 10 nm to 10 mm, for example, from 100 nm to 1 mm, for example, from 1 μm to 100 μm, for example, from 2 μm to 50 μm, for example, from 3 μm to 30 μm, for example, from 4 μm to 20 μm, for example, from 5 μm to 10 μm. In some embodiments, Dv,50 is less than 1 mm, for example, less than 100 μm, for example, less than 50 μm, for example, less than 30 μm, for example, less than 20 μm, for example, less than 10 μm, for example, less than 8 μm, for example, less than 5 μm, for example, less than 3 μm, for example, less than 1 μm. In some embodiments, Dv,100 is less than 1 mm, for example, less than 100 μm, for example, less than 50 μm, for example, less than 30 μm, for example, less than 20 μm, for example, less than 10 μm, for example, less than 8 μm, for example, less than 5 μm, for example, less than 3 μm, for example, less than 1 μm. In some embodiments, Dv,99 is less than 1 mm, for example, less than 100 μm, for example, less than 50 μm, for example, less than 30 μm, for example, less than 20 μm, for example, less than 10 μm, for example, less than 8 μm, for example, less than 5 μm, for example, less than 3 μm, for example, less than 1 μm. In some embodiments, Dv,90 is less than 1 mm, for example, less than 100 μm, for example, less than 50 μm, for example, less than 30 μm, for example, less than 20 μm, for example, less than 10 μm, for example, less than 8 μm, for example, less than 5 μm, for example, less than 3 μm, for example, less than 1 μm. In some embodiments, Dv,0 is greater than 10 nm, for example, greater than 100 nm, for example, greater than 500 nm, for example, greater than 1 μm, for example, greater than 2 μm, for example, greater than 5 μm, for example, greater than 10 μm. In some embodiments, Dv,1 is greater than 10 nm, for example, greater than 100 nm, for example, greater than 500 nm, for example, greater than 1 μm, for example, greater than 2 μm, for example, greater than 5 μm, for example, greater than 10 μm. In some embodiments, Dv,10 is greater than 10 nm, for example, greater than 100 nm, for example, greater than 500 nm, for example, greater than 1 μm, for example, greater than 2 μm, for example, greater than 5 μm, for example, greater than 10 μm.

[0080] In some implementations, the surface area of ​​the porous carbon scaffold may include greater than 400 m². 2 / g surface area, for example, greater than 500m 2 / g, for example, greater than 750m 2 / g, for example, greater than 1000m 2 / g, for example, greater than 1250m 2 / g, for example, greater than 1500m 2 / g, for example, greater than 1750m 2 / g, for example, greater than 2000m2 / g, for example, greater than 2500m 2 / g, for example, greater than 3000m 2 / g. In other embodiments, the surface area of ​​the porous carbon scaffold can be less than 500m². 2 / g. In some embodiments, the surface area of ​​the porous carbon scaffold is 200 to 500 m². 2 / g. In some embodiments, the surface area of ​​the porous carbon scaffold is 100 to 200 m². 2 / g. In some embodiments, the surface area of ​​the porous carbon scaffold is 50 to 100 m². 2 / g. In some embodiments, the surface area of ​​the porous carbon scaffold is 10 to 50 m². 2 / g. In some embodiments, the surface area of ​​the porous carbon scaffold can be less than 10m². 2 / g.

[0081] In some implementations, the pore volume of the porous carbon scaffold is greater than 0.4 cm³. 3 / g, for example, greater than 0.5cm 3 / g, for example, greater than 0.6cm 3 / g, for example, greater than 0.7cm 3 / g, for example, greater than 0.8cm 3 / g, for example, greater than 0.9cm 3 / g, for example, greater than 1.0cm 3 / g, for example, greater than 1.1cm 3 / g, for example, greater than 1.2cm 3 / g, for example, greater than 1.4cm 3 / g, for example, greater than 1.6cm 3 / g, for example, greater than 1.8cm 3 / g, for example, greater than 2.0cm 3 / g. In other embodiments, the pore volume of the porous carbon scaffold is less than 0.5 cm³. 3 For example, 0.1cm 3 / g to 0.5cm 3 / g. In some other embodiments, the pore volume of the porous carbon scaffold is 0.01 cm³. 3 / g to 0.1cm 3 / g.

[0082] In some other embodiments, the porous carbon scaffold has a pore volume of 0.2 to 2.0 cm³. 3 / g of amorphous activated carbon. In some embodiments, the carbon has a pore volume of 0.4 to 1.5 cm³. 3 / g of amorphous activated carbon. In some embodiments, the carbon has a pore volume of 0.5 to 1.2 cm³. 3 / g of amorphous activated carbon. In some embodiments, the carbon has a pore volume of 0.6 to 1.0 cm³. 3 / g of amorphous activated carbon.

[0083] In some other embodiments, the porous carbon scaffold comprises less than 1.0 g / cm³. 3 The tap density, for example, is less than 0.8 g / cm³. 3 For example, less than 0.6 g / cm³ 3 For example, less than 0.5 g / cm³ 3 For example, less than 0.4 g / cm³ 3 For example, less than 0.3 g / cm³ 3 For example, less than 0.2 g / cm³ 3 For example, less than 0.1 g / cm³ 3 .

[0084] The surface functionality of porous carbon scaffolds can vary. One property that can predict surface functionality is the pH of the porous carbon scaffold. The porous carbon scaffolds disclosed in this invention contain pH values ​​from 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, or 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.

[0085] The pore volume distribution of the porous carbon scaffold can vary. For example, the percentage of micropores can be less than 30%, such as less than 20%, less than 10%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, less than 0.5%, less than 0.2%, or less than 0.1%. In some embodiments, there is no detectable micropore volume in the porous carbon scaffold.

[0086] The mesopores constituting the porous carbon scaffold can vary. For example, the percentage of mesopores can be less than 30%, such as less than 20%, less than 10%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, less than 0.5%, less than 0.2%, or less than 0.1%. In some embodiments, there is no detectable mesopore volume in the porous carbon scaffold.

[0087] In some embodiments, the pore volume distribution of the porous carbon scaffold includes more than 50% macropores, such as more than 60% macropores, more than 70% macropores, more than 80% macropores, more than 90% macropores, more than 95% macropores, more than 98% macropores, more than 99% macropores, more than 99.5% macropores, and more than 99.9% macropores.

[0088] In some preferred embodiments, the pore volume of the porous carbon scaffold comprises a mixture of micropores, mesopores, and macropores. Therefore, in some embodiments, the porous carbon scaffold comprises 0-20% micropores, 30-70% mesopores, and less than 10% macropores. In some other embodiments, the porous carbon scaffold comprises 0-20% micropores, 0-20% mesopores, and 70-95% macropores. In some other embodiments, the porous carbon scaffold comprises 20-50% micropores, 50-80% mesopores, and 0-10% macropores. In some other embodiments, the porous carbon scaffold comprises 40-60% micropores, 40-60% mesopores, and 0-10% macropores. In some other embodiments, the porous carbon scaffold comprises 80-95% micropores, 0-10% mesopores, and 0-10% macropores. In some other embodiments, the porous carbon scaffold comprises 0-10% micropores, 30-50% mesopores, and 50-70% macropores. In some other embodiments, the porous carbon scaffold comprises 0-10% micropores, 70-80% mesopores, and 0-20% macropores. In some other embodiments, the porous carbon scaffold comprises 0-20% micropores, 70-95% mesopores, and 0-10% macropores. In some other embodiments, the porous carbon scaffold comprises 0-10% micropores, 70-95% mesopores, and 0-20% macropores.

[0089] In some embodiments, the pore volume percentage representing pores of 100 to 1000 Å (10 to 100 nm) in the porous carbon scaffold is greater than 30% of the total pore volume, for example, greater than 40% of the total pore volume, for example, greater than 50% of the total pore volume, for example, greater than 60% of the total pore volume, for example, greater than 70% of the total pore volume, for example, greater than 80% of the total pore volume, for example, greater than 90% of the total pore volume, for example, greater than 95% of the total pore volume, for example, greater than 98% of the total pore volume, for example, greater than 99% of the total pore volume, for example, greater than 99.5% of the total pore volume, for example, greater than 99.9% of the total pore volume.

[0090] In some embodiments, the specific gravity density of the porous carbon scaffold is from about 1 g / cc to about 3 g / cc, for example, from about 1.5 g / cc to about 2.3 g / cc. In other embodiments, the scaffold 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, for example, from about 2.4 cc / g to about 2.5 cc / g.

[0091] C. Silicon production via chemical vapor infiltration (CVI)

[0092] Chemical vapor deposition (CVD) is a method in which a substrate provides a solid surface comprising a first component of a composite, and a gas is thermally decomposed on the solid surface to provide a second component of the composite. For example, this CVD method can be used to produce Si-C composites, where silicon is coated on the outer surface of silicon particles. Alternatively, chemical vapor infiltration (CVI) is a method in which a substrate provides a porous scaffold comprising a first component of a composite, and a gas is thermally decomposed to enter the pores of the porous scaffold material (entering the pores) to provide the second component of the composite.

[0093] In one embodiment, silicon is generated within the pores of the 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 a silane) to decompose the gas into silicon. In some embodiments, the silicon-containing gas may include higher silanes (e.g., disilane, trisilane, and / or tetrasilane), chlorosilanes (e.g., monochlorosilane, dichlorosilane, trichlorosilane, and tetrachlorosilane), or mixtures thereof.

[0094] The silicon-containing precursor gas can be mixed with other inert gases, such as nitrogen, hydrogen, argon, helium, or combinations thereof. The process temperature and time can vary; for example, the temperature can be between 200 and 900°C, or even 200 to 250°C, 250 to 300°C, 300 to 350°C, 300 to 400°C, 350 to 450°C, 350 to 400°C, 400 to 500°C, 500 to 600°C, 600 to 700°C, 700 to 800°C, 800 to 900°C, or 600 to 1100°C.

[0095] The gas mixture may contain 0.1-1% silane and the balance inert gas. Alternatively, the gas mixture may contain 1%-10% silane and the balance inert gas. Alternatively, the gas mixture may contain 10% to 20% silane and the balance inert gas. Alternatively, the gas mixture may contain 20% to 50% silane and the balance inert gas. Alternatively, the gas mixture may contain more than 50% silane and the balance 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.

[0096] The pressure in the CVI method can vary. In some implementations, the pressure is atmospheric pressure. In some implementations, the pressure is below atmospheric pressure. In some implementations, the pressure is above atmospheric pressure.

[0097] C. Physical and electrochemical properties of silicon-carbon composites

[0098] While not wishing to be bound by theory, it is believed that the realization of nanoscale silicon (e.g., silicon with pores filled to 5 to 1000 nm or other ranges as disclosed elsewhere herein) due to certain desired pore volume structures of porous carbon scaffolds, along with the advantageous properties of other components of the composite (including low surface area and low specific gravity), results in composite materials with different and advantageous properties (e.g., electrochemical performance when the composite constitutes the anode of a lithium-ion energy storage device).

[0099] In some embodiments, the embedded silicon particles within the composite include nanoscale features. These nanoscale features may preferably have a feature length scale of less than 1 μm, less than 300 nm, less than 150 nm, less than 100 nm, less than 50 nm, less than 30 nm, less than 15 nm, less than 10 nm, or less than 5 nm.

[0100] In some embodiments, the silicon embedded within the composite is spherical. In other embodiments, the porous silicon particles are non-spherical, such as rod-shaped or fibrous structures. In some embodiments, silicon exists as a layer encapsulating the interior of the pores within a porous carbon scaffold. The depth of this silicon layer can vary, for example, it can be 5 nm to 10 nm, such as 5 nm to 20 nm, such as 5 nm to 30 nm, such as 5 nm to 33 nm, such as 10 nm to 30 nm, such as 10 nm to 50 nm, such as 10 nm to 100 nm, such as 10 nm to 150 nm, such as 50 nm to 150 nm, such as 100 nm to 300 nm, such as 300 nm to 1000 nm.

[0101] In some embodiments, the silicon embedded within the composite is nanoscale and resides within the pores of the porous carbon scaffold. For example, the embedded silicon can be impregnated, deposited via CVI, or otherwise suitably introduced into the pores within the porous carbon particles, the pore sizes of which are 5 to 1000 nm, for example 10 to 500 nm, 10 to 200 nm, 10 to 100 nm, 33 to 150 nm, or 20 to 100 nm. Other ranges of carbon pore sizes with respect to fractional pore volumes are also envisioned, whether micropores, mesopores, or macropores.

