Porous carbon materials comprising carbon additives

Abstract

The present disclosure relates to methods of forming a carbon aerogel material comprising (i.e., doped with) a carbon additive, such as graphene, graphene nanoribbons, graphene nanosheets, graphene oxide, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or a combination thereof. The methods generally include providing an organogel precursor; adding a carbon additive or a precursor thereof to the organogel precursor; inducing gelling of the organogel precursor to provide an organogel doped with the carbon additive or a precursor thereof; drying the organogel to form an organic aerogel doped with the carbon additive or a precursor thereof; and pyrolyzing the doped organic aerogel. The doped gel materials prepared according to the disclosed methods are suitable for use in environments involving electrochemical reactions, for example as electrode materials within lithium ion batteries.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 410,652, filed on September 28, 2022, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to porous carbon materials comprising (ie, doped with) carbon additives and methods of making the same. Background Art

[0004] Aerogel is a solid material containing a highly porous network of pores of micropore, mesopore and macropore size. Depending on the precursor material used and the processing performed, when the density of the aerogel is about 0.05g / cc, the pores of the aerogel can generally account for more than 90% of the volume. Aerogels are generally prepared in the following manner: solvent is removed from the gel (solid network containing solvent) in a manner that the capillary force on the pore wall of the gel can cause minimal gel shrinkage or no gel shrinkage. Solvent removal methods include but are not limited to supercritical drying (or using supercritical fluid drying so that a supercritical fluid with low surface tension replaces a high surface tension gelling solvent in the gel), exchanging solvents with supercritical fluids, exchanging solvents with fluids that are subsequently converted to a supercritical state, subcritical or near-critical drying, and sublimating frozen solvents during freeze drying. See, for example, PCT Patent Application Publication No. WO 2016127084 A1. It should be noted that when dried under ambient conditions, gel shrinkage may occur as the solvent evaporates, and xerogels may be formed. Thus, the preparation of aerogels by a sol-gel process or other polymerization process typically follows a series of steps: dissolving a solute in a solvent, adding a catalyst or reagent that induces or promotes a reaction of the solute, forming a reaction mixture, forming a gel (which may involve additional heating or cooling), and removing the solvent by supercritical drying techniques or any other method that removes the solvent from the gel without causing shrinkage or pore collapse.

[0005] Aerogels can be formed from inorganic materials, organic materials, or mixtures thereof. When organic aerogels are formed from organic materials such as, for example, phenol, resorcinol-formaldehyde (RF), phloroglucinol-furfural (PF), polyacrylonitrile (PAN), polyimide (PI), polyurethane (PU), polyurea (PUA), polyamine (PA), polybutadiene, polydicyclopentadiene, and precursors or polymer derivatives thereof, the organic aerogels can be carbonized (e.g., by pyrolysis) to form carbon aerogels, which can have properties that are different or overlapping from each other (e.g., pore volume, pore size distribution, morphology, etc.), depending on the precursor materials and methods used. As used herein, the term "organic aerogel" refers to a group of porous materials formed from organic materials. Depending on the preparation method and porosity of the porous material, the organic aerogel can be an organic xerogel, a freeze-dried gel, an ambient drying gel, a microporous material, and the like. For example, if the porous material is prepared at ambient pressure (rather than under supercritical drying conditions), the porous material may generally be referred to as an organic aerogel rather than using the more precise term "organic xerogel."

[0006] Recently, much effort has been devoted to developing and characterizing carbon aerogels as electrode materials with improved properties for application in energy storage devices such as lithium-ion batteries (LIBs). Therefore, it would be desirable in the art to provide other carbon aerogel materials with finely tuned electrochemical properties and methods for preparing the same. Summary of the invention

[0007] The present technology generally relates to porous carbon materials and porous carbon-silicon composite materials, the materials containing (i.e., doped with) carbon additives, such as soft carbon, graphene, graphene nanoribbons, graphene nanosheets, graphene oxide, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or combinations thereof. The present technology further relates to methods for preparing such porous carbon materials containing carbon additives. The methods generally include providing an organogel precursor; adding a carbon additive or a precursor thereof to the organogel precursor; optionally adding silicon particles or other functional particles and sacrificial particles, inducing gelation of the organogel precursor to provide an organogel doped with the carbon additive or a precursor thereof; drying the organogel to form an organic aerogel doped with the carbon additive or a precursor thereof; and pyrolyzing the doped organic aerogel. In the case of porous carbon materials and porous carbon-silicon composite materials containing soft carbon as an additive, the methods include adding a precursor of soft carbon, such as pitch or perylenetetracarboxylic dianhydride (PTCDA). In a subsequent pyrolysis process, such precursors are thermally converted into soft carbon.

