Polyimide bead material and its manufacturing method

Abstract

Nanoporous carbon-based scaffolds or structures, and specifically carbon aerogels, as well as their manufacture and use, are provided. Embodiments include silicon-doped anode materials for lithium-ion batteries, where the anode material comprises polyimide-derived carbon aerogel beads. The carbon aerogel may further comprise silicon particles to accommodate the expansion of the silicon particles during lithiation. The anode material provides optimal properties for use in lithium-ion batteries.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 17 / 408,841, filed August 23, 2021, and U.S. Provisional Patent Application No. 63 / 070,230, filed August 25, 2020, which is related to U.S. Patent Application No. 16 / 803,348, filed February 27, 2020, which claims priority to U.S. Provisional Patent Application No. 62 / 811,230, filed February 27, 2019, each of which is incorporated herein by reference in its entirety, and the definitions in this application are controlling.

[0002] TECHNICAL FIELD The present disclosure relates generally to nanoporous carbon-based materials and methods for their manufacture. [Background technology]

[0003] Aerogels are solid materials containing a highly porous network of micro- and meso-sized pores. Given the density of aerogels, approximately 0.05 g / cc, their pores can often account for more than 90% of their volume, depending on the precursor materials used and the processing performed. Aerogels are generally prepared by removing solvent from a gel (a solid network containing its solvent) so that capillary forces at its surface cause minimal or no shrinkage of the gel. Methods of solvent removal include, but are not limited to, supercritical drying (or drying using a supercritical fluid, where the low surface tension of the supercritical fluid exchanges with transient solvents within the gel), solvent exchange with a supercritical fluid, solvent exchange with a fluid subsequently transformed into a supercritical state, sub- or near-critical drying, and sublimation of a frozen solvent in a freeze-drying process. See, for example, PCT Patent Application Publication No. WO2016127084A1. It should be noted that upon drying at ambient conditions, gel shrinkage may occur as the solvent evaporates, potentially forming a xerogel. Thus, the preparation of aerogels by sol-gel or other polymerization processes typically proceeds through the following sequence of steps: dissolution of solute in solvent, formation of a sol / solution / mixture, formation of a gel (which may involve additional cross-linking), and solvent removal by either supercritical drying techniques or any other method that removes the solvent from the gel without causing pore collapse.

[0004] Aerogels can be formed from inorganic and / or organic materials. When formed from organic materials such as phenol, resorcinol-formaldehyde (RF), phloroglucinol furfuraldehyde (PF), polyacrylonitrile (PAN), polyimide (PI), polyurethane (PU), polybutadiene, polydicyclopentadiene, and their precursors or polymeric derivatives, the aerogels can be carbonized (e.g., by pyrolysis) to form carbon aerogels that may have different or overlapping properties (e.g., pore volume, pore size distribution, morphology, etc.) depending on the precursor materials and the method used.

[0005] However, in all cases, there were certain material- and application-based deficiencies, such as small pore volume, wide pore size distribution, and low mechanical strength. Recently, efforts have been dedicated to the development and characterization of carbon aerogels as electrode materials with improved performance for applications in energy storage devices such as lithium-ion batteries (LIBs).

[0006] LIBs are widely used in a variety of applications, from handheld electronic devices to automobiles. LIBs are a type of rechargeable battery in which lithium ions move from the anode to the cathode during discharge and from the cathode to the anode during charging. Traditionally, the cathode is made of lithium metal (e.g., cobalt, nickel, manganese) oxide, and the anode is made of graphite, with lithium ions intercalating within the graphite layers during charging (energy storage). Graphite is widely used because lithium intercalation is higher in graphite than in other known carbons.

[0007] Given the growing demand for high-capacity anode and cathode materials, a major drawback of conventional LIBs is the limited capacity of graphite. In other words, graphite can only accommodate a limited amount of lithium. Silicon has a higher affinity for lithium compared to graphite (carbon), allowing it to store much larger amounts of lithium during charging, theoretically increasing the anode capacity of LIBs. By comparison, graphite combined with lithium has a theoretical capacity of 372 mAh / g, while silicon has a theoretical capacity of 4200 mAh / g. These numbers have led to a desire to place as much silicon as possible within the anode. However, a significant problem with silicon is that when fully lithiated, its volume expands three to four times (often resulting in fracture or cracking), which significantly limits the amount of silicon that can be placed within the electrode.

[0008] Therefore, it would be desirable in the art to provide improved nanoporous carbon materials that contain functional morphologies and optimal pore structures while overcoming at least one of the above problems.

[0009] Although certain aspects of the prior art have been described to facilitate disclosure of the present invention, applicants do not in any way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects described herein, particularly in combination with the innovative aspects described herein.

[0010] The present invention may address one or more of the problems and deficiencies of the art described above. However, it is contemplated that the present invention may prove useful in addressing other problems and deficiencies in certain technical fields. Accordingly, the present invention as claimed should not necessarily be construed as limited to addressing any of the specific problems or deficiencies described herein.

[0011] Where a document, act or article of knowledge is referenced or described in this specification, this reference or description does not constitute an admission that the document, act or article of knowledge, or any combination thereof, existed at the priority date, was publicly available, was generally known, was part of the common general knowledge, or otherwise constitutes prior art under any applicable legal provision or is known to be relevant to any attempt to solve any problem to which this specification pertains. Summary of the Invention

[0012] A long-standing and heretofore unmet need for improved nanoporous carbon materials is met by embodiments of the present disclosure.

[0013] A first general aspect relates to a method for forming or manufacturing a particulate carbon composition. In an exemplary embodiment, the method includes providing a mixture of a polyimide precursor and a silicon-based material; chemically or thermally initiating imidization of the mixture, e.g., by adding an imidization catalyst or by heating; combining the mixture with a medium immiscible with the mixture to thereby form droplets of the imidized mixture; drying the droplets of the imidized mixture to produce a particulate porous polyimide silicon composite; and carbonizing, e.g., by pyrolysis, the particulate porous polyimide silicon composite to produce a particulate carbon composition having greater than about 10% by weight silicon and a porosity of about 10% to about 90%. In some embodiments, the medium immiscible with the mixture, e.g., a carrier medium, can form an emulsion containing the imidized mixture as a dispersed phase. In any embodiment, the carbon composition can include a carbon aerogel, which can be formed as a monolith or as particles.

[0014] In exemplary embodiments, the step of initiating imidization occurs before the step of combining the mixture with a medium that is immiscible with the mixture. In other embodiments, the imidization step can occur after the mixture is combined with the immiscible medium, such as imidizing the mixture while it is in the immiscible medium. In exemplary embodiments, the method can further include aging the particulate porous polyimide silicone composite material prior to carbonization.

[0015] Another general aspect relates to particulate carbon compositions, e.g., powders. In exemplary embodiments, the particulate carbon compositions include composite materials comprising silicon-based materials and carbon. Exemplary embodiments include silicon-doped nanoporous carbon materials comprising a pore structure, the pore structure comprising a fibrous morphology and an array of pores surrounding elemental silicon.

[0016] In any embodiment, the particulate carbon composition can have a particle size ranging from about 1 μm to about 15 μm, hi some embodiments, the particulate carbon composition can have a particle size ranging from about 5 μm to about 10 μm.

[0017] In some embodiments, the particulate carbon composition has a concentration of about 0.3 g / cm 3 ~Approx. 1.3g / cm 3 In some embodiments, the particulate carbon composition may have a tap density in the range of about 0.7 g / cm 3 The tap density may be

[0018] In some embodiments, the composite material comprises greater than about 10% by weight of silicon-based material. In certain embodiments, the composite material comprises between about 20% and about 60% by weight of silicon-based material. In some embodiments, the composite material comprises between about 10% and about 90% by weight of silicon-based material. For example, the composite material may comprise about 10%, about 15%, about 20%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90% by weight of silicon-based material, or a range between any two of these values.

[0019] In some embodiments, the particulate carbon composition comprises a particulate carbon aerogel, such as, for example, a polyimide-derived carbon aerogel. In other embodiments, the particulate carbon composition comprises a particulate carbon xerogel, such as, for example, a polyimide-derived carbon xerogel. In any embodiment, the particles can have a diameter ranging from about 1 micrometer to about 50 micrometers.

[0020] In any embodiment, the pore structure of the carbon composition can be characterized by pores of the carbon material partially, substantially, or completely surrounding the silicon-based material, such as by forming an interconnected structure around the silicon characterized by multiple connection points between the silicon and the pore walls. For example, the silicon-based material can be at least partially present within the pore structure of the carbon composition. In another example, the pore structure can include a fibrous morphology and an array of pores surrounding the silicon-based material.

[0021] In an exemplary embodiment, the carbon material has one or more of a pore structure comprising a fibrous morphology, a Young's modulus of at least about 0.2 GPa, a conductivity of at least about 10 S / cm, and a density of about 0.15 g / cc to about 1.5 g / cc.

[0022] In another exemplary embodiment, the carbon composition comprises a silicon-doped nanoporous carbon material having a silicon utilization of at least about 20%, wherein the carbon material is doped with more than about 25% silicon by weight of the carbon material. Optionally, the carbon material can have a conductivity of at least about 10 S / cm. Optionally, the carbon material can have a Young's modulus of at least about 0.2 GPa.

[0023] In a further exemplary embodiment, the particulate carbon composition comprises a silicon-doped nanoporous carbon material having the following properties: a pore structure including a fibrous morphology, a Young's modulus of 0.2 GPa, a density of about 0.15 g / cc to about 1.5 g / cc, and a silicon utilization of at least about 20%. Optionally, the carbon material can have an electrical conductivity of at least about 10 S / cm.

[0024] In another exemplary embodiment, the particulate carbon composition comprises a silicon-doped nanoporous carbon material having the following properties: a pore structure comprising a fibrous morphology, a conductivity of at least about 10 S / cm, a density of about 0.15 g / cc to about 1.5 g / cc, and a silicon utilization of at least about 20%. Optionally, the carbon material can have a Young's modulus of at least about 0.2 GPa.

[0025] In any embodiment, the nanoporous carbon material can be doped with about 5% to 80% silicon by weight of the carbon material, for example, the carbon material can include about 25% to about 65% silicon by weight of the carbon material.

[0026] In any embodiment, the nanoporous carbon material can have a pore volume of at least 0.3 cc / g.

[0027] In any embodiment, the nanoporous carbon material can have a pre-lithiation porosity of about 10% to about 80%.

[0028] In any embodiment, the carbon material, such as, for example, a nanoporous carbon material, can include at least about 4% by weight residual nitrogen.

[0029] In any embodiment, the silicon-doped nanoporous carbon material can have a capacity of at least about 800 mAh / g. For example, the silicon-doped nanoporous carbon material can have a capacity of up to about 2000 mAh / g.

[0030] In any embodiment, the pore structure of the nanoporous carbon material can include a full width at half maximum (ie, a narrow pore size distribution) of about 50 nm or less.

[0031] In any embodiment, the pore structure of the nanoporous carbon material can include a maximum peak pore size from the distribution of about 100 nm or less.

[0032] In any embodiment, the fibrous morphology of the nanoporous carbon material can include an average strut width of about 2-10 nm, or more specifically, about 2-5 nm.

[0033] Further embodiments provide electrodes comprising the described particulate carbon compositions. The electrodes can be anodes. Another embodiment provides electrochemical cells comprising the described particulate carbon compositions, nanoporous carbon materials, and / or electrodes. Further embodiments provide energy storage devices, such as batteries or more specifically lithium-ion batteries, comprising the described particulate carbon compositions, nanoporous carbon materials, and / or electrochemical cells.

[0034] In another aspect, a method of forming a porous carbon composition in bead form is provided, the method comprising: providing an organogel precursor in an organic solvent; initiating gelation of the organogel precursor to provide an organogel sol; combining the organogel sol with a medium immiscible with the organic solvent, thereby forming organogel droplets; Isolating droplets of the organogel; drying the droplets to produce porous organogel composite beads; and pyrolyzing the porous organogel composite beads to produce a porous carbon composition, the porous carbon composition having a porosity of about 10% to about 90%.

[0035] In some embodiments, initiating gelation occurs prior to combining the organogel sol with the medium.

[0036] In some embodiments, the organogel precursor is a polyamic acid, hi some embodiments, the polyamic acid comprises a tetracarboxylic acid and a multifunctional amine.

[0037] In some embodiments, the tetracarboxylic acid is selected from the group consisting of benzene-1,2,4,5-tetracarboxylic acid, [1,1'-biphenyl]-3,3',4,4'-tetracarboxylic acid, 4,4'-oxydiphthalic acid, 4,4'-sulfonyldiphthalic acid, 4,4'-carbonyldiphthalic acid, 4,4'-(propane-2,2-diyl)diphthalic acid, 4,4'-(perfluoropropane-2,2-diyl)diphthalic acid, naphthalene-1,4,5,8-tetracarboxylic acid, 4-(2-(4-(3,4-dicarboxyphenoxy)phenyl)propan-2-yl)phthalic acid, perylene tetracarboxylic acid, and combinations thereof.

[0038] In some embodiments, the polyfunctional amine is an alkanediamine or an aryldiamine. In some embodiments, the alkanediamine is ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, or a combination thereof. In some embodiments, the aryldiamine is 1,4-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-methylenedianiline, or a combination thereof.

[0039] In some embodiments, the gelation is chemical imidization, thermal imidization, or a combination of chemical and thermal imidization. In some embodiments, the chemical imidization comprises adding a dehydrating agent and an amine base. In some embodiments, the dehydrating agent is acetic anhydride. In some embodiments, the amine base is pyridine.

[0040] In some embodiments, the organic solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, or ethyl acetate. In some embodiments, the organic solvent is N,N-dimethylacetamide.

[0041] In some embodiments, the organic solvent further comprises water in an amount of about 100 to about 1500 parts per million (ppm), hi some embodiments, the organic solvent further comprises water in an amount of about 500 to about 1200 ppm, or about 500 to about 700 ppm.

[0042] In some embodiments, the medium has a viscosity of about 100 to about 150 cP.

[0043] In some embodiments, the medium is mineral oil, silicone oil, or a C5 to C12 hydrocarbon.

[0044] In some embodiments, the method further comprises adding one or more surfactants to the medium.

[0045] In some embodiments, the organogel precursor solution has a viscosity of about 5 to about 30 cP.

[0046] In some embodiments, the ratio of the viscosity of the medium to the viscosity of the organogel precursor solution is about 3-30, or about 5-20.

[0047] In some embodiments, the method further comprises adding a low-viscosity solvent to the medium. In some embodiments, the low-viscosity solvent is added in a single portion in an amount up to about 10% by volume of the medium. In some embodiments, the low-viscosity solvent is added in two or more portions, including a first portion up to about 10% by volume of the medium and one or more additional portions, where the total amount of low-viscosity solvent added is up to about 50% by volume of the medium. In some embodiments, the low-viscosity solvent is added sequentially, where the total amount of low-viscosity solvent added is up to about 50% by volume of the medium. In some embodiments, the low-viscosity solvent is a C1-C3 alcohol.

[0048] In some embodiments, the combining comprises stirring the organogel precursor solution under high shear conditions.

[0049] In some embodiments, drying comprises freeze-drying the organogel, exposing the organogel to elevated temperature conditions, or contacting the organogel with supercritical fluid CO2, or contacting the organogel with liquid CO2 and evaporating the liquid CO2 as a gas.

[0050] In some embodiments, the method further comprises aging the porous organogel composite prior to pyrolysis.

[0051] In some embodiments, the porous carbon composition comprises a carbon aerogel. In some embodiments, the porous carbon composition comprises a carbon xerogel.

[0052] In some embodiments, the porous carbon composition beads have a diameter ranging from about 1 micrometer to about 50 micrometers, or from about 1 micrometer to about 15 micrometers.

[0053] In some embodiments, the porous carbon composition is a porous carbon-silicon composition, the porous carbon-silicon composition comprising greater than about 10 wt. % silicon, based on the total weight of the composition, and the method further comprises providing a mixture of the organogel precursor and silicon in an organic solvent.

[0054] In some embodiments, the porous carbon-silicon composition comprises from about 20% to about 65% silicon by weight, based on the total weight of the composition.

[0055] In some embodiments, the porous carbon-silicon composition comprises a pore structure and the silicon is at least partially present within the pore structure, hi some embodiments, the pore structure comprises a fibrous morphology and an array of pores surrounding the silicon.

[0056] In some embodiments, the porous carbon-silicon composition has a capacity of at least about 800 mAh / g.

[0057] In some embodiments, the porous carbon-silicon composition has a silicon utilization of at least about 20%.

[0058] In another aspect, a porous carbon composition in the form of beads is provided, the porous carbon composition comprising a composite material comprising carbon, the beads having a diameter ranging from about 1 μm to about 15 μm and a mass of about 0.3 g / cm 3 ~Approx. 1.3g / cm 3 The tap density ranges from 0.1 to 1.0.

[0059] In some embodiments, the carbon comprises a carbon aerogel or a carbon xerogel.

[0060] In some embodiments, the composite material further comprises greater than about 10 wt% silicon, based on the total weight of the composite material, hi some embodiments, the composite material comprises about 25 wt% to about 65 wt% silicon, based on the total weight of the composite material.

[0061] In some embodiments, the carbon comprises a pore structure and the silicon resides at least partially within the pore structure.

[0062] In some embodiments, the composite material has a silicon utilization of at least about 20%.

[0063] In some embodiments, the silicon has a particle size less than about 150 nm, in some embodiments, the silicon has a particle size in the range of about 150 nm to about 500 nm, in some embodiments, the silicon has a particle size greater than about 500 nm.

[0064] In some embodiments, the composite material comprises silicon in the range of about 25 to about 65 wt % based on the total weight of the composite material, the silicon having a particle size in the range of about 100 nm to about 800 nm, and the beads have a density of about 0.2 g / cm 3 ~Approx. 1.5g / cm 3 a tap density in the range of about 1 μm to about 15 μm, a mean pore size in the range of about 10 nm to about 50 nm, and a mean pore size in the range of about 0 to about 500 μm. 2 / g.

[0065] In some embodiments, the porous carbon-silicon composition has a capacity of at least about 800 mAh / g.

[0066] In another aspect, there is provided an energy storage device comprising the porous carbon composition disclosed herein. In some embodiments, the energy storage device is a lithium ion battery.

[0067] The present disclosure herein includes, but is not limited to, the following embodiments.

[0068] Embodiment 1: A method for forming a porous carbon composition in bead form, comprising: providing an organogel precursor in an organic solvent; initiating gelation of the organogel precursor to provide an organogel sol; combining the organogel sol with a medium immiscible with the organogel sol, thereby forming organogel droplets; Isolating droplets of the organogel; drying the droplets to produce porous organogel beads; pyrolyzing the porous organogel beads to produce a porous carbon composition in bead form; wherein the porous carbon composition has a porosity of about 10% to about 90%.

[0069] Embodiment 2: The method of embodiment 1, wherein initiating gelation occurs prior to combining the mixture with the vehicle.

[0070] Embodiment 3: The method of embodiment 1 or 2, wherein the organogel precursor is a polyamic acid.

[0071] Embodiment 4: The method of any one of embodiments 1 to 3, wherein the gelation is chemical imidization, thermal imidization, or a combination of chemical and thermal imidization.

[0072] Embodiment 5: The method of any one of embodiments 1-4, wherein the polyamic acid comprises a tetracarboxylic acid and a polyfunctional amine.

[0073] Embodiment 6: The method of any one of embodiments 1-5, wherein the tetracarboxylic acid is selected from the group consisting of benzene-1,2,4,5-tetracarboxylic acid, [1,1'-biphenyl]-3,3',4,4'-tetracarboxylic acid, 4,4'-oxydiphthalic acid, 4,4'-sulfonyldiphthalic acid, 4,4'-carbonyldiphthalic acid, 4,4'-(propane-2,2-diyl)diphthalic acid, 4,4'-(perfluoropropane-2,2-diyl)diphthalic acid, naphthalene-1,4,5,8-tetracarboxylic acid, 4-(2-(4-(3,4-dicarboxyphenoxy)phenyl)propan-2-yl)phthalic acid, perylene tetracarboxylic acid, and combinations thereof.

[0074] Embodiment 7: The method of any one of embodiments 1-6, wherein the polyfunctional amine is an alkanediamine or an aryldiamine.

[0075] Embodiment 8: The method of any one of embodiments 1-7, wherein the alkanediamine is ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, or a combination thereof.

[0076] Embodiment 9: The method of any one of embodiments 1-8, wherein the aryl diamine is 1,4-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-methylenedianiline, or a combination thereof.

[0077] Embodiment 10: The method of any one of embodiments 1 to 9, wherein the chemical imidization comprises adding a dehydrating agent and an amine base.

[0078] Embodiment 11: The method of any one of embodiments 1 to 10, wherein the dehydrating agent is acetic anhydride.

[0079] Embodiment 12: The method of any one of embodiments 1 to 11, wherein the amine base is pyridine.

[0080] Embodiment 13: The method of any one of embodiments 1 to 12, wherein the organic solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, or ethyl acetate.

[0081] Embodiment 14: The method of any one of embodiments 1 to 13, wherein the organic solvent is N,N-dimethylacetamide.

[0082] Embodiment 15: The method of any one of embodiments 1 to 14, wherein the organic solvent further comprises about 100 to about 1500 parts per million (ppm) of water.

[0083] Embodiment 16: The method of any one of embodiments 1 to 3, wherein the organic solvent further comprises water in an amount of about 500 to about 1200 ppm, or about 500 to about 700 ppm.

[0084] Embodiment 17: The method of any one of embodiments 1 to 16, wherein the medium has a viscosity of about 100 to about 150 cP.

[0085] Embodiment 18: The method of any one of embodiments 1 to 17, wherein the medium is mineral oil, silicone oil, or a C5 to C12 hydrocarbon.

[0086] Embodiment 19: The method of any one of embodiments 1 to 18, further comprising adding one or more surfactants to the medium.

[0087] Embodiment 20: The method of any one of embodiments 1 to 19, wherein the organogel sol has a viscosity of about 5 to about 30 cP.

[0088] Embodiment 21: The method of any one of embodiments 1 to 20, wherein the ratio of the viscosity of the medium to the viscosity of the organogel sol is from about 3 to 30, or from about 5 to about 20.

[0089] Embodiment 22: The method of any one of embodiments 1 to 21, further comprising adding a low viscosity solvent to the medium.

[0090] Embodiment 23: The method of any one of embodiments 1 to 22, wherein the low-viscosity solvent is added in a single portion in an amount of up to about 10% by volume of the vehicle.

[0091] Embodiment 24: The method of any one of embodiments 1 to 23, wherein the low-viscosity solvent is added in two or more portions, including a first portion that is up to about 10% by volume of the medium and one or more additional portions, and the total amount of low-viscosity solvent added is up to about 50% by volume of the medium.

[0092] Embodiment 25: The method of any one of embodiments 1 to 24, wherein the low-viscosity solvent is added continuously, and the total amount of low-viscosity solvent added is up to about 50% by volume of the medium.

[0093] Embodiment 26: The method of any one of embodiments 1 to 25, wherein the low viscosity solvent is a C1 to C3 alcohol.

[0094] Embodiment 27: The method of any one of embodiments 1 to 26, wherein combining comprises stirring under high shear conditions.

[0095] Embodiment 28: The method of any one of embodiments 1 to 27, wherein drying comprises freeze-drying the organogel beads, exposing the organogel beads to elevated temperature conditions, contacting the organogel beads with supercritical fluid CO2, or contacting the organogel beads with liquid CO2 and evaporating the CO2 as a gas.

[0096] Embodiment 29: The method of any one of embodiments 1 to 28, further comprising aging the porous organogel beads prior to pyrolysis.

[0097] Embodiment 30: The method of any one of embodiments 1 to 29, wherein the porous carbon composition comprises a carbon aerogel.

[0098] Embodiment 31: The method of any one of embodiments 1 to 30, wherein the porous carbon composition comprises a carbon xerogel.

[0099] Embodiment 32: The method of any one of embodiments 1 to 31, wherein the beads of the porous carbon composition have a diameter ranging from about 1 micrometer to about 50 micrometers.

[0100] Embodiment 33: The method of any one of embodiments 1-32, wherein the porous carbon composition is a porous carbon-silicon composition comprising greater than about 10 wt. % silicon, based on the total weight of the composition, and the method further comprises providing the silicon in a mixture with an organogel precursor in an organic solvent.

[0101] Embodiment 34: The method of any one of embodiments 1 to 33, wherein the porous carbon-silicon composition comprises about 20% to about 65% by weight of silicon, based on the total weight of the composition.

[0102] Embodiment 35: The method of any one of embodiments 1 to 34, wherein the porous carbon-silicon composition comprises a pore structure, and wherein the silicon is at least partially present within the pore structure.

[0103] Embodiment 36: The method of any one of embodiments 1 to 35, wherein the pore structure comprises a fibrous morphology and an array of pores surrounding the silicon.

[0104] Embodiment 37: The method of any one of embodiments 1 to 36, wherein the porous carbon-silicon composition has a capacity of at least about 800 mAh / g.

[0105] Embodiment 38: The method of any one of embodiments 1 to 37, wherein the porous carbon-silicon composition has a silicon utilization of at least about 20%.

[0106] Embodiment 39: A porous carbon composition in the form of beads, the porous carbon composition comprising a composite material comprising carbon, the beads having a diameter ranging from about 1 μm to about 15 μm and a mass of about 0.3 g / cm 3 ~Approx. 1.3g / cm 3 The tap density ranges from 0.1 to 1.0.

[0107] Embodiment 40: The porous carbon composition of embodiment 39, wherein the carbon comprises a carbon aerogel or a carbon xerogel.

[0108] Embodiment 41: The porous carbon composition of embodiment 39 or 40, wherein the composite material further comprises silicon in an amount greater than about 10 wt. %, based on the total weight of the composition.

[0109] Embodiment 42: The porous carbon composition of any one of embodiments 39 to 41, wherein the composite material comprises about 25 wt% to about 65 wt% silicon, based on the total weight of the composition.

[0110] Embodiment 43: The porous carbon composition of any one of embodiments 39 to 42, wherein the carbon comprises a pore structure and the silicon is at least partially present within the pore structure.

[0111] Embodiment 44: The porous carbon composition of any one of embodiments 39-43, wherein the composite material has a silicon utilization of at least about 20%.

[0112] Embodiment 45: The porous carbon composition of any one of embodiments 39-44, wherein the silicon has a particle size of less than about 150 nm.

[0113] Embodiment 46: The porous carbon composition of any one of embodiments 39 to 45, wherein the silicon has a particle size of about 150 nm to about 500 nm.

[0114] Embodiment 47: The porous particulate carbon composition of any one of embodiments 39-46, wherein the silicon has a particle size greater than about 500 nm.

[0115] Embodiment 48: A composite material comprising silicon in the range of about 25 to about 65 wt. %; the silicon having a particle size in the range of about 30 nm to about 800 nm; The beads, Approximately 0.2g / cm 3 ~Approx. 1.5g / cm 3 and a tap density in the range of a diameter in the range of about 1 μm to about 15 μm; an average pore size in the range of about 10 nm to about 50 nm; Approximately 0 to approximately 500 m 2 48. The porous particulate carbon composition of any one of embodiments 39 to 47, having a BET surface area in the range of / g.

[0116] Embodiment 49: The porous carbon composition of any one of embodiments 39-49, having a capacity of at least about 800 mAh / g.

[0117] Embodiment 50: An energy storage device comprising the porous carbon composition of any one of embodiments 39-49.

[0118] Embodiment 51: The energy storage device of embodiment 50, which is a lithium ion battery.

[0119] These and other features and advantages of the present disclosure will become apparent from the following detailed description read in conjunction with the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four, or more of the above-described embodiments, and any combination of two, three, four, or more features or elements described in this disclosure, whether or not such features or combinations are explicitly combined in the description of a particular embodiment herein. The present disclosure is intended to be read as a whole such that any separable features or elements of the disclosed invention, in any of its various aspects and embodiments, should be considered as intended to be combinable unless the context clearly dictates otherwise.

[0120] The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the disclosure hereinafter described, the scope of the invention being indicated in the claims.