[0102] The embodiments of the composites with extremely durable lithium intercalation disclosed herein improve the properties of any number of energy storage devices (e.g., lithium-ion batteries). In some embodiments, the silicon-carbon composites disclosed herein exhibit a Z value less than 10, such as less than 5, less than 4, less than 3, less than 2, less than 1, less than 0.1, less than 0.01, or less than 0.001. In some embodiments, Z is 0.

[0103] In some preferred embodiments, the silicon-carbon composite comprises a desired low Z-value and a combination with another desired physicochemical and / or electrochemical property, or a combination with more than one other desired physicochemical and / or electrochemical property. Table 1 provides a description of some embodiments of the property combinations of silicon-carbon composites.

[0104] Table 1. Implementation schemes of silicon-carbon composites with realized properties.

[0105]

[0106] According to Table 1, silicon-carbon composites can contain a variety of combinations of properties. For example, silicon-carbon composites can contain Z values ​​less than 10 and m values ​​less than 100. 2 A surface area of ​​ / g, a first-cycle efficiency greater than 80%, and a reversible capacity of at least 1300 mAh / g. For example, silicon-carbon composites can contain less than 10 Z and less than 100 m. 2 A surface area of ​​ / g, a first-cycle efficiency greater than 80%, and a reversible capacity of at least 1600 mAh / g. For example, silicon-carbon composites can contain less than 10 Z and less than 20 m. 2 A surface area of ​​ / g, a first-cycle efficiency greater than 85%, and a reversible capacity of at least 1600 mAh / g. For example, silicon-carbon composites can contain less than 10 Z and less than 10 m. 2 A surface area of ​​ / g, a first-cycle efficiency greater than 85%, and a reversible capacity of at least 1600 mAh / g. For example, silicon-carbon composites can contain less than 10 Z and less than 10 m. 2A surface area of ​​ / g, a first-cycle efficiency greater than 90%, and a reversible capacity of at least 1600 mAh / g. For example, silicon-carbon composites can contain less than 10 Z and less than 10 m. 2 / g surface area, greater than 90% first cycle efficiency and at least 1800mAh / g reversible capacity.

[0107] In addition to including a carbon scaffold having the properties also described in this scheme, silicon-carbon composites may also include combinations of the above properties. Therefore, Table 2 provides descriptions of some embodiments of combinations of properties of silicon-carbon composites.

[0108] Table 2. Implementation schemes of silicon-carbon composites with realized properties.

[0109]

[0110]

[0111] As used in this article, the percentages of "micropores," "mesopores," and "macropores" refer to the percentages of micropores, mesopores, and macropores in the total pore volume, respectively. For example, a carbon scaffold with 90% micropores is a carbon scaffold in which 90% of the total pore volume of the carbon scaffold is formed by micropores.

[0112] According to Table 2, silicon-carbon composites can contain a variety of combinations of properties. For example, silicon-carbon composites can include I... D / I G ≤0.7, Z <10, surface area <100m² 2 / g, first cycle efficiency greater than 80%, reversible capacity of at least 1600mAh / g, silicon content of 15%-85%, and total pore volume of carbon scaffold of 0.2-1.2cm³. 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, silicon-carbon composites may include I D / I G ≤0.7, Z <10, surface area <20m² 2 / g, first cycle efficiency greater than 85%, reversible capacity of at least 1600mAh / g, silicon content of 15%-85%, and total pore volume of carbon scaffold of 0.2-1.2cm³. 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, silicon-carbon composites may include I D / I G ≤0.7, Z <10, surface area <10m² 2 / g, first cycle efficiency greater than 85%, reversible capacity of at least 1600mAh / g, silicon content of 15%-85%, and total pore volume of carbon scaffold of 0.2-1.2cm³. 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, silicon-carbon composites may include I D / I G ≤0.7, Z <10, surface area <10m² 2 / g, first cycle efficiency greater than 90%, reversible capacity of at least 1600mAh / g, silicon content of 15%-85%, and total pore volume of carbon scaffold of 0.2-1.2cm³. 3 / g, wherein the scaffold pore volume comprises >80% micropores, <20% mesopores, and <10% macropores. For example, silicon-carbon composites may include I D / I G ≤0.7, Z <10, surface area <10m² 2 / g, first cycle efficiency greater than 90%, reversible capacity of at least 1800mAh / g, silicon content of 15%-85%, and total pore volume of carbon scaffold of 0.2-1.2cm³. 3 / g, wherein the pore volume of the support comprises >80% micropores, <20% mesopores and <10% macropores.

[0113] Without being bound by theory, the silicon filling within the pores of porous carbon traps the pores within the porous carbon scaffold particles, creating inaccessible volumes, such as those inaccessible to nitrogen. Therefore, silicon-carbon composites can exhibit a specific gravity density of less than 2.1 g / cm³. 3 For example, less than 2.0 g / cm³ 3 For example, less than 1.9 g / cm³ 3 For example, less than 1.8 g / cm³ 3 For example, less than 1.7 g / cm³ 3 For example, less than 1.6 g / cm³ 3 For example, less than 1.4 g / cm³ 3 For example, less than 1.2 g / cm³ 3 For example, less than 1.0 g / cm³ 3 .

[0114] In some implementations, the specific gravity density exhibited by the silicon-carbon composite material can be 1.7 g / cm³. 3 Up to 2.1 g / cm 3 For example, 1.7 g / cm³ to 1.8 g / cm³. 3 1.8g.cm 3 Up to 1.9 g / cm 3 For example, 1.9g.cm 3Up to 2.0 g / cm 3 For example, 2.0g.cm 3 Up to 2.1 g / cm 3 In some implementations, the specific gravity density exhibited by the silicon-carbon composite material can be 1.8 g / cm³. 3 Up to 2.1 g / cm 3 In some implementations, the specific gravity density exhibited by the silicon-carbon composite material can be 1.8 g / cm³. 3 Up to 2.0 g / cm 3 In some implementations, the specific gravity density exhibited by the silicon-carbon composite material can be 1.9 g / cm³. 3 Up to 2.1 g / cm 3 .

[0115] The pore volume of lithium-intercalated composite materials exhibiting extremely high durability can be as low as 0.01 cm³. 3 / g to 0.2cm 3 / g. In some embodiments, the pore volume of the composite material can be 0.01 cm³. 3 / g to 0.15cm 3 / g, for example, 0.01cm 3 / g to 0.1cm 3 / g, for example 0.01cm 3 / g to 0.05cm 2 / g.

[0116] The particle size distribution of lithium-intercalated composites exhibiting extreme durability is important for determining both power performance and volumetric capacity. Volumetric capacity can increase with improved packing. In one embodiment, this distribution is a Gaussian distribution with a single-peak, bimodal, or multimodal (>2 distinct peaks, e.g., trimodal) shape. The particle size properties of the composite can be described by D0 (smallest particle in the distribution), Dv50 (average particle size), and Dv100 (largest particle size). The optimal combination of particle packing and performance will be a combination of some of the following size ranges. Particle size reduction in such embodiments can be performed as is known in the art, for example by jet milling in the presence of various gases, including air, nitrogen, argon, helium, supercritical vapor, and other gases known in the art.

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

[0118] In some embodiments, the composite material has a Dv50 of 5 nm to 20 μm. In other embodiments, the composite material has a Dv50 of 5 nm to 1 μm, for example, 5-500 nm, 5-100 nm, or 10-50 nm. In other embodiments, the composite material has a Dv50 of 500 nm to 2 μm, 750 nm to 1 μm, or 1-2 μm. In still other embodiments, the composite material has a Dv50 of 1 to 1000 μm, for example, 1-100 μm, 1-10 μm, 2-20 μm, 3-15 μm, or 4-8 μm. In some embodiments, Dv50 > 20 μm, for example, > 50 μm or > 100 μm.

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

[0120] The surface functionality of the composite materials disclosed in this invention, which exhibit extremely durable lithium intercalation, can be modified to obtain the desired electrochemical properties. One such property of particulate composite materials is the concentration of atomic matter at the surface of the composite material relative to the interior of the composite material. This difference in the concentration of atomic matter at the surface of the particulate composite material relative to the interior can be determined as is known in the art, for example by X-ray photoelectron spectroscopy (XPS).

[0121] Another property that can predict surface functionality is the pH of the composite material. The composite materials disclosed in this invention contain pH values ​​from 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 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.

[0122] The silicon-carbon composite material may contain varying amounts of carbon, oxygen, hydrogen, and nitrogen as measured by gas chromatography-CHNO analysis. In one embodiment, the composite has a carbon content greater than 98 wt.% or even greater than 99.9 wt%, as measured by CHNO analysis. In another embodiment, the carbon content of the silicon-carbon composite is about 10-90%, for example 20-80%, for example 30-70%, for example 40-60%.

[0123] In some embodiments, the nitrogen content of the silicon-carbon composite material is 0-90%, for example 0.1-1%, for example 1-3%, for example 1-5%, for example 1-10%, for example 10-20%, for example 20-30%, for example 30-90%.

[0124] In some embodiments, the oxygen content is 0-90%, for example 0.1-1%, for example 1-3%, for example 1-5%, for example 1-10%, for example 10-20%, for example 20-30%, for example 30-90%.

[0125] Silicon-carbon composites can also be incorporated with electrochemical modifiers, selected to optimize the electrochemical properties of the unmodified composite. The electrochemical modifiers can be incorporated within the pore structure and / or surface of the porous carbon scaffold, within embedded silicon, or within the final carbon layer, or within the conductive polymer, within a coating, or in any other manner. For example, in some embodiments, the composite includes a coating of an electrochemical modifier (e.g., silicon or Al₂O₃) on the surface of the carbon material. In some embodiments, the composite contains more than about 100 ppm of the electrochemical modifier. In some embodiments, the electrochemical modifier is selected from iron, tin, silicon, nickel, aluminum, and manganese.

[0126] In some embodiments, the electrochemical modifier comprises an element (e.g., silicon, tin, sulfur) capable of lithiation 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 lithiation at 3 to 0 V relative to lithium metal. In other embodiments, the electrochemical modifier comprises an element that does not lithilate at 3 to 0 V relative to lithium metal (e.g., aluminum, manganese, nickel, metal phosphates). In other embodiments, the electrochemical modifier comprises a nonmetallic element (e.g., fluorine, nitrogen, hydrogen). In other embodiments, the electrochemical modifier comprises any one or any combination of the aforementioned electrochemical modifiers (e.g., tin-silicon, nickel-titanium oxide).

[0127] Electrochemical modifiers can be provided in various 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.

[0128] The electrochemical properties of a composite material can be modified, at least in part, by the amount of an electrochemical modifier in the material, wherein the electrochemical modifier is an alloying material, such as silicon, tin, indium, aluminum, germanium, or gallium. Therefore, in some embodiments, the composite material contains 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.

[0129] Compared to the non-lithiated state, the particle size of the composite material can expand during lithiation. For example, the expansion factor is defined as the ratio of the average particle size of the composite material containing porous silicon material during lithiation to the average particle size under non-lithiation conditions. As described in the art, this expansion factor can be relatively large for previously known suboptimal silicon-containing materials, for example, about 4X (corresponding to 400% volume expansion during lithiation). The inventors have discovered that composite materials containing 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, and 1.0 to 1.5.

[0130] It is conceivable that, in some embodiments, the composite material will contain a portion of the pore volume, i.e., the volume of voids inaccessible to nitrogen as detected by nitrogen adsorption measurements. Without being bound by theory, this pore volume is important because it provides the volume into which silicon can expand during lithiation.

[0131] In some embodiments, the ratio of the void volume to the silicon volume constituting the composite particles is from 0.1:1 to 10:1. For example, the ratio is from 1:1 to 5:1 or from 5:1 to 10:1. In some embodiments, to effectively accommodate the maximum expansion of silicon during lithiation, the ratio is from 2:1 to 5:1, or about 3:1.