[0008] The disclosed process facilitates customization of the carbon additives present in the resulting porous carbon material, rather than relying on properties associated with the introduction of only commercially available carbon additives. Surprisingly, it was found in accordance with the present disclosure that carbon aerogel beads or carbon / silicon composite aerogel beads comprising certain carbon additives prepared as described herein exhibit improved first cycle efficiency, reversible capacity, and high rate performance lithiation potential relative to reference carbon aerogel beads (i.e., not comprising carbon additives). Without wishing to be bound by theory, it is believed that such enhanced performance is the result of the formation of carbon having an ideal ordered structure within the aerogel matrix and / or is due to changes in the polyimide-derived carbon induced by the presence of the carbon additive. In addition, it was surprisingly found in accordance with the present disclosure that carbon aerogel materials comprising soft carbon retain the high efficiency of carbon aerogel materials comprising hard carbon. This is advantageous because such carbon aerogels can be prepared at lower pyrolysis temperatures, thereby potentially reducing production costs by virtue of lower energy requirements. Finally, the sol-based method for preparing gel materials containing carbon additives or precursors thereof has a high degree of flexibility in the nature of the organogel precursors, can be carried out under aqueous ("green") conditions in many cases, and allows for the incorporation of a wide variety of carbon forms in the final carbon aerogel, and further allows for the incorporation of electroactive materials such as silicon. The method also allows for the incorporation of void spaces in the final carbon aerogel, which void spaces can further contain silicon particles.

[0009] In particular, this method can be applied to organogels, including but not limited to resorcinol-formaldehyde (RF) polymers, phloroglucinol-furfural (PF) polymers, polyacrylonitrile (PAN), polyurethane (PU), polyurea (PUA), polyamine (PA), polybutadiene, polydicyclopentadiene, polyamic acid, and polyimide, to produce carbon aerogels doped with carbon and / or silicon.

[0010] Therefore, in one aspect, a method for forming a carbon aerogel containing a carbon additive is provided, the method comprising: providing a solution comprising an organic gel precursor and a solvent; adding a carbon additive or a precursor thereof to the organic gel precursor solution; initiating gelation of the organic gel precursor to provide an organic gel containing the carbon additive or a precursor thereof; drying the organic gel to form an organic aerogel containing the carbon additive or a precursor thereof; and isomorphously converting the organic aerogel into a carbon aerogel containing the carbon additive, the conversion comprising pyrolyzing the organic aerogel at a temperature of at least about 650°C under an inert atmosphere.

[0011] In some aspects, the carbon additive is graphene, graphene nanoribbons, graphene nanosheets, graphene oxide, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or a combination thereof, and the method includes adding the carbon additive to the organogel precursor solution.

[0012] In some aspects, the carbon additive is a soft carbon, and the method includes adding a soft carbon precursor to the organogel precursor solution, wherein the soft carbon precursor comprises or is perylenetetracarboxylic dianhydride (PTCDA).

[0013] In some aspects, the carbon additive is a soft carbon, and the method includes adding a soft carbon precursor to the organogel precursor solution, wherein the soft carbon precursor comprises or is pitch.

[0014] In some aspects, the carbon aerogel further comprises silicon, and the method further comprises adding silicon to the organogel precursor solution.

[0015] In some aspects, the method further comprises adding poly(methyl methacrylate) particles to the organogel precursor solution.

[0016] In some aspects, the method further comprises adding sacrificial material-modified silicon particles to the organogel precursor solution.

[0017] In some aspects, drying the organogel comprises: optionally, washing or solvent exchanging the organogel; and subjecting the organogel to elevated temperature conditions, lyophilizing the organogel, or contacting the organogel with supercritical fluid carbon dioxide.

[0018] In some aspects, the washing or solvent exchange is performed with water, a C1 to C3 alcohol, acetone, acetonitrile, ether, tetrahydrofuran, toluene, liquid carbon dioxide, or a combination thereof.

[0019] In some aspects, the organogel comprises resorcinol-formaldehyde (RF) polymer, phloroglucinol-furfural (PF) polymer, polyacrylonitrile (PAN), polyurethane (PU), polyurea (PUA), polyamine (PA), polybutadiene, polydicyclopentadiene, or a combination thereof.

[0020] In some aspects, the organogel comprises polyimide, polyamic acid, or a combination thereof.

[0021] In some aspects, the organogel is a polyimide and the organogel precursor is a polyamic acid salt.

[0022] In some aspects, initiating gelation comprises imidizing the polyamic acid salt.

[0023] In some aspects, imidization includes adding a dehydrating agent to the solution of the polyamic acid salt.

[0024] In some aspects, the dehydrating agent is acetic anhydride.

[0025] In some aspects, the solvent is water. In some aspects, the solvent is a polar aprotic organic solvent. In some aspects, the solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, or a combination thereof.

[0026] In yet another aspect, a method for forming a carbon aerogel containing a carbon additive is provided, the method comprising: providing an aqueous solution of a polyamic acid salt, the polyamic acid salt comprising a polyamic acid containing a carboxylic acid group, wherein the carboxylic acid group is associated with a cationic substance and exists substantially as a carboxylate anion; adding a carbon additive or a precursor thereof to the aqueous solution; imidizing the polyamic acid salt to form a polyimide gel containing the carbon additive or a precursor thereof; drying the polyimide gel to form a polyimide aerogel containing the carbon additive or a precursor thereof; and isomorphously converting the polyimide aerogel into a carbon aerogel containing the carbon additive, the conversion comprising pyrolyzing the polyimide aerogel at a temperature of at least about 650° C. under an inert atmosphere.

[0027] In some aspects, providing an aqueous solution of a polyamic acid salt comprises: providing a polyamic acid; adding the polyamic acid to water to form an aqueous suspension of the polyamic acid; and adding a base (e.g., a non-nucleophilic amine, a hydroxide, or a carbonate or bicarbonate) to the aqueous suspension of the polyamic acid to form an aqueous solution of the polyamic acid salt.