[0121] To provide an understanding of embodiments of the technology, reference is made to the accompanying drawings, which are not necessarily drawn to scale. The drawings are illustrative only and should not be construed as limiting the technology. The disclosure described herein is illustrated in the accompanying figures by way of example and not by way of limitation. [Brief explanation of the drawings]

[0122] [Figure 1] FIG. 1 is a flow diagram illustrating the formation of carbon aerogels for use in battery applications. [Figure 2] FIG. 2 shows the discharge capacity over several cycles, comparing the silicon-doped monolith and silicon particles incorporated by the conventional slurry processing method. [Figure 3] FIG. 3 is a flow diagram illustrating the formation of polyimide-derived carbon aerogels. [Figure 4] FIG. 4 shows the density of carbonized polyimide (CPI) composites as a function of compressed thickness (initial thickness of about 250 micrometers). [Figure 5] FIG. 5 shows the density of the CPI composites as a function of compressed thickness (initial thickness of about 580 micrometers). [Figure 6A] Figure 6A is a scanning electron microscope (SEM) image of silicon-doped uncompressed PI aerogel (LS1). [Figure 6B] Figure 6B is an SEM image of silicon-doped compressed PI aerogel (LS2). [Figure 7] Figure 7 shows the discharge capacity per dopant (silicon, LS2, graphite, LG2) compressed composites (half-cell battery test, 0.1°C rate). [Figure 8] FIG. 8 shows the silicon content in CPI monoliths as a function of surface area and micropore area. [Figure 9]Figure 9 shows the pore size distribution of the Si-doped CPI monolith. [Figure 10] Figure 10 shows the discharge capacity of the CPI composites as a function of Si content at cycle 5. [Figure 11A] FIG. 11A is an SEM image of a CPI composite with 27% Si loading in the composite. [Figure 11B] FIG. 11B is an SEM image of a CPI composite with 46% Si loading in the composite. [Figure 11C] FIG. 11C is an SEM image of a CPI composite with 64% Si loading in the composite. [Figure 12A] FIG. 12A shows the cycling capacity based on a Si content of 27% (S27). [Figure 12B] FIG. 12B shows the electrode-based cycling capacity compared to FIG. 12A. [Figure 12C] FIG. 12C shows the cycling capacity based on a Si content of 46% (S46). [Figure 12D] FIG. 12D shows the electrode-based cycling capacity compared to FIG. 12C. [Figure 12E] FIG. 12E shows the cycling capacity based on a Si content of 64% (S64). [Figure 12F] FIG. 12F shows the electrode-based cycling capacity compared to FIG. 12E. [Figure 13A] FIG. 13A is an SEM image of a CPI composite having a thickness of about 337 micrometers. [Figure 13B] FIG. 13B is an SEM image of a CPI composite having a thickness of about 180 micrometers. [Figure 14A] FIG. 14A shows the discharge capacity based on the electrode weight (thickness of about 323 μm). [Figure 14B] FIG. 14B shows the discharge capacity based on the electrode weight (thickness of about 170 μm). [Figure 15A] Figure 15A is an SEM image of the CPI composite prepared without dispersant (C45) before pyrolysis. [Figure 15B]FIG. 15B is an SEM image of the CPI composite of FIG. 15A after pyrolysis. [Figure 16A] FIG. 16A is an SEM image of a CPI composite prepared without dispersant (C45—control). [Figure 16B] FIG. 16B is an SEM image of a CPI composite prepared with BYK384 dispersant (B45). [Figure 16C] FIG. 16C is an SEM image of a CPI composite prepared with Pluronic F87 dispersant (P45). [Figure 17A] FIG. 17A shows the discharge capacity of the C45 composite material of FIG. 16A. [Figure 17B] FIG. 17B shows the discharge capacity of the B45 composite material of FIG. 16B. [Figure 17C] FIG. 17C shows the discharge capacity of the P45 composite material of FIG. 16C. [Figure 18] FIG. 18 shows the density as a function of thickness for P45CPI composites. [Figure 19] FIG. 19 shows the conductivity of CPI composites doped at various Si levels as a function of density. [Figure 20] FIG. 20 is a schematic diagram showing polyamic acid formation. [Figure 21] FIG. 21 shows the isotherms for four (4) CPI samples. [Figure 22] FIG. 22 shows the pore size distribution of the CPI sample of FIG. [Figure 23] Figure 23 is an SEM image of the MT material (uncompressed). [Figure 24] FIG. 24 is an SEM image of the MTC material (compressed). [Figure 25A] FIG. 25A shows the cycling capacity based on Si content (left) and electrode (right) for the compressed CPI samples. [Figure 25B] FIG. 25B shows the cycling capacity based on Si content (left) and electrode (right) for uncompressed CPI samples. [Figure 26A]FIG. 26A shows the cycling capacity based on Si content (left) and electrode (right) for compressed CPI samples with 29 wt. % silicon per total solids. [Figure 26B] FIG. 26B shows the cycling capacity based on Si content (left) and electrode (right) for uncompressed CPI samples with 29 wt. % silicon per total solids. [Figure 27] FIG. 27 shows the properties and micrographs of carbon / Si infiltrated carbon fiber (10 g / m 2 ). [Figure 28] FIG. 28 shows the properties and micrographs of carbon / Si infiltrated carbon fiber (4 g / m2). [Figure 29] FIG. 29 shows the properties and micrographs of carbon / Si infiltrated carbon fiber (2 g / m2). [Figure 30] FIG. 30 shows the cycling capacity of carbon fiber reinforced C / Si based on Si content (left) and electrode (right). [Figure 31] FIG. 31 shows the cycling capacity of cellulose fiber reinforced C / Si based on Si content (left) and electrode (right). [Figure 32] Figure 32 shows an SEM image of a thick composite (approximately 0.6 mm) where Si and PI were mixed for 16 hours. [Figure 33] Figure 33 shows an SEM image of a thick composite (approximately 0.12 mm) where Si and PI were mixed for 16 hours. [Figure 34] Figure 34 shows an SEM image of a monolith sample in which Si and PI were mixed for 16 hours. [Figure 35] Figure 35 shows SEM cross-sectional images of C / Si monoliths, where Si and PI were mixed for 16 hours in the left image and Si and PI were mixed for 4–6 minutes in the right image. [Figure 36] Figure 36 shows SEM cross-sectional images of C / Si composites, where Si and PI were mixed for 16 hours in the left image and Si and PI were mixed for 4–6 minutes in the right image. [Figure 37] FIG. 37 shows the cycling capacity of uncompressed C / Si (16 h mixed) based on the Si content (left) and based on the electrode (right). [Figure 38] FIG. 38 shows the cycling capacity of compressed C / Si (16 h mixed) based on Si content (left) and based on electrode (right). [Figure 39] FIG. 39 shows a compressed circular Si / C electrode made using a die cutter on an aerogel. [Figure 40] Figure 40 shows the cycling capacity of uncompressed circular C / Si aerogels based on Si content (left) and based on electrode (right). [Figure 41] FIG. 41 shows the cycling capacity of compressed circular C / Si aerogels based on Si content (left) and based on electrode (right). [Figure 42] FIG. 42 shows a C / Si aerogel sample resulting from the PF / Si aerogel. [Figure 43] FIG. 43 shows an SEM image of the C / Si aerogel (derived from the PF / Si aerogel). [Figure 44] FIG. 44 shows the cycling capacity of the PF aerogel composite with Si based electrodes. [Figure 45] FIG. 45 shows the effect of silicon content on Young's modulus of samples tested by nanoindentation. [Figure 46] FIG. 46 shows the effect of density on Young's modulus as tested by nanoindentation. [Figure 47] FIG. 47 is an SEM image of a particulate C / Si aerogel sample according to embodiments disclosed herein. [Figure 48] FIG. 48 shows the cycling performance of electrodes containing CPI silicon beads according to embodiments disclosed herein. [Figure 49A] FIG. 49A is a flow diagram illustrating a non-limiting process for forming organogel material in bead form, according to one embodiment of the present disclosure. [Figure 49B] FIG. 49B is a flow diagram illustrating a non-limiting process for forming an organogel-silicon composite material in bead form, according to one embodiment of the present disclosure. [Figure 50]FIG. 50 is an SEM image of C / Si aerogel beads according to embodiments disclosed herein. [Figure 51A-51B] 51A and 51B are SEM images showing the outer and inner surfaces, respectively, of a C / Si aerogel bead according to embodiments disclosed herein. [Figure 52] FIG. 52 is an SEM image of C / Si xerogel beads according to embodiments disclosed herein. [Figure 53A-53B] 53A and 53B are micrographs of polyimide / Si composite gel beads according to embodiments disclosed herein. [Figure 54A-54B] 54A and 54B are SEM images showing the outer and inner surfaces, respectively, of a C / Si aerogel bead according to embodiments disclosed herein. [Figure 55] FIG. 55 is an SEM image of C / Si xerogel beads according to embodiments disclosed herein. [Figures 56A-56B] 56A and 56B are SEM images showing the exterior and interior surfaces, respectively, of a C / Si xerogel bead according to embodiments disclosed herein. [Figure 57A-57B] 57A and 57B are SEM images showing the outer and inner surfaces, respectively, of a C / Si aerogel bead according to embodiments disclosed herein. [Figure 58A-58B] 58A and 58B are SEM images showing the exterior and interior surfaces, respectively, of a C / Si xerogel bead according to embodiments disclosed herein. [Figure 59A-59B] 59A and 59B are SEM images showing the outer and inner surfaces, respectively, of a C / Si aerogel bead according to embodiments disclosed herein. [Figure 60] FIG. 60 is a chart showing particle size distribution of aerogel beads according to embodiments disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0123] In the following detailed description of the present invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. definition

[0124] The following definitions are provided for terms used in this disclosure: This application uses the following terms as defined below, unless the context in which the term appears requires a different meaning.

[0125] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used in this specification and the appended claims, the word "or" is generally used in its sense including "and / or" unless the context clearly dictates otherwise.

[0126] As used herein, "about" means approximately or nearly, and in the context of a stated numerical value or range, means ±15% of the numerical value. In one embodiment, the term "about" may include conventional rounding to the nearest significant figure. Furthermore, the phrase "about 'x' to 'y'" includes "about 'x' to about 'y'."

[0127] In the context of the present disclosure, the term "framework" or "framework structure" refers to the network of interconnected oligomeric, polymeric, or colloidal particles that form the solid structure of a gel, aerogel, or xerogel. The polymers or particles that make up the framework structure typically have diameters of about 100 angstroms. However, the framework structure of the present disclosure can also refer to the network of interconnected oligomeric, polymeric, or colloidal particles of any diameter size that form the solid structure within a gel, aerogel, or xerogel.

[0128] As used herein, the term "aerogel" or "aerogel material" refers to a solid body, regardless of shape or size, comprising a framework of interconnected solid structures with a corresponding network of interconnected pores integrated within the framework and containing a gas, such as air, as the dispersed pore medium. Thus, an aerogel is an open, non-fluid colloidal or polymeric network formed by removing all swelling agent from a corresponding wet gel expanded throughout its volume by a gas without substantial volume loss or network compression. Aerogels generally exhibit the following physical and structural characteristics (as measured by nitrogen porosimetry and helium isochoric pycnometry) attributed to aerogels: (a) an average pore size ranging from about 2 nm to about 100 nm; (b) a porosity of at least 60% or greater; and (c) a porosity of about 100 to about 600 nm as measured by nitrogen adsorption analysis. 2 / g, etc., approximately 100m 2 / g or greater. It is understood that the inclusion of additives such as reinforcing materials or electrochemically active species, e.g., silicon, may decrease the porosity and surface area of ​​the resulting aerogel composite. Densification may also decrease the porosity of the resulting aerogel composite. Aerogel materials (e.g., polyimide and carbon aerogels) of the present disclosure include any aerogels that meet the defining elements set forth in the previous paragraph.

[0129] Thus, the aerogel materials of the present disclosure include any aerogel or other open-cell compound that meets the defining elements set forth in the previous paragraph, including compounds that can be otherwise classified as xerogels, cryogels, ambigels, microporous materials, etc.

[0130] Within the context of this disclosure, the term "aerogel composition" refers to any composite material that includes an aerogel material as a component of the composite. Examples of aerogel compositions include, but are not limited to, fiber-reinforced aerogel composites, aerogel composites containing added elements such as opacifiers and electrochemically active species, aerogel-foam composites, aerogel-polymer composites, and composites that incorporate aerogel particulates, particles, granules, beads, or powders into solid or semi-solid materials such as binders, resins, cements, foams, polymers, or similar solid materials.

[0131] Within the context of this disclosure, the term "reinforced aerogel composition" refers to an aerogel composition that includes a reinforcing phase within the aerogel material that is not part of the aerogel framework or that can be modified to be covalently bonded to the aerogel framework. The reinforcing phase can be any material that provides the aerogel material with enhanced flexibility, resilience, conformability, or structural stability. Examples of well-known reinforcing materials include, but are not limited to, open-cell foam reinforcement, closed-cell foam reinforcement, open-cell membranes, honeycomb reinforcement, polymer reinforcement, and fibrous reinforcement such as discrete fibers, woven fabrics, nonwoven materials, batting, webs, mats, and felts. Furthermore, the reinforcement can be combined with one or more other reinforcement materials and can be oriented continuously throughout the composition or in a limited, preferred portion. In other embodiments, the aerogel material and / or aerogel framework may not utilize a reinforcing phase at all, where the aerogel material and / or the aerogel framework is structurally stable (i.e., self-supporting) by itself. This self-supporting nature of certain carbon aerogels will become more apparent as this specification continues.

[0132] As used herein, the term "xerogel" refers to a gel containing an open, non-fluid colloidal or polymeric network formed by removing all swelling agents from the corresponding gel, without precautions being taken to avoid substantial volume loss or to retard compaction. In contrast to aerogels, xerogels generally contain compact structures. Xerogels undergo substantial volume loss during ambient pressure drying, resulting in a volume loss of about 0 to about 20 m, as measured by nitrogen sorption analysis. 2 / g, etc. 0 to 100m 2 / g of surface area.

[0133] As used herein, the terms "gelation" or "gel transition" refer to the formation of a wet gel from a polymer system, such as the polyimide or polyamic acid described herein. At a certain point in the polymerization or dehydration reactions described herein, defined as the "gel point," the sol loses its fluidity. While not intending to be bound by any particular theory, the gel point can be considered the point at which a gelling solution exhibits resistance to flow. In this context, gelation progresses from an initial sol state, in which the solution primarily contains the amine salt of the polyamic acid, through a fluid colloidal dispersion state, until enough polyimide has formed to reach the gel point. Gelation may continue thereafter, producing a polyimide wet gel dispersion with increasing viscosity. The time it takes for the polymer in solution (i.e., the polyamic acid and / or polyimide) to transform into a gel, a form that is no longer flowable, is referred to as the "phenomenal gel time." Formally, gel time is measured using rheology. At the gel point, the elastic properties of a solid gel begin to dominate over the viscous properties of a fluid sol. The formal gelation time is approximately the time at which the real and imaginary components of the complex modulus of the gelling sol intersect. The two moduli are monitored as a function of time using a rheometer. Time begins counting from the moment the last component of the sol is added to the solution. See, for example, the discussion of gelation in H.H. Winter, "Can the Gel Point of a Crosslinking Polymer Be Detected by the G'-G" Crossover?", Polym. Eng. Sci., 1987, 27, 1698-1702; S.-Y. Kim, D.-G. Choi, and S.-M. Yang, "Rheological analysis of the gelation behavior of tetraethylorthosilane / vinyltriethoxysilane hybrid solutions," Korean J. Chem. Eng., 2002, 19, 190-196; and M. Muthukumar, "Screening effect on viscoelasticity near the gel point," Macromolecules, 1989, 22, 4656-4658.

[0134] Within the context of this disclosure, the term "wet gel" refers to a gel in which the mobile pore phase within a network of interconnected pores is primarily composed of a liquid phase such as a conventional solvent, a liquefied gas such as liquid carbon dioxide, or a combination thereof. Aerogels typically require first producing a wet gel, followed by processing and extraction to replace the mobile pore liquid phase within the gel with air or another gas. Examples of wet gels include, but are not limited to, alcogels, hydrogels, ketogels, carbonogels, and any other wet gels known to those skilled in the art.

[0135] Within the context of this disclosure, the term "additive" or "additive element" refers to a material that can be added to a composition before, during, or after its formation. Additives can be added, for example, to modify or improve desirable properties of the aerogel composition or to neutralize or mitigate undesirable properties of the aerogel composition. Additives are typically added to the aerogel composition either before or during gelation. Additives can also be added to the aerogel composition by atomic layer deposition or chemical vapor deposition (CVD). A particular example of an additive is an electrochemically active species, such as silicon, e.g., silicon particles.

[0136] In the context of this disclosure, the term "average particle size" is synonymous with D50, meaning that half of the particle population has a particle size above this point and half has a particle size below this point. Particle size can be measured by laser light scattering or microscopy techniques. A D90 particle size distribution indicates that 90% of the particles (by number) have a Feret diameter below a specified size as measured by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). A D10 particle size distribution indicates that 10% of the particles (by number) have a Feret diameter below a specified size as measured by scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0137] Within the context of this disclosure, the term "electrical conductivity" refers to a measurement of a material's ability to conduct electric current or otherwise allow the flow of electrons through or within it. Conductivity is specifically measured as the electrical conductance / susceptance / admittance of a material per unit size of the material. Conductivity is typically reported as S / m (Siemens / meter) or S / cm (Siemens / centimeter). The electrical conductivity or resistivity of a material can be determined by methods known in the art, including, but not limited to, in-line four-point resistivity (using the ASTM F84-99 dual configuration test method). Within the context of this disclosure, unless otherwise specified, conductivity measurements are obtained according to ASTM F84—resistivity (R) measurements obtained by measuring voltage (V) divided by current (I). In certain embodiments, the aerogel material or aerogel composition of the present disclosure has a conductivity of about 10 S / cm or greater, 20 S / cm or greater, 30 S / cm or greater, 40 S / cm or greater, 50 S / cm or greater, 60 S / cm or greater, 70 S / cm or greater, 80 S / cm or greater, or a range between any two of these values.

[0138] In the context of this disclosure, the term "electrochemically active species" refers to an additive capable of accepting and releasing ions within an energy storage device. Using a LIB as an example, the electrochemically active species in the anode accepts lithium ions during charging and releases lithium ions during discharge. The electrochemically active species can be stabilized within the anode by having a direct / physical connection with nanoporous carbon (e.g., carbon-silicon composite aerogel beads). In certain embodiments, the nanoporous carbon network forms an interconnected structure around the electrochemically active species. The electrochemically active species connects to the nanoporous carbon at multiple points. An example of an electrochemically active species is silicon, which expands upon lithiation and can crack or break as described above. However, because the silicon has multiple connection points with the nanoporous carbon (e.g., carbon aerogel), the silicon can be retained and remain active within the nanoporous structure, e.g., within the pores, or otherwise remain enclosed by the structure even if it breaks or cracks.

[0139] Within the context of this disclosure, the terms “compressive strength,” “flexural strength,” and “tensile strength” refer to the resistance of a material to fracture or crushing when subjected to compressive, flexural, or bending forces, and tensile or tension forces, respectively. These strengths are specifically measured as the amount of load / force per unit area resisting the load / force. It is usually recorded as pounds per square inch (psi), megapascals (MPa), or gigapascals (GPa). Among other factors, the compressive strength, flexural strength, and tensile strength of a material collectively contribute to the structural integrity of the material, which is useful, for example, for withstanding the volume expansion of silicon particles during lithiation in LIBs. With specific reference to Young's modulus, a measure of mechanical strength, Young's modulus can be determined by methods known in the art, including, but not limited to, standard test methods for Instrumented Indentation Testing (ASTM E2546, ASTM International, West Conshocken, PA) or standardized nanoindentation (ISO 14577, International Organization for Standardization, Switzerland). Within the context of the present disclosure, Young's modulus measurements are taken in accordance with ASTM E2546 and ISO 14577 unless otherwise specified. In certain embodiments, the aerogel materials or aerogel compositions of the present disclosure have a Young's modulus of about 0.2 GPa or greater, 0.4 GPa or greater, 0.6 GPa or greater, 1 GPa or greater, 2 GPa or greater, 4 GPa or greater, 6 GPa or greater, 8 GPa or greater, or a range between any two of these values.

[0140] In the context of this disclosure, the term "pore size distribution" refers to the statistical distribution or relative amount of each pore size within a sample volume of a porous material. A narrower pore size distribution refers to a relatively large proportion of pores within a narrow range of pore sizes, thus optimizing the amount of pores that can accommodate electrochemically active species and maximizing the use of pore volume. Conversely, a wider pore size distribution refers to a relatively small proportion of pores within a narrow range of pore sizes. Therefore, pore size distribution is typically measured as a function of pore volume and reported as the unit size of the full width at half maximum of the dominant peak on a pore size distribution chart. The pore size distribution of a porous material can be determined by methods known in the art, including, but not limited to, surface area and porosity analyzers by nitrogen adsorption and desorption, which can calculate the pore size distribution. In the context of this disclosure, pore size distribution measurements are obtained according to this method unless otherwise specified. In certain embodiments, the aerogel material or aerogel composition of the present disclosure has a relatively narrow pore size distribution (full width at half maximum) of about 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, 30 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, 5 nm or less, or a range between any two of these values.

[0141] In the context of the present disclosure, the term "pore volume" refers to the total volume of pores within a sample of porous material. Pore volume is specifically measured as the volume of voids within the porous material, which voids may be measurable and / or accessible by another material, e.g., an electrochemically active species such as silicon particles. Pore volume is typically measured in cubic centimeters per gram (cm 3Pore ​​volume of a porous material can be determined by methods known in the art, including, but not limited to, surface area and porosity analyzers by nitrogen adsorption and desorption, which can calculate pore volume. Within the context of the present disclosure, pore volume measurements are obtained according to this method unless otherwise specified. In certain embodiments, aerogel materials or aerogel compositions of the present disclosure (e.g., without incorporating an electrochemically active species such as silicon) have a relatively large pore volume of about 1 cc / g or more, 1.5 cc / g or more, 2 cc / g or more, 2.5 cc / g or more, 3 cc / g or more, 3.5 cc / g or more, 4 cc / g or more, or a range between any two of these values. In other embodiments, the aerogel materials or aerogel compositions of the present disclosure (e.g., incorporating an electrochemically active species such as silicon) have a relatively large pore volume of about 0.3 cc / g or more, 0.6 cc / g or more, 0.9 cc / g or more, 1.2 cc / g or more, 1.5 cc / g or more, 1.8 cc / g or more, 2.1 cc / g or more, 2.4 cc / g or more, 2.7 cc / g or more, 3.0 cc / g or more, 3.3 cc / g or more, 3.6 cc / g or more, or a range between any two of these values.

[0142] Within the context of this disclosure, when used with respect to the porous carbon and carbon-silicon composite materials disclosed herein, the term "porosity" refers to the volume fraction of pores that does not contain additional material (e.g., electrochemically active species such as silicon particles) bound to the pore walls. For clarity and explanation, it should be noted that in certain embodiments of silicon-doped carbon aerogels as primary anode materials in LIBs, porosity refers to the void space after including silicon particles. Thus, the porosity may be, for example, about 10% to 70% when the anode is in a pre-lithiation state (to accommodate ion transport and silicon expansion) and about 1% to 50% when the anode is in a post-lithiation state (to accommodate ion transport). More generally, porosity may be determined by methods known in the art, including, but not limited to, the ratio of the pore volume of an aerogel material to its bulk density. Within the context of this disclosure, porosity measurements are obtained according to this method unless otherwise specified. In certain embodiments, the aerogel material or aerogel composition of the present disclosure has a porosity of about 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or a range between any two of these values.

[0143] It should be noted that pore volume and porosity are different measures of the same property of pore structure, namely, the "empty space" within the pore structure. For example, when silicon is used as the electrochemically active species contained within the pores of a nanoporous carbon material (e.g., the porous carbon-silicon composite beads described herein), pore volume and porosity refer to the space that is "empty," i.e., the space not utilized by silicon or carbon. As will be appreciated, densification of a nanoporous material (e.g., a polyimide gel material) prior to carbonization, for example, by compression, can also affect pore volume and porosity, among other properties.

[0144] In the context of the present disclosure, the term "pore diameter at the maximum peak from a distribution" refers to the value at a distinct peak on a graph showing the pore diameter distribution. The pore diameter at the maximum peak from a distribution is specifically measured as the pore diameter at which the largest percentage of pores are formed. The pore diameter at the maximum peak from a distribution is usually recorded as an arbitrary unit length of pore diameter, such as micrometers or nanometers (nm). The pore diameter at the maximum peak from a distribution can be determined by methods known in the art, including, but not limited to, surface area and porosity analyzers by nitrogen adsorption and desorption, which can calculate the pore diameter distribution and calculate the pore diameter at the maximum peak from the distribution. In the context of the present disclosure, the measurement of the pore diameter at the maximum peak from a distribution is obtained according to this method unless otherwise specified. In certain embodiments, the aerogel material or aerogel composition of the present disclosure has a pore size at the largest peak from a distribution of about 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 5 nm or less, 2 nm or less, or a range between any two of these values.

[0145] Within the context of this disclosure, the term "BET surface area" has its ordinary meaning, referring to the Brunauer-Emmett-Teller method for determining surface area by N2 adsorption measurements. 2 BET surface area, expressed in g / g, is a measure of the total surface area of ​​a porous material (e.g., the nanoporous carbon described herein) per unit mass. Unless otherwise specified, "surface area" refers to BET surface area. As an alternative to BET surface area, the external geometric surface area of, for example, polyimide beads or carbon beads, can be calculated based on the diameter of the beads. Generally, such external geometric surface areas of beads of the present disclosure range from about 3 to about 700 μm 2 is within the range.

[0146] Within the context of this disclosure, the term "strut width" refers to the average diameter of the nanostruts, nanorods, nanofibers, or nanofilaments that form aerogels having a fiber morphology. Strut width is typically reported as an arbitrary unit length, such as micrometers or nanometers. Strut width can be determined by methods known in the art, including, but not limited to, scanning electron microscopy image analysis. Within the context of this disclosure, strut width measurements are taken according to this method unless otherwise specified. In certain embodiments, the aerogel materials or compositions of the present disclosure have strut widths of about 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2 nm or less, or a range between any two of these values. An exemplary strut width range seen in the examples below (particularly in the SEM images in the figures) is about 2-5 nm. These smaller strut widths allow a greater amount of struts to be present within the network and thus in contact with electrochemically active species, which in turn allows a greater amount of electrochemically active species to be present within the composite. This increases the electrical conductivity and mechanical strength.

[0147] Within the context of this disclosure, the term "cycle life" refers to the number of complete charge / discharge cycles that an anode or battery (e.g., a LIB) can support before its capacity drops below approximately 80% of its original rated capacity. Cycle life may be affected by various factors that are not significantly affected over time, such as the mechanical strength of the underlying substrate (e.g., carbon aerogel), the connectivity of silicon particles within the aerogel, and the maintenance of aerogel interconnectivity. It is noted that it is a surprising aspect of certain embodiments of the present invention that these factors actually remain relatively unchanged over time. Cycle life may be determined by methods known in the art, including, but not limited to, cycle testing, in which a battery cell is subjected to repeated charge / discharge cycles at a predetermined current rate and operating voltage. Within the context of this disclosure, cycle life measurements are obtained according to this method unless otherwise specified. In certain embodiments of the present disclosure, an energy storage device, such as a battery or electrode thereof, has a cycle life of about 25 cycles or more, 50 cycles or more, 75 cycles or more, 100 cycles or more, 200 cycles or more, 300 cycles or more, 500 cycles or more, 1000 cycles or more, or a range between any two of these values.

[0148] In the context of this disclosure, the term "capacity" refers to the specific amount of energy or charge that a battery can store. Capacity is specifically measured as the discharge current that a battery can deliver per unit mass over time. Capacity is typically reported as ampere-hours or milliampere-hours per gram of total electrode mass, Ah / g or mAh / g. The capacity of a battery (and particularly an anode) can be determined by methods known in the art, including, but not limited to, applying a constant current load to a fully charged cell until the cell voltage reaches an end-of-discharge voltage value; the time to reach the discharge voltage multiplied by the constant current is the discharge capacity; and specific and volumetric capacity can be determined by dividing the discharge capacity by the weight or volume of the electrode material. In the context of this disclosure, capacity measurements are obtained according to this method unless otherwise specified. In certain embodiments, the aerogel materials or aerogel compositions of the present disclosure have a capacity of about 200 mAh / g or greater, 300 mAh / g or greater, 400 mAh / g or greater, 500 mAh / g or greater, 600 mAh / g or greater, 700 mAh / g or greater, 800 mAh / g or greater, 900 mAh / g or greater, 1000 mAh / g or greater, 1200 mAh / g or greater, 1400 mAh / g or greater, 1600 mAh / g or greater, 1800 mAh / g or greater, 2000 mAh / g or greater, 2400 mAh / g or greater, 2800 mAh / g or greater, 3200 mAh / g or greater, or a range between any two of these values. Unless otherwise noted, when the present nanoporous carbon materials are used in batteries, capacity is reported at cycle 10 of the battery.

[0149] In the context of this disclosure, the term "silicon utilization efficiency" refers to the difference between the theoretical capacity of silicon to be lithiated and the measured capacity of the electrode based on the weight of silicon. Silicon utilization efficiency is specifically measured as the efficiency of silicon utilization in the electrode. Silicon utilization efficiency is reported herein as a percentage using the following formula:

number

[0150] To calculate the silicon utilization efficiency, the electrode capacity and silicon capacity are measured as described above. In certain embodiments, the aerogel materials or aerogel compositions of the present disclosure have a silicon utilization efficiency of about 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or a range between any two of these values, with a higher percentage indicating better or more efficient silicon utilization. Unless otherwise noted, when the present nanoporous carbon material (e.g., porous carbon-silicon composite beads) is used in a battery, the silicon utilization efficiency is reported at cycle 10 of the battery.

[0151] As used herein, the term "alkyl" refers to a straight-chain or branched saturated hydrocarbon, generally having 1 to 20 carbon atoms. Representative alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl. Branched alkyl groups, on the other hand, include, but are not limited to, isopropyl, sec-butyl, isobutyl, tert-butyl, isopentyl, and neopentyl. Alkyl groups can be unsubstituted or substituted.

[0152] The term "alkenyl," as used herein, refers to a hydrocarbon containing straight-chain, secondary, or tertiary carbon atoms, generally having 1 to 20 carbon atoms, with at least one site of unsaturation, i.e., a carbon-carbon double bond. Examples include, but are not limited to, ethylene or vinyl, allyl, 1-butenyl, 2-butenyl, isobutylenyl, 1-pentenyl, 2-pentenyl, 3-methyl-1-butenyl, 2-methyl-2-butenyl, 2,3-dimethyl-2-butenyl, and the like. Alkenyl groups can be unsubstituted or substituted.