[0132] In some embodiments, the electrochemical performance of the disclosed composites is tested in a half-cell; alternatively, the performance of the disclosed composites with extremely durable lithium intercalation is tested in a full cell (e.g., a full-cell button cell, a full-cell pouch cell, a prismatic cell, or other battery structures known in the art). As known in the art, anode compositions comprising the disclosed composites with extremely durable lithium intercalation may further comprise a variety of 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 sodium carboxymethyl cellulose (SBR-Na-CMC), polyvinylidene fluoride (PVDF), polyimide (PI), polyacrylic acid (PAA), etc., and combinations thereof. In some embodiments, the binder may contain lithium ions as counterions.

[0133] Other substances constituting the electrode are known in the art. The percentage of active material in the electrode by weight can vary, for example, 1 to 5%, for example, 5 to 15%, for example, 15 to 25%, for example, 25 to 35%, for example, 35 to 45%, for example, 45 to 55%, for example, 55 to 65%, for example, 65 to 75%, for example, 75 to 85%, for example, 85 to 95%. In some embodiments, the active material constitutes 80 to 95% of the electrode. In some embodiments, the amount of conductive additive in the electrode can vary, for example, 1 to 5%, 5 to 15%, for example, 15 to 25%, for example, 25 to 35%. In some embodiments, the amount of active material in the electrode is 5 to 25%. In some embodiments, the amount of binder can vary, for example, 1 to 5%, 5 to 15%, for example, 15 to 25%, for example, 25 to 35%. In some embodiments, the amount of conductive additive in the electrode is 5 to 25%.

[0134] As is known in the art, silicon-carbon composite materials can be pre-lithiated. In some embodiments, pre-lithiation is electrochemically achieved, for example, in a half-cell, before assembling a lithium-ion anode containing porous silicon material into a full-cell lithium-ion battery. In some embodiments, pre-lithiation is achieved by doping a cathode with a lithium-containing compound, such as a lithium salt. Examples of suitable lithium salts herein include, but are not limited to, lithium(II) tetrabromonickel oxide, lithium(II) tetrachlorocopper oxide, lithium azide, lithium benzoate, lithium bromide, lithium carbonate, lithium chloride, lithium cyclohexanebutyrate, lithium fluoride, lithium formate, lithium hexafluoroarsenic(V) oxide, 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.

[0135] Anodes incorporating silicon-carbon composite materials can be paired with a variety of cathode materials to obtain 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) and LiNi. 0.8 Co 0.15 Al 0.05 O2(NCA), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NMC), LiMn2O4 and its variants (LMO), and LiFePO4 (LFP).

[0136] For full-cell lithium-ion batteries that include an anode also comprising a silicon-carbon composite material, the cathode-anode pairing can be varied. For example, the cathode-to-anode capacity ratio can be varied from 0.7 to 1.3. In some embodiments, the cathode-to-anode capacity ratio can be varied from 0.7 to 1.0, such as 0.8 to 1.0, 0.85 to 1.0, 0.9 to 1.0, or 0.95 to 1.0. In other embodiments, the cathode-to-anode capacity ratio can be varied from 1.0 to 1.3, such as 1.0 to 1.2, 1.0 to 1.15, 1.0 to 1.1, or 1.0 to 1.05. In other embodiments, the cathode-to-anode capacity ratio can be varied from 0.8 to 1.2, such as 0.9 to 1.1 or 0.95 to 1.05.

[0137] For full-cell lithium-ion batteries, including anodes that also contain silicon-carbon composite materials, the voltage windows for charging and discharging can be varied. In this respect, the voltage window can be varied as is known in the art, depending on 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. Examples of voltage windows, for example, vary from 2.0V to 5.0V, such as 2.5V to 4.5V, or 2.5V to 4.2V, depending on the potential variation relative to Li / Li+.

[0138] For a full-cell lithium-ion battery that also includes an anode comprising a silicon-carbon composite material, the battery conditioning strategy 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 rates slower than the desired cycle rate). As is known in the art, the conditioning process can also include the steps of unsealing the lithium-ion battery, evacuating any gases generated therein during the conditioning process, and then resealing the lithium-ion battery.

[0139] For a full-cell lithium-ion battery including an anode that also comprises a silicon-carbon composite material, the cycle rate can vary as known in the art, for example, it can be C / 20 to 20C, such as C10 to 10C, such as C / 5 to 5C. In some embodiments, the cycle rate is C / 10. In some embodiments, the cycle rate is C / 5. In some embodiments, the cycle rate is C / 2. In some embodiments, the cycle rate is 1C. In some embodiments, the cycle rate is 1C, wherein the rate is periodically reduced to a slower rate, such as cycling at 1C, wherein every 20th cycle uses a C / 10 rate. In some embodiments, the cycle rate is 2C. In some embodiments, the cycle rate is 4C. In some embodiments, the cycle rate is 5C. In some embodiments, the cycle rate is 10C. In some embodiments, the cycle rate is 20C.

[0140] The first cycle efficiency of the lithium-intercalated composite disclosed herein is determined by comparing the lithium intercalated into the anode during the first cycle with the lithium deintercalated from the anode during the first cycle (before pre-lithiation modification). The efficiency is 100% when intercalation and deintercalation are equal. 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 some embodiments, the electrolyte may contain various additives known to provide improved performance, such as fluoroethylene carbonate (FEC) or other related fluorinated carbonate compounds, or ester cosolvents such as methyl butyrate, vinylene carbonate, and other electrolyte additives known to improve the electrochemical performance of silicon-containing anode materials.

[0141] Coulombic efficiency can be averaged, for example, when tested in a half-cell, by averaging from cycle 7 to cycle 25. In some embodiments, the average efficiency of the complex with extremely durable lithium intercalation is greater than 0.9 or 90%. In some embodiments, the average efficiency is greater than 0.95 or 95%. In some 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.

[0142] In other embodiments, this disclosure provides a composite material exhibiting extremely durable lithium intercalation, wherein when the composite material is incorporated into the electrode of a lithium-based energy storage device, the volumetric capacity of the composite material is at least 10% greater than that of a lithium-based energy storage device including 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%, or at least 15% greater than the volumetric capacity of the same 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 energy storage device having a graphite electrode.

[0143] As is known in the art, the composite material can be pre-lithiated. 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 using techniques known to those skilled in the art:

[0144] #Li=Q x 3.6x MM / (C%x F)

[0145] Where Q is the lithium intercalation / deintercalation capacity relative to lithium metal at voltages between 5 mV and 2.0 V, measured in mAh / g; MM is the molecular weight of 72 or 6 carbons; F is the Faraday constant of 96,500; and C% is the mass percentage of carbon present in the structure as measured by CHNO or XPS.

[0146] The composite material can be characterized by a lithium to carbon atom ratio (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 in which lithium is in ionic rather than metallic form is 2.2:6. In some 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.

[0147] In some other embodiments, the Li:C ratio of the composite material is about 1:6 to about 2.5:6, about 1.4:6 to about 2.2:6, or about 1.4:6 to about 2:6. In other embodiments, the composite material may not necessarily contain lithium, but rather possess lithium absorption capacity (i.e., the ability to absorb a certain amount of lithium), for example, when cycling the material between two voltage conditions (in the case of a lithium-ion half-cell, exemplary voltage windows are located between 0 and 3V, such as 0.005 to 2.7V, such as 0.005 to 1V, such as 0.005 to 0.8V). While not wishing to be bound by theory, it is believed that the lithium absorption capacity of composite materials contributes to their excellent performance in lithium-based energy storage devices. Lithium absorption capacity is expressed as the ratio of lithium atoms absorbed by the composite material. In some other embodiments, the lithium absorption capacity of the composite material exhibiting extremely durable lithium intercalation is about 1:6 to about 2.5:6, about 1.4:6 to about 2.2:6, or about 1.4:6 to about 2:6.

[0148] In some other embodiments, the lithium absorption capacity is about 1.2:6 to about 2:6, about 1.3:6 to about 1.9:6, about 1.4:6 to about 1.9:6, about 1.6:6 to about 1.8:6, or about 1.7:6 to about 1.8:6. In other embodiments, the lithium absorption capacity 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.

[0149] D. Enhance the graphite properties of porous carbon scaffolds

[0150] In some embodiments, the electrochemical properties of the silicon-carbon material can be enhanced by improving the electrochemical properties of the carbon scaffold. In some embodiments, the graphitic properties of the carbon scaffold are enhanced, resulting in increased conductivity, such as increased ionic and / or electronic conductivity, and / or decreased reactivity, such as decreased reactivity when in contact with various other components present in the LIB, such as electrolyte components, and / or other beneficial properties, such as a more stable SEI formed in the LIB.

[0151] The graphitic properties of carbon scaffolds can be enhanced by heat-treating porous carbon scaffolds to partially transform the carbon structure from amorphous to graphite. For this purpose, the heat treatment temperature can be ≥900℃, for example ≥1000℃, ≥1100℃, ≥1200℃, ≥1300℃, ≥1400℃, ≥1500℃, ≥1600℃, ≥1700℃, ≥1800℃, ≥2000℃, or ≥3000℃. In some embodiments, the heat treatment temperature is 1000°C to 3000°C, for example 1000°C to 2700°C, for example 1000°C to 2500°C, for example 1000°C to 2300°C, for example 1000°C to 2000°C, for example 1100°C to 3000°C, for example 1100°C to 2700°C, for example 1100°C to 2500°C, for example 1100°C to 2000°C, for example 1200°C to 2000°C, for example 1100°C to 1700°C.

[0152] In some embodiments, the pressure during heat treatment may be below atmospheric pressure. In some other embodiments, the pressure during heat treatment may be above atmospheric pressure. In a preferred embodiment, the pressure during heating of the porous carbon scaffold may be atmospheric pressure. The heat treatment time may vary, for example, from 1 minute to 24 hours, and in some embodiments, the heat treatment may be carried out for more than 24 hours. In some embodiments, relatively rapid heating, relatively short residence time, and relatively rapid cooling are preferred to minimize the impact of heat treatment on the total pore volume and pore volume distribution of the porous carbon. In some embodiments, the residence time is from 1 minute to 1 hour, or in other embodiments, the residence time is from 1 hour to 24 hours, for example, 1 to 2 hours, 2 to 4 hours, 4 to 8 hours, or 8 to 24 hours.

[0153] In some implementations, microwave energy can be used to heat and / or otherwise enhance the graphitic properties of the carbon scaffold. Without being bound by theory, carbon particles are effective microwave absorbers, and reactors can be envisioned in which the particles are subjected to microwave heating before the silicon-containing gas to be deposited is introduced.

[0154] Temperature is related to the average kinetic energy (energy of motion) of atoms or molecules in a material, so stirring molecules in this way raises the temperature of the material. Therefore, dipole rotation is a mechanism by which energy in the form of electromagnetic radiation can raise the temperature of an object. Dipole rotation is a mechanism commonly referred to as dielectric heating and is most widely observed in microwave ovens. In microwave ovens, dipole rotation is most effective with liquid water, but it also works on fats, sugars, and other carbon-containing materials, albeit to a much smaller extent.

[0155] Dielectric heating involves heating electrically insulating materials through dielectric loss. The changing electric field across a material causes energy dissipation as molecules attempt to align with it. This changing electric field could be caused by electromagnetic waves propagating in free space (such as in a microwave oven), or it could be caused by a rapidly alternating electric field within a capacitor. In the latter case, there are no freely propagating electromagnetic waves, and the changing electric field can be considered an electrical component similar to the near-field of an antenna. In this case, although heating is achieved by changing the electric field within the capacitor cavity at radio frequency (RF), no actual radio waves are generated or absorbed. In this sense, the effect is a direct electrical analog of magnetic induction heating, which is also a near-field effect (and therefore does not involve radio waves).

[0156] At very high frequencies, the wavelength of the electromagnetic field becomes shorter than the distance between the metal walls of the heating cavity, or even shorter than the dimensions of the walls themselves. This is the case inside a microwave oven. In this situation, conventional far-field electromagnetic waves are formed (the cavity no longer acts as a pure capacitor, but as an antenna) and are absorbed to induce heating, but the dipole rotation mechanism of heat deposition remains the same. However, microwaves are not very efficient at inducing heating effects in low-frequency fields, which rely on slower molecular motion, such as molecular motion caused by ion dragging.