[0028] In some aspects, the base is an alkali metal hydroxide and the cationic species is an alkali metal cation. In some aspects, the alkali metal hydroxide is lithium hydroxide, sodium hydroxide or potassium hydroxide.

[0029] In some aspects, the base is a water soluble carbonate or bicarbonate salt.

[0030] In some aspects, the base is a non-nucleophilic amine, and wherein the cationic species is an ammonium cation. In some aspects, the non-nucleophilic amine has a solubility of at least about 4 grams per 1L of water at 20°C. In some aspects, the non-nucleophilic amine is a tertiary amine. In some aspects, the non-nucleophilic amine is selected from triethylamine, trimethylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, diisopropylethylamine and combinations thereof. In some aspects, the non-nucleophilic amine is triethylamine or diisopropylethylamine

[0031] In some aspects, the non-nucleophilic amine is added in an amount sufficient to maintain substantially all of the polyamic acid in solution. In some aspects, the molar ratio of the non-nucleophilic amine to the polyamic acid is from about 2 to about 4 or from about 2.2 to about 2.5.

[0032] In some aspects, the polyamic acid comprises 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, perylenetetracarboxylic acid, and combinations thereof.

[0033] In some aspects, polyamic acid comprises C2-C6 alkylenediamines, wherein one or more carbon atoms of C2-C6 alkylene groups are optionally substituted by one or more alkyl groups. In some aspects, C2-C6 alkylenediamines are selected from the group consisting of ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane or a combination thereof. In some aspects, polyamic acid comprises 1,3-phenylenediamine, 1,4-phenylenediamine, 4,4'-methylenedianiline, 4,4'-diaminodiphenyl ether or a combination thereof. In some aspects, polyamic acid comprises diamines, and the diamines are selected from the group consisting of 1,4-phenylenediamine, 4,4'-methylenedianiline, 4,4'-diaminodiphenyl ether and a combination thereof.

[0034] In some aspects, the concentration of the polyamic acid salt in the solution ranges from about 0.01 to about 0.3 g / cm based on the weight of the polyamic acid. 3 .

[0035] In some aspects, the polyimide gel is in the form of a monolith, and imidizing the polyamic acid salt comprises adding a dehydrating agent to an aqueous solution of the polyamic acid salt to form a gelling mixture, the method further comprising pouring the gelling mixture into a mold and allowing the gelling mixture to gel.

[0036] In some aspects, the polyimide gel is in the form of a monolith, and the imidization of the polyamic acid salt is performed thermally, the method further comprising: adding δ-gluconolactone to an aqueous solution of the polyamic acid salt to form a gelling mixture; pouring the gelling mixture into a mold and allowing the gelling mixture to gel; washing the resulting polyamic acid gel with water; and thermally imidizing the polyamic acid gel to form a polyimide gel, wherein the thermal imidization comprises exposing the polyamic acid gel to microwave frequency irradiation.

[0037] In some aspects, the polyimide gel is in the form of beads, and imidizing the polyamic acid salt includes adding a dehydrating agent to an aqueous solution of the polyamic acid salt to form a gelled mixture; the method further includes adding the gelled mixture to a solution of a water-soluble acid in water to form polyimide gel beads, wherein the adding includes dropping the gelled mixture into a solution of a water-soluble acid in water, spraying the gelled mixture under pressure through one or more nozzles into a solution of a water-soluble acid in water using pressure; or electrospraying the gelled mixture into a solution of a water-soluble acid in water.

[0038] In some aspects, the dehydrating agent is acetic anhydride.

[0039] In some aspects, the water-soluble acid is a mineral acid or acetic acid.

[0040] In some aspects, the polyimide gel is in the form of beads, and imidizing the polyamic acid salt comprises adding a dehydrating agent to an aqueous solution of the polyamic acid salt to form a gelled mixture, the method further comprising adding the gelled mixture to a water-immiscible solvent, optionally comprising an acid, wherein the adding comprises dropping the gelled mixture into the water-immiscible solvent, spraying the gelled mixture under pressure through one or more nozzles into the water-immiscible solvent using pressure; or electrospraying the gelled mixture into the water-immiscible solvent.

[0041] In some aspects, the dehydrating agent is acetic anhydride.

[0042] In some aspects, the optional acid is acetic acid.

[0043] In some aspects, the method includes electrospraying the gelling mixture through one or more needles at a voltage in the range of about 5 to about 60 kV.

[0044] In some aspects, the polyimide gel is in the form of beads, and imidizing the polyamic acid salt comprises adding a dehydrating agent to an aqueous solution of the polyamic acid salt to form a gelling mixture, the method further comprising combining the aqueous solution of the polyamic acid salt with a water-immiscible solvent comprising a surfactant; and mixing the resulting mixture under high shear conditions.

[0045] In some aspects, the polyimide gel is in the form of beads, and imidizing the polyamic acid salt comprises chemical imidization, the method comprising: combining an aqueous solution of the polyamic acid salt with a water-immiscible solvent comprising a surfactant; mixing the resulting mixture under high shear conditions to form a quasi-stable emulsion; and adding a dehydrating agent to the quasi-stable emulsion.

[0046] In some aspects, the water-immiscible organic solvent is a C5-C12 hydrocarbon. In some aspects, the C5-C12 hydrocarbon is mineral spirits.