[0153] The term "alkynyl," as used herein, refers to a hydrocarbon containing straight-chain, secondary, or tertiary carbon atoms, generally having 1 to 20 carbon atoms, with at least one site of unsaturation, i.e., a carbon-carbon triple bond. Examples include, but are not limited to, acetylene and propargyl. Alkynyl groups can be unsubstituted or substituted.

[0154] As used herein, the term "aryl" refers to a carbocyclic aromatic group generally having 6 to 20 carbon atoms. Examples of aryl groups include, but are not limited to, phenyl, naphthyl, and anthracenyl. Aryl groups can be unsubstituted or substituted.

[0155] The term "cycloalkyl" as used herein refers to a saturated carbocyclic group that can be monocyclic or bicyclic. Cycloalkyl groups include rings having 3 to 7 carbon atoms as a monocycle, or 7 to 12 carbon atoms as a bicycle. Examples of monocyclic cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Cycloalkyl groups can be unsubstituted or substituted.

[0156] As used herein, the term "substituted" as applied to any of the above alkyl, alkenyl, alkynyl, aryl, cycloalkyl, etc. means that one or more hydrogen atoms are each independently replaced with a substituent. Exemplary substituents include -X, -R, -OH, -OR, -SH, -SR, NH, -NHR, -N(R), -N +(R)3, -CX3, -CN, -OCN, -SCN, -NCO, -NCS, -NO, -NO2, -N3, -NC(=O)H, -NC(=O)R, -C(=O)H, -C(=O)R, -C(=O)NH2, -C(=O)N(R)2, -S O3-, -SO3H, -S(=O)2R, -OS(=O)2OR, -S(=O)2NH2, -S(=O)2N(R)2, -S(=O)R, -OP(=O)(OH)2, -OP(=O)(OR)2, -P(=O)(OR)2, -PO3, - including, but not limited to, PO3H2, -C(=O)X, -C(=S)R, -CO2H, -C2R, -CO2-, -C(=S)OR, -C(=O)SR, -C(=S)SR, -C(=O)NH2, -C(=O)N(R)2, -C(=S)NH2, -C(=S)N(R)2, -C(=NH)NH2, and -C(=NR)N(R)2, wherein each X, for each occurrence, is independently selected from F, Cl, Br, and I; and each R, for each occurrence, is selected from C1-C 20 Alkyl and C6-C 20 When a group is described as "optionally substituted," that group may be substituted, independently at each occurrence, with one or more of the above substituents.

[0157] It is understood that certain radical naming conventions may include either monoradicals or diradicals, depending on the context. For example, if a substituent requires two points of attachment to the rest of the molecule, the substituent is understood to be a diradical. For example, a substituent specified as alkyl, which requires two points of attachment, includes diradicals such as -CH2-, -CH2CH2-, -CH2CH(CH3)CH2-, etc. Other radical naming conventions explicitly indicate that the radical is a diradical, such as "alkylene," "alkenylene," "arylene," etc.

[0158] When a substituent is depicted as a diradical (ie, having two points of attachment to the rest of the molecule), it is understood that the substituent may be attached in any orientation unless otherwise indicated.

[0159] In the context of this disclosure, the term "free-standing" refers to the ability of an aerogel material or aerogel composition to possess flexibility and / or resilience based primarily on the physical properties of the aerogel. Free-standing aerogel materials or aerogel compositions of the present disclosure can be distinguished from other aerogel materials, such as coatings, that rely on an underlying substrate or reinforcing material to impart flexibility and / or resilience to the material.

[0160] In the context of this disclosure, the term "density" refers to a measure of the mass per unit volume of an aerogel material or aerogel composition. The term "density" generally refers to the true density of an aerogel material and the bulk density of an aerogel composition. Density is typically measured in kg / m 3or g / cc. The density of an aerogel material or aerogel composition can be determined by methods known in the art, including, but not limited to, Standard Test Methods for Dimensions and Density of Preformed Block and Board Insulation (ASTM C303, ASTM International, West Conshohocken, Pa.), Standard Test Methods for Thickness and Density of Blanket or Batt Insulation (ASTM C167, ASTM International, West Conshohocken, Pa.), or Measurement of Apparent Density of Preformed Pipe Insulation (ISO 18098, International Organization for Standardization, Switzerland). Within the context of this disclosure, density measurements are taken according to the ASTM C167 standard unless otherwise specified. Preferably, the aerogel material or aerogel composition of the present disclosure has a density of about 1.50 g / cc or less, about 1.40 g / cc or less, about 1.30 g / cc or less, about 1.20 g / cc or less, about 1.10 g / cc, about 1.00 g / cc or less, about 0.90 g / cc or less, about 0.80 g / cc or less, about 0.70 g / cc or less, about 0.60 g / cc or less, about 0.50 g / cc or less, about 0.40 g / cc or less, about 0.30 g / cc or less, about 0.20 g / cc or less, about 0.10 g / cc or less, or a range between any two of these values, such as, for example, between about 0.15 g / cc and 1.5 g / cc, or more specifically, between 0.50 g / cc and 1.30 g / cc.

[0161] In the context of this disclosure, the term "tap density" of a material or composition, such as carbon-silicon composite beads, refers to the maximum density achieved when the particulate material is vibrated or tapped under specified conditions. Tap density reflects the empty space between particles (e.g., beads) caused by random, dense packing. Tap density is always lower than the bulk (or envelope) density of the particles. Tap density can be calculated using the formula M / Vf, where M=mass in grams and V f= tapped volume in milliliters. Tapped density is generally measured by first gently introducing a known sample mass into a graduated cylinder and carefully flattening it without compressing the powder. The cylinder is then mechanically tapped by lifting the cylinder and allowing it to fall under its own weight using a suitable mechanical tapped density tester that provides an appropriate constant drop distance and nominal drop velocity. Standard test methods for tapped density measurement are described in MPIF-46, ASTM B-527, and ISO 3953. In some embodiments, the materials and compositions of the present disclosure have a tap density of about 1.50 g / cc or less, about 1.40 g / cc or less, about 1.30 g / cc or less, about 1.20 g / cc or less, about 1.10 g / cc or less, about 1.00 g / cc or less, about 0.90 g / cc or less, about 0.80 g / cc or less, about 0.70 g / cc or less, about 0.60 g / cc or less, about 0.50 g / cc or less, about 0.40 g / cc or less, about 0.30 g / cc or less, or about 0.20 g / cc or less. In some embodiments, the tap density is between about 0.2 g / cc and about 1.5 g / cc.

[0162] Method for forming organic aerogel beads According to certain embodiments, the production of aerogel generally involves the following steps: i) forming a solution containing gel precursors; ii) forming a gel from the solution; and iii) extracting the solvent from the gel material to obtain a dry aerogel material.

[0163] According to certain embodiments, the production of aerogel beads follows a general process for producing aerogels, generally including the following steps: i) forming a solution containing gel precursors; ii) dispersing the gel precursors in a medium that is immiscible with the gel precursors; iii) forming gel beads from the gel precursor solution in the immiscible medium; iv) removing the gel beads from the medium; and v) extracting the solvent from the gel beads to obtain a dry aerogel material. These processes are described in more detail below, particularly with respect to forming organic aerogels such as polyimide aerogels. However, the specific examples and descriptions provided herein are not intended to limit the present disclosure to any particular type of aerogel and / or preparation method. The present disclosure may include any aerogel formed by any relevant preparation method known to those of skill in the art.

[0164] An exemplary solution for producing an organic aerogel is formed by combining at least one organogel precursor with a solvent. Suitable solvents for use in forming the solution include lower alcohols having 1 to 6 carbon atoms, preferably 2 to 4, although other solvents known to those skilled in the art can also be used. Examples of useful solvents include, but are not limited to, methanol, ethanol, isopropanol, ethyl acetate, ethyl acetoacetate, acetone, dichloromethane, tetrahydrofuran, 1-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAC), formamide, and the like. Multiple solvents may be combined to achieve a desired level of dispersion or to optimize the properties of the gel material. Therefore, the selection of optimal solvents for the polymerization and gel-formation steps depends on the specific precursors, fillers, and additives incorporated into the solution, as well as the target processing conditions for gelation and liquid-phase extraction, and the desired properties of the final aerogel material.

[0165] An exemplary solution for producing polyimide aerogels is formed by combining at least one diamine and at least one dianhydride in a common polar aprotic solvent(s). In some embodiments, the dianhydride component(s) are dissolved in a solvent, and then the diamine component(s) are added to the solution. Within the context of this disclosure, the addition of the diamine to the dianhydride solution is referred to as a "standard addition" process. In other embodiments, the diamine component(s) are dissolved in a solvent, and then the dianhydride component(s) are added. Within the context of this disclosure, the addition of the dianhydride to the diamine solution is referred to as a "reverse addition" process.

[0166] Additional details regarding the formation of polyimide gels / aerogels can be found in U.S. Pat. Nos. 7,074,880 and 7,071,287 to Rhine et al., U.S. Pat. No. 6,399,669 to Suzuki et al., U.S. Pat. No. 9,745,198 to Leventis et al., Leventis et al., "Polyimide Aerogels by Ring-Opening Metathesis Polymerization (ROMP)," Chem. Mater. 2011, 23, 8, 2250-2261, Leventis et al., "Isocyanate-Derived Organic Aerogels: Polyureas, Polyimides, Polyamides," MRS Proceedings, 1306 (2011), Mrsf10-1306-bb03-01. doi:10.1557 / opl.2011.90, and Chidambareswarapattar et al., each of which is incorporated herein by reference in its entirety. al., "One-step room-temperature synthesis of fibrous polyimide aerogels from anhydrides and isocyanates and conversion to isomorphic carbons", J.Mater.Chem., 2010, 20, 9666-9678, Guo et al., "Polyimide Aerogels Cross-Linked through Amine Functionalized Polyoligomeric Silsesquioxane", ACS Appl.Mater.Interfaces 2011, 3, 546-552, Nguyen et.al, "Development of High Temperature, Flexible Polyimide Aerogels", American Chemical Society, Proceedings Publication 2011, Meador et.al., "Mechanically Strong, Flexible Polyimide Aerogels Cross-Linked with Aromatic Triamine", ACS Appl.Mater.Interfaces, 2012, 4(2), pp536-544; Meador et al., "Polyimide Aerogels with Amide Cross-Links: A Low Cost Alternative for Mechanically Strong Polymer Aerogels", ACS Appl.Mater.Interfaces 2015, 7, 1240-1249; Pei et al., "Preparation and Characterization of Highly Cross-Linked Polyimide Aerogels Based on Polyimide Containing Trimethoxysilane Side Groups", Langmuir 2014, 30, 13375-13383.

[0167] To optimize the properties of the gel material, triamines, tetraamines, pentamines, hexamines, etc. can also be used in place of or in addition to diamines or combinations thereof. To optimize the properties of the gel material, trianhydrides, tetraanhydrides, pentaanhydrides, and hexanhydrides can also be used in place of or in addition to dianhydrides or combinations thereof. Dehydrating agents and catalysts can be incorporated into the solution to initiate and drive imidization. The solution can contain additional co-gelling precursors, as well as filler materials and other additives. Filler materials and other additives can be dispensed into the solution at any time before or during gel formation. Filler materials and other additives can also be incorporated into the gel material after gelation by various techniques known to those skilled in the art. Preferably, the solution containing the gelling precursor, solvent, catalyst, water, filler material, and other additives is a homogeneous solution capable of effective gel formation under appropriate conditions.

[0168] Once the solution is formed and optimized, the gel-forming components in the solution can be converted into a gel material. The process of converting the gel-forming components into a gel material involves an initial gel-forming step in which the gel solidifies to the gel point of the gel material. The gel point of the gel material can be considered the point at which the gelling solution exhibits resistance to flow and / or forms a substantially continuous polymeric framework throughout its volume. A range of gel-forming techniques are known to those skilled in the art. Examples include, but are not limited to, maintaining the mixture under quiescence for a sufficient period of time, adjusting the concentration of a catalyst, adjusting the temperature of the solution, directing a form of energy (ultraviolet, visible, infrared, microwave, ultrasound, particle radiation, electromagnetic) at the mixture, or combinations thereof.

[0169] In some embodiments, the gel material (e.g., organoaerogels or carbon aerogels and xerogels) may be in bead form (i.e., a plurality of beads). As used herein, the term "bead" means to include small, discrete units or particles having a generally spherical shape. In some embodiments, the beads are substantially spherical. The beads are generally uniform in composition, such that each bead in a plurality contains the same components in approximately the same amounts, within normal variations expected in preparing such beads. The size of the beads may vary according to the desired properties and preparation method.

[0170] The process of forming gel beads from a gel solution can include mixing the solution with a medium that is immiscible with the solution, such as a dispersion medium. For example, silicone oil or mineral oil can be used as the dispersion medium. The gel solution can be added, for example, by pouring, or otherwise combined with the immiscible dispersion medium. Agitation, for example, by mixing, of the combined dispersion medium and gel precursor solution can be used to promote the formation of droplets, such as beads, before or during the process of transferring the gel-forming components into a gel material. For example, the combination of the dispersion medium and gel precursor can form an emulsion in which the gel precursor solution is the dispersed phase. An exemplary method of producing gel beads is described in U.S. Patent Application Publication No. 2006 / 0084707 to Ou et al., which is incorporated herein by reference in its entirety.

[0171] Due to interfacial tension, spherical droplets of the gel precursor are formed in the dispersion medium. The droplets gel and harden while in the dispersion medium, such as silicone oil. Agitation of the mixture is typically used to prevent the droplets from agglomerating. For example, the mixture of gel precursor and dispersion medium can be agitated to prevent the droplets from agglomerating.

[0172] Heat or radiation can also be applied to the dispersion medium to induce or accelerate the gelation of the droplets or to strengthen the gel beads so that they are strong enough to resist collisions. The production capacity of gel beads in a given space depends on precisely controlling the droplet gelation process.

[0173] The process further includes removing the gel beads from the carrier fluid, such as silicone oil, mineral oil, or mineral spirits. The gel beads are filtered from the carrier fluid and then washed or rinsed with a fluid, such as an alcohol, such as ethanol, methanol, isopropanol, or a higher alcohol. Hydrocarbon solvents, such as heptane, hexane, or octane, can also be used. The basic requirement for the rinse is that it can remove the oil (or other carrier fluid) without chemically reacting with the gel. After removing the excess medium (e.g., silicone oil), the gel beads can be placed in a solvent for aging, as described in more detail below. For example, the gel beads can be aged in ethanol. The gel beads are suitable for interstitial solvent removal, for example, using the supercritical fluid drying method described herein. The gel beads can also be dried at ambient conditions to produce a xerogel. Dried gel beads, such as aerogel or xerogel beads, are suitable for heat treatment and carbonization, as described in more detail below.

[0174] In an exemplary embodiment, the organogel beads are polyimide beads, which are prepared in a three-step process including preparing a polyamic acid sol, optionally incorporating an electroactive material such as silicon into the polyamic acid sol, and imidizing the polyamic acid sol (optionally in the mixture with the silicon) while the mixture is under shear conditions, such as high or low shear (i.e., high or low rpm) mixing. In certain exemplary embodiments, the polyamic acid sol is prepared at ambient temperature. N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAC), or N,N-dimethylformamide (DMF) solvents can be used to prepare polyimide precursors. In certain embodiments, starting monomers, such as aromatic dianhydrides and aromatic diamines, can be dissolved in the aforementioned solvents and stirred under ambient conditions. In a preferred embodiment, the monomer solution can be prepared under a flow of inert gas, such as nitrogen or argon.

[0175] In some embodiments, silicon particles are incorporated into the compositions disclosed herein during the sol-gel process. In a first embodiment, the silicon particles are dispersed in the polyamic acid sol before imidization. In a second embodiment, the silicon particles are dispersed in a solvent, such as DMAC or other solvent compatible with the polyamic acid sol, before the solvent is combined with the polyimide precursor. In a third embodiment, the silicon particles are dispersed in the polyamic acid sol during the imidization process. In other embodiments, the silicon particles are incorporated after imidization of the organogel, or even after carbonization.

[0176] In one aspect of the present disclosure, a porous carbon composition in bead form is provided. In one embodiment, such a porous carbon composition is generally prepared according to a method including providing an organogel precursor in an organic solvent, initiating gelation of the organogel precursor to form an organogel sol, combining the organogel sol with a medium immiscible with the organogel sol to form organogel droplets, isolating the organogel droplets, drying the droplets to produce organogel beads, and pyrolyzing the porous organogel beads to produce porous carbon composition beads. A general, non-limiting flow diagram for preparing porous organogel beads is provided in FIG. 49A. Referring to FIG. 49A, an organogel precursor is provided in an organic solvent, gelation is initiated, and the gelling precursor (i.e., the organogel sol) is combined with a medium immiscible with the organogel sol. Gelled droplets are then produced by mixing under high shear conditions, and the droplets are isolated and optionally further processed (eg, washed, solvent exchanged, dried, or pyrolyzed).

[0177] In some embodiments, the organogel is a resorcinol-formaldehyde polymer, a phloroglucinol-formaldehyde polymer, a cellulose polymer, a polyurea, a polyurethane, an alginate, or a polyacrylonitrile. Such organogel polymers are further described herein below.

[0178] In some embodiments, the organogel is a polyimide. In some embodiments, the organogel is a polyimide and the organogel precursor is a polyamic acid. In some embodiments, a preformed polyamic acid may be provided. For example, the polyamic acid may be purchased. Alternatively, the polyamic acid may be prepared from the reaction of a polyfunctional amine with a polyfunctional anhydride in an organic solvent. Thus, in some embodiments, the method includes allowing a polyfunctional amine and a polyfunctional anhydride to react with each other to form a polyamic acid as the organogel precursor.

[0179] As used herein, the term "polyfunctional anhydride" refers to a molecule having at least two dicarboxylic acid anhydride groups available for reactions as described herein below. In some embodiments, the polyfunctional anhydride is a tetracarboxylic acid dianhydride. In some embodiments, trianhydrides, tetraanhydrides, pentaanhydrides, hexanhydrides, etc. may be used in place of or in addition to the tetracarboxylic acid dianhydride to optimize the properties of the gel material.

[0180] In such embodiments, one skilled in the art will recognize that the polyamic acid comprises amide units comprising the amino groups of the polyfunctional amine and the carboxylic acid groups corresponding to the tetracarboxylic acid anhydride. Accordingly, such polyamic acids may be described herein as "comprising a tetracarboxylic acid" and "comprising a polyfunctional amine" (e.g., a diamine).

[0181] The structure of the tetracarboxylic dianhydride can vary. In some embodiments, the tetracarboxylic dianhydride has a structure according to Formula I: [ka] In the above formula, L comprises an alkyl group, a cycloalkyl group, an aryl group, or a combination thereof, each as described herein above. In some embodiments, L comprises an aryl group. In some embodiments, L comprises a phenyl group, a biphenyl group, or a diphenyl ether group. In some embodiments, the tetracarboxylic dianhydride of Formula I has a structure selected from one or more structures provided in Table 1. [Table 1]

[0182] In some embodiments, the tetracarboxylic dianhydride is selected from the group consisting of pyromellitic anhydride (PMDA), biphthalic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), benzophenonetetracarboxylic dianhydride (BTDA), ethylenediaminetetraacetic dianhydride (EDDA), 1,4,5,8-naphthalenetetracarboxylic dianhydride, and combinations thereof. In some embodiments, the tetracarboxylic dianhydride is PMDA. Thus, polyamic acids produced from such tetracarboxylic dianhydrides can be described as comprising a tetracarboxylic acid selected from the group consisting of benzene-1,2,4,5-tetracarboxylic acid, [1,1'-biphenyl]-3,3',4,4'-tetracarboxylic acid, 4,4'-oxydiphthalic acid, 4,4'-sulfonyldiphthalic acid, 4,4'-carbonyldiphthalic acid, 4,4'-(propane-2,2-diyl)diphthalic acid, 4,4'-(perfluoropropane-2,2-diyl)diphthalic acid, naphthalene-1,4,5,8-tetracarboxylic acid, 4-(2-(4-(3,4-dicarboxyphenoxy)phenyl)propan-2-yl)phthalic acid, perylene tetracarboxylic acid, and combinations thereof.

[0183] As used herein, the term "multifunctional amine" refers to a molecule having at least two primary amino groups available for reactions as described herein below. In some embodiments, the multifunctional amine is a triamine, tetramine, pentamine, hexamine, or the like. In some embodiments, the multifunctional amine is a diamine. In some embodiments, triamines, tetramines, pentamines, hexamines, or the like may be used in addition to diamines to optimize the properties of the gel material. In some embodiments, the multifunctional amine includes or is a triamine. Non-limiting examples of suitable triamines include propane-1,2,3-triamine, benzene-1,3,5-triamine, cyclohexane-1,3,5-triamine, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), tris(4-aminophenyl)methane, and 1,3,5-triazine-2,4,6-triamine (melamine). In some embodiments, the polyfunctional amine is 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), tris(4-aminophenyl)methane, melamine, or a combination thereof. In some embodiments, the polyfunctional amine is melamine.

[0184] In a preferred embodiment, the polyfunctional amine is a diamine. Thus, a polyamic acid produced from a diamine can be described as comprising such a diamine. The structure of the diamine can vary. In some embodiments, the diamine has the structure of Formula II: [ka] In the above formula, Z is aliphatic (i.e., alkyl, alkenyl, alkynyl, or cycloalkyl) or aryl, each as described herein above. In some embodiments, Z is alkyl, such as a C2-C12 alkyl. In some embodiments, the diamine is an alkanediamine, such as a C2-C6 alkanediamine. Suitable alkanediamines include, but are not limited to, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, or 1,6-diaminohexane. In some embodiments, the C2-C6 alkanediamine is substituted with one or more alkyl groups, such as methyl.

[0185] In some embodiments, Z is aryl and the polyfunctional amine is an aryl diamine. In some embodiments, the aryl diamine is 1,4-phenylenediamine (PDA), 4,4'-diaminodiphenyl ether, 4,4'-methylenedianiline, or a combination thereof. In some embodiments, the diamine is PDA. In some embodiments, the diamine is 4,4'-diaminodiphenyl ether. In some embodiments, the diamine is 4,4'-methylenedianiline.

[0186] The molecular weight of polyamic acids and the corresponding organogel (i.e., polyimide gel) can vary based on the reaction conditions (e.g., diamine and dianhydride concentration, temperature, duration of reaction, nature, etc.). The molecular weight is based on the number of polyamic acid repeat units. A repeat unit, as defined herein, is a portion of a polyamic acid or polyimide whose repetitions create a complete polymer chain (excluding the terminal amino groups) by linking the repeat units to each other consecutively along the polymer chain.

[0187] The specific molecular weight range of the polyimides produced by the disclosed methods may vary. In general, the reaction conditions described above may be varied to impart desired physical properties to the polyimide without specific consideration of molecular weight. In some embodiments, a surrogate for molecular weight may be provided for the viscosity of the polyamic acid solution, which may be controlled by adjusting the variables described (temperature, concentration, molar ratio of components, reaction time, solvent, presence of water, etc.), as further disclosed herein below.

[0188] The molar ratio of polyfunctional anhydride (e.g., tetracarboxylic dianhydride) to polyfunctional amine (e.g., diamine) can vary according to the desired reaction time, reagent structure, and desired material properties. In some embodiments, the molar ratio is about 0.9 to about 3, such as about 0.9 or about 1 to about 2 or about 3. In some embodiments, the ratio is about 1 (i.e., stoichiometric), such as about 0.9 to about 1.1. In certain embodiments, the ratio is about 0.99 to about 1.01.

[0189] Generally, a polyfunctional amine (e.g., a diamine) and a polyfunctional anhydride (e.g., a tetracarboxylic dianhydride) are reacted for a period of time to complete the reaction between the amino and anhydride groups and provide a polyamic acid. The reaction is generally allowed to proceed until all of the available reactants (e.g., a diamine and a dianhydride) have reacted with each other. The time required for complete reaction may vary based on the structure, concentration, and temperature of the reagents. In some embodiments, the reaction time is from about 1 minute to about 1 week, e.g., from about 15 minutes to about 5 days, from about 30 minutes to about 3 days, or from about 1 hour to about 1 day. In some embodiments, the reaction time is from about 0.5 hours to about 17 hours. In some embodiments, the reaction time is from about 1 hour to about 12 hours.

[0190] The organic solvent used may vary but is generally a polar aprotic solvent. In some embodiments, the organic solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, or ethyl acetate. In some embodiments, the organic solvent is N,N-dimethylacetamide.

[0191] In some embodiments, the organic solvent is anhydrous, meaning that the organic solvent is free or substantially free of water. In other embodiments, the organic solvent further comprises water. The amount of water present can vary based on several factors, such as the target density, viscosity, intended particle size, and scale. Surprisingly, in accordance with the present disclosure, it has been found that including low levels of water in the organic solvent prior to gelation provides smaller organogel droplets, leading to smaller bead sizes (i.e., smaller organogel and corresponding porous carbon bead sizes). While not wishing to be bound by any particular theory, it is believed that the presence of water reduces the viscosity of the medium and delays gelation of the organogel precursor (e.g., polyamic acid). In some embodiments, water is present in the organic solvent in an amount of about 100 to about 1500 parts per million (ppm), such as about 500 to about 1200 ppm, or about 500 to about 700 ppm. In some embodiments, water is present in the organic solvent in an amount of about 500, about 600, about 700, about 800, about 900, about 1000, about 1100, or about 1200 ppm.

[0192] The temperature at which the reaction between the polyfunctional anhydride (e.g., tetracarboxylic dianhydride) and the polyfunctional amine (e.g., diamine) is carried out can vary. A suitable temperature range is generally between about 10°C and about 100°C. In some embodiments, the reaction temperature is from about 10 to about 100°C, or from about 15 to about 60°C, or from about 15 to about 50°C, or from about 15 to about 25°C.

[0193] The concentration of the polyamic acid in the resulting solution may vary. For example, in some embodiments, the concentration of the polyamic acid (i.e., the density of the polyamic acid in the solution) may range from about 0.01 to about 0.3 g / cm. 3 In some embodiments, the volume of solvent is adjusted to a specific target density (T d Generally, the concentration range of the polyamic acid present in the solution is from about 0.01 to about 0.3 g / cm, based on the weight of the polyamic acid. 3 is.

[0194] In some embodiments, the porous carbon composition is a porous carbon-silicon composition comprising greater than about 10% silicon by weight. In such embodiments, the method further comprises providing a mixture of organogel precursor and silicon in an organic solvent. Typically, the silicon is in particulate form, and the silicon particles are incorporated during the sol-gel process. A general, non-limiting flow diagram for preparing porous organogel-silicon composite beads is provided in FIG. 49B. Referring to FIG. 49B, the method comprises providing a mixture of silicon and organogel precursor in an organic solvent. In some embodiments, the silicon particles are dispersed in a solvent, such as a polar aprotic solvent, prior to combining with the organogel precursor. In one non-limiting embodiment, the silicon particles are dispersed in a polyamic acid sol prior to imidization. In another non-limiting embodiment, the silicon particles are dispersed in a polyamic acid sol during the imidization process.

[0195] Within the context of the present disclosure, the term "silicon particles" refers to silicon in a particle size range suitable for use with the organo (e.g., polyimide) or carbon gels disclosed herein. Silicon particles of the present disclosure can be nanoparticles, e.g., particles with two or three dimensions ranging from about 1 nm to about 150 nm. Silicon particles of the present disclosure can be microparticles, e.g., micron-sized particles having a maximum dimension, e.g., diameter in the case of substantially spherical particles, ranging from about 150 nm to about 10 micrometers or more. For example, silicon particles of the present disclosure can have a maximum dimension, e.g., about 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 500 nm, 1 micrometer, 1.5 micrometers, 2 micrometers, 3 micrometers, 5 micrometers, 10 micrometers, 20 micrometers, 40 micrometers, 50 micrometers, 100 micrometers, or a diameter in the case of substantially spherical particles ranging between any two of these values. In some embodiments, the particles are flat, piecemeal, e.g., platelets, having two dimensions, e.g., a length and width of about 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 500 nm, 1 micron, 1.5 microns, 2 microns, 3 microns, 5 microns, 10 microns, 20 microns, 40 microns, 50 microns, 100 microns, or a range between any two of these values. In some embodiments, the silicon particles can be monodisperse or substantially monodisperse. In other embodiments, the silicon particles can have a particle size distribution. Within the context of the present disclosure, the dimensions of the silicon particles are provided based on the median, or D50, of the particle size distribution.

[0196] Silicon particles can be produced by a variety of techniques, including electrochemical reduction and mechanical milling, or grinding. Grinding can be carried out using wet or dry processes. In dry milling, powder is added to a vessel along with grinding media, which typically include zirconium oxide (stabilized yttrium), silicon carbide, silicon oxide, quartz, or stainless steel balls or rods. The particle size distribution of the resulting milled material is controlled by the energy applied to the system and by matching the particle size of the starting material to the size of the grinding media. However, dry milling is an inefficient and energy-consuming process. Wet milling is similar to dry milling, except that a grinding fluid is added. The advantage of wet milling is that it consumes 15-50% less energy than dry milling to produce the same results. An additional advantage of wet milling is that the grinding fluid protects the milled material from oxidation. Wet milling has also been found to produce finer particles, resulting in less particle agglomeration.