[0157] Microwave heating is a subclass of dielectric heating with frequencies above 100 MHz, in which electromagnetic waves can be emitted from a small transmitter and guided through space to reach a target. Modern microwave ovens utilize electromagnetic waves with electric fields having much higher frequencies and shorter wavelengths than RF heaters. Typical household microwave ovens operate at 2.45 GHz, but ovens at 915 MHz also exist. This means that the wavelengths used in microwave heating are 12 or 33 cm (4.7 or 13.0 inches). This provides efficient but less penetrating dielectric heating. Although a set of plates similar to a capacitor can be used at microwave frequencies, they are not necessary because microwaves already exist as far-field electromagnetic radiation, and their absorption does not require proximity to a small antenna as in RF heating. Therefore, the material to be heated (non-metallic) can simply be placed in the path of the wave and heated in a non-contact process.

[0158] Therefore, microwave absorbing materials can dissipate electromagnetic waves by converting them into heat energy. Without being bound by theory, the microwave absorption capability of a material is primarily determined by its relative complex permittivity, relative permeability, electromagnetic impedance matching, and the material's microstructure, such as its porosity and / or nanostructures or microstructures. When a microwave beam irradiates the surface of a microwave absorbing material, appropriate electromagnetic impedance matching can result in near-zero reflectivity of the incident microwaves, ultimately leading to heat transfer to the absorbing material.

[0159] Carbon materials can absorb microwaves, meaning they are easily heated by microwave radiation, specifically infrared radiation and radio waves in the electromagnetic spectrum. More specifically, they are defined as those waves with wavelengths from 0.001 to 1 m, corresponding to frequencies from 300 to 0.3 GHz. The ability of carbon to be heated in the presence of a microwave field is defined by its dielectric loss tangent: tanδ = ε” / ε’. The dielectric loss tangent consists of two parameters: the dielectric constant (or real complex dielectric constant) ε’ and the dielectric loss factor (or imaginary complex dielectric constant) ε”; that is, ε = ε’ – iε”, where ε is the complex dielectric constant. The dielectric constant (ε’) determines how much incident energy is reflected and how much energy is absorbed, while the dielectric loss factor (ε”) measures the dissipation of electrical energy within the material as heat. To achieve optimal microwave energy coupling, a moderate ε' should be combined with a high ε” (and therefore a high tanδ value) to convert microwave energy into heat. Thus, while some materials do not have sufficiently high loss factors to allow dielectric heating (through which microwaves can pass), others, such as some inorganic oxides and most carbon materials, are excellent microwave absorbers. On the other hand, electrically conductive materials reflect microwaves. For example, graphite and highly graphitized carbon can reflect a significant portion of microwave radiation. In the case of carbon, where delocalized π electrons move freely over a relatively wide region, other and very interesting phenomena can occur. The kinetic energy of some electrons can increase, enabling them to jump out of the material, leading to ionization of the surrounding atmosphere. At the macroscopic level, this phenomenon is thought to be the formation of sparks or arcs. But at the microscopic level, these hotspots are actually plasmas. Most of the time, from a spatial and temporal perspective, these plasmas can be considered microplasmas because they are confined to tiny regions of space and last only a fraction of a second. The dense generation of such microplasmas can have significant implications for the processes involved.

[0160] Without being bound by theory, heating carbon materials via microwave heating offers many advantages over conventional heating, such as: (i) non-contact heating; (ii) energy transfer rather than heat transfer; (iii) rapid heating; (iv) selective material heating; (v) volumetric heating; (vi) rapid start-up and shutdown; (vii) heating from within the material bulk; and (viii) a higher level of safety and automation. The high capacity of carbon materials to absorb microwave energy and convert it into heat is illustrated in Table 3 (provided by the following reference, J.A. Menéndez, A. Arenillas, B. Fidalgo, Y. Fernández, L. Zubizarreta, E.G. Calvo, J.M. Bermúdez, “Microwave heating processes involving carbon materials”, Fuel Processing Technology, 2010, 91(1), 1-8), which lists the dielectric loss tangent for examples of different carbons. It can be seen that, except for coal, the loss tangent of most carbons is higher than that of distilled water (tanδ = 0.118 for distilled water at 2.45 GHz and room temperature).

[0161] Table 3. Examples of dielectric loss tangents for different carbon materials at a frequency of 2.45 GHz and room temperature.

[0162] carbon type tanδ=ε” / ε' coal 0.02-0.08 Carbon foam 0.05-0.20 charcoal 0.11-0.29 carbon black 0.35-0.83 Activated carbon 0.22-2.95 carbon nanotubes 0.25-1.14

[0163] Whether through conventional heat treatment or microwave treatment, a crucial consideration for enhancing the graphitic properties of porous carbon scaffolds is the impact on the total pore volume and pore volume distribution. Therefore, the total pore volume and pore volume distribution of porous carbon scaffolds can be determined by gas adsorption analysis, such as nitrogen and / or carbon dioxide gas adsorption analysis, as known in the art. In this way, the pore volume and pore volume distribution can be determined before and after the graphitization-enhancing treatment. In some embodiments, the surface area of ​​the porous carbon scaffold is reduced by at least 30 μm² after treatment. 2 / g, for example, at least 50m 2 / g, for example, at least 100m 2 / g, for example, at least 200m 2 / g, for example, at least 300m 2 / g, for example, at least 500m 2 / g. In some embodiments, the pore volume of the porous carbon scaffold is reduced by at least 0.01 cm³ after treatment. 3 / g, for example, at least 0.05cm 3 / g, for example, at least 0.1cm 3 / g, for example, at least 0.2cm3 / g, for example, at least 0.3cm 3 / g, for example, at least 0.5cm 3 / g.

[0164] In some implementations, the surface area of ​​the porous carbon scaffold increases by at least 30 m² after treatment. 2 / g, for example, at least 50m 2 / g, for example, at least 100m 2 / g, for example, at least 200m 2 / g, for example, at least 300m 2 / g, for example, at least 500m 2 / g. In some embodiments, the pore volume of the porous carbon scaffold increases by at least 0.01 cm³ after treatment. 3 / g, for example, at least 0.05cm 3 / g, for example, at least 0.1cm 3 / g, for example, at least 0.2cm 3 / g, for example, at least 0.3cm 3 / g, for example, at least 0.5cm 3 / g. In some embodiments in which the surface area of ​​the porous carbon support increases after treatment, and / or the pore volume of the porous carbon support increases after treatment, the porous carbon support contains an electrochemical modifier that acts as a graphitization catalyst, such as Al, Cr, Mn, Fe, Co, Ni, Ca, Ti, V, Mo, or W, or combinations thereof.

[0165] Without being bound by theory, the graphitization of porous carbon scaffolds containing graphitization catalysts occurs under milder conditions, such as shorter times and / or lower temperatures, compared to graphitization of porous carbon scaffolds in the absence of a graphitization catalyst. Graphitization catalysts can be introduced into methods for preparing silicon-carbon composites at various steps. For example, graphitization catalysts can be added to solid precursor materials prior to pyrolysis and subsequent activation to produce porous carbon scaffolds containing graphitization catalysts. In one embodiment, graphitization catalysts can be added to solid precursor materials prior to combined pyrolysis and activation to produce porous carbon scaffolds containing graphitization catalysts. In another embodiment, graphitization catalysts can be added to pyrolyzed porous carbon materials prior to activation to produce porous carbon scaffolds containing graphitization catalysts. In yet another embodiment, graphitization catalysts can be added to activated porous carbon materials to produce porous carbon scaffolds containing graphitization catalysts.

[0166] Graphitization can be achieved at various steps in the process of preparing silicon-carbon composites. For example, pyrolytic porous carbon materials can be graphitized prior to activation and subsequent CVI processing to produce silicon-carbon composites. In one embodiment, activated porous carbon materials can be graphitized prior to CVI processing to produce silicon-carbon composites.

[0167] Pulverization can be performed at various steps in the method for preparing silicon-carbon composite particles to reduce particle size. For example, pyrolytic porous carbon materials can be pulverized prior to graphitization and subsequent activation and CVI processing to produce silicon-carbon composite particles. In another embodiment, pyrolytic and graphitized porous carbon materials can be pulverized prior to activation and subsequent CVI processing to produce silicon-carbon composite particles. In another embodiment, activated porous carbon materials can be pulverized prior to graphitization and subsequent CVI processing to produce silicon-carbon composite particles. In yet another embodiment, activated and graphitized porous carbon materials can be pulverized prior to CVI processing to produce silicon-carbon composite particles.

[0168] In the above embodiments, the degree of graphitization of carbon can vary between the surface of the carbon particles and the surface of the pores within the carbon particles. In some embodiments, the degree of graphitization of carbon at the surface of the carbon particles is greater than that at the surface of the pores within the carbon particles. Without being bound by theory, such embodiments allow for enhanced electronic and / or ionic conductivity at the particle surface, which in turn provides electrochemical benefits when silicon-carbon composite particles are used as the anode in lithium-ion batteries, such as increased rate capacity and faster charging and / or discharging, a more stable SEI, and lower carbon surface reactivity, resulting in increased high-temperature stability and / or lifespan.

[0169] In some implementations, the carbon at the surface of the pores within the carbon particles exhibits a greater degree of graphitization than the carbon particle surface. Without being bound by theory, such implementations allow for enhanced electronic and / or ionic conductivity at the surface or pores, which in turn provides electrochemical benefits, such as increased rate capacity and faster charging and / or discharging, when the silicon-carbon composite particles are used as the anode in a lithium-ion battery.

[0170] In some embodiments, the silicon-carbon composite material includes a particle size distribution, and the degree of graphitization of the carbon particles varies with the particle size. For this characteristic, the silicon composite particles can be size-graded (as is known in the art) to produce two or more material fractions, wherein each fraction has a different Dv50. For example, the silicon composite particles can be graded into one fraction containing Dv50 < 1 μm and another fraction containing Dv50 > 1 μm, the difference in the degree of graphitization between the two fractions being, for example, measurand (Dv50) measured by Raman spectroscopy. D / I GA comparison is made. Therefore, the difference in graphitization between the two grades can be expressed as:

[0171] ΔI D / I G＝ ([I D / I G ]Dv,50>1–[I D / I G ]Dv,50<1)

[0172] Where [I] D / I G Dv,50>1 is the I of the granular fraction containing Dv50>1. D / I G , and [I D / I G Dv,50<1 is the I of the granular fraction containing Dv50<1. D / I G Therefore, ΔI D / I G It can be varied from 0 to 2, for example 0 to 1, for example 0.01 to 0.8, for example 0.01 to 0.7, for example 0.01 to 0.6, for example 0.01 to 0.5, for example 0.01 to 0.4, for example 0.01 to 0.3, for example 0.01 to 0.2, for example 0.01 to 0.1, 0.1 to 0.8, for example 0.1 to 0.7, for example 0.1 to 0.6, for example 0.1 to 0.5, for example 0.1 to 0.4, for example 0.1 to 0.3, for example 0.1 to 0.2, for example 0.1 to 0.7, for example 0.2 to 0.6, for example 0.3 to 0.5.

[0173] In some embodiments, the electrochemical properties of porous carbon scaffolds and / or silicon-carbon composites can be enhanced by adding conductive carbon additive particles, including but not limited to graphite particles, Super C45 particles, Super P particles, carbon black particles, nanoscale carbon particles such as carbon nanotubes or other carbon nanostructures, or combinations thereof. In such embodiments, the addition of conductive carbon additives promotes improvements in the electronic conductivity, packing density, and / or electrochemical efficiency of the doped porous carbon scaffolds and / or the silicon-carbon composites prepared therefrom.

[0174] Therefore, conductive carbon additive particles can be added at various steps in the preparation of the silicon-carbon composite. In one embodiment, conductive carbon additive particles are added to a carbon precursor used to prepare a porous carbon scaffold, followed by pyrolysis, activation, and graphitization of the porous carbon scaffold, and then CVI processing to prepare the silicon-carbon composite. In another embodiment, conductive carbon additive particles are added to a carbon precursor used to prepare a porous carbon scaffold, followed by pyrolysis, graphitization, and activation of the porous carbon scaffold, and then CVI processing to prepare the silicon-carbon composite. In yet another embodiment, conductive carbon additive particles are added to a carbon precursor used to prepare a porous carbon scaffold, followed by pyrolysis, activation, and graphitization of the porous carbon scaffold, and then CVI processing to prepare the silicon-carbon composite.