[0047] In some aspects, providing an aqueous solution of a polyamic acid salt comprises: dissolving a water-soluble diamine in water to form an aqueous diamine solution; adding a non-nucleophilic amine to the aqueous diamine solution; adding a tetracarboxylic dianhydride to the aqueous diamine solution; and stirring the resulting solution at a temperature in the range of about 15° C. to about 60° C. for a time period in the range of about 1 hour to about 24 hours.

[0048] In some aspects, providing an aqueous solution of a polyamic acid salt includes: dissolving a water-soluble diamine in water to form an aqueous diamine solution; adding tetracarboxylic dianhydride to the aqueous diamine solution; stirring the resulting suspension at a temperature in the range of about 15°C to about 60°C for a time period in the range of about 1 hour to about 24 hours; adding a non-nucleophilic amine to the aqueous diamine solution; and stirring the resulting suspension at a temperature in the range of about 15°C to about 60°C for a time period in the range of about 1 hour to about 24 hours.

[0049] In some aspects, providing an aqueous solution of a polyamic acid salt comprises: adding a water-soluble diamine, a tetracarboxylic dianhydride, and a non-nucleophilic amine to water simultaneously or in rapid succession; and stirring the resulting mixture at a temperature in the range of about 15° C. to about 60° C. for a period of time in the range of about 1 hour to about 24 hours.

[0050] In some aspects, the water-soluble diamine, tetracarboxylic dianhydride, and non-nucleophilic amine are added to the water simultaneously. In some aspects, the water-soluble diamine, tetracarboxylic dianhydride, and non-nucleophilic amine are added to the water in rapid succession.

[0051] In some aspects, the resulting mixture is stirred at a temperature in the range of about 15° C. to about 25° C. In some aspects, the resulting mixture is stirred at a temperature in the range of about 50° C. to about 60° C.

[0052] In some aspects, the non-nucleophilic amine has a solubility of at least about 4 grams per 1 L of water at 20°C.

[0053] In some aspects, the non-nucleophilic amine is a tertiary amine. In some aspects, the non-nucleophilic amine is selected from triethylamine, trimethylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, diisopropylethylamine and combinations thereof. In some aspects, the non-nucleophilic amine is triethylamine or diisopropylethylamine.

[0054] In some aspects, the molar ratio of the non-nucleophilic amine to the diamine is from about 2 to about 2.5.

[0055] In some aspects, the tetracarboxylic dianhydride is selected from the group consisting of pyromellitic anhydride (PMDA, diphthalic anhydride (BPDA), oxydiphthalic anhydride (ODPA), perylenetetracarboxylic anhydride, and combinations thereof.

[0056] In some aspects, the diamine is a C2-C6 alkylenediamine, wherein one or more carbon atoms of the C2-C6 alkylene are optionally substituted by one or more alkyl groups. In some aspects, the C2-C6 alkylenediamine is selected from the group consisting of ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane and combinations thereof. In some aspects, the diamine is 1,3-phenylenediamine, 1,4-phenylenediamine or a combination thereof. In some aspects, the diamine is 1,4-phenylenediamine.

[0057] In some aspects, the molar ratio of tetracarboxylic dianhydride to diamine is from about 0.9 to about 1.1.

[0058] In another aspect, a method for forming a carbon aerogel containing a carbon additive or a precursor thereof is provided, the method comprising: providing an aqueous solution of a polyamic acid salt; adding a carbon additive or a precursor thereof to the aqueous solution; acidifying the polyamic acid salt solution to form a polyamic acid gel containing a carbon additive or a precursor thereof; drying the polyamic acid gel to form a polyamic acid aerogel containing a carbon additive or a precursor thereof; and isomorphously converting the polyamic acid aerogel containing a carbon additive or a precursor thereof into a carbon aerogel containing a carbon additive, the conversion comprising pyrolyzing the polyamic acid aerogel material at a temperature of at least about 650° C. under an inert atmosphere.

[0059] In some aspects, the polyamic acid gel is in the form of a monolith, and the acidification of the polyamic acid salt comprises adding delta-gluconolactone to an aqueous solution of the polyamic acid salt to form a gelling mixture, and pouring the gelling mixture into a mold and allowing the gelling mixture to gel.

[0060] In some aspects, the polyamic acid gel is in the form of beads, and acidification of the polyamic acid salt comprises adding an aqueous solution of the polyamic acid salt to a solution of a water-soluble acid in water to form polyamic acid gel beads, wherein the adding comprises dropping the aqueous solution of the polyamic acid salt into the solution of the water-soluble acid in water, spraying the aqueous solution of the polyamic acid salt under pressure through one or more nozzles into the solution of the water-soluble acid in water using pressure; or electrospraying the aqueous solution of the polyamic acid salt into the solution of the water-soluble acid in water.

[0061] In some aspects, the water-soluble acid is a mineral acid or acetic acid.

[0062] In some aspects, the method comprises electrospraying an aqueous solution of a polyamic acid salt through one or more needles at a voltage in the range of about 5 to about 60 kV.

[0063] In some aspects, the polyamic acid gel is in the form of microbeads, and the method further comprises: combining an aqueous solution of a polyamic acid salt with a water-immiscible solvent comprising a surfactant; mixing the resulting mixture under high shear conditions to form an emulsion; and adding an organic acid to the emulsion.

[0064] In some aspects, the water-immiscible organic solvent is a C5-C12 hydrocarbon. In some aspects, the water-immiscible organic solvent is mineral spirits.

[0065] In some aspects, the organic acid is acetic acid.