[0197] Wet milling can be carried out using a variety of liquid components. In an exemplary embodiment, the milling liquid or components contained therein are selected to reduce or eliminate chemical functionalization on the surface of the silicon particles during or after milling. In other embodiments, the milling liquid or components contained therein are selected to provide desired surface chemical functionalization of particles, such as silicon particles, during or after milling. The milling liquid or components contained therein can also be selected to control the chemical reactivity or crystalline morphology of particles, such as silicon particles. In an exemplary embodiment, the milling liquid or components contained therein can be selected based on compatibility or reactivity with downstream materials, such as processing steps or applications of particles, such as silicon particles. For example, the milling liquid or components contained therein can be compatible with, useful in, or identical to liquids or solvents used in processes for forming or producing organic or inorganic aerogel materials. In yet another embodiment, the milling liquid or components contained therein can be selected such that the milling liquid or components contained therein produce coatings on the silicon particle surfaces or intermediate species, such as aliphatic or aromatic hydrocarbons, or by cross-linking or producing cross-functional compounds that react with organic or inorganic aerogel materials.

[0198] The solvent or mixture of solvents used for milling can be selected to control the chemical functionalization of the particles during or after milling. Using silicon as an example, without being bound by theory, milling silicon in an alcoholic solvent such as isopropanol can functionalize the silicon surface, covalently attaching alkoxide surface groups, such as isopropoxide, to the surface of the silicon particles. In an exemplary embodiment, milling can be carried out in a polar aprotic solvent such as DMSO, DMF, NMP, DMAC, THF, 1,4-dioxane, diglyme, acetonitrile, water, or any combination thereof, which has numerous advantages. Milling in a solvent compatible with the process for producing aerogel materials, such as the polar aprotic solvents mentioned above, can eliminate the need to remove the milling liquid from the particles before adding it to the aerogel production process, since the milling liquid is the same as or compatible with the solvent used in the aerogel process. In other embodiments, the milling liquid can include precursors to monomers, oligomers, or polymers. For example, the milling liquid can include a polyimide precursor monomer, such as polyacrylic acid (PAA). In another example, the grinding liquid can include a sol-gel liquid. In these embodiments, the grinding liquid including the precursor components or sol-gel liquid can impart sol-gel functionality to the surface of the particles, such as, for example, silicon particles. In further embodiments, the grinding liquid can be selected to impart functionality to the surface of the particles, such as, for example, silicon particles, such that the functionalized particles react or interact with each other during or after the grinding process.

[0199] The silicon particles of the present disclosure can be silicon wire, crystalline silicon, amorphous silicon, silicon alloys, coated silicon, such as carbon-coated silicon, and any combination of silicon particle materials disclosed herein. In some embodiments, the silicon particles can have a substantially planar flake, i.e., flat, piecewise shape, sometimes referred to as a platelet shape. For example, the particles have two substantially flat major surfaces connected by a minor surface that defines a thickness between the major surfaces. In other embodiments, the particles of silicon or other electroactive material can be substantially spherical, cubic, ellipsoidal, oval, discoidal, or toroidal.

[0200] The amount of silicon (e.g., silicon particles) present in the organic solvent solution of the organogel precursor can vary, but is generally selected so that the final porous carbon-silicon composition contains from about 20% to about 65% silicon by weight.

[0201] Continuing with reference to Figures 49A-49B, after the reaction forming or dissolving the organogel precursor is complete (e.g., after forming the polyamic acid or dissolving the preformed polyamic acid in an organic solvent), gelation is initiated. Generally, initiation of gelation is performed before combining the gelling organogel precursor, or a mixture of the gelling organogel precursor and silicon, with the immiscible medium. Gelation (and its initiation) can be performed chemically, thermally, or a combination thereof. In some embodiments, the organogel precursor is a polyamic acid, and initiating gelation involves chemically imidizing the polyamic acid to form a corresponding polyimide gel. In some embodiments, performing chemical imidization of the polyamic acid involves adding a dehydrating agent and an amine base to the polyamic acid sol. The presence of the dehydrating agent and the amine base initiates and promotes imidization of the polyamic acid carboxylic acid and amide groups, thus forming the polyimide gel.

[0202] The structure of the dehydrating agent may vary, but generally it is a reagent that can react with the carboxylate groups of the polyamic acid and promote imidization of the carboxyl and amide groups of the polyamic acid. One suitable example of a suitable class of dehydrating agents is a carboxylic acid anhydride, such as acetic anhydride or propionic anhydride. In some embodiments, the dehydrating agent is a carboxylic acid anhydride. In some embodiments, the carboxylic acid anhydride is acetic anhydride.

[0203] In some embodiments, the amount of dehydrating agent may vary based on the amount of polyfunctional anhydride (e.g., tetracarboxylic dianhydride). For example, in some embodiments, the dehydrating agent is present in various molar ratios relative to the dianhydride. The molar ratio of dehydrating agent to tetracarboxylic dianhydride may vary according to the desired reaction time, reagent structure, and desired material properties. In some embodiments, the molar ratio is from about 2 to about 10, such as from about 2, about 3, about 4, or about 5 to about 6, about 7, about 8, about 9, or 10. In some embodiments, the ratio is from about 3 to about 6, or from about 4 to about 5. In some embodiments, the ratio is 4.3.

[0204] The term "amine base" in the context of this disclosure refers to a molecule having a single amino group with a lone pair of electrons available to accept a proton. Suitable amine bases include tertiary alkylamines, tertiary cycloalkylamines, heteroaromatic amines, guanidines, and quaternary ammonium hydroxides.

[0205] In some embodiments, the amine base is a tertiary alkyl or cycloalkylamine. As used herein with respect to an amine, "tertiary" means that the amine nitrogen atom has three organic (i.e., carbon) substituents attached thereto. In some embodiments, the tertiary amine is triethylamine, trimethylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, or diisopropylethylamine.

[0206] In some embodiments, the amine base is a heteroaromatic amine. As used herein, the term "heteroaromatic amine" refers to an aromatic ring system in which one or more ring atoms is nitrogen. Heteroaromatic amines generally contain 2 to 20 carbon atoms and 1 to 3 heteroatoms selected from N, O, P, and S, with at least one heteroatom being nitrogen. Heteroaromatic amines can be monocyclic with 3 to 7 ring members (2 to 6 carbon atoms and 1 to 3 selected heteroatoms) or bicyclic with 7 to 10 ring members (4 to 9 carbon atoms and 1 to 3 heteroatoms), such as bicyclo[4,5], [5,5], [5,6], or [6,6] systems. Heteroaromatic amines can be unsubstituted or substituted. Particularly suitable are heteroaromatic amines with a monocyclic structure containing 5 carbon atoms and 1 nitrogen atom, such as pyridine. In some embodiments, the amine base is pyridine. In some embodiments, the amine base is pyridine with one or more alkyl substituents at appropriate positions on the aromatic ring. For example, suitable pyridines include pyridines substituted with one or more methyl groups, t-butyl groups, or combinations thereof. Non-limiting examples include 2-, 3-, and 4-picoline, 2,6-lutidine, 2,6-di-tert-butylpyridine, etc. In some embodiments, the amine base is pyridine.

[0207] The amount of amine base added can vary. The amount of amine base added can be based on a molar ratio, e.g., the molar ratio to polyamic acid. The molar ratio of amine base to polyamic acid can vary according to the desired reaction time, reagent structure, and desired material properties. In some embodiments, the molar ratio is about 0.1 to about 8. In some embodiments, the molar ratio is about 0.1, about 0.2, about 0.3, about 0.43, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, or about 1 to about 2, about 3, about 4, about 5, about 6, about 7, or about 8.

[0208] With continued reference to Figures 49A-49B, the process of forming organogel beads involves combining an organogel precursor solution (e.g., a polyamic acid solution) that has begun to gel with a medium, such as a dispersion medium, that is immiscible with the solution.

[0209] The dispersion medium can have a range of viscosities. In some embodiments, the medium has a viscosity of about 100 to about 150 centipoise (cP). In some embodiments, the organic solvent solution of the organogel precursor (i.e., organogel sol) has a viscosity ranging from about 5 to about 30 cP. In some embodiments, the medium has a viscosity of about 100 to about 150 cP, and the organic solvent solution of the organogel precursor (i.e., organogel sol) has a viscosity ranging from about 5 to about 30 cP. Surprisingly, in accordance with the present disclosure, it has been found that in some embodiments, combining a low-viscosity organogel solution with a higher-viscosity dispersion medium produces small-diameter droplets (i.e., beads), which may be desirable in certain embodiments. Without wishing to be bound by theory, it is believed that in some embodiments, the difference in viscosity between the medium and the organogel sol can facilitate droplet size reduction. Thus, in some embodiments, the ratio of the viscosity of the vehicle to the viscosity of the organogel sol ranges from about 3 to about 50, or from about 3 to about 30, such as from about 5 to about 20. In some embodiments, this ratio is from about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10 to about 15, about 20, about 25, or about 30. In some embodiments, this ratio is about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, or about 30.

[0210] In some embodiments, the medium is mineral oil, silicone oil, or a C5-C12 hydrocarbon. In some embodiments, the medium is an aliphatic hydrocarbon, an aromatic hydrocarbon, or a chlorinated hydrocarbon. In some embodiments, the medium is hexane or mineral spirits.

[0211] The gelling solution (i.e., organogel sol) can be added, for example, by pouring or otherwise combining with the immiscible dispersion medium. In some embodiments, the immiscible dispersion medium and, optionally, surfactant(s) are added to the sol. In some embodiments, the sol is added to the immiscible dispersion medium and, optionally, surfactant(s).

[0212] Agitation, such as by mixing, of the combined dispersion medium and gelling solution can be used to promote the formation of droplets, e.g., beads, before or during the process of transferring the gel-forming components into the gel material. For example, combining the dispersion medium and the gelling organogel sol can form an emulsion with the organogel sol as the dispersed phase. An exemplary method for producing gel beads is described in U.S. Patent Application Publication No. 2006 / 0084707 to Ou et al., which is incorporated herein by reference in its entirety.

[0213] Exemplary embodiments of mixing to provide gel beads from a sol mixture in a dispersion medium include magnetic stirring (up to about 600 rpm), mechanical mixing (up to about 800 rpm), and homogenization (up to about 9000 rpm). Mixing can be high-shear or low-shear. In some embodiments, mixing is high-shear (e.g., at a speed of about 4000 to about 9000 rpm). Interfacial tension causes spherical droplets of organogel precursor to form in the dispersion medium. The droplets gel and solidify while in the dispersion medium. Agitation of the mixture is typically used to prevent the droplets from agglomerating. For example, the combination of organogel and dispersion medium can be agitated for a period of time to prevent the droplets from agglomerating.

[0214] In some embodiments, the medium further comprises one or more surfactants. As used herein, the term "surfactant" refers to a substance that aids in the formation and stabilization of emulsions by promoting the dispersion of hydrophobic and hydrophilic (e.g., oil and water) components. When present, the surfactant may vary. Suitable surfactants are generally nonionic and include, but are not limited to, polyethylene glycol esters of fatty acids, propylene glycol esters of fatty acids, polysorbates, polyglycerol esters of fatty acids, sorbitan esters of fatty acids, and the like. Suitable surfactants have an HLB value ranging from about 0 to about 20. In some embodiments, the HLB value is from about 3.5 to about 6. As will be understood by those skilled in the art, HLB is the hydrophilic-lipophilic balance of an emulsifier or surfactant and is a measure of the degree to which a surfactant is hydrophilic or lipophilic. HLB values ​​can be determined by calculating values ​​for different regions of the molecule, as explained in Griffin in Griffin, William C. (1949), "Classification of Surface-Active Agents by 'HLB'" (PDF), Journal of the Society of Cosmetic Chemists, 1(5):311-26, and Griffin, William C. (1954), "Calculation of HLB Values ​​of Non-Ionic Surfactants" (PDF), Journal of the Society of Cosmetic Chemists, 5(4):249-56, and Davies in Davies JT (1957), "A quantitative kinetic theory of emulsion type, I. Physical chemistry of the emulsifying agent" (PDF), Gas / Liquid and Liquid / Liquid Interface, Proceedings of the International Congress of Surface Activity, pp. 426-38.HLB values ​​can be determined according to the industry standard textbook, "The HLB SYTEM, a time-saving guide to emulsifier selection," ICI Americas Inc., published 1976 and revised March 1980.

[0215] Examples of suitable surfactants are generally polyoxyethylene-sorbitan-fatty acid esters, such as mono- and trilauryl esters, palmityl esters, stearyl esters, and oleyl esters, for example, the type of products known as polysorbates and sold under the trade name Tween®, polyoxyethylene fatty acid esters, for example, polyoxyethylene stearates of the type known and sold under the trade name Myrj®, polyoxyethylene ethers such as those available under the trade name Brij®, polyoxyethylene castor oil derivatives, for example, the type known and sold under the trade name Cremophors®, Examples of surfactants include, but are not limited to, sorbitan fatty acid esters of the type commercially known as Span® (e.g., Span 80), polyoxyethylene-polyoxypropylene copolymers such as those commercially known as Pluronic® or Poloxamer®, glycerol triacetate, and monoglycerides and acetylated monoglycerides such as glycerol monodicocoate (Imwitor® 928), glycerol monocaprylate (Imwitor® 308), and monoacetylated and diacetylated monoglycerides. In some embodiments, the one or more surfactants comprise commercially available polymeric polyester-polyol surfactants of the type known under the trade name Hypermer® (Croda Industrial Chemicals, Edison, NJ, USA).

[0216] In some embodiments, the one or more surfactants include Tween 20, Tween 80, Span 20, Span 40, Span 60, Span 80, or a combination thereof. In some embodiments, the surfactant is Span 20, Tween 80, or a mixture thereof. In some embodiments, the one or more surfactants is Hypermer® B246SF. In some embodiments, the one or more surfactants is Hypermer® A70.

[0217] The concentration of the surfactant may vary, in some embodiments, the surfactant, or mixture of surfactants, is present in the medium in an amount of about 1 to about 5% by weight, such as about 1, about 2, about 3, about 4, or about 5%.

[0218] In some embodiments, a low-viscosity solvent is added. In some embodiments, the low-viscosity solvent is a C1-C3 alcohol. In some embodiments, the low-viscosity solvent is ethanol. When utilized, the low-viscosity solvent (e.g., ethanol) is added to the mixture of droplets and dispersion medium after gelation. In some embodiments, the addition produces smaller beads and reduces aggregation of large groups of beads. The amount and method of addition of the low-viscosity solvent may vary. In some embodiments, the low-viscosity solvent is added in a single portion in an amount up to about 10% by volume of the medium. In some embodiments, the low-viscosity solvent is added in two or more portions, including a first portion up to about 10% by volume of the medium and one or more additional portions, where the total amount of low-viscosity solvent added is up to about 50% by volume of the medium. In some embodiments, the low-viscosity solvent is added sequentially, where the total amount of low-viscosity solvent added is up to about 50% by volume of the medium.

[0219] The process further includes removing the organogel beads from the carrier fluid, such as silicone oil. The organogel beads are filtered from the carrier fluid and then washed or rinsed with a hydrocarbon solvent, such as heptane, and / or an alcohol, such as ethanol, methanol, isopropanol, or a higher alcohol. The basic requirement for the rinse is that it can remove the carrier fluid (e.g., oil or silicone oil) without chemically reacting with the organogel, and that it be sufficiently volatile so that it can be easily removed from the organogel beads afterward.

[0220] The process of transferring gel-forming components into an organogel material can also include an aging step (also called curing) before performing liquid-phase extraction. Aging an organogel material after it reaches its gel point can further strengthen the gel framework by increasing the number of crosslinks within the network. The duration of gel aging can be adjusted to control various properties within the resulting aerogel material. This aging procedure can be useful in preventing potential volume loss and shrinkage during liquid-phase extraction. Aging can include maintaining the gel at rest for an extended period of time (prior to extraction), maintaining the gel at an elevated temperature, adding a crosslinking-promoting compound, or any combination of these. Preferred temperatures for aging are typically between about 10°C and about 200°C. Aging of the gel material typically continues until liquid-phase extraction of the wet gel material. In some embodiments, organogel beads are aged in ethanol.

[0221] The time for transitioning the gel-forming material into a gel material includes both the duration of initial gel formation (from the onset of gelation to the gel point) and the duration of any subsequent hardening and aging of the gel material prior to liquid-phase extraction (from the gel point to the onset of liquid-phase extraction). The total time for transitioning the gel-forming material into a gel material is typically between about 1 minute and several days, preferably about 30 hours or less, about 24 hours or less, about 15 hours or less, about 10 hours or less, about 6 hours or less, about 4 hours or less, about 2 hours or less, about 1 hour or less, about 30 minutes or less, or about 15 minutes or less.

[0222] The resulting organogel material can be washed with a suitable secondary solvent to replace the primary reaction solvent present in the wet gel. Such secondary solvents can be linear monohydric alcohols having one or more aliphatic carbon atoms, dihydric alcohols having two or more carbon atoms, branched alcohols, cyclic alcohols, alicyclic alcohols, aromatic alcohols, polyhydric alcohols, ethers, ketones, cyclic ethers, or derivatives thereof.

[0223] After removing the organogel beads from the dispersion medium, the gel beads can undergo an aging and rinsing process. In an exemplary embodiment, the first step involves rinsing the organogel beads with a solvent, such as ethanol or a hydrocarbon solvent, such as hexane or octane, under low vacuum filtration. The second step involves aging the organogel beads in a solvent, such as ethanol, at a temperature ranging from about 50°C to 70°C for about 24 to 48 hours. The aging fluid bath can be changed during the aging period, referred to herein as solvent exchange, to remove unreacted compounds and replace the sol-gel solvent, such as DMAC, with the aging solvent, such as ethanol.

[0224] After the aging step, the organogel beads typically cluster together as wet gel aggregates. These aggregates are dispersed, in an exemplary embodiment, by sonication in a solvent such as ethanol. For example, a probe sonicator can be used to disperse the aggregated beads. In certain embodiments, a decantation step can be used to remove fine, non-settled beads from the top of the bead suspension after sonication. The remaining bead suspension can then be diluted with more ethanol and sonicated again. The sonication, decantation, and dilution steps can be repeated until the majority of the organogel beads are dispersed. The dispersed beads can then be filtered to produce a wet cake of organogel beads. The wet cake of organogel beads is then dried according to embodiments disclosed herein.

[0225] The size of the wet gel beads can vary, in some embodiments, the wet gel beads have a size ranging from about 5 to 500 microns in diameter, such as from about 5, about 10, about 20, about 30, about 40, or about 50 microns in diameter to about 60, about 70, about 80, about 90, about 100, about 200, about 300, about 400, or about 500 microns in diameter.

[0226] While the methods of forming organogel beads and organogel-silicon composite beads disclosed herein above have been described with particular reference to imidizing polyamic acid organogel precursor materials with a dehydrating agent, other suitable methods of producing polyimide organogels and corresponding aerogels are described, for example, in U.S. Pat. No. 6,399,669 to Suzuki et al.; U.S. Pat. No. 9,745,198 to Leventis et al.; Leventis et al., Polyimide Aerogels by Ring-Opening Metathesis Polymerization (ROMP), Chem. Mater. 2011, 23, 8, 2250-2261; Leventis et al., Isocyanate-Derived Organic Aerogels: Polyureas, Polyimides, Polyamides, MRS Proceedings, 1306 (2011), Mrsf10-1306-bb03-01. doi:10.1557 / opl.2011.90, Chidambareswarapattar et al., One-step room-temperature synthesis of fibrous polyimide aerogels from anhydrides and isocyanates and conversion to isomorphic carbons, J. Mater.Chem., 2010, 20, 9666-9678, Guo et al., Polyimide Aerogels Cross-Linked through Amine Functionalized Polyoligomeric Silsesquioxane, ACS Appl.Mater.Interfaces 2011, 3, 546-552, Nguyen et al., Development of High Temperature, Flexible Polyimide Aerogels, American Chemical Society, Proceedings Publication 2011, Meador et al., Mechanically Strong, Flexible Polyimide Aerogels Cross-Linked with Aromatic Triamine, ACS Appl. Mater. Interfaces, 2012, 4 (2), pp 536-544; Meador et al., Polyimide Aerogels with Amide Cross-Links: A Low Cost Alternative for Mechanically Strong Polymer Aerogels, ACS Appl. Mater. Interfaces 2015, 7, 1240-1249; Pei et al., Preparation and Characterization of Highly Cross-Linked Polyimide Aerogels Based on Polyimide Containing Trimethoxysilane Side Groups, Langmuir 2014, 30, 13375-13383.

[0227] Furthermore, although the methods disclosed herein above are described with specific reference to polyamic acids as organogel precursor materials and corresponding polyimides as organogels, those skilled in the art will recognize that other suitable organogel precursor materials may be utilized in the present methods. Thus, gelation may be carried out under conditions appropriate for any particular organogel precursor. Examples of suitable organogels include, but are not limited to, resorcinol-formaldehyde (RF), phenol-formaldehyde (PF), polyamides, polyacrylates, polymethyl methacrylates, acrylate oligomers, polyoxyalkylenes, polyurethanes, polyphenols, polybutadiene, trialkoxysilyl-terminated polydimethylsiloxanes, polystyrene, polyacrylonitrile, polyfurfural, melamine-formaldehyde, cresol-formaldehyde, phenol-furfural, polyethers, polyols, polyisocyanates, polyhydroxybenzenes, polyvinyl alcohol dialdehyde, polycyanurates, polyacrylamides, various epoxies, agar, agarose, chitosan, and combinations and derivatives thereof. Precursors of any of these materials can be used to create and use the resulting materials. For example, organogel materials can be formed from synthetic polymer or biopolymer precursor materials. Synthetic polymers useful for forming organogels include phenolic resins, polymers formed from isocyanates or amines (e.g., the polyimide compositions disclosed herein), polyolefins, and conductive polymers. Phenolic resins suitable for forming organogels include phenol-formaldehyde (PF), resorcinol-formaldehyde (RF), polyurea-crosslinked RF, phloroglucinol-formaldehyde (FPOL), cresol-formaldehyde, phenol-furfural, resorcinol-furfural, phloroglucinol-furfural (PF), phloroglucinol-terephthalaldehyde (TPOL), polybenzoxazine (PBO), and melamine-formaldehyde (MF).Suitable isocyanates and amines for producing organogels include polyurethanes (PU), polyureas (PUA), polyimides (PI), and polyamides (PA). Suitable polyolefins for producing organogels include polydicyclopentadiene (PDCPD) and polyacrylonitrile (PAN). Suitable conductive polymers for producing organogels include polypyrrole (PPY). Benzimidazoles can also be used to produce organogels. Biopolymers such as polysaccharides or proteins can also be used to produce organogels. For example, suitable polysaccharides useful for producing organogels include cellulose, chitin, chitosan, starch, pectin, and alginates.

[0228] A non-limiting list of suitable organogel precursors, gelling catalysts, and corresponding aerogel material types is provided in Table 2 below. [Table 2] In some embodiments, porous carbon or porous carbon-silicon compositions in bead form are obtained from the pyrolysis of organogel beads (e.g., xerogels or aerogels) comprising RF, PF, cellulose, polyurea, polyurethane, alginate, or polyacrylonitrile.

[0229] Methods for forming aerogels and xerogels from organogels In some embodiments, the porous carbon or porous carbon-silicon composition in bead form comprises a carbon aerogel. In some embodiments, the porous carbon or porous carbon-silicon composition in bead form comprises a carbon xerogel. In other words, in some embodiments, an initial porous organogel or organogel-silicon composite (e.g., polyimide or polyimide-silicon) material described herein is converted to the corresponding aerogel or xerogel and then pyrolyzed to provide the corresponding carbon or carbon-silicon composite in the form of an aerogel bead composite or xerogel bead composite.

[0230] Once an organogel material (e.g., an organogel or organogel-silicon composite, such as polyimide or polyimide-silicon composite beads) has been formed and processed, the liquid phase of the organogel can then be at least partially extracted from the wet gel using extraction methods, including processing and extraction techniques, to form porous or highly porous materials, such as xerogel or aerogel beads. Among other factors, liquid phase extraction plays an important role in engineering aerogel properties, such as porosity and density, as well as related properties such as thermal conductivity.

[0231] In some embodiments, the method further includes converting an organogel, such as a polyimide or polyimide-silicon composition, obtained as described herein above into an organic aerogel or organic xerogel. Aerogels are generally obtained when a liquid phase is extracted from a gel in a manner that induces low shrinkage in the porous network and framework of the wet gel. Aerogels (e.g., polyimide aerogels) are typically formed by removing a liquid mobile phase from a wet organogel material at temperatures and pressures near or above the critical point of the liquid mobile phase. Upon reaching (near-critical) or surpassing (supercritical) the critical point (i.e., the system pressure and temperature are at or above the critical pressure and critical temperature, respectively), a new supercritical phase appears in a fluid distinct from the liquid or gas phase. The solvent can then be removed without introducing a liquid-gas interface, capillary pressure, or any of the associated mass transfer limitations typically associated with liquid-gas boundaries. Furthermore, the supercritical phase is generally more miscible with organic solvents and therefore has better extraction potential. Co-solvent and solvent exchanges are also used to optimize the supercritical fluid drying process.

[0232] If evaporation or extraction occurs below the supercritical point, capillary forces generated by evaporation of the liquid can cause shrinkage and pore collapse within the gel material. Maintaining the mobile phase near or above the critical pressure and temperature during the solvent extraction process reduces the adverse effects of such capillary forces. In certain embodiments of the present disclosure, the use of near-critical conditions just below the critical point of the solvent system allows for the production of aerogel materials or aerogel compositions with sufficiently low shrinkage, thus producing a commercially viable final product.

[0233] As described herein, the wet gel beads can be dried using various techniques to provide aerogel beads. In exemplary embodiments, the organogel beads can be dried at ambient pressure, subcritical conditions, or supercritical conditions.

[0234] Both room temperature and high pressure processes can be used to dry the beads at ambient pressure. In some embodiments, a slow ambient pressure drying process can be used in which the wet gel beads are spread in a thin layer and exposed to air in an open container for a period of time sufficient to remove the solvent from the beads, such as a period in the range of 24 to 36 hours. The thickness of the bead layer can range from about 5 mm to about 15 mm. The beads can optionally be manually agitated or fluffed during the drying process to prevent the beads from fusing together during the drying process.

[0235] The fluidized bed method can also be used for ambient temperature drying of gels. In an exemplary embodiment, a fritted funnel is fixed to the top of a filter flask, the wet cake or gel slurry is placed on the frit, the top of the funnel is covered with tissue, and compressed air is connected to the inlet of the filter flask and enters through the pores in the frit. The beads are maintained in the fluidized bed until the solvent is removed. The dry powder material can then be collected from the funnel.

[0236] In another embodiment, the organogel beads are dried by heating. For example, the gel beads can be heated in a convection oven. As another example, the gel beads can be spread in a layer and placed on a hot plate. The hot plate can be at a temperature of 50°C to about 100°C, and the beads are heated for a period ranging from about 2 minutes to about 5 minutes to evaporate most of the ethanol. After partial drying, the beads can be left at ambient temperature or heated at a temperature of 50°C to about 100°C for a period ranging from about 6 hours to about 12 hours at ambient temperature to completely dry. Without being bound by theory, the volatile solvent can act as a fluidizer or separator because the solvent quickly leaves the gel bead material, which leads to reduced bead clumping.

[0237] Organogel beads (e.g., polyimide or polyimide-silicone composite gel beads) dried at ambient conditions may be referred to as xerogel beads. An exemplary polyimide xerogel with a target density of about 0.05 g / cc may have a density of, for example, about 0.10 m 2 / g ~ approx. 1.10m 2 / g, approx. 0.10m 2 / g ~ approx. 1.00m 2 / g, approx. 0.10m 2 / g~approx.0.50m 2 / g, or approximately 0.10 m 2 / g~approx.0.20m 2 / g range, approximately 0.00m 2 / g ~ approx. 1.5m 2 / g.

[0238] Both supercritical and subcritical drying can be used to dry the beads. In an exemplary embodiment of supercritical drying, the beads are filtered, collected, and immobilized in a porous container with pores smaller than the size of the dried beads, e.g., 5 micron pores. The container with the beads can then be placed in a high-pressure vessel for extraction of the solvent using supercritical CO2. After removal of the solvent, e.g., ethanol, the container can be held above the critical point of CO2 for a period of time, e.g., about 30 minutes. After supercritical drying, the container is depressurized to atmospheric pressure.

[0239] In an exemplary embodiment of subcritical drying, gel beads are dried using liquid CO2 at room temperature at pressures ranging from about 800 psi to about 1200 psi. This operation is faster than supercritical drying; for example, ethanol can be extracted in about 15 minutes. Within the context of this disclosure, beads dried using subcritical drying are referred to as aerogel-like.