[0175] In such embodiments, the addition of conductive carbon additives serves as a graphitization catalyst for the graphitized porous carbon scaffold. In other embodiments, the addition of conductive carbon additives serves as graphitized seed particles for the graphitized porous carbon scaffold. In other embodiments, the addition of conductive carbon additives promotes improvements in the electronic conductivity, packing density, and / or electrochemical efficiency of the doped porous carbon scaffold and / or the silicon-carbon composite prepared therefrom.

[0176] In other embodiments, the electrochemical properties of the porous carbon scaffold and / or silicon-carbon composite can be enhanced by adding conductive carbon additive particles to a pyrolytic porous carbon scaffold, followed by graphitization and subsequent activation, and subsequent CVI processing to prepare the silicon-carbon composite. In other embodiments, the electrochemical properties of the porous carbon scaffold and / or silicon-carbon composite can be enhanced by adding conductive carbon additive particles to an activated porous carbon scaffold, followed by graphitization and subsequent activation, and subsequent CVI processing to prepare the silicon-carbon composite.

[0177] The percentage of conductive carbon additive by mass of the porous carbon can vary. For example, the conductive carbon additive can account for 0.1% to 90% of the total mass of the porous carbon scaffold, such as 1% to 50%, 1% to 40%, 1% to 30%, 1% to 20%, 1% to 10%, 1% to 5%, 5% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, or 40% to 50%.

[0178] Example

[0179] Example 1. Preparation of silicon-carbon composite material 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, the silicon-carbon composite (silicon-carbon composite 1) was prepared by CVI as follows: 0.2 g of amorphous porous carbon was placed in a 2 inch × 2 inch ceramic crucible and then placed in the center of a horizontal tube furnace. The furnace was sealed and continuously purged with nitrogen at 500 cubic centimeters per minute (ccm). The furnace temperature was increased to a peak temperature of 450 °C at 20 °C / min and allowed to equilibrate at this peak temperature for 30 minutes. At this point, the nitrogen was turned off, and silane and hydrogen were introduced at flow rates of 50 ccm and 450 ccm, respectively, for a total residence time of 30 minutes. After this residence time, the silane and hydrogen were turned off, and nitrogen was introduced into the furnace again to purge the internal atmosphere. Simultaneously, the furnace heat was turned off and allowed to cool to ambient temperature. The completed Si-C material was then removed from the furnace.

[0180] Table 3. Description of the carbon support used in Example 1.

[0181]

[0182] Example 2. Analysis of various silicon composite materials. Various carbon scaffold materials were used, and the carbon scaffold materials were characterized by nitrogen adsorption gas analysis to determine 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, namely, the data on carbon scaffold surface area, pore volume, and pore volume distribution (% micropores, % mesopores, and % macropores), all determined by nitrogen adsorption analysis.

[0183] Table 4. Properties of various carbon support materials.

[0184]

[0185]

[0186] Various silicon-carbon composites were prepared using the CVI method with carbon scaffold samples as described in Table 4 and in a static bed configuration as generally described in Example 1. These silicon-carbon samples were prepared using a range of process conditions: silane concentrations from 1.25% to 100%, dilution gases of nitrogen or hydrogen, and starting carbon scaffold masses from 0.2 g to 700 g.

[0187] The surface area of ​​the silicon-carbon composite was determined. The silicon-carbon composite was also analyzed by TGA to determine the silicon content and Z. The silicon-carbon composite was also tested in a half-cell coin cell. The anode of the half-cell coin cell may comprise 60-90% silicon-carbon composite, 5-20% Na-CMC (as a binder), and 5-20% Super C45 (as a conductivity enhancer), and the electrolyte may comprise a 2:1 ratio of ethylene carbonate:diethyl carbonate, 1M LiPF6, and 10% fluoroethylene carbonate. The half-cell coin cell can be cycled for 5 cycles at C / 5 at 25°C, followed by cycling at C / 10. The voltage can be cycled between 0V and 0.8V, or alternatively, between 0V and 1.5V. Based on the half-cell coin cell data, the maximum capacity and the average coulombic efficiency (CE) over a cycle range of 7 to 20 cycles can be measured. The physicochemical and electrochemical properties of various silicon-carbon composites are shown in Table 5.

[0188] Table 5. Properties of various silicon-carbon materials.

[0189]

[0190] The graph of the average Coulomb efficiency as a function of Z is shown in... Figure 1 As can be seen, the average coulombic efficiency increases significantly for silicon-carbon samples with low Z. Specifically, all silicon-carbon samples with Z below 10.0 exhibit an average coulombic efficiency ≥0.9941, and all silicon-carbon samples with Z above 10 (silicon-carbon composite sample 12 to silicon-carbon composite sample 16) are observed to have an average coulombic efficiency ≤0.9909. Without being bound by theory, the higher coulombic efficiency of silicon-carbon samples with Z < 10 provides excellent cycle stability in full-cell lithium-ion batteries. Further tests in the table reveal a surprising and unexpected finding: the combination of Z < 10 in the silicon-carbon composite samples and the carbon scaffold also containing >69.1 micropores provides an average coulombic efficiency ≥0.9969.

[0191] Therefore, in a preferred embodiment, the silicon-carbon composite material contains less than 10 Z, for example less than 5 Z, for example less than 3 Z, for example less than 2 Z, for example less than 1 Z, for example less than 0.5 Z, for example less than 0.1 Z, or 0 Z.

[0192] In some preferred embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z of less than 10 and >70% micropores, such as a Z of less than 10 and >80% micropores, such as a Z of less than 10 and >90% micropores, such as a Z of less than 10 and >95% micropores, such as a Z of less than 5 and >70% micropores, such as a Z of less than 5 and >80% micropores, such as a Z of less than 5 and >90% micropores, such as a Z of less than 5 and >95% micropores, such as a Z of less than 3 and >70% micropores, such as a Z of less than 3 and >80% micropores, such as a Z of less than 3 and >90% micropores, such as a Z of less than 3 and >95% micropores, such as a Z of less than 2 and >70% micropores, such as a Z of less than 2 and >80% micropores, such as a Z of less than 2 and >90% micropores, such as a Z of less than 2... Z and >95% micropores, e.g., less than 1 Z and >70% micropores, e.g., less than 1 Z and >80% micropores, e.g., less than 1 Z and >90% micropores, e.g., less than 1 Z and >95% micropores, e.g., less than 0.5 Z and >70% micropores, e.g., less than 0.5 Z and >80% micropores, e.g., less than 0.5 Z and >90% micropores, e.g., less than 0.5 Z and >95% micropores, e.g., less than 0.1 Z and >70% micropores, e.g., less than 0.1 Z and >80% micropores, e.g., less than 0.1 Z and >90% micropores, e.g., less than 0.1 Z and >95% micropores, e.g., 0 Z and >70% micropores, e.g., 0 Z and >80% micropores, e.g., 0 Z and >90% micropores, e.g., 0 Z and >95% micropores.

[0193] In some preferred embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 15%-85% silicon and has a surface area of ​​less than 100 m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 30m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 10 m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 5m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 30m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 10 m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 5m². 2 / g; for example, less than 10 Z and >90% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, Z < 10 and > 90% micropores, wherein the silicon-carbon composite also contains 15%–85% silicon and has a surface area of ​​less than 30 m². 2 / g; for example, Z less than 10 and >90% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 10 m². 2 / g; for example, less than 10 Z and >90% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 5m². 2 / g; for example, less than 10 Z and >95% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, less than 10 Z and >95% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 30m². 2 / g; for example, Z less than 10 and >95% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 10m². 2 / g; for example, Z less than 10 and >95% micropores, wherein the silicon-carbon composite also contains 15%-85% silicon and has a surface area of ​​less than 5m². 2 / g.

[0194] In some preferred embodiments, the silicon-carbon composite material comprises a carbon scaffold with a Z-axis of less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 30m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 10 m². 2 / g; for example, less than 10 Z and >70% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 5m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 30m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 10 m². 2 / g; for example, less than 10 Z and >80% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 5m². 2 / g; for example, Z < 10 and > 90% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, Z less than 10 and >90% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 30m². 2 / g; for example, Z less than 10 and >90% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 10 m². 2 / g; for example, Z less than 10 and >90% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 5m². 2 / g; for example, Z < 10 and > 95% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 50 m². 2 / g; for example, Z less than 10 and >95% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 30m². 2 / g; for example, Z < 10 and > 95% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 10 m². 2 / g; for example, Z less than 10 and >95% micropores, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area of ​​less than 5m². 2 / g.

[0195] Example 3. dV / dQ of various silicon composite materials. Differential capacity curves (dQ / dV versus voltage) are commonly used as a non-destructive tool to understand phase transitions as a function of voltage in lithium-ion battery electrodes (MNObrovac 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 curves given here were calculated from data obtained by constant current cycling at 0.1C rate from 5mV to 0.8V in a half-cell coin cell at 25°C. Typical differential capacity curves of silicon-based materials versus lithium in half-cells can be found in many references (Loveridge, MJ 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); MNObrovac et al., Li15Si4 Formation in SiliconThin 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 metalpowder, Journal of Power Sources 347 (2017)170-177). The first-cycle lithiation behavior depends on factors such as the crystallinity of silicon and oxygen content.

[0196] Following the first cycle, previous amorphous silicon materials in the art exhibited two distinct phase transition peaks in the dQ / dV vs. V diagrams for lithiation, and correspondingly two distinct phase transition peaks in the dQ / dV vs. V diagrams for delithiation. For lithiation, one peak corresponding to the lithium-poor Li-Si alloy phase appears between 0.2 and 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 intercalation appears below 0.4 V, while another peak appears between 0.4 V and 0.55 V. If the Li15Si4 phase forms during lithiation, it delithiates at ~0.45 V and exhibits a very narrow, sharp peak.

[0197] Figure 2 Cycle 2 dQ / dV versus voltage curves for the silicon-carbon composite material corresponding to silicon-carbon composite 3 of Example 1 are plotted. Silicon-carbon composite 3 contains a Z of 0.6. For ease of identification, the graph is divided into regions I, II, III, IV, V, and VI. Regions I (0.8V to 0.4V), II (0.4V to 0.15V), and III (0.15V to 0V) constitute the lithiation potential, and regions IV (0V to 0.4V), V (0.4V to 0.55V), and VI (0.55V to 0.8V) include the delithiation potential. As described above, previous amorphous silicon-based materials in the art exhibit phase transition peaks in two regions (regions II and III) of the lithiation potential and two regions (regions IV and V) of the delithiation potential.

[0198] from Figure 2 As can be seen, the dQ / dV versus voltage curves reveal surprising and unexpected results. The silicon-carbon composite 3 (containing 0.6 Z) exhibits two additional peaks in the dQ / dV versus voltage curves: region I in the lithiation potential and region VI in the delithiation potential. All six peaks are reversible and were also observed in subsequent cycles, such as... Figure 3 As shown in the image.

[0199] Without being bound by theory, this three-peak behavior of the dQ / dV curve with respect to V is novel and also reflects a novel form of silicon.

[0200] It is noteworthy that the novel peaks observed in regions I and VI are more pronounced in some scaffold matrices, but are not present at all in other samples illustrating the prior art (silicon-carbon composite samples with Z>10, see explanation and table below).

[0201] Figure 4The dQ / dV versus V curves of silicon-carbon composite 3 are shown, where the new peaks in regions I and VI are evident compared to those of silicon-carbon composites 15, 16, and 14 (all three of which contain Z>10 and whose dQ / dV versus V curves have no peaks in regions I and VI).

[0202] Without being bound by theory, these novel peaks observed in Regions I and VI relate to the properties of silicon impregnated into the porous carbon scaffold, specifically the interactions between and within the properties of the porous carbon scaffold, silicon, and lithium impregnated into the porous carbon scaffold via CVI. To provide quantitative analysis, we define parameters in this paper. Its calculation is the normalized peak I relative to peak III:

[0203]

[0204] In this study, dQ / dV was measured in a half-cell coin cell, with region I being 0.8V–0.4V and region III being 0.15V–0V; the half-cell coin cell was manufactured as is known in the art. If the Si-C sample exhibited a graphite-related peak in region III of the differential curve, this was omitted when calculating the D-factor, and the Li-Si-related phase transition peak was used instead. For this example, the half-cell coin cell included an anode comprising 60–90% silicon-carbon composite, 5–20% SBR-Na-CMC, and 5–20% Super C45. Figure 5 The image shows silicon-carbon composite 3. Example of calculation. 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 above formula can be used to calculate... get The data were determined from the half-cell coin cell data of various silicon-carbon composites given in Example 2. The values ​​are summarized in Table 6.