[0066] In some aspects, providing an aqueous solution of a polyamic acid salt comprises: providing polyamic acid in substantially pure form; adding polyamic acid to water to form an aqueous suspension of polyamic acid; adding a base to the aqueous suspension of polyamic acid to form an aqueous solution of polyamic acid salt.

[0067] In some aspects, the base is a non-nucleophilic amine.

[0068] In some aspects, the non-nucleophilic amine has a solubility of at least about 4 grams per 1 L of water at 20°C.

[0069] In some aspects, the non-nucleophilic amine is a tertiary amine. In some aspects, the non-nucleophilic amine is selected from triethylamine, trimethylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, diisopropylethylamine and combinations thereof. In some aspects, the non-nucleophilic amine is triethylamine or diisopropylethylamine.

[0070] In some aspects, the non-nucleophilic amine is added in an amount sufficient to maintain substantially all of the polyamic acid in solution.

[0071] In some aspects, the molar ratio of the non-nucleophilic amine to the polyamic acid is from about 2 to about 4 or from about 2.2 to about 2.5.

[0072] In some aspects, the polyamic acid comprises 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, perylenetetracarboxylic acid, and combinations thereof.

[0073] In some aspects, polyamic acid comprises C2-C6 alkylenediamine, wherein optionally, one or more carbon atoms of C2-C6 alkylene are substituted by one or more alkyl. In some aspects, C2-C6 alkylenediamine is selected from the group consisting of: ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane and combination thereof.

[0074] In some aspects, the polyamic acid comprises 1,3-phenylenediamine, 1,4-phenylenediamine, 4,4'-methylenedianiline, 4,4'-diaminodiphenyl ether, or a combination thereof. In some aspects, the polyamic acid comprises a diamine selected from the group consisting of 1,4-phenylenediamine, 4,4'-methylenedianiline, 4,4'-diaminodiphenyl ether, and a combination thereof.

[0075] In some aspects, the concentration of the polyamic acid salt in the solution ranges from about 0.01 to about 0.3 g / cm based on the weight of the polyamic acid. 3 .

[0076] In some aspects, providing an aqueous solution of a polyamic acid salt comprises: dissolving a water-soluble diamine in water to form an aqueous diamine solution; adding a non-nucleophilic amine to the aqueous diamine solution; adding a tetracarboxylic dianhydride to the aqueous diamine solution; and stirring the resulting mixture at a temperature in the range of about 15° C. to about 60° C. for a time period in the range of about 1 hour to about 24 hours.

[0077] In some aspects, the resulting mixture is stirred at a temperature in the range of about 15° C. to about 25° C. In some aspects, the resulting mixture is stirred at a temperature in the range of about 50° C. to about 60° C.

[0078] In some aspects, providing an aqueous solution of a polyamic acid salt includes: dissolving a water-soluble diamine in water to form an aqueous diamine solution; adding tetracarboxylic dianhydride to the aqueous diamine solution; stirring the resulting mixture at a temperature in the range of about 15°C to about 60°C for a time period in the range of about 1 hour to about 24 hours; adding a non-nucleophilic amine to the mixture; and stirring the resulting mixture at a temperature in the range of about 15°C to about 60°C for a time period in the range of about 1 hour to about 24 hours.

[0079] In some aspects, the resulting mixture is stirred at a temperature in the range of about 15° C. to about 25° C. In some aspects, the resulting mixture is stirred at a temperature in the range of about 50° C. to about 60° C.

[0080] In some aspects, providing an aqueous solution of a polyamic acid salt comprises: adding a water-soluble diamine, a tetracarboxylic dianhydride, and a non-nucleophilic amine to water simultaneously or in rapid succession; and stirring the resulting mixture at a temperature in the range of about 15° C. to about 60° C. for a period of time in the range of about 1 hour to about 24 hours.

[0081] In some aspects, the resulting mixture is stirred at a temperature in the range of about 15° C. to about 25° C. In some aspects, the resulting mixture is stirred at a temperature in the range of about 50° C. to about 60° C.

[0082] In some aspects, the water-soluble diamine, tetracarboxylic dianhydride, and non-nucleophilic amine are added to the water simultaneously. In some aspects, the water-soluble diamine, tetracarboxylic dianhydride, and non-nucleophilic amine are added to the water in rapid succession.

[0083] In some aspects, the non-nucleophilic amine has a solubility of at least about 4 grams per 1 L of water at 20°C.

[0084] In some aspects, the non-nucleophilic amine is a tertiary amine. In some aspects, the non-nucleophilic amine is selected from triethylamine, trimethylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine and diisopropylethylamine. In some aspects, the non-nucleophilic amine is triethylamine or diisopropylethylamine

[0085] In some aspects, the molar ratio of the non-nucleophilic amine to the diamine is from about 2 to about 2.5.

[0086] In some aspects, the tetracarboxylic dianhydride is selected from the group consisting of pyromellitic anhydride (PMDA, diphthalic anhydride (BPDA), oxydiphthalic anhydride (ODPA), perylenetetracarboxylic anhydride, and combinations thereof.

[0087] In some aspects, the diamine is a C2-C6 alkylenediamine, and one or more carbon atoms of the C2-C6 alkylene are optionally substituted with one or more alkyl groups. In some aspects, the C2-C6 alkylenediamine is selected from the group consisting of ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, and combinations thereof.

[0088] In some aspects, the diamine is 1,4-phenylenediamine.