[0240] Several additional aerogel extraction techniques are known in the art, including a range of different approaches using supercritical fluids to dry aerogels and ambient drying techniques. For example, Kistler (J. Phys. Chem. (1932) 36: 52-64) describes a simple supercritical extraction process in which the gel solvent is maintained above its critical pressure and temperature, thereby reducing evaporation capillary forces and maintaining the structural integrity of the gel network. U.S. Patent No. 4,610,863 describes an extraction process in which the gel solvent is exchanged with liquid carbon dioxide, followed by extraction while the carbon dioxide is in a supercritical state. U.S. Patent No. 6,670,402 teaches extracting the liquid phase from the gel via rapid solvent exchange by injecting supercritical carbon dioxide (rather than liquid) into an extractor preheated and prepressurized to or beyond substantially supercritical conditions, thereby producing an aerogel. U.S. Patent No. 5,962,539 describes a process for obtaining aerogels from polymeric materials in sol-gel form in organic solvents by exchanging the organic solvent with a fluid having a critical temperature below the temperature of polymer decomposition and subjecting the fluid / sol-gel to supercritical extraction. U.S. Patent No. 6,315,971 discloses a process for producing gel compositions that involves drying a wet gel containing gel solids and a desiccant to remove the desiccant under conditions sufficiently dry to reduce gel shrinkage during drying. U.S. Patent No. 5,420,168 describes a process by which resorcinol / formaldehyde aerogels can be produced using a simple air-drying procedure. U.S. Patent No. 5,565,142 describes a drying technique in which the gel surface is modified to become stronger and more hydrophobic so that the gel framework and pores can resist collapse during ambient drying or subcritical extraction. Other examples of extracting liquid phases from gel materials are described in U.S. Patents Nos. 5,275,796 and 5,395,805.

[0241] One preferred embodiment for extracting the liquid phase from a wet gel uses supercritical carbon dioxide conditions, including, for example, first substantially exchanging the primary solvent present in the gel's pore network with liquid carbon dioxide, then heating the wet gel (typically in an autoclave) above the critical temperature of carbon dioxide (approximately 31.06°C) and increasing the system pressure to above the critical pressure of carbon dioxide (approximately 1070 psig). The pressure surrounding the gel material can be slightly varied to facilitate the removal of the supercritical carbon dioxide fluid from the gel. The carbon dioxide can be recirculated through the extraction system to facilitate the continued removal of the primary solvent from the wet gel. Finally, the temperature and pressure are slowly returned to ambient conditions to produce a dry aerogel material. The carbon dioxide can also be pretreated to a supercritical state before being injected into the extraction chamber. In other embodiments, extraction can be performed using any suitable mechanism, such as varying the pressure, timing, and solvent as described above.

[0242] In certain embodiments of the present disclosure, the dried polyimide aerogel composition may be heated for 3 hours or more, between 10 seconds and 3 hours, between 10 seconds and 2 hours, between 10 seconds and 1 hour, between 10 seconds and 45 minutes, between 10 seconds and 30 minutes, between 10 seconds and 15 minutes, between 10 seconds and 5 minutes, between 10 seconds and 1 minute, between 1 minute and 3 hours, between 1 minute and 1 hour, between 1 minute and 45 minutes, between 1 minute and 30 minutes, between 1 minute and 15 minutes, between 1 minute and 5 minutes, or between 10 and 3 hours. , may be subjected to one or more heat treatments for durations ranging from 10 minutes to 1 hour, between 10 minutes and 45 minutes, between 10 minutes and 30 minutes, between 10 minutes and 15 minutes, between 30 minutes and 3 hours, between 30 minutes and 1 hour, between 30 minutes and 45 minutes, between 45 minutes and 3 hours, between 45 minutes and 90 minutes, between 45 minutes and 60 minutes, between 1 hour and 3 hours, between 1 hour and 2 hours, between 1 hour and 90 minutes, or between any two of these values.

[0243] Methods for forming porous carbon and porous carbon-silicon compositions from organogels Provided herein are porous carbon compositions and porous carbon-silicon compositions, which may also be referred to as nanoporous carbon materials and silicon-doped nanoporous carbon materials, respectively. Such compositions may be in the form of xerogel beads or aerogel beads. Organogel beads, such as the polyimide gel beads disclosed herein, may be converted to carbon materials. In some embodiments, a dried xerogel or aerogel (e.g., a polyimide xerogel or aerogel) disclosed herein may be pyrolyzed (i.e., carbonized), meaning that the xerogel or aerogel (e.g., a polyimide xerogel or aerogel) is heated to a temperature and for a time sufficient to convert substantially all of the organic material to carbon. The required time and temperature may vary. In some embodiments, the dried organic aerogel or organic xerogel is subjected to a processing temperature of 400°C or greater, 600°C or greater, 800°C or greater, 1000°C or greater, 1200°C or greater, 1400°C or greater, 1600°C or greater, 1800°C or greater, 2000°C or greater, 2200°C or greater, 2400°C or greater, 2600°C or greater, 2800°C or greater, or a range between any two of these values, for carbonization of the aerogel or xerogel. Without being bound by theory, it is contemplated herein that the electrical conductivity of the aerogel composition increases with carbonization temperature.

[0244] Carbon xerogels and carbon aerogels according to exemplary embodiments of the present disclosure, such as polyimide-derived carbon aerogels, can have a residual nitrogen content. For example, carbon aerogels according to embodiments disclosed herein can have a residual nitrogen content of at least about 0.1 wt%, at least about 0.5 wt%, at least about 1 wt%, at least about 2 wt%, at least about 3 wt%, at least about 4 wt%, at least about 5 wt%, at least about 6 wt%, at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt%, or a range between any two of these values.

[0245] Alternative methods for forming porous carbon-silicon compositions As disclosed herein above, in some embodiments, silicon (e.g., silicon particles) is introduced into the carbon-silicon composite material prior to or during gelation of the corresponding organogel precursor, such as a polyamic acid. Alternatively, silicon may be grown, infiltrated, deposited, or otherwise formed within the organogel or carbon material described herein (e.g., organogel or organogel-derived carbon xerogel or carbon aerogel).

[0246] In an alternative exemplary embodiment, silicon is generated within the pores of a carbon material (or a precursor material thereto, such as an organogel material) by exposing the material to elevated temperatures in the presence of a silicon-containing gas, preferably silane (SiH), to achieve silicon deposition / infiltration by a process such as chemical vapor deposition (CVD) or chemical vapor infiltration (CVI). In some embodiments, silicon can be co-deposited or co-infiltrated simultaneously with, or alternatively sequentially with, other electroactive materials. For example, silicon and tin can be deposited or infiltrated simultaneously or alternatively sequentially into a material. As another example, silicon and germanium, or an alloy of silicon and germanium, can be deposited or infiltrated simultaneously or alternatively sequentially into a material.

[0247] Silane gas can be mixed with other inert gases, such as nitrogen gas. The temperature and time of the treatment can vary; for example, the temperature can be 300-400°C, such as 400-500°C, 500-600°C, 600-700°C, 700-800°C, or 800-900°C. The gas mixture can include 0.1-1% silane and the remainder an inert gas. Alternatively, the gas mixture can include 1%-10% silane and the remainder an inert gas. Alternatively, the gas mixture can include 10%-20% silane and the remainder an inert gas. Alternatively, the gas mixture can include 20%-50% silane and the remainder an inert gas. Alternatively, the gas mixture can include more than 50% silane and the remainder an inert gas. Alternatively, the gas can be essentially 100% silane gas. The reactor in which the CVD process is carried out can be of various designs known in the art, such as a fluidized bed reactor, static bed reactor, elevator furnace, rotary furnace, box furnace, or other suitable reactor type. As known in the art, reactor materials are suitable for this task. In a preferred embodiment, the carbon material is processed under conditions that provide uniform access to the gas phase, for example, in a reactor in which the particles of the carbon material are fluidized or otherwise agitated to provide said uniform gas access.

[0248] In some embodiments, the CVD process is a plasma-enhanced chemical vapor deposition (PECVD) process. This process is known in the art to be useful for depositing thin films on substrates from a gaseous (vapor) to a solid state. The process involves a chemical reaction that occurs after the generation of a plasma of a reactive gas. The plasma is typically generated by a radio frequency (RF, i.e., AC) or DC discharge between two electrodes, filling the space between them with the reactive gas. In certain embodiments, the PECVD process is utilized to coat porous carbon on a suitable substrate, such as a copper foil substrate. PECVD can be performed at various temperatures, e.g., 300-800°C, e.g., 300-600°C, e.g., 300-500°C, e.g., 300-400°C, e.g., 350°C. The power can be varied, e.g., 25W RF, the silane gas flow rate required for the process can be varied, and the process time can be varied as known in the art.

[0249] CVD / CVI is generally accomplished by exposing a carbon material or its precursor to elevated temperatures for a period of time in the presence of a suitable deposition gas containing carbon atoms. Suitable gases in this context include, but are not limited to, methane, propane, butane, cyclohexane, ethane, propylene, and acetylene. The temperature can vary, for example, from 350 to 1050°C, e.g., 350-450°C, e.g., 450-550°C, e.g., 550-650°C, e.g., 650-750°C, e.g., 750-850°C, e.g., 850-950°C, e.g., 950-1050°C. The deposition time can vary, for example, from 0 to 5 minutes, e.g., from 5 to 15 minutes, e.g., from 15 to 30 minutes, e.g., from 30 to 60 minutes, e.g., from 60 to 120 minutes, e.g., from 120 to 240 minutes. In some embodiments, the deposition time exceeds 240 minutes. In certain embodiments, the deposition gas is methane and the deposition temperature is 950° C. or greater. In certain embodiments, the deposition gas is propane and the deposition temperature is 750° C. or less. In certain embodiments, the deposition gas is cyclohexane and the deposition temperature is 800° C. or greater.

[0250] In certain embodiments, the reactor itself can be agitated to agitate the particles of the carbon material for silicon impregnation. For example, the impregnation process can be carried out in a static mode in which the particles are not agitated, and the silicon-containing reactant flows over, around, or otherwise contacts the particles to be coated. In another exemplary mode, the particles can be fluidized; for example, impregnation with the silicon-containing reactant can be carried out in a fluidized bed reactor. A variety of different reactor designs can be used in this context, including, but not limited to, elevator furnaces, roller hearth kilns, rotary furnaces, box furnaces, and modified fluidized bed designs, as are known in the art. Excess or scrap silicon produced from the processes disclosed herein, i.e., silicon not deposited within the carbon material, can be isolated and recycled as input material.

[0251] Properties of porous carbon and porous carbon-silicon composites As described hereinabove, the porous carbon and porous carbon-silicon compositions (e.g., silicon-doped nanoporous carbon materials) of the present disclosure may be in the form of xerogel or aerogel beads. The properties of the porous particulate carbon-silicon compositions may vary depending on the particular combination of variables utilized in their production, as described hereinabove.

[0252] The diameter of the particles (i.e., beads) can vary. For example, in some embodiments, beads of porous carbon or porous carbon-silicon compositions have diameters ranging from about 1 micrometer to about 50 micrometers, such as about 1 micrometer, about 2 micrometers, about 3 micrometers, about 4 micrometers, about 5 micrometers, about 6 micrometers, about 7 micrometers, about 8 micrometers, about 9 micrometers, about 10 micrometers, about 15 micrometers, about 20 micrometers, about 25 micrometers, about 30 micrometers, about 35 micrometers, about 40 micrometers, about 45 micrometers, about 50 micrometers, or a range between any two of these values. In certain embodiments, beads have diameters ranging from about 1 to about 15 μm. In some embodiments, beads have a particle size D10 ranging from about 5 to about 15 μm, or from about 5 to about 10 μm. In some embodiments, beads have a particle size D50 ranging from about 5 to about 25 μm, or from about 10 to about 15 μm. In some embodiments, the beads have a particle size D90 ranging from about 15 to about 35 μm, or from about 10 to about 20 μm.

[0253] The density of the beads may vary. In some embodiments, the beads have a density of about 0.2 g / cm 3 ~Approx. 1.5g / cm 3 , or about 0.3 to about 1.3 g / cm 3 The tap density ranges from 0.1 to 1.0.

[0254] In some embodiments, the porous carbon-silicon composition has a pore structure that includes a fibrous morphology and an array of pores surrounding elemental silicon. In some embodiments, the elemental silicon resides at least partially within the pore structure of the carbon. Within the context of this disclosure, the term "fibrous morphology" refers to a structural morphology of nanoporous carbon (e.g., aerogel) that includes struts, rods, fibers, or filaments. For example, in one embodiment, the choice of solvent, such as dimethylacetamide (DMAC), can affect the formation of such morphologies. Furthermore, in certain embodiments, when carbon aerogels are derived from polyimides, crystalline polyimides result from polyimides that form linear polymers. As will be demonstrated in the examples below, it has been surprisingly observed that certain embodiments include a fibrous morphology as an interconnected polymer structure, where long linear structures were expected based on the known behavior of polyimide precursors. In comparison, the product morphology of nanoporous carbon (e.g., porous carbon or porous carbon-silicon composite) may instead be particulate or powder in nature, while the fibrous morphology of the carbon aerogel persists. As will become clear as this specification continues, the fibrous morphology can offer certain advantages over the particulate morphology, such as mechanical stability / strength and electrical conductivity, especially when nanoporous carbon is implemented in certain applications, such as anode materials in lithium-ion batteries (LIBs). It should be noted that this fibrous morphology is present in both monolithic and powder forms of nanoporous carbon; in other words, monolithic carbon can have a fibrous morphology, and aerogel powders / particles / beads can have a fibrous morphology. Furthermore, in certain embodiments, when a nanoporous carbon material includes an additive, such as silicon, the inherent fibrous nanostructure of the carbon material is preserved and acts as a bridge between the additive particles. Furthermore, in certain embodiments, when a nanoporous carbon material includes an additive, such as silicon or other additives, the inherent fibrous nanostructure of the carbon material is maintained and acts as a bridge between the additive particles.

[0255] As described herein above, in some embodiments, the porous carbon composition further comprises silicon. The amount of silicon (e.g., elemental silicon) present in the composition (e.g., carbon-silicon composite aerogel beads) can vary. In some embodiments, the porous carbon-silicon composition comprises greater than about 10 wt.% silicon. In some embodiments, the composition comprises about 25 wt.% to 65 wt.% silicon based on the weight of the carbon material. In some embodiments, the composition comprises about 25, about 30, about 35, about 40, about 45, about 50, about 55, about 60, or about 65 wt.% silicon.

[0256] The particle size of the silicon (e.g., elemental silicon) present in the composition can vary. In some embodiments, the silicon has a particle size less than about 150 nm. In some embodiments, the silicon has a particle size ranging from about 150 nm to about 500 nm. In some embodiments, the silicon has a particle size greater than about 500 nm.

[0257] In some embodiments, the porous carbon-silicon composition in bead form comprises silicon in the range of about 25 to about 65 wt %, the silicon having a particle size in the range of about 100 nm to about 800 nm, and the porous carbon-silicon composition beads have a density of about 0.2 g / cm 3 ~Approx. 1.5g / cm 3 a tap density in the range of about 1 μm to about 15 μm, a bead diameter in the range of about 10 nm to about 50 nm, and an average pore size in the range of about 0 to about 500 nm. 2 / g.

[0258] Electrode materials and energy storage devices comprising porous carbon or porous carbon-silicon compositions In certain embodiments, the present invention involves the formation and use of nanoporous carbon-based scaffolds or structures, such as carbon or carbon-silicon aerogels, as electrode materials in energy storage devices, such as primary anode materials in LIBs. The pores of the nanoporous scaffold are designed, organized, and structured to accommodate silicon or other semimetallic or metallic particles and the expansion of such particles upon lithiation, for example, in LIBs. Alternatively, the pores of the nanoporous scaffold can be filled with sulfides, hydrides, any suitable polymer, or other additives where it is advantageous to contact the additive with the conductive material (i.e., the scaffold / aerogel) to provide a more effective electrode. A general process for utilizing silicon-doped carbon aerogels in battery applications can be seen in Figure 1.

[0259] To further expand on the exemplary applications in LIBs, when carbon aerogel materials are utilized as primary anode materials, as in certain embodiments of the present invention, the aerogel nanoporous structure has a narrow pore size distribution, high electrical conductivity, high mechanical strength, and a morphology and sufficient pore volume (at final density) to accommodate a high weight percent of silicon particles and their expansion. Structurally, certain embodiments of the present invention have, among other properties, the narrow pore size distribution, high pore volume, and strut-sized fiber morphology described above, which results in enhanced connectivity.

[0260] In additional or alternative embodiments, the carbon aerogel itself functions as a current collector due to its electrical conductivity and mechanical strength, thus eliminating the need for a separate current collector on the anode side (when the anode is formed from carbon aerogel) in preferred embodiments. Note that in conventional LIBs, copper foil is bonded to the anode as its current collector. However, removing one or both of these components, depending on the carbon aerogel application, provides additional space for more electrode material, resulting in greater capacity for the cell / individual electrodes and greater overall energy density for the packaged battery system. However, in certain embodiments, existing current collectors may be integrated with the anode materials of various other embodiments to enhance the current collection capability or capacity of copper or aluminum foil.

[0261] In certain embodiments, nanoporous carbon-based scaffolds or structures, particularly carbon aerogels described herein, can be used as conductive networks or current collectors on the anode side of energy storage devices. The fully interconnected carbon aerogel network is filled with electrochemically active species, which are in direct contact with or physically connected to the carbon network. The loading of the electrochemically active species is tuned with respect to pore volume and porosity for high and stable capacity and improved safety of the energy storage device. When utilized on the anode side, the electrochemically active species can include, for example, silicon, graphite, lithium, or other metalloids or metals. In yet another embodiment, the anode can include nanoporous carbon-based scaffolds or structures, particularly carbon aerogel beads disclosed herein.

[0262] In the context of the present disclosure, the term "collectorless" refers to the absence of a separate current collector directly connected to the electrode. As noted, in conventional LIBs, copper foil is typically bonded to the anode as its current collector. Electrodes formed from nanoporous carbon-based scaffolds or structures (e.g., carbon aerogels or carbon-silicon composite aerogels described herein), according to embodiments of the present invention, may be freestanding or otherwise capable of being collectorless, as the scaffold or structure itself acts as a current collector due to its high electrical conductivity. Collectorless electrodes can be connected to form circuits within an electrochemical cell by embedding a solid mesh woven tab in the solution step that creates the continuous porous carbon, or by soldering, welding, or metal-depositing leads onto a portion of the porous carbon surface. Other mechanisms for contacting the carbon with the rest of the system are also contemplated herein. In alternative embodiments, the nanoporous carbon-based scaffolds or structures, and particularly the carbon aerogels, may be disposed on or otherwise communicate with a dedicated current collecting substrate (e.g., copper foil, aluminum foil, etc.). In this situation, the carbon aerogel can be attached to a solid current collector using a conductive adhesive and applied with varying amounts of pressure.

[0263] Additionally, it is contemplated herein that the nanoporous carbon-based scaffold or structure, and particularly the carbon aerogels described herein, can take the form of a monolithic structure. When essentially monolithic, the carbon aerogel eliminates the need for a binder. In other words, the anode can be binder-free. As used herein, the term "monolithic" refers to an aerogel material in which the majority (by weight) of the aerogel contained in the aerogel material or aerogel composition is in the form of a single, continuous, interconnected aerogel nanostructure. Monolithic aerogel materials include aerogel materials that are initially formed to have a single, interconnected gel or aerogel nanostructure, but can later be cracked, fractured, or split into non-single aerogel nanostructures. Monolithic aerogels can take the form of freestanding or reinforced (fiber or foam) materials. By comparison, using the lithiation of silicon as an example, silicon incorporated into monolithic aerogels can be more efficiently utilized in terms of theoretical capacity compared to the same amount of silicon incorporated into a slurry using conventional processes (see Figure 2).

[0264] Monolithic aerogel materials are distinguished from particulate (e.g., bead) aerogel materials. The term "particulate aerogel material" refers to an aerogel material in which the majority (by weight) of the aerogel particles contained in the aerogel material are in the form of particulates, particles, granules, beads, or powders that may be bound together (i.e., by a binder, such as a polymer binder) but lack interconnected aerogel nanostructures between individual particles. Collectively, aerogel materials in this form are referred to as having a powder, particulate, or bead morphology (as opposed to a monolithic morphology). Note that despite the individual particles of the powder having a unitary structure, the individual particles are not considered monoliths herein. Integration of aerogel powder into an electrochemical cell typically involves preparing a paste or slurry from the powder, pouring it onto a substrate, and drying, which may optionally include calendering.

[0265] Particulate aerogel materials, such as aerogel beads, offer certain advantages. For example, particulate materials according to embodiments disclosed herein can be used as a direct replacement for other materials, such as graphite, in LIB anodes and anode manufacturing processes. Particulate materials according to embodiments disclosed herein can also provide improved lithium ion diffusion rates due to shorter diffusion paths within the particulate material. Particulate materials according to embodiments disclosed herein can also enable electrodes with optimized packing densities, for example, by tailoring particle size and packing arrangement. Particulate materials according to embodiments disclosed herein can also provide improved silicon access due to inter- and intra-particle porosity.

[0266] Within the context of this disclosure, the terms "binder-free" or "binder-free" (or derivatives thereof) refer to a material that is substantially free of binders or adhesives to hold the material together. For example, a monolithic nanoporous carbon material does not contain a binder because its framework is formed as a single, continuous, interconnected structure. Advantages of being binder-free include avoiding any binder effects, such as on electrical conductivity and pore volume. On the other hand, aerogel particles require a binder to hold them together to form larger, functional materials. Such larger materials are not contemplated as monoliths herein. Furthermore, the term "binder-free" does not exclude all use of binders. For example, a monolithic aerogel according to the present invention may be secured to another monolithic aerogel or non-aerogel material by placing a binder or adhesive on a major surface of the aerogel material. In this manner, a binder is used to create a laminated composite material, but the binder does not function to maintain the stability of the monolithic aerogel framework itself.

[0267] Furthermore, the monolithic polymer aerogel materials or compositions of the present disclosure can be compressed to strains of up to 95% without significant destruction or fracture of the aerogel framework, while increasing the density of the aerogel and minimizing porosity. In certain embodiments, the compressed polymer aerogel materials or compositions are subsequently carbonized using various methods described herein to form nanoporous carbon materials. As will become more apparent as the present specification continues, it will be understood that the amount of compression affects the thickness of the resulting carbon material, which in turn affects its capacity. The examples described below illustrate various thicknesses formed and contemplated by the present invention, which can be adjusted based on compression. Thus, the thickness of the composite material (typically compressed) may be approximately 10 to 1000 micrometers, or any narrower range therein, depending on the benefits desired for the final composite. The present invention also contemplates powder or particulate forms of carbon aerogel, where a binder is required and particle size may be optimized. The particle (e.g., bead) diameter range can be approximately 1 to 50 micrometers.

[0268] In one embodiment, the invention is an anode for a LIB comprising a silicon-doped polyimide-derived carbon aerogel disclosed herein, wherein the silicon particles are at least partially contained within the pores of the carbon aerogel. The general reaction and process for developing a polyimide-derived carbon aerogel (i.e., without silicon) can be seen in FIG. 3 and further described with reference to FIG. 49B. As can be seen, the structure of the carbon aerogel pores can be tailored to have different properties (e.g., pore volume, pore size distribution) based on the needs (e.g., the size or capacity of the electrode in the LIB). In another embodiment, the invention is an electrode in a LIB or electrochemical cell thereof comprising such an anode. In yet a further embodiment, the invention is an apparatus or system incorporating such an energy storage device. Examples include, but are not limited to, electric vehicles and electronic devices (e.g., mobile devices and drones).

[0269] In certain embodiments, the present invention is a method for forming or producing a continuous porous carbon-silicon composite material, such as a carbon aerogel. Polyimide precursors, such as a diamine and a dianhydride, each of which may contain aromatic and / or aliphatic groups, are mixed in a suitable solvent (e.g., a polar aprotic solvent). Silicon particles are mixed with the polyimide precursor in the solvent before adding an imidization gelation catalyst. The imidization gelation catalyst is then added to initiate the mixing for gelation. Such an embodiment is described herein above with respect to bead formation.

[0270] In alternative embodiments, imidization can be achieved by thermal imidization, with any suitable temperature and time range being contemplated (e.g., about 100-200°C for about 20 minutes to about 8 hours, followed by heating at about 300-400°C for about 20 minutes to about 1 hour). The gelled mixture is then dried to produce a continuous porous polyimide silicone composite; drying can be performed using subcritical and / or supercritical carbon dioxide. Optionally, the polyimide silicone composite can be compressed, preferably uniaxially (e.g., up to 95% strain), to increase its density, which can be adjusted up to 1.5 g / cc based on the amount of compression. In an exemplary embodiment, the polyimide silicone composite can be compressed to greater than about 80% strain before pyrolyzing the composite. Regardless of whether compression occurs, the polyimide silicone composite is pyrolyzed to produce a continuous porous carbon-silicon composite, with the resulting composite containing greater than 0% and less than about 95% silicon by weight and about 5% to 99% porosity. In certain embodiments, pyrolysis can be carried out at a maximum temperature of about 750°C to about 1600°C, optionally with graphitization from about 1600°C up to about 3000°C.

[0271] In certain embodiments, the carbon-silicon composite material may be a monolith or a free-standing structure, prepared on or off a substrate, pulverized into a grain powder form, or prepared as a particulate material, such as, for example, beads. Furthermore, the composite material may be reinforced with or without a nonwoven or woven material (e.g., fiber, foam, etc.). Optionally, the composite material may be pre-doped with a metal or metal oxide, including, but not limited to, tin, sulfur, phosphorus, nickel, cobalt, manganese, lithium, magnesium, iron, zinc, boron, titanium, aluminum oxide, titanium oxide, niobium oxide, molybdenum oxide, silica, and aluminosilicates. Furthermore, the silicon particles may be pre-doped with p-type acceptors (e.g., boron, aluminum, gallium, and indium) or n-type donors (e.g., phosphorus, lithium, arsenic, antimony, bismuth).

[0272] In an alternative embodiment, the above methodology can be utilized to form or manufacture porous carbon-silicon composite materials, with the exception that rather than a silicon precursor being mixed into a mixture of polyimide precursors in a solvent, a silicate (e.g., silicon dioxide, aluminosilicate, and / or halloysite) and a reducing agent (e.g., magnesium, lithium, sodium, potassium, aluminum, calcium, or a combination thereof) are mixed into a mixture of polyimide precursors in a solvent. Upon drying, a continuous porous polyimide-silicate and reducing agent composite is formed, which can optionally be compressed to adjust density. In this case (i.e., when a silicate and reducing agent are used), the silicate and reducing agent react to form silicon in situ within the carbon composite material under inert conditions with hydrogen gas at temperatures above about 700°C.

[0273] In a further alternative embodiment, the above methodology can be utilized, with the exception that rather than adding silicon or silicate plus a reducing agent to a polyimide precursor, a continuous porous carbon can be formed first (i.e., imidization using a polyimide precursor, catalyst, or heat, drying, and pyrolysis), followed by deposition of silicon onto or into the porous carbon. In this case, silicon is deposited by dip-coating the porous carbon in a silicon-forming silane precursor, followed by heating under inert conditions to decompose the silane and form a conformal silicon coating within the porous carbon. This dip process can be performed multiple times to increase the thickness and silicon content, up to about 95% by weight. In other embodiments, silicon can be deposited by atomic layer deposition or CVD.

[0274] Furthermore, it is contemplated herein that the pore size of the porous carbon composite material can be adjusted as needed. There are five main ways to adjust the pore size taught herein. First, the solids content, specifically the amount of polyimide precursor monomers (e.g., aromatic or aliphatic diamines and aromatic or aliphatic dianhydrides), can adjust the pore size. A larger amount of solids per unit volume of fluid results in smaller pore sizes because there is less space available for closer interconnections to occur. Note that the strut width does not change appreciably, regardless of the amount of solids used. The amount of solids has a significant bearing on how dense the network will be.

[0275] Another method for tailoring pore size is to use radiation (e.g., radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays) on the composite in either the polyimide or carbon state. Radiation has an oxidative effect, resulting in an increase in surface area, an increase in pore size, and a broadening of the pore size distribution. Third, pore size is affected by macroscopic compression of the polyimide composite. As demonstrated in the examples below, pore size decreases with compression.

[0276] Yet another method for adjusting pore size is ion bombardment of the composite in either the polyimide or carbon state. The effect of ion bombardment depends on the method specified. For example, additive ion bombardment (e.g., CVD) can result in a reduction in pore size, while destructive ion bombardment can result in an increase in pore size. Finally, pore size can be adjusted (increased or decreased) by heat treatment in different gas environments, such as in the presence of carbon dioxide or carbon monoxide, chemically active environments, or hydrogen reduction environments. For example, a carbon dioxide environment is known to produce activated carbon; activation removes mass, enlarges pore size, and increases surface area.

[0277] While each of the above methods of adjusting pore size are contemplated, the present disclosure focuses more on the compaction of the converted solids (polyimide precursors) and polyimide composites prior to carbonization. [Example]

[0278] Example The following examples are set forth for illustrative purposes only and are not intended to limit the scope of various embodiments of the present invention in any way.

[0279] Example 1: Carbonized Polyimide (CPI) Composites with Low Levels of Doping A. CPI with 9% dopant dispersed in polyimide Polyimide (PI) gel was prepared from pyromellitic dianhydride (PMDA) and 1,4-phenylenediamine (PDA) in a 1:1 molar ratio in DMAC solvent with a target density of 0.06 g / cc. The precursors were mixed at room temperature for 3 hours, and then acetic anhydride (AA) was added to the PMDA in a 4.3:1 molar ratio and mixed with the solution for 2 hours. Powder dopants, such as graphite CNGT0112, approximately 40 nm thick and 400-600 nm long, and silicon BASIC005, with spherical particles approximately 30 nm in diameter, were obtained from ACS Materials. The solution was doped with graphite or silicon (Si) at 4.5% per total solids. The graphite was mixed with the solution for 10 minutes using a magnetic bar stirrer, and the doped mixture and imidization were catalyzed with pyridine (Py). The graphite was well dispersed based on visual evaluation. After stirring the silicone with the polyimide solution for 10 minutes, the dispersion was visually poor (i.e., evidence of settling and / or particle aggregation in the solution), and the mixture was sonicated for an additional 3 minutes. Once the dispersion quality improved, a pyridine catalyst was added to the mixture. The molar ratio of Py to PMDA was 4.0.