[0205] Table 6. Properties of various silicon-carbon materials.

[0206]

[0207] The data in Table 6 reveal the effects of decreasing Z and increasing Z. An unexpected relationship exists between them. All silicon-carbon complexes with Z < 10 possess... Furthermore, all silicon-carbon composites with Z>10 possess In fact, all silicon-carbon composites with Z>10 have This relationship also Figure 6This has been proven. Without being bound by theory, it contains... For example The silicon material corresponds to a new form of silicon. Alternatively, it contains... Silicon materials correspond to a new form of silicon. Without being bound by theory, containing... The silicon material is characterized by being amorphous, nanoscale silicon confined within pores, such as those in porous carbon scaffolds. This includes... For example The silicon-carbon composite material corresponds to a novel silicon-carbon composite material. Alternatively, it contains... The silicon-carbon composite material corresponds to the novel silicon-carbon composite material.

[0208] In some embodiments, the silicon-carbon composite contains or In some implementation schemes, In some implementation schemes, or

[0209] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and a micropore content of >70%, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0210] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0211] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and a micropore content of >70%, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0212] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >70% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m².2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 70%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0213] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0214] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0215] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0216] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >80% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 80%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0217] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content >90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content >90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0218] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content >90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0219] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content >90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content >90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0220] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >90% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content >90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content greater than 90%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0221] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 5 and a micropore content greater than 95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m².2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0222] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0223] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 30%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 30%-60% silicon and has a surface area less than 5 m². 2 / g,

[0224] In some embodiments, the silicon-carbon composite comprises a carbon scaffold with a Z-axis of less than 10 and >95% micropores, and wherein the silicon-carbon composite further comprises 40%-60% silicon and has a surface area of ​​less than 100 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 50 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 30 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 10 m². 2 / g, For example, a Z value less than 10 and a micropore content >95%, wherein the silicon-carbon composite also contains 40%-60% silicon and has a surface area less than 5 m². 2 / g,

[0225] Example 4. Particle size distribution of various carbon scaffold materials. The particle size distribution of various carbon scaffold materials was determined using a laser diffraction particle size analyzer known in the art. Table 7 shows the data, specifically Dv,1, Dv10, Dv50, Dv,90, and Dv,100.

[0226] Table 7. Properties of various carbon support materials.

[0227]

[0228]

[0229] Example 5. Graphite properties of porous carbon scaffolds determined by Raman spectroscopy. Various porous carbon scaffold samples were prepared by solvent-free processing, by mixing solid carbon precursors bisphenol A (BPA) and hexamethylenetetramine (HMT), heating to 650–1100 °C and holding for 1–6 hours, using process gases containing nitrogen, carbon dioxide, vapor, or combinations thereof. Table 8 shows the properties of these porous carbon scaffolds, including the mass ratio of the precursor BPA:HMT used for solvent-free processing, and the surface area and pore volume determined by nitrogen adsorption analysis and Ig determined by Raman spectroscopy for the obtained porous carbon scaffolds. D / IG To prepare carbon scaffold sample 14, carbon precursors were polymerized by heating to 150 to 250 °C for several hours prior to carbonization.

[0230] Table 8. Properties of various carbon support materials.

[0231]

[0232] Comparative analysis of the Raman spectra of carbon scaffold sample 11 and carbon scaffold sample 15 showed that... Figure 7 In these samples, the mass ratio of precursor BPA to HMT was 2.44:1 to 3:1, and the process gas was varied; specifically, for carbon scaffold sample 11, the process gas contained CO2, while for carbon scaffold sample 15, the process gas contained vapor. For both samples, the measured I... D / I G Similarly (in the range of 0.79 to 0.80), therefore the two samples exhibit similar graphite properties.

[0233] Comparative analysis of the Raman spectra of carbon scaffold sample 12 and carbon scaffold sample 10 showed that... Figure 8 In these samples, the mass ratio of precursor BPA to HMT varied from 9:1 (carbon scaffold sample 12) to 1:3 (carbon scaffold sample 10), and the process gas for both samples contained vapor. Compared to carbon scaffold sample 10 (I... D / I G Compared to (=0.85), carbon scaffold sample 12 includes a lower Ig. D / I G (0.79), therefore, carbon scaffold sample 12 contains a higher degree of graphite compared to carbon scaffold sample 10.

[0234] Comparative analysis of the Raman spectra of carbon scaffold sample 13 and carbon scaffold sample 14 showed that... Figure 9 In this study, the mass ratio of precursor BPA to HMT was 2.44:1 to 3:1. The process gas was varied; specifically, the process gas for preparing carbon scaffold sample 13 contained CO2, while the process gas for preparing carbon scaffold sample 14 contained vapor. Furthermore, a polymerization step was performed before carbonization to prepare carbon scaffold sample 14. It can be seen that, compared with carbon scaffold sample 14 (I... D / I G Compared to (=0.88), carbon scaffold sample 13 includes higher Ig. D / I G(0.78), therefore, carbon scaffold sample 13 contains a higher degree of graphitization compared to carbon scaffold sample 14. Without being bound by theory, the polymerization step prior to carbonization in preparing carbon scaffold sample 14 resulted in a greater degree of polymer growth relative to polymer nucleation, and thus fewer defects in both the polymer structure and carbon structure of the resulting porous carbon scaffold. Therefore, the degree of defect in the carbon structure of carbon scaffold sample 13 is relatively high. Without being bound by theory, the greater degree of defect in the carbon structure of carbon scaffold sample 13 provides this sample with a greater tendency for graphitization, which is consistent with the lower I measured for this sample. D / I G Consistent.

[0235] Silicon-carbon composite particles can be prepared from mixtures of solid carbon precursor materials according to various embodiments through various process steps in various sequences. Examples of such embodiments are shown in Table 9. For clarity, note each process sequence, which is carried out to process the mixture of carbon precursors, whether its polymerization is performed as a separate step prior to pyrolysis or during the pyrolysis step.

[0236] Table 9. Various implementation schemes for preparing silicon composite particles using various process steps in various sequences.

[0237]

[0238] For all the above-described process sequences implemented, I was calculated using Raman spectroscopy. D / I G To determine the graphite properties of the porous carbon scaffold. In some embodiments, the silicon-carbon composite comprises a porous carbon scaffold, said porous carbon scaffold comprising I... D / I G <0.9, for example, I D / I G <0.8, for example, I D / I G <0.7, for example, I D / I G <0.6, for example, I D / I G <0.5, for example, I D / I G <0.4, for example, I D / I G <0.3, for example, I D / I G <0.2, for example, I D / I G <0.1, for example, I D / I G <0.01, for example, I D / IG <0.001.

[0239] Example 6. An example of reducing carbon specific surface area and total pore volume by graphitization treatment.

[0240] To achieve an initial specific surface area of ​​500-2000 m² 2 / g of various pyrolyzed and activated carbon were treated under an inert gas (e.g., nitrogen or argon) at a temperature of 1000°C to 2850°C for 1-6 hours. For example... Figure 10 As shown, the specific surface area decreases with increasing processing temperature, which is consistent with carbon graphitization.

[0241] Table 10 presents representative data for several pyrolytic carbon materials, excluding pyrolytically activated carbon materials. These carbon materials underwent the heat treatment described above, and the resulting data are shown in Table 11.

[0242] Table 10. Various carbon materials

[0243]

[0244] Table 11. Various carbon materials after graphitization treatment.

[0245]

[0246] NA indicates that the data is unavailable.

[0247] In Table 11, I D / I G Data were calculated using Raman spectroscopy, and the graphite crystallite size (L) a The data were calculated using XRD methods known in the art. With increasing temperature, a decrease in pore volume is beneficial for maintaining mesopores and macropores, while micropores decrease. D / I G The ratio increases with increasing temperature, corresponding to the transformation of amorphous carbon into graphitic properties. The graphite crystallite size calculated by XRD also increases with increasing temperature, indicating the transformation of amorphous carbon into graphitic properties.

[0248] The sheet resistance of carbon supports 17 and 18 was measured using the sheet resistance method. The sheet resistance method involves preparing a slurry of carbon supports, polymer binder, and deionized water for casting into a thin film. The sheet resistance was then measured using a four-point probe by applying a DC current to the two outer probes and measuring the voltage drop across the two intermediate probes. To calculate the sheet resistance, the sheet resistances of carbon substrate 17 and carbon substrate 18 are 411 and 220 ohms / cm, respectively. 2In contrast, the treated carbon scaffolds exhibited reduced sheet resistivity, consistent with the properties of graphitic carbon. For example, the sheet resistivity of the treated carbon scaffold 8 was only 26 ohms / cm. 2 .

[0249] The specific gravity density of treated carbon scaffold 6, treated carbon scaffold 7, and treated carbon scaffold 8 was 1.67 g / cm³. 3 1.52 / cm 3 and 1.75g / cm 3 Surprisingly, these figures are far lower than the theoretical values ​​for graphite. Without being bound by theory, this low specific gravity density reflects the porosity present within the graphitic carbon. In some embodiments, the specific gravity density of the treated carbon scaffold is less than 2.0 g / cm³. 3 For example, less than 1.9 g / cm³ 3 For example, less than 1.8 g / cm³ 3 For example, less than 1.7 g / cm³ 3 For example, less than 1.6 g / cm³ 3 For example, less than 1.5 g / cm³ 3 For example, less than 1.4 g / cm³ 3 .

[0250] Example 7. Preparation of silicon-carbon composites using heat-treated porous carbon scaffold materials.

[0251] As generally disclosed herein, various silicon-carbon composites were prepared by contacting a heat-treated porous carbon scaffold in the presence of silane gas at elevated temperatures. Multiple process sequences were used, according to those defined in Table 9. Tables 12 and 13 present the physicochemical and electrochemical characterization data for these silicon-carbon composites, respectively.

[0252] Table 12. Physicochemical properties of various silicon-carbon materials.

[0253]

[0254] Table 13. Electrochemical properties of various silicon-carbon materials.

[0255]

[0256] Example 8. Comparison of activation after graphitization of carbon with different pore volumes.

[0257] For this embodiment, we compared two different process sequences by characterizing the carbon scaffolds prepared therein. To this end, we investigated and compared treated carbon scaffold 1 and treated carbon scaffold 2 (both generated by processing carbon precursors, from polymerization to pyrolysis to activation to pulverization to heat treatment to complete graphitization) with treated carbon scaffold 8 (generated by processing carbon precursors, from polymerization to pyrolysis to pulverization to heat treatment to complete graphitization). It was observed that treated carbon scaffold 1 and treated carbon scaffold 2 could not be activated; that is, in the presence of an activating gas (vapor and / or carbon dioxide), the surface area and pore volume obtained after 4-6 hours at 900-950°C were only 13 m², respectively. 2 / g and 0.0206cm 3 / g, 1.86m 2 / g and 0.0024cm 3 / g, in both cases, the surface area and pore volume decreased significantly rather than increased. A surprising and unexpected result was that the treated carbon support 8 was able to achieve increased surface area and pore volume under similar conditions, specifically, a value of 40.5m². 2 / g and 0.0539cm 3 / g. Without being bound by theory, the graphitization of pyrolytic carbon produces carbon, which, upon subsequent activation, can be converted into high surface areas and pore volumes, for example, greater than 40 μm. 2 / g and greater than 0.05cm 3 / g, for example, greater than 80m 2 / g and greater than 0.1cm 3 / g, for example, greater than 400m 2 / g and greater than 0.5cm 3 / g, for example, greater than 500m 2 / g and greater than 0.6cm 3 / g, for example, greater than 1000m 2 / g and greater than 0.5cm 3 / g, for example, greater than 1500m 2 / g and greater than 0.6cm 3 / g.