[0089] In some aspects, the molar ratio of tetracarboxylic dianhydride to diamine is from about 0.9 to about 1.1.

[0090] In yet another aspect, a carbon aerogel doped with a metal or metal oxide in the form of beads containing a carbon additive is provided, the method comprising: providing an aqueous solution of a polyamic acid ammonium salt or an alkali metal salt; adding a carbon additive or a precursor thereof to the aqueous solution; performing metal ion exchange, comprising adding a solution of a polyamic acid salt to a solution containing a soluble metal salt to form polyamic acid metal salt gel beads containing a carbon additive or a precursor thereof; drying the polyamic acid metal salt gel beads to form polyamic acid metal salt aerogel beads containing a carbon additive or a precursor thereof; and isomorphously converting the polyamic acid metal salt aerogel beads containing a carbon additive or a precursor thereof into carbon aerogel beads doped with a metal or metal oxide containing a carbon additive, the conversion comprising pyrolyzing the polyamic acid metal salt aerogel beads at a temperature of at least about 650° C. under an inert atmosphere.

[0091] In some aspects, the soluble metal salt comprises a main group transition metal, a rare earth metal, an alkaline earth metal, or a combination thereof. In some aspects, the soluble metal salt comprises copper, iron, nickel, silver, calcium, magnesium, or a combination thereof. In some aspects, the soluble metal salt comprises lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or a combination thereof.

[0092] In some aspects, adding the polyamic acid salt solution to the solution comprising a soluble metal salt comprises dripping the aqueous solution of the polyamic acid salt into the soluble metal salt solution, spraying the aqueous solution of the polyamic acid salt into the soluble metal salt solution under pressure through one or more nozzles, or electrospraying the aqueous solution of the polyamic acid salt into the soluble metal salt solution.

[0093] In some aspects, the method comprises electrospraying the polyamic acid salt solution through one or more needles at a voltage in the range of about 5 to about 60 kV.

[0094] In some aspects, drying the polyimide gel comprises: optionally washing or solvent exchanging the polyimide gel; and subjecting the optionally washed or solvent exchanged polyimide gel to elevated temperature conditions, freeze drying the optionally washed or solvent exchanged polyimide gel, or contacting the optionally washed or solvent exchanged polyimide gel with supercritical fluid carbon dioxide.

[0095] In some aspects, the washing or solvent exchange is performed with water, a C1 to C3 alcohol, acetone, acetonitrile, ether, tetrahydrofuran, toluene, liquid carbon dioxide, or a combination thereof.

[0096] In some aspects, the carbon additive is graphene, graphene oxide, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or combinations thereof.

[0097] In some aspects, the carbon additive is a soft carbon, and the method includes adding a soft carbon precursor. In some aspects, the soft carbon precursor comprises or is perylenetetracarboxylic dianhydride (PTCDA). In some aspects, the soft carbon precursor comprises or is pitch.

[0098] In some aspects, the carbon aerogel further comprises silicon, and the method further comprises adding the silicon to the aqueous solution.

[0099] In some aspects, the carbon aerogel further comprises void space within the aerogel, and the method further comprises adding a sacrificial material to the aqueous solution. In some aspects, the sacrificial material is poly(methyl methacrylate) particles.

[0100] In some aspects, the carbon aerogel further comprises silicon and void space within the aerogel, wherein at least a portion of the silicon is present in the void space, and the method further comprises adding silicon particles modified with a sacrificial material to the aqueous solution. In some aspects, the sacrificial material comprises poly(methyl methacrylate).

[0101] In yet another aspect, a carbon aerogel comprising a carbon additive is provided, wherein the carbon aerogel is prepared according to the method disclosed herein.

[0102] In some aspects, the carbon aerogel comprises from about 0.1% to about 20% carbon black by weight.

[0103] In some aspects, the carbon aerogel comprises from about 0.01% to about 5% by weight graphene or graphene oxide.

[0104] In some aspects, the carbon aerogel comprises from about 0.1% to about 20% by weight soft carbon.

[0105] In some aspects, the carbon aerogel comprises from about 0.01% to about 10% by weight of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or combinations thereof.

[0106] In some aspects, the carbon aerogel further comprises silicon.

[0107] In some aspects, the carbon aerogel further comprises void space.

[0108] In some aspects, the carbon aerogel further comprises silicon and void space, wherein at least a portion of the silicon is present in the void space.

[0109] In some aspects, the carbon aerogel is in the form of a monolith. In some aspects, the carbon aerogel is in the form of beads. BRIEF DESCRIPTION OF THE DRAWINGS

[0110] In order to provide an understanding of various aspects of the present technology, reference is made to the accompanying drawings, which are not necessarily drawn to scale. The accompanying drawings are exemplary only and should not be construed as limiting the present technology. The disclosure described herein is illustrated in the accompanying drawings by way of example and not by way of limitation.

[0111] Figure 1 is a flow chart depicting a general process for preparing a carbon aerogel material doped with a carbon additive according to non-limiting aspects of the present disclosure.

[0112] Figure 2 is a flow chart outlining several general routes for forming carbon aerogel materials doped with carbon additives according to non-limiting aspects of the present disclosure.

[0113] Figure 3Ais a flow chart depicting a process for preparing a polyamic acid alkali metal salt solution according to non-limiting aspects of the present disclosure.

[0114] Figure 3B is a flow chart depicting a process for preparing a polyamic acid ammonium salt solution according to non-limiting aspects of the present disclosure.