[0280] To prepare the PI composites, the solution was poured between glass plates with spacers at the edges to control thickness. Other suitable methods of pouring the solution are also contemplated herein. The spacers were made from 200-micrometer-thick aluminum foil. Monoliths approximately 2 inches in diameter were cast in Teflon containers. The gelation time at ambient temperature was approximately 11.5 minutes for the graphite-doped sample and approximately 15.5 minutes for the silicon-doped sample. The gels were cured overnight at room temperature and subsequently exchanged three times with ethanol at 68°C before supercritical CO2 extraction. The PI aerogel composites were compressed to thicknesses ranging from approximately 250 micrometers and pyrolyzed at 1050°C for 2 hours under an inert atmosphere for carbonization to form CPI composites. The dopant % in CPI was calculated to be approximately 9% based on the amount of dopant in the formulation and the weight of the composite retained after pyrolysis.

[0281] The densities of the compressed CPI composites with thicknesses of approximately 80 to 50 micrometers ranged from approximately 0.24 to 0.36 g / cc (Table 3 and Figure 4). [Table 3]

[0282] Porosity was calculated based on the actual density and skeletal density of the CPI composites. Because the density of amorphous carbon ranges from approximately 2.0 to 2.3 g / cc, and the density of silicon or graphite is approximately 2.3 g / cc, the skeletal density used in these calculations was approximately 2.2 g / cc for all composites. High porosity values ​​of 84 to 89% were calculated for these low-density composites.

[0283] B. CPI dispersed in a solvent with 9% dopant by mixing. Similar experiments were performed using a solution with a target density of 0.10 g / cc polyimide. In this case, the dopant was mixed with a portion of DMAC for 10 minutes and added to the mixture before catalysis. A 500-micrometer-thick Teflon spacer was used for casting. The molar ratio of Py to PMDA was 2.0. The gelation time was approximately 2.5 minutes for the graphite-doped sample and approximately 4.0 minutes for the silicon-doped sample. The gel was extracted using supercritical CO2. PI aerogel composites were compressed to various thicknesses, starting from approximately 580 micrometers, and pyrolyzed at 1050 °C for 2 hours for carbonization to form CPI composites.

[0284] The properties of the CPI composites are shown in Table 4. As expected, the more compacted composites exhibited slightly lower porosity. [Table 4]

[0285] The densities of the compressed CPI composites (approximately 115–80 micrometers thick) ranged from approximately 0.57–0.87 g / cc. Silicon-doped CPI composites had slightly lower densities compared to the graphite-doped samples (Figure 5).

[0286] The density and shrinkage of the doped PI aerogel monoliths after pyrolysis are shown in Table 5. The densities of the uncompressed monoliths (LS1 and LG1) were lower compared to the densities of the compressed composites (LS2 and LG2). [Table 5]

[0287] SEM images of the silicon-doped post-pyrolysis composite are shown in Figures 6A-6B. Note that Figure 6B shows the fibrous morphology of the silicon-doped CPI composite. Pockets of silicon aggregates and silicon nanowires were embedded in the carbon matrix. The anode discharge capacity per dopant content from half-cell battery tests is shown in Figure 7. Silicon provided significantly higher initial capacity compared to the graphite dopant. Although the initial capacity decreased with cycling, its reversible capacity was still dramatically higher than that of graphite alone, as in conventional anodes. Furthermore, the capacity decline is likely due to the foil electrode used in these half-cell battery tests, which was unable to operate at the high capacity of the silicon-containing electrode.

[0288] Example 2: CPI composites with high PI solids and high levels of silicon doping A. 27% silicon-doped CPI dispersed in solvent by ultrasonication Polyimide gels were prepared using a target density of 0.10 g / cc. PMDA precursors and PDA precursors were mixed at room temperature for 3 hours. Separately, 30 nm particle size silicon powder was sonicated in DMAC solvent for 20 seconds and added to the mixture at 15.0% total solids and stirred for 15 minutes. AA was added to the doped mixture at a molar ratio of 4.3 to PMDA and mixed for 2 hours. The mixture was catalyzed using pyridine at a molar ratio of 2.0 to PMDA. The composite was cast between glass plates using 500 micrometer thick Teflon spacers. 2-inch diameter monoliths were also cast in Teflon containers. The gelation time at ambient temperature was approximately 3.5 minutes. The gel was cured overnight at room temperature and subsequently ethanol-exchanged three times at 68°C before supercritical CO2 extraction. The PI aerogel composites were compressed and pyrolyzed at 1050 °C for 2 h for carbonization to form CPI composites.

[0289] B. 46% and 64% silicon-doped CPI dispersed in solvent by ultrasonication Polyimide gels were prepared with a target density of 0.08 g / cc. The PMDA and PDA precursors were mixed at room temperature for 4 hours. AA was then added and mixed with the solution for 2 hours. Separately, 30 nm silicon powder was sonicated in DMAC solvent for 1 minute and added to the mixture 5 minutes before the addition of the pyridine catalyst. The silicon was added at approximately 29.7% and 49.6% total solids. The doped mixture was catalyzed using a 3.2 molar ratio of Py to PMDA. The composites were cast using a 500 micrometer thick spacer. The gelation time at ambient temperature was approximately 6.5 minutes. After processing and extraction, the PI aerogel composites were compacted and pyrolyzed at 1050 °C for 2 hours for carbonization to form CPI composites.

[0290] A comparison of the surface area and porosimetry of pyrolyzed, uncompacted monoliths doped with different amounts of silicon is shown in Table 6 and Figure 8. The surface area, micropore area, and pore volume decreased with increasing silicon content in the CPI. [Table 6]

[0291] The pore size distribution at the maximum peak depended on the silicon content and how dispersed the silicon was (Figure 9). In general, increasing the silicon content shifted the pore size distribution from the dispersion to the maximum peak toward larger sizes. As the Si content increased from about 9% to about 46% and about 64%, respectively, a shift in the main peak in the maximum size distribution was observed from about 23 nm to about 26 nm and about 34 nm. The basic pore size distribution became broader with increasing silicon content.

[0292] However, when comparing the Td 0.10 g / cc samples, the 27% Si monoliths prepared by adding silicon before AA and mixing with the solution for a longer time showed a shift in the pore size of the main peak to approximately 15 nm, compared to approximately 23 nm for the 9% Si monoliths prepared by mixing with the solution for a shorter time. The 27% Si content doped sample showed a bimodal pore size distribution, with another small, broad band centered around 30 nm. This was likely due to incomplete dispersion of the silicon in the high target density, high viscosity mixture. This was also true for the higher silicon content samples in this series (64%), which also showed a bimodal pore size distribution.

[0293] The compressed, pyrolyzed composites had higher densities, smaller surface areas, and pore volumes compared to their uncompressed monolith counterparts (Table 7). Densities were calculated as the average of six (6) samples. [Table 7]

[0294] Half-cell units (2032 coin cells) were constructed using the CPI composite as an electrode, lithium foil as a counter electrode, and CELGARD 2500 as a microporous separator between the electrodes. The electrolyte was 1.0 M LiPF6 in EC:EMC (3:7) by weight. Unless otherwise noted, all cells were tested in an ARBIN BT2043 tester and at a charge / discharge rate of 0.1 C. The discharge capacities of the compressed CPI composite at the fifth cycle are shown in Table 8. [Table 8]

[0295] The optimum performance of these samples was obtained at a Si content of 30–50% per CPI, as shown in Figure 10 .

[0296] SEM images of the composites doped with high Si content are shown in Figures 11A-11C, which also show the fibrous morphology of the composites. The silicon (light areas) is more compacted in the samples with higher doping levels. Si nanowires can be observed in all samples at high magnification. As can be seen, there is direct contact and interpenetration between the silicon and the carbon porous structure (dark areas).

[0297] The cycling capacities based on Si and electrode content are shown in Figures 12A-12F, along with the raw data found in Table 9. Increasing the Si loading of the CPI composites resulted in a faster capacity loss with cycling. That said, the capacity loss is likely due to the foil electrode used in these half-cell battery tests, which was unable to operate at the high capacity of silicon-containing electrodes. [Table 9]

[0298] As seen in Table 9, silicon utilization can be calculated to be about 20% to about 90%, or even more optimally about 50% to about 90%, depending on the amount of silicon incorporated into the electrode. Narrower ranges are also contemplated herein based on the desired benefit (e.g., desired amount of silicon) in the final composite. Overall, this broader range is significantly higher than that seen in the prior art. Furthermore, capacity at cycle 10 is seen to vary based on silicon concentration, but is beneficial to be about 800 mAh / g or greater.

[0299] Example 3: Silicon-doped CPI composite with low PI solids A. 66% silicon-doped CPI dispersed in solvent by ultrasonication Polyimide gel was prepared with a target density of 0.05 g / cc. The PMDA and PDA precursors were mixed at room temperature for 3 hours. AA was then added and mixed with the solution for 2 hours. Separately, silicon powder with a particle size of approximately 30 nm was sonicated in DMAC solvent for 2 minutes and added to the mixture 30 minutes before the addition of the pyridine catalyst. The silicon was added at approximately 60.5% total solids. The Py / PMDA molar ratio was 7.5. The gelation time at ambient temperature was approximately 5.5 minutes. The composite was cast using a 500-micrometer-thick spacer. After processing and extraction, the PI aerogel composite was compressed and pyrolyzed at 1050 °C for 2 hours for carbonization to form the CPI composite. The Si content per CPI was 66%.

[0300] The CPI composites compressed to different thicknesses were examined by SEM, as shown in Figures 16A-16B, which show the fibrous morphology of the CPI composites. No silicon nanowires were observed in these images. The properties of the less compressed (LC) and more compressed (MC) composites tested in half-cell batteries are shown in Table 10. [Table 10]

[0301] Figures 14A-14B show that thickness played a role in anode performance. By reducing the thickness by approximately half, the electrode capacity essentially doubled, with the 170-micrometer-thick electrode demonstrating a discharge capacity of over 1500 mAh / g after the fourth cycle. While these high-capacity CPI composites loaded with high amounts of silicon (66%) were not stable over multiple cycles, the capacity decline was likely due to the foil electrode used in these half-cell battery tests, which prevented the electrode from operating at the high capacity of the silicon-containing electrode.

[0302] B. 45% silicon-doped CPI dispersed by mixing in solvent with and without dispersant. Polyimide gels were prepared with a target density of 0.05 g / cc. The PMDA and PDA precursors were mixed at room temperature for 17 hours. AA was then added and mixed with the solution for 3 hours. Separately, 30 nm particle size silicon powder was mixed in DMAC solvent with or without a dispersant for 20 hours. A control sample, C45, was prepared without a dispersant. BYK384 was used as a dispersant at 20 wt% per silicon weight in sample B45. Pluronic F87 was used as a non-ionic surfactant at 20 wt% per silicon weight in sample P45. The dispersant was added to the mixture 30 minutes before the addition of the pyridine catalyst. Silicon was added at 27.3% per total solids. The Py / PMDA molar ratio was 7.0. The gel time at ambient temperature was approximately 11 minutes. The composites were cast using a 500 micrometer thick spacer. After treatment and extraction, the PI aerogel composite was compressed and pyrolyzed at 1050 °C for 2 h for carbonization to form a CPI composite. The Si content per CPI was 45%.

[0303] SEM images of the compressed C45 polyimide composites before and after pyrolysis are shown in Figures 15A-15B, with Figure 15B also showing the fiber morphology of the CPI composites. Si nanowires were not visible in the non-pyrolyzed composites, only in the CPI. SEM images of the CPI composites with and without dispersant are shown in Figures 16A-16C. The properties of the CPI composites submitted for battery testing are shown in Table 11. Conductivities of approximately 26-27 S / cm were obtained for these samples. [Table 11]

[0304] The results of half-cell battery tests showed that the P45 composite had a higher discharge capacity and lower irreversible capacity loss compared to the other two samples (Figures 17A-17C). The capacity loss was likely due to the foil electrode used in these half-cell battery tests, which was unable to operate at the high capacity of the silicon-containing electrode.

[0305] Composites of the P45 formulation were cast at three (3) thicknesses: 780 microns, 580 microns, and 370 microns. Each of these PI batches was compressed at three (3) different levels using a hydraulic press and then divided into approximately 0.5 x 0.5 square inch composite pieces that were pyrolyzed. The results are shown in Table 12 and Figure 18. [Table 12]

[0306] The density of the Si-doped CPI composites varied between 0.3 and 1.0 g / cc at thicknesses of approximately 50 to 130 micrometers (Figure 18). The density increased as the initial thickness of the PI composites increased. The porosity ranged from approximately 50 to 90%.

[0307] Conductivity of Silicon-Doped CPI Composites. The conductivity of CPI composites doped with various levels of silicon and pyrolyzed at 1050°C was measured using a Keithley four-point probe apparatus. The conductivity of the samples varied from about 5 to 80 S / cm (Table 13). The conductivity of the undoped carbon composite was expected to be about 13.6 S / cm, which is within the expected range for amorphous carbon, as known in the art. The reported conductivity of silicon is 1.6 x 10 -5 S / cm, whereas silicon nanowires can exhibit three orders of magnitude higher conductivity (0.03 S / cm) (Sabar D. Hutagalung, Mohammed M. Fadhali, Raed A. Areshi, and Fui D. Tan, "Optical and Electrical Characteristics of Silicon Nanowires Prepared by Electroless Etching," Nanoscale Research Letters, 2017, 12:425). [Table 13]

[0308] Generally, conductivity increased with increasing density. However, at silicon concentrations above 60%, conductivity was lower than expected (Figure 19). At this high silicon content, the carbon network connectivity was disrupted, resulting in decreased conductivity. The sample doped with 27 wt% Si per CPI exhibited the highest conductivity, suggesting optimal silicon dispersion for high conductivity. A broader optimal range is found between about 5 wt% and about 80 wt% Si per CPI, or more specifically, between about 5 wt% and 50 wt% Si per CPI. Tables 11 and 13 show that varying the silicon content can adjust the conductivity up to about 80 S / cm. Thus, conductivity can exceed about 5 S / cm, 10 S / cm, 15 S / cm, 25 S / cm, 50 S / cm, and 75 S / cm, and it is contemplated that a wider range and more precise conductivity can be adjusted based on the silicon content.

[0309] Example 4: Carbonized polyimide aerogel with high pore volume and narrow pore size distribution Polyimide gels are prepared by reacting 6 g of PMDA and 3 g of PDA to form polyamic acid in 100 mL of DMAC at room temperature for 2–24 hours. Subsequently, 8.86 g of AA is added to the polyamic acid solution as a chemical imidization reagent (see Figure 20). The acidified polyamide solution is vigorously mixed for at least 2 hours. The resulting mixture is diluted with DMAC to the desired target density of the PI aerogel. 1–4 g of Py per 100 mL of mixture is added to the final solution to promote gelation, which occurs in 4–25 minutes. Prior to gelation, the mixture is cast into the desired form (e.g., membrane, monolith, reinforcing fiber, etc.). The resulting gel is then aged in an oven at 65–70 °C and washed / rinsed with ethanol several times before supercritical drying. The PI aerogel is converted to carbon aerogel by pyrolysis at 1,050 °C for 2 hours in an inert environment (nitrogen gas flow). Without being bound by theory, the physical and structural properties of the carbonized PI aerogel depend on the precursor mixing time and the amount of Py.

[0310] The structural properties of four CPI aerogels tested by nitrogen adsorption-desorption technique are reported in Table 14. The four samples differ in mixing time and amount of Py. The target density was fixed at 0.05 g / cc. Interestingly, all samples exhibit relatively similar surface BET, but the pore size distribution and pore volume appear to be affected by the synthesis parameters. [Table 14]

[0311] Example 5: Si-loaded carbonized polyimide aerogels Silicon particles (30 nm) were added to polyamic acid solutions at various concentrations. The synthesis of the solutions was the same as that described in Example 4. However, for this composite system (PI / Si), the silicon particles were first dispersed in DMAC for at least 2 hours before mixing them with the polyamic acid solution. To avoid silicon sedimentation, the gelation time of the Si / polyamic acid solution was kept relatively short (4-6 minutes). Therefore, 4 g of pyridine per 100 mL of mixture was used to achieve the target gelation time. Prior to gelation, the mixture was cast into the desired form (e.g., membrane, monolith, or reinforcing fiber). The resulting gel was then aged in an oven at 65-70 °C and washed / rinsed with ethanol several times before supercritical drying.

[0312] A. 22-25 wt% silicon in polyimide-carbon aerogel composites The target density of the composite was fixed at 0.06 g / cc, and the Si loading was approximately 11.88 wt% during the polymerization step. Since a loss of more than 50% was recorded in all samples, the silicon content was adjusted after pyrolysis of the polyimide aerogel at 1050 °C for 2 h. Four different thicknesses of composites were produced. MT (medium thickness composite material approx. 0.3~0.4mm) T (thick composite material approx. 0.6-0.8mm) MTC (medium thickness compression composite material, approximately 0.07-0.09 mm) TC (thick compressed composite material approximately 0.12-0.16mm)

[0313] Different PI / Si samples were pyrolyzed at 1050°C for 2 hours and battery tested. The physical properties of the samples are shown in Table 15. [Table 15]

[0314] An SEM image of the pyrolyzed composite material (MT material) doped with approximately 25% Si can be seen in Figure 23. The SEM image shows at high magnification the aggregation of Si and silicon nanowires embedded in the carbon matrix.

[0315] The cycling capacities of the MTC5 and MT5 samples based on Si and electrode content are shown in Figures 25A-25B. Cycling was performed up to 400 cycles for MTC5 (compressed CPI aerogel) and up to 150 cycles for MT5 (uncompressed CPI aerogel). The two samples exhibited different behaviors. As noted above, MTC5 exhibited a relatively stable capacity discharge up to 200 cycles, followed by a decrease in capacity, likely due to the foil electrode in the half-cell battery test.

[0316] B. 39 wt% silicon in polyimide-carbon aerogel composite In the next period of synthesis, the Si content was increased to 39 wt% in the hopes of reducing capacity loss during first discharge. Polyimide gels were prepared with a target density of 0.05 g / cc. Polyamic acid solutions were prepared by mixing PMDA and PDA precursors in DMAC over a 16-hour period. Separately, silicon powder was dispersed in DMAC for 2 hours and then added to the polyamic acid solution before adding pyridine. After adding pyridine, the composite was prepared between Teflon plates using a 500-micron spacer. The aerogel composite was compressed and pyrolyzed at 1050 °C for 2 hours. The silicon content was 39 wt% based on total solids.

[0317] The properties of the compressed (PISi1NC(C)) and uncompressed (PISi7NC) composites tested in half-cell batteries are shown in Table 16. [Table 16]

[0318] 26A-26B show the discharge capacity as a function of cycling for anodes made with the two materials reported in Table 16. A clear improvement in the discharge capacity of the anodes is noticeable when the silicon content is increased from 25 wt% (previous materials, i.e., MT5 and MTC5) to 39 wt%.

[0319] Example 6: Fiber-reinforced C / Si aerogel Different areal densities (2, 4, and 10 g / m 2 Three different carbon fiber reinforcements with different thicknesses (e.g., 1000 psi ...) were tested as reinforcements for C / Si aerogels. The synthesis and processing of PI / Si aerogels was the same as described previously, with one exception: during the gelation step, the mixture was poured into fibers. After supercritical drying, the carbon fiber-reinforced PI / Si composites were cut into 15 mm (inner diameter (ID)) circular samples using a die cutter and pyrolyzed at 1050 °C for 2 h. Figures 27-29 show the properties and micrographs of the carbonized PI / Si / carbon fiber samples.

[0320] After pyrolysis, 2g / m 2 and 4 g / m 2 The sample reinforced with 10 g / m of carbon fiber experienced significant shrinkage and stiffening of the carbon aerogel. Figures 28-29 show the high porosity that characterizes these two materials as particularly unsuitable for battery testing. In Figure 27, the 10 g / m 2 The carbon fiber-reinforced C / Si composites exhibited a better microstructure and showed no evidence of porosity, although the Si content was low (approximately 21%) and the fiber density was high (>30 wt%). The composites were tested for charge and discharge capacity within such systems. The cycling capacities of the samples shown in Figure 27 based on Si and electrode content are reported in Figure 30.

[0321] In another experiment, cellulose fibers were also tested as a reinforcement for C / Si. The synthesis route was the same as that used for carbon fibers. Cellulose fibers constitute 68% (by weight) of the C / Si composite, but much of this fiber is decomposed after pyrolysis, as the % of Si increased from 6% to 24% after pyrolysis. The physical properties of C / Si reinforced with cellulose fibers are shown in Table 17. [Table 17]

[0322] The cycling capacity of cellulose fiber reinforced C / Si based on Si and electrode content is shown in Figure 31. The performance of this material is similar to that seen with carbon fiber reinforced C / Si.

[0323] Example 7: Improving Silicon Dispersion in PI Aerogel Polyimide composite and monolith gels with a 47% silicon loading were prepared with a target density of 0.05 g / cc. To avoid clumping, a route was taken to better disperse the silicon within the polyimide matrix. Silicon was dispersed from the beginning of the solution synthesis and mixed with PMDA and PDA. The polyamic acid solution and silicon were mixed for 16 hours. Acetic anhydride was added and mixed with the solution for 4 hours. Rapid gelation (approximately 4 minutes) was ensured by adding an appropriate amount of PI to the acidified polyamide / Si mixture. Composites and thick monoliths approximately 200-300 microns thick were cast. After supercritical drying, the PI / Si aerogel composites were compacted and pyrolyzed at 1050°C for 2 hours.

[0324] Subsequently, several different samples (e.g., compressed, uncompressed, monolith, etc.) were analyzed by SEM to evaluate the silicon dispersion in the carbon matrix. Figure 32 shows three cross-sectional SEM images of a thick uncompressed composite (0.60 mm). At low magnification (left image), uniform and well-distributed silicon is evident. Large clusters of silicon are also visible. At higher magnification (right image), dense silicon is seen well embedded in the carbon matrix. Figure 33 shows three cross-sectional SEM images of a thin composite (0.12 mm). The same observations were made: good Si dispersion and adequate impregnation into the carbon matrix. The cross-sectional SEM image of the monolith (Figure 34) clearly confirms the same structure shown in the thick and thin composites.

[0325] Figures 35-36 show a side-by-side comparison of two C / Si composites processed by different methods. The left images (in both figures) are for monoliths and composites cast from Si / polyamic acid solutions mixed for 16 hours (long contact). The right images are for monoliths and composites made from Si / polyamic acid solutions mixed for 4-6 minutes (short contact). The silicon distribution is observed to be different for the two processes; long contact ensured better Si dispersion than short contact.

[0326] Half-cell tests were performed on the compressed and uncompressed C / Si composites. In both samples, PISi3 (uncompressed) and PISi6C (compressed), the Si was well dispersed within the carbon aerogel matrix. The physical properties of the two samples are reported in Table 18. [Table 18]

[0327] The charge-discharge cycling of the two samples is shown in Figures 37-38. The samples performed surprisingly well, with the compressed sample (PISi6C) showing stable cycling performance.

[0328] Example 8: Fabrication of C / Si circular electrodes In the previous example, the C / Si electrode is a square (approximately 1 cm 2 The battery performance was tested in a circular cell (ID=15 mm) in the form of a circular C / Si electrode. For higher efficiency and more reliable test results, a circular C / Si electrode needs to be tested. Therefore, a route to create a circular electrode using a die cutter was implemented.

[0329] PI aerogel composites were fabricated with a target density of 0.13 g / cc and a Si loading of 31.4% (using 16 hours of mixing). After extraction, the final aerogel density was measured to be approximately 0.213 g / cc. Using a die cutter, multiple circular aerogel composites with an ID of 15 mm were produced (see Figure 39). The sample thickness was approximately 0.43 mm. Some of the samples were compressed before pyrolysis at 1050°C for 2 hours. The pyrolyzed circular electrodes were characterized as follows: Weight loss: about 41% Uncompressed sample: approx. 0.261 g / cc (inner diameter 1.1 cm, thickness 0.38 mm) Compressed sample: approx. 0.652 g / cc (inner diameter 1.35 cm, thickness 0.11 mm)

[0330] Compressed and uncompressed half-cell battery performance is shown in Figures 40-41. The capacity of the uncompressed sample appears to be higher than the compressed sample, although the uncompressed sample also produced a more erratic capacity.

[0331] Example 9: Si-loaded carbonized phloroglucinol / formaldehyde (PF) aerogels Carbon aerogels made from PF are also contemplated herein for the fabrication of C / Si aerogel electrodes. For PF systems, high target density (>0.7 g / cc) aerogels can be achieved through synthetic routes. The resulting aerogels do not need to be compressed. A dense PF gel composite was fabricated as follows: Phloroglucinol (22 g) was dissolved in 100 mL of ethanol, and 44 mL of 2-furaldehyde was added to the phloroglucinol solution. The resulting solution was mixed for 30 minutes. 5 wt% silicon was added to the mixture and vigorously mixed for an additional 30 minutes. The PF mixture can be gelled with a base (diamine or triamine), and the gelation time is approximately 20–40 minutes, depending on the concentration of the base. In this case, and when silicon is present, the gelation time should be short (less than 1 minute) to avoid any precipitation of silicon during gelation. Hydrochloric acid (HCl) was used to catalyze the gelation of PF, resulting in a gelation time as short as 20 seconds. Therefore, a high concentration of HCl (0.012 g per 100 mL of mixture) was added to the mixture, mixed for 20 seconds, and cast between Teflon plates for gel fabrication. After aging and solvent exchange, the PF gel composite was dried with supercritical CO2. The resulting PF / Si aerogel had the following properties: Two thicknesses of composite material: approximately 0.2 mm and approximately 0.1 mm Final density of aerogel: approx. 0.7g / cc

[0332] After pyrolysis under inert gas at 1050 °C for 2 h, the resulting C / Si aerogel had a density of 0.77 g / cc and a regulated Si content of 10 wt%. Pre-cut samples (1 cm 2 ) (see Figure 42) was prepared.

[0333] The C / Si aerogel tested by liquid nitrogen adsorption-desorption showed a 541m 2The carbon aerogel composite samples exhibited a high surface area of ​​0.32 cc / g and a pore volume of 0.32 cc / g. Interestingly, the micropore area represented 80% of the total surface area, confirming the dense, compact structure shown in the SEM images (see Figure 43). Furthermore, carbon aerogel composite samples containing Si, where the carbon was derived from PF, exhibited high capacity loss after the first cycle and very low overall capacity (see Figure 44). These results highlight the unique properties of Si, which provides excellent performance in fibrous morphologies, such as those found in polyimide-derived nanoporous carbon / carbon aerogels.

[0334] Example 10: Nanoindentation as a measure of mechanical strength Using the methodology described above, multiple CPI composite samples were fabricated, and the variables within the samples included silicon content and density. The Young's modulus of each sample was measured using nanoindentation, which tests the hardness of the material. More specifically, twenty (20) indentations were made into the sample surface. Approximately 8-10 indentations were selected to obtain average data and standard deviations for each mechanical property. The indentation locations were selected under a microscope, and the surfaces were relatively clean and smooth, lacking many surface features, providing more reliable data. Samples 1 and 2 were softer than the other samples, so a maximum load of 50 mN was selected. For Samples 3-7, an indentation load of 300 mN was used. Results and other properties are shown in Table 20. Figure 45 shows the modulus as a function of density, and Figure 46 shows the modulus as a function of density. [Table 19]

[0335] Example 11: 45% Silicon Doped CPI Beads Polyimide gel beads were prepared with a target density of 0.10 g / cc. PMDA and PDA precursors were mixed with DMAC solvent for 3 hours at room temperature. AA was then added and mixed with the solution for 2 hours. Separately, 30 nm silicon powder was sonicated in DMAC solvent for 1 minute and added to the mixture 5 minutes before the addition of the pyridine catalyst. Silicon was added at approximately 24% total solids. The doped mixture was catalyzed using a 3.2 molar ratio of Py to PMDA. Prior to gelation, the catalyst-loaded sol containing silicon particles was poured into a stirred container of silicone oil (at a volume ratio of silicone oil to catalyst-loaded sol of 10:1) as a dispersant. The gelled PI beads were isolated from the silicone oil by filtration, subsequently rinsed with ethanol, and then dried by supercritical CO2 extraction. The PI aerosol-silicon composite beads were then pyrolyzed at 1050° C. for 2 hours to form CPI silicon composite beads with a tap density of 0.7 g / cc and D50=15 μm.

[0336] Example 12: Electrodes prepared from CPI beads An anode electrode was prepared using the CPI silicon composite beads prepared according to Example 11 on a Cu foil as a current collector with a slurry containing 80 wt. % CPI silicon composite beads, 10 wt. % polyacrylic acid (PAA) binder, and 10 wt. % hard carbon conductive additive (C65) mixed in water at approximately 36 wt. % total solids. The slurry was cast onto the Cu foil using a doctor blade. After drying and calendering, a 3.1 mg / cm2 concentration was obtained. 2 An electrode with a loading of 0.7 g / cc and a density of 0.7 g / cc was obtained.