[0258] Specific implementation plan

[0259] Implementation Scheme 1. A method for preparing silicon-carbon composite particles, the method comprising:

[0260] a. Providing mixtures of solid carbon precursor materials;

[0261] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0262] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0263] d. Crushing and activating carbon materials;

[0264] e. Graphitizing porous carbon scaffold particles at temperatures ranging from 1200°C to 3000°C in the presence of an inert gas;

[0265] f. Heating the porous carbon scaffold particles to a temperature of 400°C to 525°C in the presence of silane gas; and

[0266] g. The silicon-carbon composite comprises:

[0267] i. Carbon scaffold containing less than or equal to 0.9 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores.

[0268] Implementation Scheme 2. A method for preparing silicon-carbon composite particles, the method comprising:

[0269] a. Providing mixtures of solid carbon precursor materials;

[0270] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0271] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0272] d. Pulverizing activated carbon materials at temperatures ranging from 1200°C to 3000°C in the presence of an inert gas;

[0273] e. Graphitized porous carbon scaffold particles;

[0274] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0275] g. The silicon-carbon composite comprises:

[0276] i. Carbon scaffold containing less than or equal to 0.9 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores; and

[0277] ii. Greater than or equal to 0.1 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0278] Implementation Scheme 3. A method for preparing silicon-carbon composite particles, the method comprising:

[0279] a. Providing mixtures of solid carbon precursor materials;

[0280] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0281] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0282] d. Crushing and activating carbon materials;

[0283] e. Graphitizing porous carbon scaffold particles at temperatures ranging from 1200°C to 3000°C in the presence of an inert gas;

[0284] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0285] g. The silicon-carbon composite comprises:

[0286] i. Carbon scaffold containing less than or equal to 0.9 I D / I G and pore volume, wherein the pore volume comprises more than 50% micropores; and

[0287] ii. Z less than 10, where Z = 1.875 x [(M1100 - 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.

[0288] Implementation Scheme 4. A method for preparing silicon-carbon composite particles, the method comprising:

[0289] a. Providing mixtures of solid carbon precursor materials;

[0290] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0291] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0292] d. Crushing and activating carbon materials;

[0293] e. Graphitizing porous carbon scaffold particles at temperatures ranging from 1200°C to 3000°C in the presence of an inert gas;

[0294] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0295] g. The silicon-carbon composite comprises:

[0296] i. Carbon scaffold containing <0.9 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores; and

[0297] ii. Silicon content of 30% to 60% by weight;

[0298] iii. Z less than 10, where Z = 1.875 x [(M1100 - 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;

[0299] iv. Less than 30m 2 / g surface area; and

[0300] v. greater than or equal to 0.1 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0301] Implementation Scheme 5. A method for preparing silicon-carbon composite particles, the method comprising:

[0302] a. Providing mixtures of solid carbon precursor materials;

[0303] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0304] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0305] d. Graphitized and activated carbon materials in the presence of an inert gas at temperatures ranging from 1200°C to 3000°C;

[0306] e. Crushing porous carbon scaffolds;

[0307] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0308] g. The silicon-carbon composite comprises:

[0309] i. Carbon scaffold containing <0.9 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores.

[0310] Implementation Scheme 6. A method for preparing silicon-carbon composite particles, the method comprising:

[0311] a. Providing mixtures of solid carbon precursor materials;

[0312] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0313] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0314] d. Graphitized and activated carbon materials in the presence of an inert gas at temperatures ranging from 1200°C to 3000°C;

[0315] e. Crushing porous carbon scaffolds;

[0316] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0317] g. The silicon-carbon composite comprises:

[0318] i. Carbon scaffold containing <0.9 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores; and

[0319] ii. Greater than or equal to 0.1 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0320] Implementation Scheme 7. A method for preparing silicon-carbon composite particles, the method comprising:

[0321] a. Providing mixtures of solid carbon precursor materials;

[0322] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0323] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0324] d. Graphitized and activated carbon materials in the presence of an inert gas at temperatures ranging from 1200°C to 3000°C;

[0325] e. Crushing porous carbon scaffolds;

[0326] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0327] g. The silicon-carbon composite comprises:

[0328] i. Carbon scaffold containing <0.9 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores; and

[0329] ii. Z less than 10, where Z = 1.875 x [(M1100 - 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.

[0330] Implementation Scheme 8. A method for preparing silicon-carbon composite particles, the method comprising:

[0331] a. Providing mixtures of solid carbon precursor materials;

[0332] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0333] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0334] d. Graphitized and activated carbon materials in the presence of an inert gas at temperatures ranging from 1200°C to 3000°C;

[0335] e. Crushing porous carbon scaffolds;

[0336] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0337] g. The silicon-carbon composite comprises:

[0338] i. Carbon scaffold containing <0.9 I D / I Gand pore volume, wherein the pore volume comprises more than 50% micropores; and

[0339] ii. Silicon content of 30% to 60% by weight;

[0340] iii. Z less than 10, where Z = 1.875 x [(M1100 - 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;

[0341] iv. Less than 30m 2 / g surface area; and

[0342] v. greater than or equal to 0.1 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0343] Implementation Scheme 9. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 8, wherein the pore volume comprises more than 80% micropores.

[0344] Implementation Scheme 10. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 9, wherein the pore volume comprises more than 90% micropores.

[0345] Implementation Scheme 11. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 10, wherein the pore volume comprises more than 95% micropores.

[0346] Implementation Scheme 12. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 11, wherein the porous carbon scaffold particles are heated to a temperature of 400°C to 525°C in the presence of silane gas.

[0347] Implementation Scheme 13. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 12, wherein the silicon-carbon composite contains 40-60% silicon.

[0348] Implementation Scheme 14. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 13, wherein the silicon-carbon composite contains less than 5 Z.

[0349] Implementation Scheme 15. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 14, wherein the silicon-carbon composite comprises particles smaller than 10 μm 2 / g of surface area.

[0350] Implementation Scheme 16. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 15, wherein the silicon-carbon composite comprises greater than or equal to 0.2 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0351] Implementation Scheme 17. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 16, wherein the silicon-carbon composite comprises greater than or equal to 0.3 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0352] Implementation Scheme 18. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 17, wherein the silicon-carbon composite comprises Dv50 of 5 nm to 20 micrometers.

[0353] Implementation Scheme 19. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 18, wherein the silicon-carbon composite has a capacity of greater than 900 mAh / g.

[0354] Implementation Scheme 20. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 319, wherein the silicon-carbon composite has a capacity of greater than 1300 mAh / g.

[0355] Implementation Scheme 21. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 20, wherein the silicon-carbon composite has a capacity of greater than 1600 mAh / g.

[0356] Implementation Scheme 22. A method for preparing silicon-carbon composite particles according to any one of the embodiments 1 to 21, wherein the porous carbon scaffold comprises <0.8 I D / I G .

[0357] Implementation Scheme 23. A method for preparing silicon-carbon composite particles according to any one of embodiments 1 to 22, wherein the porous carbon scaffold comprises <0.7 I D / I G .

[0358] Implementation Scheme 24. A method for preparing silicon-carbon composite particles according to any one of Implementation Schemes 1 to 23, wherein the porous carbon scaffold comprises <0.6% I D / I G .

[0359] Implementation Scheme 25. A method for preparing silicon-carbon composite particles according to any one of embodiments 1 to 24, wherein the porous carbon scaffold comprises <0.5% I D / I G .

[0360] Implementation Scheme 26. A method for preparing silicon-carbon composite particles according to any one of embodiments 1 to 25, wherein the porous carbon scaffold comprises <0.4% I D / I G .

[0361] Implementation Scheme 27. A method for preparing silicon-carbon composite particles according to any one of embodiments 1 to 26, wherein the porous carbon scaffold comprises <0.3% I D / I G .

[0362] Implementation Scheme 28. A method for preparing silicon-carbon composite particles according to any one of embodiments 1 to 27, wherein the porous carbon scaffold comprises <0.2 I D / I G .

[0363] Implementation Scheme 29. A method for preparing silicon-carbon composite particles according to any one of embodiments 1 to 28, wherein the porous carbon scaffold comprises <0.1% I D / I G .

[0364] Implementation Scheme 30. A method for preparing silicon-carbon composite particles according to any one of embodiments 1 to 29, wherein the porous carbon scaffold comprises <0.01 I D / I G .

[0365] Implementation Scheme 31. A method for preparing silicon-carbon composite particles according to any one of the embodiments 1 to 30, wherein the porous carbon scaffold comprises <0.001 I D / I G .

[0366] Implementation Scheme 32. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 31, wherein graphitization is achieved by heating the carbon to a temperature of 1100°C to 3000°C in the presence of an inert gas.

[0367] Implementation Scheme 33. A method for preparing silicon-carbon composite particles according to any one of the implementation schemes 1 to 32, wherein the carbon is graphitized by heating it with microwave radiation.

[0368] Implementation Scheme 34. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 33, wherein the porous carbon scaffold comprises Al, Cr, Mn, Fe, Co, Ni, Ca, Ti, V, Mo or W, or combinations thereof.

[0369] Implementation Scheme 35. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 34, wherein the porous carbon scaffold comprises conductive carbon additive particles.

[0370] Implementation Scheme 36. The method for preparing silicon-carbon composite particles according to Implementation Scheme 35, wherein the conductive carbon additive particles include graphite particles, Super C45 particles, Super P particles, carbon black particles, nanoscale carbon particles such as carbon nanotubes or other carbon nanostructures, or combinations thereof.

[0371] Implementation Scheme 37. The method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 36, wherein the inert gas is nitrogen.

[0372] Implementation Scheme 38. A method for preparing silicon-carbon composite particles according to any one of the embodiments of Scheme 1 to Scheme 36, wherein the activating gas is carbon dioxide, vapor, or a combination thereof.

[0373] Implementation Scheme 39. A silicon-carbon composite, comprising:

[0374] a. A carbon scaffold, comprising a carbon scaffold, comprising I D / I G <0.9 and pore volume, wherein the pore volume comprises more than 70% micropores;

[0375] b. Silicon content of 30% to 60% by weight;

[0376] c. Z less than 10, where Z = 1.875 x [(M1100 - 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;

[0377] d. Less than 30m 2 / g surface area; and

[0378] e. Greater than or equal to 0.1 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0379] Implementation Scheme 40. The silicon-carbon composite according to Implementation Scheme 39, wherein the porous carbon scaffold comprises 40% to 60% silicon by weight.

[0380] Implementation Scheme 41. The silicon-carbon composite according to any one of Implementation Schemes 39 to 40, wherein the silicon-carbon composite contains less than 5 Z.

[0381] Implementation Scheme 42. The silicon-carbon composite according to any one of Implementation Schemes 39 to 41, wherein the silicon-carbon composite comprises less than 10 mg / L 2 / g of surface area.

[0382] Implementation Scheme 43. The silicon-carbon composite according to any one of Implementation Schemes 39 to 42, wherein the silicon-carbon composite comprises greater than or equal to 0.2

[0383] Implementation Scheme 44. The silicon-carbon composite according to any one of Implementation Schemes 39 to 43, wherein the silicon-carbon composite comprises greater than or equal to 0.3

[0384] Implementation Scheme 45. The silicon-carbon composite according to any one of Implementation Schemes 39 to 44, wherein the silicon-carbon composite comprises a Dv50 of 5 nm to 20 micrometers.

[0385] Implementation Scheme 46. The silicon-carbon composite according to any one of Implementation Schemes 39 to 45, wherein the silicon-carbon composite has a capacity of greater than 900 mAh / g.

[0386] Implementation Scheme 47. The silicon-carbon composite according to any one of Implementation Schemes 39 to 46, wherein the silicon-carbon composite has a capacity greater than 1300 mAh / g.

[0387] Implementation Scheme 48. The silicon-carbon composite according to any one of Implementation Schemes 39 to 47, wherein the silicon-carbon composite has a capacity greater than 1600 mAh / g.

[0388] Implementation Scheme 49. The silicon-carbon composite according to any one of Implementation Schemes 39 to 48, wherein the porous carbon scaffold comprises <0.8 I D / I G .

[0389] Implementation Scheme 50. The silicon-carbon composite according to any one of Implementation Schemes 39 to 49, wherein the porous carbon scaffold comprises <0.7 I D / I G .

[0390] Implementation Scheme 51. The silicon-carbon composite according to any one of Implementation Schemes 39 to 50, wherein the porous carbon scaffold comprises <0.6% I D / I G .