[0115] Figure 3C is a flow chart depicting three pathways for in situ preparation of polyamic acid ammonium salt solutions according to non-limiting aspects of the present disclosure.

[0116] Figure 4 is a flow chart depicting a process for preparing a polyimide aerogel monolith doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0117] Figure 5 is a flow chart depicting another process for preparing a polyimide aerogel monolith doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0118] Figure 6 is a flow chart depicting a process for preparing polyimide aerogel beads doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0119] Figure 7 is a flow chart depicting another process for preparing polyimide aerogel microbeads doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0120] Figure 8 is a flow chart depicting another process for preparing polyimide aerogel microbeads doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0121] Fig. 9 is a flow chart depicting a process for preparing a polyamic acid aerogel monolith doped with a carbon additive or precursor according to non-limiting aspects of the present disclosure.

[0122] Fig. 10A is a flow chart depicting a process for preparing polyamic acid aerogel beads doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0123] Fig. 10B is a cartoon illustration depicting the formation of polyamic acid wet gel beads according to non-limiting aspects of the present disclosure.

[0124] Fig.11 is a flow chart depicting a process for preparing polyamic acid aerogel microbeads doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0125] Fig.12 is a flow chart depicting a process for preparing metal polyamic acid salt aerogel beads doped with carbon additives or precursors according to non-limiting aspects of the present disclosure.

[0126] Fig.13 is a flow chart depicting a process for preparing a carbon aerogel doped with a carbon additive from a polyamic acid aerogel according to a non-limiting aspect of the present disclosure.

[0127] Fig.14 is a flow chart depicting a process for preparing a carbon aerogel from a polyamic acid or polyimide aerogel and a carbon aerogel doped with a carbon additive according to non-limiting aspects of the present disclosure.

[0128] Fig.15 is a flow chart depicting a process for preparing a metal or metal oxide doped carbon aerogel further comprising a carbon additive from a metal polyamic acid salt aerogel according to non-limiting aspects of the present disclosure.

[0129] Fig.16A is a micrograph of polyimide gel beads doped with graphene oxide according to non-limiting aspects of the present disclosure.

[0130] Fig. 16B is a high-magnification scanning electron microscope (SEM) photograph of carbon aerogel beads doped with graphene oxide according to non-limiting aspects of the present disclosure.

[0131] Fig.17A is a micrograph of soft carbon-doped polyimide gel beads according to non-limiting aspects of the present disclosure.

[0132] Fig. 17B is a high-magnification scanning electron microscope (SEM) photograph of carbon aerogel beads doped with soft carbon according to non-limiting aspects of the present disclosure.

[0133] Fig.18A is a micrograph of carbon black-doped polyimide gel beads according to non-limiting aspects of the present disclosure.

[0134] Fig.18B is a high-magnification scanning electron microscope (SEM) photograph of carbon aerogel beads doped with carbon black according to non-limiting aspects of the present disclosure.

[0135] Fig.19A is a micrograph of silicon / hard carbon doped polyimide aerogel beads according to non-limiting aspects of the present disclosure.

[0136] Fig.19B is a high-magnification scanning electron microscope (SEM) photograph of silicon / carbon composite aerogel beads doped with hard carbon according to non-limiting aspects of the present disclosure.

[0137] Fig. 20A is a micrograph of silicon / PTCDA doped polyimide aerogel beads according to non-limiting aspects of the present disclosure.

[0138] Fig. 20B is a high-magnification scanning electron microscope (SEM) photograph of silicon / carbon composite aerogel beads doped with soft carbon according to non-limiting aspects of the present disclosure.

[0139] Fig.21 is a graph showing first cycle charge-discharge curves versus first cycle efficiency (FCE) of carbon aerogel beads tested in a half-cell using lithium metal as a counter electrode according to non-limiting aspects of the present disclosure.

[0140] Fig. 22 is a graph showing the delithiation capacity of silicon / carbon composite aerogel beads over different numbers of cycles according to non-limiting aspects of the present disclosure. DETAILED DESCRIPTION

[0141] Before describing several exemplary aspects of the present technology, it should be understood that the present technology is not limited to the details of the construction or process steps set forth in the following description. The present technology can have other aspects and can be practiced or performed in various ways. The aspects described herein are interchangeable, that is, features mentioned in the context of a particular aspect are not limited to this aspect, but can be applied to and combined with each of the other aspects.

[0142] The present technology generally relates to carbon materials, such as porous carbon materials, which contain (i.e., are doped with) carbon additives, such as soft carbon, graphene, graphene nanoribbons, graphene nanosheets, graphene oxide, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or combinations thereof, and are optionally further doped with silicon. The present technology further relates to methods for preparing such porous carbon materials containing carbon additives. The methods generally include providing an organogel precursor; adding a carbon additive or a precursor thereof to the organogel precursor; inducing gelation of the organogel precursor to provide an organogel doped with the carbon additive or a precursor thereof; drying the organogel to form an organic aerogel doped with the carbon additive or a precursor thereof; and pyrolyzing the doped organic aerogel. In the case of a porous carbon material containing soft carbon as an additive, the method includes adding a precursor of the soft carbon, such as pitch or perylenetetracarboxylic dianhydride (PTCDA). In a subsequent pyrolysis process, such precursors are thermally converted to soft carbon.