[0337] Example 13: Half-cell units constructed from CPI electrodes Half-cell units (2032 coin cells) were constructed using the CPI composite electrodes prepared according to Example 12, with lithium foil as the counter electrode and CELGARD 2500 as the microporous separator between the electrodes. The electrolyte was 1.0 M LiPF in ethylene carbonate (EC) / ethyl methyl carbonate (EMC) (weight ratio 3:7) and 5 wt% fluoroethylene carbonate (FEC). All cells were tested in an ARBIN BT2043 tester. The protocol for testing the cells included four formation cycles at a charge / discharge rate of C / 20. Subsequent cycling occurred at various rates between C / 20 and 5C. Figure 48 shows the half-cell cycling performance of a CPI composite electrode containing 30 wt% silicon particles prepared as an electrode from a slurry containing 80 wt% CPI silicon composite beads, 10 wt% polyacrylic acid (PAA) binder, and 10 wt% hard carbon conductive additive (C65). The chart in Figure 48 shows the discharge capacity (mAh / g based on the total weight of the electrode) and coulombic efficiency versus cycle number in 1.0 M LiPF in ethylene carbonate (EC) / ethyl methyl carbonate (EMC) (3:7 wt ratio) and 5 wt% fluoroethylene carbonate (FEC).

[0338] Example 14: Low-density silicon-doped carbonized polyimide beads by standard precursor addition and low-shear bead processing Silicon-doped polyimide (PI) sol was prepared with a target density of 0.03-0.05 g / cc. Pyromellitic dianhydride (PMDA) and p-phenylenediamine (PDA) were mixed in a 1:1 molar ratio in dimethylacetamide (DMAC) solvent to obtain polyamic acid (PAA) sol. The PMDA precursor was stirred in DMAC at room temperature for 5-30 minutes, during which time complete dissolution occurred. PDA powder was added to the PMDA solution, and the mixture was stirred at room temperature for 2-17 hours. The process of adding diamine to dianhydride is called the standard addition process. Chemical imidization of polyamic acid to polyimide was carried out using acetic anhydride and pyridine. Acetic anhydride (AA) was added to the sol at a molar ratio of 4.3 to PMDA and mixed for 2-4 hours. Separately, 30 nm-sized silicon (Si) nanopowder from ACS Material was dispersed in DMAC for 1 minute using an ultrasonicator bath. A molar ratio of approximately 2:1 silicon to PMDA was used to dope the sol. The silicon dispersion was mixed with the sol for 5 to 30 minutes at room temperature. A pyridine (Py) catalyst was added to the sol at a molar ratio of Py to PMDA of 2.4 to 5.4. The catalyst was mixed with the sol for 2 minutes before pouring.

[0339] To prepare gel beads, the silicon-doped PI sol was poured into silicone oil with a viscosity of 10 cSt and stirred at 400 rpm using a magnetic rod or mechanical mixer. The volume ratio of silicone oil to sol was 10 / 1 or 20 / 1. A higher oil-to-sol ratio produced beads with less clumping and larger beads. Gelation occurred at room temperature for 20–45 minutes, and spherical, light brown beads emerged from the emulsion. The beads were stirred in the oil overnight at room temperature, decanted from the oil, and filtered through 20-micron filter paper. The beads were kept moist during filtration by washing with ethanol. The gel beads collected from the filter paper were placed in an ethanol bath, aged, and rinsed at 68°C for 1–3 days. After two hot ethanol rinses, the gel beads were filtered again and dried. Drying was carried out at ambient temperature for 1 day by spreading the gel beads in an open container and exposing them to air. Occasionally, the beads were agitated and manually fluffed with a spatula during the drying process.

[0340] After drying, the beads were placed in graphite crucibles and pyrolyzed in a CM box furnace under a nitrogen flow of 10-40 scfh. Most of the samples were pyrolyzed at 1050°C for 2 hours using a temperature ramp of 3°C / min. One sample was pyrolyzed up to 690°C using a temperature ramp of 3°C / min. These formulations targeted 10-35 wt% Si in the carbonized beads.

[0341] Example 15: Low-density silicon-doped carbonized polyimide beads by inverse precursor addition and low-shear bead processing A silicon-doped polyimide (PI) sol with a target density of 0.03 g / cc was prepared using the same precursors as in Example 14. After dissolving PDA in DMAC, PMDA powder was added to the solution. The process of adding a dianhydride to a diamine is called the reverse addition process. The viscosity of the sol increased significantly, much higher than that of the standard addition process. The mixture was stirred overnight at room temperature, and then acetic anhydride was added at a molar ratio of 4.3 to PMDA. After 3 hours, the sol was doped with 30 nm particle size silicon from ACS Materials. A silicon dispersion was prepared using a double asymmetric centrifugal mixer from FlackTek Inc. and 1 mm zirconia beads. An amount of silicon corresponding to a 2.0 molar ratio to PMDA was dispersed at 3000 rpm for 5 minutes at 40% by weight of the total DMAC amount. After mixing the resulting silicon dispersion with the sol for 1 minute, pyridine catalyst was added at a molar ratio of 5.4 to PMDA.

[0342] The silicon-doped PI sol was poured into silicone oil of 10 cSt viscosity and stirred at 400 rpm using a mechanical mixer. The gelation time was 21 minutes at room temperature, approximately twice as fast as the control formulation prepared by the standard addition process. The gel beads were processed as in Example 14. After drying, the xerogel beads were pyrolyzed up to 690°C under nitrogen using a heating rate of 3°C / min. The PI beads lost 39% weight after pyrolysis. These formulations targeted 30% Si by weight in the carbonized beads.

[0343] Example 16: Low-density silicon-doped carbonized polyimide beads by standard precursor addition and high-shear bead processing Silicon-doped polyimide (PI) sols were prepared using a standard addition process from the same precursors as in Example 14, with a target density of 0.05 g / cc. The PMDA precursor was stirred in DMAC for 30 minutes at room temperature, during which time complete dissolution occurred. The mixing time is critical to the outcome of the process. Mixing PMDA in DMAC for less than 30 minutes resulted in higher sol viscosity and larger bead size. PDA was added to the dianhydride solution in DMAC and stirred at room temperature for 2 to 17 hours. The resulting polyamic acid sol was chemically imidized with acetic anhydride (4.3 mole ratio relative to PMDA) and pyridine (4.2 to 8.1 mole ratio relative to PMDA).

[0344] Various silicon sources and particle sizes were used to dope the PI beads. 30 nm polycrystalline silicon from ACS Materials was dispersed in DMAC solvent either by bath sonication for 1 hour or by using a FlackTek mixer at 2500-3000 rpm for 5 minutes. Zirconia beads with 1 mm or 2 mm diameter were used at a weight ratio of 5-20% to the weight of Si. Amorphous silicon (VP Si a) from Evonik with a particle size D50 of 230 nm was dispersed in polyamic acid sol for 5 minutes using a FlackTek mixer.

[0345] Polycrystalline silicon from Silrec with particle sizes between 1 and 5 microns was prepared by different milling methods. Using an Across International high-energy ball mill, the particle size of Silrec Si was reduced to approximately 500 nm. A FlackTek mixer was also used to reduce the particle size of Si in DMAC by operating with zirconia beads for times ranging from approximately 20 to approximately 60 minutes. This method reduced the particle size to approximately 700 to 1000 nm. In another embodiment, Si was milled in ethanol using a FlackTek mixer and ceramic media, then dried and redispersed in DMAC using the same FlackTek process. In these embodiments, the Si particles had a particle size of approximately 760 nm.

[0346] The Si particle dispersion prepared as described above was mixed with PAA sol for 2–20 min at room temperature. After chemical imidization with acetic anhydride and pyridine, the sol was stirred for 1–2 min and slowly poured into a stirred oil bath. The silicone oil had a viscosity of 10 or 100 cSt, and the volume ratio of oil to PAA sol was 5 / 1 or 10 / 1. The higher the oil viscosity and the lower the sol viscosity, the smaller the beads produced. Although the 5 / 1 oil-to-sol ratio resulted in some bead aggregation, this was preferable compared to the 10 / 1 ratio for scaling purposes and for easier separation of the beads from the oil.

[0347] The oil bath containing the PAA sol was stirred at high shear using a Ross mixer at 3800–9400 rpm. Generally, the higher the shear, the smaller the beads. The high shear caused the oil temperature to rise rapidly to 50–70°C over 5–10 minutes. During this time, the bead droplets gelled and typically clustered together. Due to overheating, the total mixing time with the Ross mixer was generally less than 30 minutes. Ethanol was poured into the oil a few minutes after gelation and stirred for a few more minutes to minimize bead aggregation and clustering. The beads remained in the upper ethanol layer and could be separated from the oil. Separation by decantation or a separatory funnel was possible, especially for oils with a high viscosity of 100 cSt. After filtration through 20-micron filter paper and multiple washes with ethanol, the gel beads were placed in ethanol at 68°C for 1–2 days and then rinsed twice with ethanol at the same temperature.

[0348] Drying was carried out either at ambient pressure, leading to xerogels, or under supercritical CO2 conditions, leading to aerogels. Several methods were used for ambient drying: room temperature for 1–3 days with occasional stirring of the wet cake spread on a surface; heating in an oven at 110 °C in a closed container with a small vent for several hours; and finally, heating the wet cake spread on a hot plate at 100 °C for 2–5 minutes, followed by overnight drying at room temperature. A fluidized bed method was also used for ambient drying of gels. A fritted Büchner funnel was fixed on top of a filtering flask. The wet cake or gel slurry was placed on the frit, and the top of the funnel was covered with laboratory tissue. Compressed air connected to the filter flask inlet was passed through the pores of the frit. The beads were maintained in the fluidized bed until the volatiles were removed, and then the xerogel was recovered from the funnel. Yields of PI xerogel or aerogel beads of 75–96% were obtained.

[0349] After drying, the beads were placed in a graphite crucible and pyrolyzed in a box furnace at 1050 °C for 2 hours at a heating rate of 3 °C / min. The PI beads lost 42.47% of their weight after pyrolysis. The target Si content in the carbonized beads was 30%.

[0350] Example 17: Low-density silicon-doped carbonized polyimide beads by surfactant-mediated process Silicon-doped polyimide (PI) sols were prepared from the same precursors as in Example 14 using a standard additive process with the addition of surfactants to a target density of 0.05 g / cc. Generally, surfactants were added to reduce bead crowding during and after gelation while stirring in an oil bath and to modify the surface of the beads.

[0351] In one embodiment, cetyltrimethylammonium bromide (CTAB) surfactant was added to the sol at a concentration of 0.09 moles per mole of PMDA after the addition of acetic anhydride. The surfactant did not completely dissolve in the sol. One-micron-sized silicon particles from US Nano Research were previously sonicated in a portion of the total DMAC solvent and added to the CTAB / sol mixture. Silicon was added at 2.1 moles per mole of PMDA. After mixing with pyridine for 2 minutes, the sol was cast in an oil bath stirred at 6500 rpm using a Ross homogenizer. The oil was pre-cooled to 10°C, and the oil temperature was increased to 50°C for 7 minutes, during which gelation occurred. After separating from the oil, rinsing the beads, and treating them by aging them in ethanol at 68°C, the beads were sonicated in ethanol for 1 minute using a sonicator probe to disperse gel clusters. Drying of the beads was carried out in ambient air, as described in Example 16.

[0352] The PI xerogel beads lost 46% weight during pyrolysis at 1050°C. The target weight of Si in the pyrolyzed beads was 30 wt%. The tap density of the beads was 0.65 g / cc.

[0353] Example 18: High density silicon-doped carbonized polyimide beads by inverse precursor addition and high shear bead processing Aerogels with a target density of 0.02 g / cc were prepared by the reverse addition protocol, as shown in Example 15. The precursors were mixed for 17 hours, then acetic anhydride was added and mixed for 2.5 hours. 1-5 micron-sized Si powder from Silrec was first dry-milled in a FlackTek using zirconia beads and then dispersed with a portion of the PAA sol for 5 minutes using the same equipment at 2500 rpm. The Si dispersion (after removal of the zirconia beads by filtration) was mixed with the remaining sol, and pyridine catalyst was added at a molar ratio of 10.1 to PMDA. The mixture was stirred for 25 minutes before pouring.

[0354] The silicon-doped PI sol was slowly poured into silicone oil of 100 cSt viscosity and stirred at 6000 rpm using a Ross mixer. The beads gelled after 5 minutes in an oil bath at 50 °C. After stirring for an additional 2 minutes, the beads were decanted from the oil, washed three times with ethanol at room temperature, and then placed in ethanol at 68 °C for 1 day. The hot rinsing procedure was repeated three times using an 800 / 1 volume ratio of ethanol to gel beads. The beads filtered from the ethanol were exposed to air for 25 minutes to form a skin with lower porosity than the core. These beads were extracted using subcritical CO2 conditions. The resulting beads were approximately 200 m 2 / g, indicating that the beads were primarily aerogel-like.

[0355] The beads were pyrolyzed under nitrogen up to 1050°C using a heating rate of 3°C / min. The PI beads lost 40% weight after pyrolysis. The target weight of Si was 50% by weight in the carbonized beads. The tap density of the beads was 0.37 g / cc.

[0356] Example 19: High density silicon-doped carbonized polyimide beads by standard precursor addition Silicon-doped polyimide (PI) sol was prepared with a target density of 0.1 g / cc and a silicon loading of 60 wt%. PMDA precursor was dissolved in DMAC by stirring with a magnetic mixer for approximately 30 minutes. PDA was added to the PMDA solution in a 1:1 molar ratio of PDA to PMDA and stirred using a magnetic mixer at room temperature for 2-17 hours. The resulting polyamic acid sol was chemically imidized with acetic anhydride (4.3 mole ratio to PMDA) and mixed for 1-4 hours. Separately, 1-micron-sized silicon in a 9:1 molar ratio of silicon to PMDA was dispersed in a portion of the polyamic acid sol. In this example, 10 g of silicon was dispersed in 70 g of polyamic acid sol in the presence of 25 g of 1 mm and 0.25 mm zirconia beads in a 1:1 ratio to prevent clumping and provide silicon dispersion. The silicon dispersion was mixed with the sol for approximately 5 minutes using a Flackteck mixer at approximately 2500 rpm. The dispersed silicone solution was poured back into the mother liquor (the other part of the polyamic acid sol) and stirred for an additional 30-60 minutes using a magnetic mixer.

[0357] Pyridine (Py) catalyst was added to the sol at a molar ratio of Py to PMDA of 5:1. Py was mixed with the sol for approximately 1 minute under high shear mixing (using a Ross mixer) before pouring into silicone oil. Silicon oil (polydimethylsiloxane, 100 cSt) was used as the medium for bead gel formation, with a volume ratio of oil to sol of approximately 10:1. In this example, approximately 100 ml of catalyzed silicon-doped polyamic acid sol was poured into approximately 1000 ml of silicone oil mixed at approximately 9400 rpm. A suspension of gel beads began to form in approximately 2-3 minutes at approximately 9400 rpm and a temperature ranging from approximately 60-70°C. In comparison, the remaining sol in a separate, unmixed container gelled in approximately 7 minutes at room temperature. After gel bead formation, the mixture was maintained at high rpm (approximately 9400 rpm) for an additional 4-5 minutes.

[0358] The majority of the oil was decanted, and the gel beads were filtered from the remaining oil using 20-micron filter paper. The gel beads were rinsed with ethanol during filtration. The gel beads collected from the filter paper were placed in an ethanol bath, aged, and rinsed at 68°C for 1 to 3 days.

[0359] After completing the aging and rinsing process, the silicon-doped polyimide gel beads were filtered, collected, and secured in two layers of laboratory tissue. The tissue-protected gel beads were placed in a 5-micron filter bag before being loaded into a high-pressure vessel for subcritical drying. The silicon-doped polyimide gel beads were then dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in the vessel at pressures ranging from approximately 800 to 1200 psi for at least approximately 15 minutes. The vessel was then depressurized to atmospheric pressure. The resulting aerogel-like silicon-doped polyimide beads were less than approximately 70 microns in size and free of bead agglomerates or clusters.

[0360] The aerogel-like silicon-doped polyimide beads were carbonized at 1050°C under nitrogen flow for 2 hours. The physical and structural properties (surface area, pore size, and average pore size) of the silicon-doped carbonized polyimide beads are reported in Tables 21 and 22 below. [Table 20] [Table 21]

[0361] Example 20. C / Si composite beads prepared from polyimide in DMAC / silicone oil emulsion. 0 ppm water Carbon / Si composite beads containing 55 wt% silicon were prepared from polyimide with a target density of 0.085. Benzene-1,2,4,5-tetracarboxylic acid anhydride (pyromellitic dianhydride, PMDA, 8.30 g) was added to dimethylacetamide (97.6 mL, anhydrous). The mixture was heated at 35 °C until all solids dissolved, followed by stirring at room temperature for 30 minutes. Solid p-phenylenediamine (PDA, 4.1 g, 1 molar equivalent) was added to the solution, and the resulting mixture was stirred for 2 hours. Acetic anhydride (16.7 g, 4.3 molar equivalents) was added to the stirred solution, followed by stirring for 2 hours. Silicon particles (6.2 g) and 1 mm diameter zirconia beads (7 g) were dispersed in 12 g of the above sol by stirring at 2500 rpm for 2 minutes. After the zirconia media was removed by filtration, the Si suspension was added to the above sol, followed by stirring for 10 minutes.

[0362] Pyridine (10.8 mL, 8% by volume) was added to initiate gelation, forming a polyamic acid presol. After 1 minute, this presol was quickly poured into silicone oil (polydimethylsiloxane, 100 cSt, 650 mL) while stirring in a Ross mixer at 9000 rpm. Approximately 6 minutes after pyridine addition, gelation occurred, and 750 mL of ethanol was added, and the stirring speed was reduced to 7000 rpm. After stirring for an additional 2 minutes, the phases were separated, and the beads were isolated using a separatory funnel. The gel beads accumulated in the light ethanol phase, while the oil separated as the heavy phase. After filtration from the ethanol, the beads were mixed with heptane (150 mL) for approximately 10 minutes and then recovered by filtration. The heptane wash was repeated, followed by a wash with a mixture of 120 mL of heptane and 120 mL of ethanol. The resulting filter cake was stirred with 150 mL of ethanol for 15 minutes and left at room temperature overnight.

[0363] A portion of the polyimide / Si gel beads was dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in a container at a pressure ranging from about 800 to 1200 psi for at least about 15 minutes. The container was then depressurized to atmospheric pressure to provide the polyimide / Si aerogel beads. The polyimide / Si aerogel beads were then carbonized at 1050°C under a nitrogen stream for 2 hours to provide the C / Si aerogel beads (Example 20A). The properties of the aerogel beads are shown in Table 1 below. An SEM image showing the interior surface of the C / Si aerogel beads is provided in Figure 50.

[0364] Another portion of the beads was oven-dried at 68°C to give polyimide / Si xerogel beads, which were then carbonized at 1050°C under nitrogen flow for 2 hours to give C / Si xerogel beads (Example 20B).

[0365] Example 21. C / Si composite beads prepared from polyimide in DMAC / silicone oil emulsion. 716 ppm water Carbon / Si composite beads containing 35 wt% silicon were prepared from polyimide with a target density of 0.085. Water (0.07 g) and benzene-1,2,4,5-tetracarboxylic acid anhydride (pyromellitic dianhydride, PMDA, 8.30 g) were added to dimethylacetamide (88.5 mL, containing 237 ppm water), followed by stirring for 30 minutes. Solid p-phenylenediamine (PDA, 4.1 g, 1 molar equivalent) was added to the solution, and the mixture was stirred for 2 hours. Acetic anhydride (16.7 g, 4.3 molar equivalents) was added to the stirred solution, followed by stirring for 2 hours.

[0366] Separately, a silicone dispersion was prepared by suspending a silicone dispersion in isopropanol (71 wt%, 9.4 g) in dimethylacetamide (14.6 g). The mixture was heated at 120 °C with stirring until the isopropanol was completely evaporated (measured by a weight loss of 6.7 g, approximately 30 minutes). This silicone dispersion was added to the PDA / PMDA / acetic anhydride mixture. After approximately 5 minutes of stirring, pyridine (10.4 mL, 8 vol%) was added to initiate gelation, forming a polyamic acid presol. This presol was quickly poured into silicone oil (polydimethylsiloxane, 100 cSt, 650 mL, pre-cooled to 14 °C) while stirring in a Ross mixer at 9000 rpm. Approximately 5 minutes after the pyridine addition, 200 mL of ethanol was added. Approximately 9 minutes after the presol was added to the silicone oil, the temperature rose to approximately 65 °C and gelation occurred. The polyimide / Si bead suspension was transferred to a 2 L beaker, and ethanol (400 mL) was added, followed by stirring at 7000 rpm for 3 minutes. The phases were separated, and the beads were isolated by filtration. The beads were mixed with heptane (150 mL) for approximately 10 minutes and then collected by filtration. The heptane wash was repeated, followed by a wash with a mixture of 120 mL of heptane and 120 mL of ethanol. The resulting filter cake was stirred with 400 mL of ethanol for 30 minutes and left at room temperature overnight. This was followed by an additional ethanol exchange (400 mL, 3 hours at room temperature).

[0367] A portion of the polyimide / Si gel beads was dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in a container at a pressure ranging from about 800 to 1200 psi for at least about 15 minutes. The container was then depressurized to atmospheric pressure to provide the polyimide / Si aerogel beads. The polyimide / Si aerogel beads were then carbonized at 1050°C under a nitrogen stream for 2 hours to provide the C / Si aerogel beads (Example 21A). The properties of the aerogel beads are provided in Table 21 below. SEM images showing the exterior and interior surfaces of the C / Si aerogel beads are provided in Figures 51A and 51B, respectively.

[0368] Another portion of the beads was oven-dried at 68°C to give polyimide / Si xerogel beads. The polyimide / Si xerogel beads were then carbonized at 1050°C under a nitrogen flow for 2 hours to give C / Si xerogel beads (Example 21B). An SEM image of the C / Si xerogel beads is provided in Figure 52.

[0369] Example 22. C / Si composite beads prepared from polyimide in DMAC / petroleum spirits emulsion. 550 ppm water Carbon / Si composite gel beads containing 14 wt% silicon were prepared with a target density of 0.085. Water (0.07 g) and benzene-1,2,4,5-tetracarboxylic acid anhydride (pyromellitic dianhydride, PMDA, 8.30 g) were added to dimethylacetamide (104 mL, containing 145 ppm water), followed by stirring for 30 minutes. Solid p-phenylenediamine (PDA, 4.1 g, 1 molar equivalent) was added to the solution, and the mixture was stirred for 2 hours. To provide a polyamic acid sol, acetic anhydride (16.7 g, 4.3 molar equivalents) was added to the stirred solution, followed by stirring for 2 hours.

[0370] Separately, petroleum spirits (650 mL) was stirred with Hypermer A70® (13 g) at room temperature for 1 hour using a magnetic stir bar.

[0371] Silicon particles (2.74 g) and 1 mm diameter zirconia beads (4 g) were dispersed in 40 g of the sol by stirring at 2500 rpm for 5 minutes, and this suspension (after removal of the zirconia beads by filtration) was added to the sol, followed by stirring for 10 minutes.

[0372] Pyridine (10.4 mL, 8% by volume) was then added to the sol while stirring (4500 rpm), and the mixture was stirred for 50 seconds to initiate gelation of the sol. The sol was then quickly poured into the mineral spirits / surfactant mixture. Six minutes after the addition of pyridine, ethanol (150 mL) was added, followed by stirring at 5500 rpm for 3 minutes. Stirring was stopped, and the polyimide / Si gel bead suspension was allowed to stand for 30 minutes. The polyimide / Si gel beads were isolated by filtration and washed with 400 mL of ethanol. Three additional ethanol washes were performed. A micrograph of the resulting polyimide / Si gel beads is shown in Figure 53A.

[0373] A portion of the polyimide / Si gel beads was dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in a container at a pressure ranging from about 800 to 1200 psi for at least about 15 minutes. The container was then depressurized to atmospheric pressure to provide polyimide aerogel beads. The polyimide / Si aerogel beads were then carbonized at 1050°C under a nitrogen stream for 2 hours to provide C / Si aerogel beads (Example 22A). Properties of the aerogel and xerogel beads are provided in Table 23 below. SEM images showing the exterior and interior surfaces of the C / Si aerogel beads are provided in Figures 54A and 54B, respectively.

[0374] Another portion of the beads was oven-dried at 68°C to give polyimide / Si xerogel beads. The polyimide / Si xerogel beads were then carbonized at 1050°C under a nitrogen stream for 2 hours to give C / Si xerogel beads (Example 22B). SEM images of the C / Si xerogel beads are provided in Figure 55. Notably, as shown in Figure 55, fewer xerogel aggregates and larger bead sizes were obtained for the beads prepared according to Example 22 compared to those prepared according to Example 21 (Figure 52). SEM images showing the outer and inner surfaces of the C / Si xerogel beads are provided in Figures 56A and 56B, respectively. No BET surface area was detected for the xerogel prepared according to Example 22B.

[0375] Example 23. Polyimide / silicone composite beads prepared from polyimide in a surfactant-free DMAC / petroleum spirits emulsion. 550 ppm water Polyimide / Si composite gel beads containing 14 wt% silicon were prepared with a target density of 0.085 using the procedure in Example 22A, but without the presence of surfactant. Micrographs of the resulting polyimide / Si gel beads are provided in Figure 53B, which show bead sizes 2-5 times larger than those produced in the presence of surfactant (Figure 53A).

[0376] Example 24. Carbon beads prepared from polyimide in DMAC / mineral oil emulsion. 330 ppm water Carbon aerogel and xerogel beads were prepared from polyimide with a target density of 0.085. Benzene-1,2,4,5-tetracarboxylic acid anhydride (pyromellitic dianhydride, PMDA, 8.30 g) was added to dimethylacetamide (106.7 mL, containing 145 ppm water). The mixture was heated at 35 °C until all solids dissolved, followed by stirring at room temperature for 30 minutes. After stirring at room temperature for 28 minutes, water (0.042 g) was added to the mixture. Solid p-phenylenediamine (PDA, 4.1 g, 1 molar equivalent) was added to the solution, and the mixture was stirred for 2 hours. Acetic anhydride (16.7 g, 4.3 molar equivalents) was added to the stirred solution, followed by stirring for 2 hours. Pyridine (7.8 mL, 6% by volume) was added to initiate gelation, forming a polyamic acid presol. After stirring for 1 minute, the presol was quickly poured into mineral oil while stirring in a Ross mixer at 9000 rpm. Approximately 4.5 minutes after the pyridine addition, 100 mL of ethanol was added, and stirring was continued at 9000 rpm for an additional 2 minutes. Room-temperature gelation occurred 7.5 minutes after the pyridine addition. The polyimide gel bead suspension was transferred to a 2 L beaker, and ethanol (500 mL) was added, followed by stirring at 6500 rpm for 3 minutes. After stirring was stopped, the gel beads settled to the bottom of the beaker. The upper oil layer was removed, and the gel beads were rinsed three times with ethanol. The beads were mixed with ethanol (500 mL) for approximately 10 minutes and allowed to settle. After the ethanol was decanted, the beads were washed twice with heptane (150 mL). The gel was separated from the heptane phase by filtration.

[0377] A portion of the polyimide gel beads was dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in a container at a pressure ranging from about 800 to 1200 psi for at least about 15 minutes. The container was then depressurized to atmospheric pressure to provide polyimide aerogel beads. The polyimide aerogel beads were then carbonized at 1050°C under a nitrogen stream for 2 hours to provide carbon aerogel beads (Example 24A). Properties of the aerogel beads are provided in Table 23 below. SEM images showing the exterior and interior surfaces of the carbon aerogel beads are provided in Figures 57A and 57B, respectively.

[0378] Another portion of the polyimide gel beads was oven-dried at 68°C to provide polyimide xerogel beads. The polyimide xerogel beads were then carbonized at 1050°C under a nitrogen stream for 2 hours to provide the carbon xerogel beads described below (Example 24B). SEM images showing the exterior and interior surfaces of the carbon xerogel beads are provided in Figures 58A and 58B, respectively. [Table 22]

[0379] Example 25. C / Si composite beads prepared from polyimide in DMAC / mineral oil emulsion. 330 ppm water Carbon / Si composite beads containing 14 wt% silicon were prepared with a target density of 0.085. 8.30 g of benzene-1,2,4,5-tetracarboxylic acid anhydride (pyromellitic dianhydride, PMDA) was added to dimethylacetamide (106.7 mL, containing 145 ppm water). The mixture was heated at 35°C until all solids dissolved, followed by stirring at room temperature for 30 minutes. After stirring at room temperature for 28 minutes, water (0.042 g) was added to the mixture. Solid p-phenylenediamine (PDA, 4.1 g, 1 molar equivalent) was added to the solution, and the mixture was stirred for 2 hours. Acetic anhydride (16.7 g, 4.3 molar equivalents) was added to the stirred solution, followed by stirring for 2 hours.

[0380] Silicon particles (2.74 g) and 1 mm diameter zirconia beads (4 g) are dispersed in 40 g of the above sol by stirring at 2500 rpm for 5 minutes. The zirconia beads are used to break up silicon agglomerates (if present) and ensure better dispersion of the silicon within the sol. The suspension (after removal of the zirconia beads by filtration) is then added to the above sol, followed by stirring for 10 minutes.