[0391] Implementation Scheme 52. The silicon-carbon composite according to any one of Implementation Schemes 39 to 51, wherein the porous carbon scaffold comprises <0.5 I D / I G .

[0392] Implementation Scheme 53. The silicon-carbon composite according to any one of Implementation Schemes 39 to 52, wherein the porous carbon scaffold comprises <0.4% I D / I G .

[0393] Implementation Scheme 54. The silicon-carbon composite according to any one of Implementation Schemes 39 to 53, wherein the porous carbon scaffold comprises <0.3% I D / I G .

[0394] Implementation Scheme 55. The silicon-carbon composite according to any one of Implementation Schemes 39 to 54, wherein the porous carbon scaffold comprises <0.2 I D / I G .

[0395] Implementation Scheme 56. The silicon-carbon composite according to any one of Implementation Schemes 39 to 55, wherein the porous carbon scaffold comprises <0.1 I D / I G .

[0396] Implementation Scheme 57. The silicon-carbon composite according to any one of Implementation Schemes 39 to 56, wherein the porous carbon scaffold comprises <0.01 I D / I G .

[0397] Implementation Scheme 58. The silicon-carbon composite according to any one of Implementation Schemes 39 to 57, wherein the porous carbon scaffold comprises <0.001 I D / I G .

[0398] Implementation Scheme 59. The silicon-carbon composite according to any one of Implementation Schemes 39 to 58, wherein the porous carbon scaffold comprises Al, Cr, Mn, Fe, Co, Ni, Ca, Ti, V, Mo or W, or combinations thereof.

[0399] Implementation Scheme 60. The silicon-carbon composite according to any one of Implementation Schemes 39 to 59, wherein the porous carbon scaffold comprises conductive carbon additive particles, the conductive carbon additive particles including graphite particles, Super C45 particles, Super P particles, carbon black particles, nanoscale carbon particles such as carbon nanotubes or other carbon nanostructures, or combinations thereof.

[0400] Implementation Scheme 61. The silicon-carbon composite according to any one of Implementation Schemes 39 to 60, wherein the silicon-carbon composite comprises a Dv50 of 5 nm to 20 micrometers.

[0401] Implementation Scheme 62. The silicon-carbon composite according to any one of Implementation Schemes 39 to 61, wherein the silicon-carbon composite comprises 0.1 to 0.7 ΔI D / I G , where ΔI D / I G＝ ([I D / I G ]Dv,50>1–[I D / IG ]Dv,50<1), where [I D / I G Dv,50>1 is the I of the granular fraction containing Dv50>1. D / I G , and [I D / I G Dv,50<1 is the I of the granular fraction containing Dv50<1. D / I G .

[0402] Implementation Scheme 63. A silicon-carbon composite comprising 0.1 to 0.7 ΔI D / I G , where ΔI D / I G＝ ([I D / I G ]Dv,50>1–[I D / I G ]Dv,50<1), where [I D / I G Dv,50>1 is the I of the granular fraction containing Dv50>1. D / I G , and [I D / I G Dv,50<1 is the I of the granular fraction containing Dv50<1. D / I G .

[0403] Implementation Scheme 64. A method for preparing silicon-carbon composite particles, the method comprising:

[0404] a. Providing mixtures of solid carbon precursor materials;

[0405] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0406] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0407] d. Graphitized and activated carbon materials in the presence of an inert gas at temperatures ranging from 1200°C to 3000°C;

[0408] e. Crushing porous carbon scaffolds;

[0409] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0410] g. The silicon-carbon composite comprises:

[0411] i. Carbon scaffold containing <0.9 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores; and

[0412] ii. Silicon content of 30% to 60% by weight;

[0413] iii. Z less than 10, where Z = 1.875 x [(M1100 - 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;

[0414] iv. Less than 30m 2 / g of surface area;

[0415] v. greater than or equal to 0.1 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0416] vi. First-cycle efficiency greater than or equal to 75%;

[0417] vii. Average coulomb efficiency greater than or equal to 0.998; and

[0418] viii. Capacity greater than or equal to 1000mAh / g.

[0419] Implementation Scheme 65. A method for preparing silicon-carbon composite particles, the method comprising:

[0420] a. Providing mixtures of solid carbon precursor materials;

[0421] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0422] c. Activating pyrolytic carbon materials in the presence of an activating gas at a temperature of 650°C to 1100°C;

[0423] d. Graphitized and activated carbon materials in the presence of an inert gas at temperatures ranging from 1200°C to 3000°C;

[0424] e. Crushing porous carbon scaffolds;

[0425] f. Heating the porous carbon scaffold particles to a temperature of 350°C to 550°C in the presence of silane gas; and

[0426] g. The silicon-carbon composite comprises:

[0427] ix. Carbon scaffold containing <0.9 I D / I G and pore volume, in

[0428] The pore volume comprises more than 70% micropores; and

[0429] x. Silicon content of 30% to 60% by weight;

[0430] xi. 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, determined by thermogravimetric analysis;

[0431] xii. Less than 30m 2 / g of surface area;

[0432] xiii. Greater than or equal to 0.2 in The dQ / dV was measured in a half-cell button cell, with region I being 0.8V-0.4V and region III being 0.15V-0V.

[0433] xiv. First-cycle efficiency greater than or equal to 90%;

[0434] xv. Average coulomb efficiency greater than or equal to 0.999; and

[0435] xvi. Capacity greater than or equal to 1400mAh / g.

[0436] Implementation Scheme 66. A method for preparing graphitized activated carbon particles, the method comprising:

[0437] a. Providing mixtures of solid carbon precursor materials;

[0438] b. Pyrolyze the mixture at a temperature of 650°C to 1100°C in the presence of an inert gas;

[0439] c. Crushing and pyrolyzing porous carbon scaffolds;

[0440] d. Graphitized and activated carbon materials in the presence of an inert gas at temperatures ranging from 1200°C to 3000°C;

[0441] e. Activating pyrolytic carbon materials at temperatures ranging from 650°C to 1100°C in the presence of an activating gas.

[0442] Implementation Scheme 67. A material comprising graphitized activated carbon particles, comprising:

[0443] a. Greater than or equal to 40m 2 / g of surface area;

[0444] b. Greater than or equal to 0.05cm 3 / g pore volume;

[0445] c. L greater than or equal to 5A a ;

[0446] d. I less than or equal to 0.8 D / I G .

[0447] Implementation Scheme 68. A material comprising graphitized activated carbon particles, comprising:

[0448] a. Greater than or equal to 400m 2 / g of surface area;

[0449] b. Greater than or equal to 0.5cm 3 / g pore volume;

[0450] c. L greater than or equal to 5A a ;

[0451] d. I less than or equal to 0.8 D / I G .

[0452] Implementation Scheme 69. A material comprising graphitized activated carbon particles, comprising:

[0453] a. Greater than or equal to 1000m 2 / g of surface area;

[0454] b. Greater than or equal to 0.6cm 3 / g pore volume;

[0455] c. L greater than or equal to 5A a ;

[0456] d. I less than or equal to 0.8 D / I G .

[0457] As can be understood from the foregoing, although specific embodiments of the invention have been described herein for illustrative purposes, various modifications may be made without departing from the spirit and scope of the invention. Therefore, the invention is not limited except by the appended claims.

[0458] This application claims priority to U.S. Provisional Patent Application No. 63 / 083,614, filed on September 25, 2020, which is incorporated herein by reference in its entirety.

Claims

1. A method for preparing silicon-carbon composite particles, the method comprising: a. Providing mixtures of solid carbon precursor materials; b. In the presence of nitrogen, the mixture is pyrolyzed at a temperature of 650°C to 1100°C to obtain pyrolyzed carbon materials; c. Activating the pyrolytic carbon material at a temperature of 650°C to 1100°C in the presence of carbon dioxide gas, vapor, or a combination thereof to obtain activated carbon material; d. Crush the activated carbon material to obtain porous carbon scaffold particles; e. In the presence of nitrogen, the porous carbon scaffold particles are heated to a temperature of 1100°C to 3000°C; f. Heating the porous carbon scaffold particles to a temperature of 400°C to 525°C in the presence of silane gas; and g. The silicon-carbon composite comprises: i. Carbon scaffold containing less than 0.8 I D / I G and pore volume, wherein the pore volume comprises more than 70% micropores; ii. Silicon content of 40% to 60% by weight; iii. Z less than 10, where Z = 1.875 x [(M1100 [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 25°C to 1100°C, determined by thermogravimetric analysis; iv. Less than 30 m 2 / g surface area; and v. greater than or equal to 0.1 ,in =(maximum peak height dQ / dV in region I) / (maximum peak height dQ / dV in region III), where dQ / dV is measured in a half-cell coin cell, and the voltage curve is plotted against dQ / dV and divided into regions I, II, III, IV, V and VI, where regions I, II and III include the lithium-ion potential, and region I is 0.8V to 0.4V, region II is 0.4V to 0.15V, region III is 0.15V to 0V, and region IV, V and VI include the lithium-delithiation potential, and region IV is 0V to 0.4V, region V is 0.4V to 0.55V, and region VI is 0.55V to 0.8V.

2. The method of claim 1, wherein the solid carbon precursor material comprises bisphenol A and hexamethylenetetramine.

3. The method of claim 1, wherein the carbon support pore volume comprises more than 80% micropores.

4. The method of claim 1, wherein I D / I G Less than 0.

7.

5. The method of claim 1, wherein Z is less than 5.

6. The method of claim 1, wherein the surface area of ​​the silicon-carbon composite is less than 10 m². 2 / g.

7. The method of claim 1, wherein Greater than or equal to 0.

2.

8. A silicon-carbon composite comprising: a. Carbon scaffold, including those containing I D / I G Carbon scaffolds with a pore volume of <0.8 and wherein the pore volume comprises more than 70% micropores; b. Silicon content of 40% to 60% by weight; c. Z less than 10, where Z = 1.875 x [(M1100 [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 25°C to 1100°C, determined by thermogravimetric analysis; d. Less than 30 m 2 / g surface area; and e. Greater than or equal to 0.1 ,in =(maximum peak height dQ / dV in region I) / (maximum peak height dQ / dV in region III), where dQ / dV is measured in a half-cell coin cell, and the voltage curve is plotted against dQ / dV and divided into regions I, II, III, IV, V and VI, where regions I, II and III include the lithium-ion potential, and region I is 0.8V to 0.4V, region II is 0.4V to 0.15V, region III is 0.15V to 0V, and region IV, V and VI include the lithium-delithiation potential, and region IV is 0V to 0.4V, region V is 0.4V to 0.55V, and region VI is 0.55V to 0.8V.

9. The silicon-carbon composite of claim 8, wherein the carbon support pore volume comprises more than 80% micropores.

10. The silicon-carbon composite of claim 8, wherein I D / I G Less than 0.

7.

11. The silicon-carbon composite of claim 8, wherein Z is less than 5.

12. The silicon-carbon composite of claim 8, wherein the surface area of ​​the silicon-carbon composite is less than 10 m². 2 / g.

13. The silicon-carbon composite of claim 8, wherein... Greater than or equal to 0.

2.

14. The silicon-carbon composite of claim 8, further comprising one or more of Al, Cr, Mn, Fe, Co, Ni, Ca, Ti, V, Mo and W.

15. The silicon-carbon composite of claim 8, further comprising Ni.

16. The silicon-carbon composite of claim 8, further comprising conductive carbon additive particles.

17. The silicon-carbon composite of claim 8 further comprises one or more of graphite particles, Super C45 particles, Super P particles, carbon black particles, and nanoscale carbon particles.

18. The silicon-carbon composite of claim 17, wherein the nanoscale carbon particles are carbon nanotubes.

19. The silicon-carbon composite of claim 8, further comprising conductive carbon additive particles.

20. The silicon-carbon composite of claim 8, comprising Dv50 of 5 nm to 20 micrometers.

21. The silicon-carbon composite of claim 8, wherein the silicon-carbon composite comprises 0.1 to 0.7% [amount missing]. I D / I G ,in I D / I G = ([I D / I G ]Dv,50>1 – [I D / I G ]Dv,50<1), where [I D / I G Dv,50>1 is the I-value of particle size fractions containing Dv50 > 1 μm. D / I G , and [I D / I G Dv,50<1 is the I of the particle size fraction containing Dv50 < 1 μm. D / I G .

Images