[0381] Pyridine (7.8 mL, 6% by volume) was added to initiate gelation, forming a polyamic acid presol. After stirring for 1 minute, this presol was quickly poured into mineral oil while stirring in a Ross mixer at 9000 rpm. Approximately 4.5 minutes after pyridine addition, 100 mL of ethanol was added, and stirring was continued at 9000 rpm for an additional 2 minutes. The polyimide / Si gel bead suspension was transferred to a 2 L beaker, and ethanol (500 mL) was added, followed by stirring at 6500 rpm for 3 minutes. After stirring was stopped, the gel beads were allowed to settle to the bottom of the beaker. The upper oil layer was removed, and the gel beads were rinsed three times with ethanol. The beads were mixed with ethanol (500 mL) for approximately 10 minutes and allowed to settle. After decanting the ethanol, the beads were washed twice with heptane (150 mL). The gel was separated from the heptane phase by filtration.

[0382] A portion of the polyimide / Si gel beads is dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in a vessel at a pressure ranging from about 800 to 1200 psi for at least about 15 minutes. The vessel is then depressurized to atmospheric pressure to yield polyimide aerogel beads. The polyimide / Si aerogel beads are then carbonized at 1050°C under a nitrogen stream for 2 hours to yield C / Si aerogel beads.

[0383] Example 26. C / Si composite beads prepared from polyimide in DMAC / silicone oil emulsion. 0 ppm water Carbon / Si composite beads containing 35 wt% silicon were prepared from polyimide with a target density of 0.085. Benzene-1,2,4,5-tetracarboxylic acid anhydride (pyromellitic dianhydride, PMDA, 8.0 g) was added to dimethylacetamide (79.7 mL) followed by stirring for 30 minutes. Solid p-phenylenediamine (PDA, 4.0 g, 1 molar equivalent) was added to the solution, and the mixture was stirred for 2 hours. Acetic anhydride (16.1 g, 4.3 molar equivalents) was added to the stirred solution followed by stirring for 2 hours.

[0384] Separately, a silicone dispersion was prepared by suspending a silicone dispersion in isopropanol (71 wt%, 9.1 g) in dimethylacetamide (14.1 g). The mixture was heated at 120 °C with stirring until the isopropanol was completely evaporated (measured by a weight loss of 6.4 g, approximately 30 minutes). This silicone dispersion was added to the PDA / PMDA / acetic anhydride mixture. After approximately 5 minutes of stirring, pyridine (10.0 mL, 8% by volume) was added to initiate gelation, forming a polyamic acid presol. This presol was quickly poured into silicone oil (polydimethylsiloxane, 100 cSt, 625 mL) while stirring in a Ross mixer at 9000 rpm. Approximately 5 minutes after pyridine addition, room temperature gelation occurred, at which point 100 mL of ethanol was added, and stirring was continued for another minute. Ethanol (300 mL) was added, followed by stirring at 7000 rpm for 3 minutes. The phases were separated, and the beads were isolated by filtration. The beads were mixed with heptane (150 mL) for approximately 10 minutes and then collected by filtration. The heptane wash was repeated, followed by a wash with a mixture of 120 mL of heptane and 120 mL of ethanol. The resulting filter cake was stirred overnight in 300 mL of ethanol.

[0385] A portion of the polyimide / Si gel beads was dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in a vessel at a pressure ranging from approximately 800 to 1200 psi for at least approximately 15 minutes. The vessel was then depressurized to atmospheric pressure to give polyimide / Si aerogel beads. The polyimide / Si aerogel beads were then carbonized at 1050 °C under a nitrogen stream for 2 hours to give C / Si aerogel beads.

[0386] Example 27. C / Si composite beads prepared from polyimide in DMAC / silicone oil emulsion. 530 ppm water Carbon / Si composite beads containing 35 wt% silicon were prepared from polyimide with a target density of 0.085. To dimethylacetamide (63.8 mL), water (0.046 g) and benzene-1,2,4,5-tetracarboxylic acid anhydride (pyromellitic dianhydride, PMDA, 6.4 g) were added, followed by stirring for 30 minutes. Solid p-phenylenediamine (PDA, 3.2 g, 1 molar equivalent) was added to the solution, and the mixture was stirred for 2 hours. Acetic anhydride (12.8 g, 4.3 molar equivalents) was added to the stirred solution, followed by stirring for 2 hours.

[0387] Separately, a silicone dispersion was prepared by suspending a silicone dispersion in isopropanol (71 wt%, 7.3 g) in dimethylacetamide (11.3 g). The mixture was heated at 120 °C with stirring until the isopropanol was completely evaporated (measured by a weight loss of 4.6 g, approximately 30 minutes). This silicone dispersion was added to the PDA / PMDA / acetic anhydride mixture. After approximately 5 minutes of stirring, pyridine (8.0 mL, 8% by volume) was added to initiate gelation, forming a polyamic acid presol. This presol was quickly poured into silicone oil (polydimethylsiloxane, 100 cSt, 450 mL) while stirring in a Ross mixer at 9000 rpm. Approximately 5 minutes after pyridine addition, 100 mL of ethanol was added, and stirring was continued for another minute. Room temperature gelation occurred in 7 minutes. Ethanol (300 mL) was added, followed by stirring at 7000 rpm for 3 minutes. The phases were separated, and the beads were isolated by filtration. The beads were mixed with heptane (150 mL) for approximately 10 minutes and then collected by filtration. The heptane wash was repeated, followed by a wash with a mixture of 120 mL of heptane and 120 mL of ethanol. The resulting filter cake was stirred in 300 mL of ethanol for 30 minutes.

[0388] A portion of the polyimide / Si gel beads was dried using subcritical liquid CO2 by exchanging the solvent in the gel beads with liquid CO2 in a vessel at a pressure ranging from approximately 800 to 1200 psi for at least approximately 15 minutes. The vessel was then depressurized to atmospheric pressure to give polyimide / Si aerogel beads. The polyimide / Si aerogel beads were then carbonized at 1050 °C under a nitrogen stream for 2 hours to give C / Si aerogel beads.

[0389] Example 28. C / Si composite beads prepared from polyimide in DMAC / silicone oil emulsion. Water 1190 ppm Carbon / Si composite beads containing 35 wt % silicon were prepared from polyimide according to Example 27 with a target density of 0.085, but with a sol water content of 1190 ppm.

[0390] Example 29. C / Si composite beads prepared from polyimide in DMAC / silicone oil emulsion. 620 ppm water Carbon / Si composite beads containing 35 wt % silicon were prepared from polyimide according to Example 27 with a target density of 0.06, but with a sol water content of 620 ppm.

[0391] result In Example 26, beads were prepared without adding water, and ethanol was added at the gel point (5.3 minutes after pyridine addition). In contrast, in Example 27, 530 ppm of water was added to the sol solvent, which not only reduced viscosity but also delayed gelation. As a result, ethanol was added 5.3 minutes after pyridine addition, before the gel point was reached. SEM images showing C / Si AeroL beads prepared according to Examples 26 and 27 are provided in Figures 59A and 59B, respectively, showing that beads produced in the presence of 530 ppm water were approximately 50% smaller than beads prepared in the absence of water. The average bead size distributions for Examples 26 and 27 are provided in Figure 60 (average sizes of 23 and 11 μm, respectively). Data for bead sizes D10, D50, and D90 are provided in Table 24, which shows that the addition of water on the order of 500-600 ppm reduced the bead size compared to the bead size obtained in the absence of water, and that further increases in water content in the sol (e.g., 1190 ppm) did not further reduce the bead size. Without wishing to be bound by theory, it is believed that the addition of water reduces the molecular weight of the polyamic acid, resulting in a decrease in sol viscosity and consequently a decrease in bead size. [Table 23]

[0392] Example 30: Alternative Method for Producing Polyimide Aerogels The above examples described herein teach specific methodologies for forming PI gels (e.g., aerogels or xerogels). In certain embodiments, the present invention further contemplates alternative methods for forming PI gels that can be converted to carbon aerogels or carbon xerogels by pyrolysis. A non-exhaustive and non-limiting set of examples of such alternative methodologies is described herein.

[0393] For example, U.S. Patent No. 6,399,669 to Suzuki et al. teaches four (4) related methods for making PI dry gels (aerogels). In the first method, a PI precursor is synthesized, followed by imide formation from the PI precursor, leading to the production of polyimides. A PI solution or swollen bulk is prepared, and the solution / swollen bulk is gelled to produce a PI wet gel. This wet gel is dried, resulting in a PI dry gel (aerogel).

[0394] In the second method, a PI precursor is synthesized, followed by preparation of a PI precursor solution or swollen bulk. The solution / swollen bulk is gelled to produce a PI precursor wet gel. An imide is then formed from the PI precursor to form a PI wet gel. This wet gel is dried, resulting in a PI dry gel (aerogel). In the third method, a PI precursor is synthesized, followed by preparation of a PI precursor solution or swollen bulk. An imide is then formed from the PI precursor while gelling the PI precursor to produce a PI wet gel.

[0395] In the third method, a PI precursor is synthesized, followed by preparation of a PI precursor solution or swollen bulk. The solution / swollen bulk is gelled to produce a PI precursor wet gel. This wet gel is then dried to produce a PI precursor dry gel. An imide is then formed from the PI precursor dry gel to form a PI dry gel (aerogel).

[0396] As a further example, Leventis et al. ("Polyimide Aerogels by Ring-Opening Metathesis Polymerization (ROMP)", Chem. Mater. 2011, 23, 8, 2250-2261) describe the formation of PI aerogels using the ROMP method. Generally, a low molecular weight imidized oligomer end-capped with a polymerizable group is provided and mixed with a polymerization (e.g., ROMP) catalyst. Polymerization is thus initiated, producing a crosslinked polyimide. This polyimide is gelled and dried to form a PI aerogel.

[0397] As a further example, U.S. Patent No. 9,745,198 to Leventis et al. and Chidambareswarapattar et al., "One-step room-temperature synthesis of fibrous polyimide aerogels from anhydrides and isocyanates and conversion to isomorphic carbons," J. Mater. Chem., 2010, 20, 9666-9678, teaches the formation of PI aerogels by mixing a dianhydride (such as PMDA) with an isocyanate (e.g., 4,4'-diisocyanatodiphenylmethane or methylenedi-p-phenyldiisocyanate) to form a sol. The sol-gel material is then dried to produce the PI aerogel. Leventis et al. ("Isocyanate-Derived Organic Aerogels: Polyureas, Polyimides, Polyamides", MRS Proceedings, 1306 (2011), Mrsf10-1306-bb03-01.doi:10.1557 / opl.2011.90) also note that DESMODUR® N3300A, DESMODUR® RE, and MONDUR® CD, all available from Convestro AG, Pittsburgh, PA, USA, can be utilized as the isocyanate.

[0398] In an alternative methodology, Guo et al. ("Polyimide Aerogels Cross-Linked through Amine Functionalized Polyoligomeric Silsesquioxane," ACS Appl. Mater. Interfaces 2011, 3, 546-552) describe the formation of PI aerogels by reacting aminosilsesquioxane with polyamic acid oligomers end-capped with anhydride groups. The product is imidized using pyridine (although thermal imidization is also contemplated), gelled, and subsequently dried to yield the PI aerogel. Nguyen et al. ("Development of High Temperature, Flexible Polyimide Aerogels," American Chemical Society, Proceedings, 2011) describe mixing a diamine and a dianhydride, imidizing them, followed by reaction with a multi-amino compound (e.g., 1,3,5-tris(4-aminophenoxybenzene)). This product is then reacted with 4,4'-methylene diisocyanate and dried to form a PI urea aerogel.

[0399] In another embodiment, Meador et al. ("Mechanically Strong, Flexible Polyimide Aerogels Cross-Linked with Aromatic Triamine," ACS Appl. Mater. Interfaces, 2012, 4(2), pp. 536-544) describe the production of PI gels by crosslinking anhydride-endcapped polyamic acid oligomers using aromatic triamines in solution, followed by imidization. The resulting wettability is dried to form PI aerogels. Furthermore, Meador et al. ("Polyimide Aerogels with Amide Cross-Links: A Low Cost Alternative for Mechanically Strong Polymer Aerogels," ACS Appl. Mater. Interfaces 2015, 7, 1240-1249) describe the formation of PI gels by crosslinking amine-capped oligomers with 1,3,5-benzenetricarbonyl trichloride. The resulting gel is dried to form PI aerogels.

[0400] In yet another embodiment, Pei et al. ("Preparation and Characterization of Highly Cross-Linked Polyimide Aerogels Based on Polyimide Containing Trimethoxysilane Side Groups," Langmuir 2014, 30, 13375-13383) produced PI aerogels from polyimides containing trimethoxysilane side groups, which were the condensation products of polyimides containing acid chloride side groups and 3-aminopropyltrimethoxysilane. The resulting gel was dried to form the PI aerogel.

[0401] A suspension of graphene can be added using any one of these methods (see Zhang et al., “Graphene / carbon aerogels derived from graphene crosslinked polyimide as electrode materials for supercapacitors,” RSC Adv., 2015, 5, 1301).

[0402] Each of these methodologies may lead to polyimide aerogels, and the present invention contemplates any suitable method for producing such polyimide aerogels. According to certain embodiments of the present invention, regardless of which methodology is utilized to produce PI aerogels, the resulting PI aerogels can be pyrolyzed to form PI-derived carbon aerogels. Additives such as silicon can also be introduced according to certain embodiments described herein.

[0403] All referenced publications are incorporated by reference in their entirety. Furthermore, to the extent that the definition or use of a term in a reference incorporated herein by reference contradicts or is contrary to the definition of that term provided herein, the definition of that term provided herein shall apply and the definition of that term in the reference shall be disregarded.

[0404] The advantages set forth above and those made apparent from the foregoing description are efficiently attained. Since certain changes may be made in the above-described constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

[0405] It is also to be understood that the following claims are intended to cover all of the general and specific features of the invention described herein, and to cover all statements of the scope of the invention that, as a matter of terminology, may be found therebetween. Some of the embodiments of the invention related to the present invention are shown below. [Embodiment 1] 1. A method for forming a porous carbon composition in bead form, comprising: providing an organogel precursor in an organic solvent; initiating gelation of the organogel precursor to provide an organogel sol; combining the organogel sol with a medium immiscible with the organogel sol, thereby forming organogel droplets; Isolating the droplets of the organogel; drying the droplets to form porous organogel beads; pyrolyzing the porous organogel beads to produce the porous carbon composition in bead form; wherein the porous carbon composition has a porosity of about 10% to about 90%. [Embodiment 2] 2. The method of embodiment 1, wherein initiating gelation occurs prior to combining the mixture with the vehicle. [Embodiment 3] 3. The method of claim 1 or 2, wherein the organogel precursor is a polyamic acid. [Embodiment 4] 4. The method of embodiment 3, wherein the gelation is chemical imidization, thermal imidization, or a combination of chemical and thermal imidization. [Embodiment 5] 4. The method of embodiment 3, wherein the polyamic acid comprises a tetracarboxylic acid and a polyfunctional amine. [Embodiment 6] 6. The method of embodiment 5, wherein the tetracarboxylic acid is selected from the group consisting of benzene-1,2,4,5-tetracarboxylic acid, [1,1'-biphenyl]-3,3',4,4'-tetracarboxylic acid, 4,4'-oxydiphthalic acid, 4,4'-sulfonyldiphthalic acid, 4,4'-carbonyldiphthalic acid, 4,4'-(propane-2,2-diyl)diphthalic acid, 4,4'-(perfluoropropane-2,2-diyl)diphthalic acid, naphthalene-1,4,5,8-tetracarboxylic acid, 4-(2-(4-(3,4-dicarboxyphenoxy)phenyl)propan-2-yl)phthalic acid, perylene tetracarboxylic acid, and combinations thereof. [Embodiment 7] 6. The method of embodiment 5, wherein the polyfunctional amine is an alkanediamine or an aryldiamine. [Embodiment 8] 8. The method of embodiment 7, wherein the alkanediamine is ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, or a combination thereof. [Embodiment 9] 8. The method of embodiment 7, wherein the aryl diamine is 1,4-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-methylenedianiline, or a combination thereof. [Embodiment 10] 5. The method of embodiment 4, wherein the chemical imidization comprises adding a dehydrating agent and an amine base. [Embodiment 11] 11. The method of embodiment 10, wherein the dehydrating agent is acetic anhydride. [Embodiment 12] 11. The method of embodiment 10, wherein the amine base is pyridine. [Embodiment 13] 13. The method of any one of embodiments 1 to 12, wherein the organic solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, or ethyl acetate. [Embodiment 14] 14. The method of any one of embodiments 1 to 13, wherein the organic solvent is N,N-dimethylacetamide. [Embodiment 15] 15. The method of any one of the preceding embodiments, wherein the organic solvent further comprises about 100 to about 1500 parts per million (ppm) of water. [Embodiment 16] 16. The method of embodiment 15, wherein the organic solvent further comprises water in an amount of from about 500 to about 1200 ppm, or from about 500 to about 700 ppm. [Embodiment 17] 17. The method of any one of the preceding claims, wherein the medium has a viscosity of about 100 to about 150 cP. [Embodiment 18] 18. The method of any one of the preceding embodiments, wherein the medium is mineral oil, silicone oil, or a C5 to C12 hydrocarbon. [Embodiment 19] 19. The method of embodiment 18, further comprising adding one or more surfactants to said medium. [Embodiment 20] 20. The method of any one of the preceding embodiments, wherein the organogel sol has a viscosity of about 5 to about 30 cP. [Embodiment 21] 21. The method of any one of the preceding embodiments, further comprising adding a low viscosity solvent to the medium. [Embodiment 22] 22. The method of embodiment 21, wherein the low viscosity solvent is added in a single portion in an amount of up to about 10% by volume of the vehicle. [Embodiment 23] 22. The method of embodiment 21, wherein the low-viscosity solvent is added in two or more portions, including a first portion of up to about 10% by volume of the vehicle and one or more additional portions, the total amount of low-viscosity solvent added being up to about 50% by volume of the vehicle. [Embodiment 24] 22. The method of embodiment 21, wherein the low-viscosity solvent is added continuously and the total amount of the low-viscosity solvent added is up to about 50% by volume of the medium. [Embodiment 25] 22. The method of embodiment 21, wherein the low viscosity solvent is a C1 to C3 alcohol. [Embodiment 26] 26. The method of any one of embodiments 1-25, wherein combining comprises stirring under high shear conditions. [Embodiment 27] Drying may include lyophilizing the organogel beads, exposing the organogel beads to elevated temperature conditions, and immersing the organogel beads in supercritical fluid CO. 2 or contacting the organogel beads with liquid CO. 2 and contacting the CO 2 27. The method of any one of embodiments 1-26, comprising evaporating the compound as a gas. [Embodiment 28] 28. The method of any one of the preceding embodiments, further comprising aging the porous organogel beads prior to pyrolysis. [Embodiment 29] 29. The method of any one of the preceding embodiments, wherein the porous carbon composition comprises a carbon aerogel. [Embodiment 30] 29. The method of any one of embodiments 1-28, wherein the porous carbon composition comprises a carbon xerogel. [Embodiment 31] 31. The method of any one of the preceding embodiments, wherein the beads of the porous carbon composition have a diameter ranging from about 1 micrometer to about 50 micrometers. [Embodiment 32] 32. The method of any one of the preceding claims, wherein the porous carbon composition is a porous carbon-silicon composition comprising greater than about 10 wt% silicon, based on the total weight of the composition, and the method further comprises providing silicon in admixture with the organogel precursor in the organic solvent. [Embodiment 33] 33. The method of embodiment 32, wherein the porous carbon-silicon composition comprises about 20% to about 65% by weight of silicon, based on the total weight of the composition. [Embodiment 34] 34. The method of embodiment 32 or 33, wherein the porous carbon-silicon composition comprises a pore structure, and the silicon is at least partially present within the pore structure. [Embodiment 35] 35. The method of embodiment 34, wherein the pore structure comprises a fibrous morphology and an array of pores surrounding the silicon. [Embodiment 36] 36. The method of any one of embodiments 32-35, wherein the porous carbon-silicon composition has a capacity of at least about 800 mAh / g. [Embodiment 37] 37. The method of any one of embodiments 32-36, wherein the porous carbon-silicon composition has a silicon utilization of at least about 20%. [Embodiment 38] A porous carbon composition in the form of beads, the porous carbon composition comprising a composite material comprising carbon, the beads having a diameter ranging from about 1 μm to about 15 μm and a density of about 0.3 g / cm 3 ~Approx. 1.3g / cm 3 The porous carbon composition has a tap density in the range of [Embodiment 39] 39. The porous carbon composition of embodiment 38, wherein the carbon comprises a carbon aerogel or a carbon xerogel. [Embodiment 40] 40. The porous carbon composition of embodiment 38 or 39, wherein the composite material further comprises silicon in an amount greater than about 10 wt.%, based on the total weight of the composition. [Embodiment 41] 41. The porous carbon composition of embodiment 40, wherein the composite material comprises about 25 wt% to about 65 wt% silicon, based on the total weight of the composition. [Embodiment 42] 42. The porous carbon composition of embodiment 40 or 41, wherein the carbon comprises a pore structure and the silicon is at least partially present within the pore structure. [Embodiment 43] 43. The porous carbon composition of any one of embodiments 40-42, wherein the composite material has a silicon utilization of at least about 20%. [Embodiment 44] 44. The porous carbon composition of any one of embodiments 40-43, wherein the silicon has a particle size of less than about 150 nm. [Embodiment 45] 44. The porous carbon composition of any one of embodiments 40 to 43, wherein the silicon has a particle size in the range of about 150 nm to about 500 nm. [Embodiment 46] 44. The porous particulate carbon composition of any one of embodiments 40-43, wherein the silicon has a particle size greater than about 500 nm. [Embodiment 47] the composite material comprises silicon in the range of about 25 to about 65 wt %, the silicon having a particle size in the range of about 30 nm to about 800 nm; The beads are Approximately 0.2g / cm 3 ~Approx. 1.5g / cm 3 and a tap density in the range of a diameter in the range of about 1 μm to about 15 μm; an average pore size in the range of about 10 nm to about 50 nm; Approximately 0 to approximately 500 m 2 / g and BET surface area having 47. The porous carbon composition according to any one of embodiments 40 to 46. [Embodiment 48] 48. The porous carbon composition of any one of embodiments 40 to 47, having a capacity of at least about 800 mAh / g. [Embodiment 49] 49. An energy storage device comprising the porous carbon composition of any one of embodiments 38-48. [Embodiment 50] 50. The energy storage device of embodiment 49, which is a lithium ion battery.

Claims

1. 1. A method for forming a porous carbon composition in bead form, comprising: providing an organogel precursor in an organic solvent; initiating gelation of the organogel precursor by adding a dehydrating agent and an amine base to the organogel precursor in the organic solvent to provide an organogel sol; combining the organogel sol with a medium immiscible with the organogel sol and allowing gelation to continue, thereby forming organogel droplets; Isolating the droplets of the organogel; drying the droplets to form porous organogel beads; pyrolyzing the porous organogel beads to produce the porous carbon composition in bead form; wherein said combining comprises stirring under high shear conditions, and wherein said porous carbon composition has a porosity of about 10% to about 90%.

2. The method of claim 1 , wherein the organogel precursor is a polyamic acid.

3. The method of claim 2 wherein the polyamic acid comprises a tetracarboxylic acid and a polyfunctional amine.

4. 4. The method of claim 3, wherein the tetracarboxylic acid is selected from the group consisting of benzene-1,2,4,5-tetracarboxylic acid, [1,1'-biphenyl]-3,3',4,4'-tetracarboxylic acid, 4,4'-oxydiphthalic acid, 4,4'-sulfonyldiphthalic acid, 4,4'-carbonyldiphthalic acid, 4,4'-(propane-2,2-diyl)diphthalic acid, 4,4'-(perfluoropropane-2,2-diyl)diphthalic acid, naphthalene-1,4,5,8-tetracarboxylic acid, 4-(2-(4-(3,4-dicarboxyphenoxy)phenyl)propan-2-yl)phthalic acid, perylene tetracarboxylic acid, and combinations thereof.

5. The method of claim 3 wherein the polyfunctional amine is an alkanediamine or an aryldiamine.

6. 6. The method of claim 5, wherein the alkanediamine is ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, or a combination thereof.

7. The method of claim 5, wherein the aryl diamine is 1,4-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-methylenedianiline, or a combination thereof.

8. 2. The method of claim 1, wherein the dehydrating agent is acetic anhydride.

9. 2. The method of claim 1, wherein the amine base is pyridine.

10. 2. The method of claim 1, wherein the organic solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, or ethyl acetate.

11. The method of claim 1, wherein the organic solvent is N,N-dimethylacetamide.

12. 10. The method of claim 1, wherein the organic solvent further comprises about 100 to about 1500 parts per million (ppm) of water.

13. 13. The method of claim 12, wherein the organic solvent further comprises water in an amount of from about 500 to about 1200 ppm, or from about 500 to about 700 ppm.

14. The method of claim 1, wherein the medium has a viscosity of about 100 to about 150 cP.

15. The method of claim 1, wherein the medium is a mineral oil, a silicone oil, or a C5 to C12 hydrocarbon.

16. 16. The method of claim 15, further comprising adding one or more surfactants to the medium.

17. The method of claim 1, wherein the organogel sol has a viscosity of about 5 to about 30 cP.

18. The method of claim 1 further comprising adding a low viscosity solvent to the medium.

19. 20. The method of claim 18, wherein the low viscosity solvent is added in a single portion in an amount of up to about 10% by volume of the vehicle.

20. 20. The method of claim 18, wherein the low-viscosity solvent is added in two or more portions, including a first portion of up to about 10% by volume of the vehicle and one or more additional portions, the total amount of low-viscosity solvent added being up to about 50% by volume of the vehicle.

21. 20. The method of claim 18, wherein the low-viscosity solvent is added continuously, and the total amount of the low-viscosity solvent added is up to about 50% by volume of the medium.

22. 19. The method of claim 18, wherein the low viscosity solvent is a C1 to C3 alcohol.

23. Drying may include freeze-drying the organogel droplets, exposing the organogel droplets to elevated temperature conditions, and immersing the organogel droplets in supercritical fluid CO. ２ or contacting the organogel droplets with liquid CO ２ and contacting the liquid CO ２ and evaporating the compound as a gas.

24. 10. The method of claim 1, further comprising aging the porous organogel beads prior to pyrolysis.

25. The method of claim 1 , wherein the porous carbon composition comprises a carbon aerogel.

26. The method of claim 1 , wherein the porous carbon composition comprises a carbon xerogel.

27. The method of claim 1 , wherein the beads of the porous carbon composition have a diameter ranging from about 1 micrometer to about 50 micrometers.

28. 10. The method of claim 1, wherein the porous carbon composition is a porous carbon-silicon composition comprising greater than about 10 wt. % silicon, based on the total weight of the composition, and the method further comprises providing silicon in admixture with the organogel precursor in the organic solvent.

29. 30. The method of claim 28, wherein the porous carbon-silicon composition comprises from about 20% to about 65% by weight of silicon, based on the total weight of the composition.

30. 29. The method of claim 28, wherein the porous carbon-silicon composition comprises a pore structure and the silicon is at least partially present within the pore structure.

31. 31. The method of claim 30, wherein the pore structure comprises a fibrous morphology and an array of pores surrounding the silicon.

32. 30. The method of claim 28, wherein the porous carbon-silicon composition has a capacity of at least about 800 Ah / g.

33. 30. The method of claim 28, wherein the porous carbon-silicon composition has a silicon utilization of at least about 20%.

34. A porous carbon composition in the form of beads, the porous carbon composition comprising a composite material comprising carbon, the beads having a diameter ranging from about 1 μm to about 15 μm and a mass of about 0.3 g / cm ３ ~Approx. 1.3g / cm ３ The porous carbon composition has a tap density in the range of

35. 35. The porous carbon composition of claim 34, wherein the carbon comprises a carbon aerogel or a carbon xerogel.

36. 36. The porous carbon composition of claim 34 or 35, wherein the composite material further comprises silicon in an amount greater than about 10 wt.%, based on the total weight of the composition.

37. 37. The porous carbon composition of claim 36, wherein the composite material comprises about 25 wt% to about 65 wt% silicon, based on the total weight of the composition.

38. 37. The porous carbon composition of claim 36, wherein the carbon comprises a pore structure and the silicon resides at least partially within the pore structure.

39. 37. The porous carbon composition of claim 36, wherein the composite material has a silicon utilization of at least about 20%.

40. 37. The porous carbon composition of claim 36, wherein the silicon has a particle size of less than about 150 nm.

41. 37. The porous carbon composition of claim 36, wherein the silicon has a particle size ranging from about 150 nm to about 500 nm.

42. 37. The porous particulate carbon composition of claim 36, wherein said silicon has a particle size greater than about 500 nm.

43. the composite material comprises silicon in the range of about 25 to about 65 weight percent, the silicon having a particle size in the range of about 30 nm to about 800 nm; The beads are Approximately 0.2g / cm ３ ~Approx. 1.5g / cm ３ and a tap density in the range of a diameter in the range of about 1 μm to about 15 μm; an average pore size in the range of about 10 nm to about 50 nm; Approximately 0 to approximately 500 m ２ / g and having 37. The porous particulate carbon composition of claim 36.

44. 37. The porous carbon-silicon composition of claim 36, having a capacity of at least about 800 Ah / g.

45. 35. An energy storage device comprising the porous carbon composition of claim 34.

46. 46. ​​The energy storage device of claim 45, wherein the energy storage device is a lithium ion battery.

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