[0143] As described above, it is surprising to find, according to the present disclosure, that carbon aerogel beads comprising certain carbon additives prepared as described herein exhibit improved first cycle efficiency, reversible capacity, and lithiation potential relative to reference carbon aerogel beads (i.e., not comprising carbon additives). In addition, it is surprising to find, according to the present disclosure, that carbon aerogel materials comprising soft carbon retain the high efficiency of carbon aerogel materials comprising hard carbon. The disclosed sol-based methods have a high degree of flexibility in the nature of the organogel precursors, the diversity of forms of carbon additives that can be provided, and the overall ability to tailor various aspects of the method, for example, to provide carbon aerogel materials having different physical forms and properties and having different properties of carbon additives therein.

[0144] Therefore, a method for forming a carbon aerogel containing a carbon additive is provided herein, the method comprising: providing a solution comprising an organogel precursor and a solvent; adding a carbon additive or a precursor thereof to the organogel precursor solution; initiating gelation of the organogel precursor to provide an organogel containing the carbon additive or a precursor thereof; drying the organogel to form an organic aerogel containing the carbon additive or a precursor thereof; and isomorphously converting the organic aerogel into a carbon aerogel containing the carbon additive, the conversion comprising pyrolyzing the organic aerogel at a temperature of at least about 650° C. under an inert atmosphere. The method can be performed using aqueous or organic conditions, a wide variety of organogel precursors, and a wide variety of carbon additives or precursors thereof. In the general method, there are a variety of method changes to accommodate different additives, organogel precursors, and conditions, as well as the ability to prepare carbon aerogel materials in different forms (e.g., beads, microbeads, monoliths) and carbon aerogel materials doped with other electroactive materials (e.g., silicon). Each of the various methods is further described below.

[0145] definition

[0146] With respect to terms used in this disclosure, the following definitions are provided. This application will use the following terms as defined below, unless the context of the text in which the term appears requires a different meaning.

[0147] The articles "a" and "an" are used herein to refer to one or more than one (i.e., at least one) of the grammatical objects of the article. The term "about" used throughout this specification is used to describe and explain small fluctuations. For example, the term "about" can refer to less than or equal to ±10% or less than or equal to ±5%, such as less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.2%, less than or equal to ±0.1%, or less than or equal to ±0.05%. All numerical values ​​herein are modified by the term "about", whether or not explicitly stated. The value modified by the term "about" certainly includes the specific value. For example, "about 5.0" must include 5.0.

[0148] In the context of the present disclosure, the term "framework" or "framework structure" refers to a network of interconnected oligomers, polymers or colloidal particles that form the solid structure of a gel or aerogel. The polymers or particles that make up the framework structure typically have a diameter of about 100 angstroms. However, the framework structure of the present disclosure may also include a network of interconnected oligomers, polymers or colloidal particles of all diameter sizes that form the solid structure within the gel or aerogel.

[0149] As used herein, the term "aerogel" refers to a solid object (regardless of shape or size) comprising a framework of interconnected solid structures with a corresponding interconnected network of pores integrated therein and containing a gas such as air as a dispersed interstitial medium. Thus, and regardless of the drying method used, an aerogel is an open non-fluid colloid or polymer network that is expanded by a gas throughout its volume and is formed by removing all swelling agents from a corresponding wet gel. References to "aerogel" herein include any open porous material that can be classified as an aerogel, xerogel, lyophilized gel, ambient dried gel, microporous material, etc., regardless of the material (e.g., polyimide, polyamic acid, or carbon), unless otherwise specified.

[0150] Typically, aerogels have one or more of the following physical and structural properties: (a) an average pore diameter ranging from about 2 nm to about 100 nm; (b) a porosity of about 60% or more; (c) a specific surface area of ​​about 0 to about 100 m 2 / g or more, typically about 0 to about 20, about 0 to about 100, or about 100 to about 1000 m 2 / g. Typically, such properties are determined using nitrogen porosimetry testing and / or helium pycnometry. It will be appreciated that the inclusion of additives such as reinforcing materials or electrochemically active materials (e.g., silicon) can reduce the porosity and specific surface area of ​​the resulting aerogel composite. Densification can also reduce the porosity of the resulting aerogel composite.

[0151] In some aspects, the gel material may be specifically referred to as a xerogel. As used herein, the term "xerogel" refers to a type of aerogel that comprises an open non-fluid colloid or polymer network formed by removing all swelling agents from the corresponding gel without taking any precautions to avoid a substantial reduction in volume or to prevent compaction. Xerogels typically include a compact structure. In some embodiments, the xerogel may be a non-porous material. Xerogels undergo a substantial reduction in volume during ambient pressure drying and typically have a microstructure of 0-100 m / s. 2 / g of surface area, such as about 0 to about 20 m 2 / g, as measured by nitrogen adsorption analysis.

[0152] As used herein, reference to a "conventional" or "organic solvent-based" process for forming a polyamic acid or polyimide gel refers to a process in which a polyamic acid or polyimide gel is prepared by condensing a diamine with a tetracarboxylic dianhydride in an organic solvent solution to form a polyamic acid and optionally dehydrating the polyamic acid to form a polyimide. See, for example, U.S. Patent Nos. 7,071,287 and 7,074,880 to Rhine et al. and U.S. Patent Application Publication No. 2020 / 0269207 to Zafiropoulos et al.

[0153] As used herein, the term "gelation" or "gel transition" refers to the formation of a wet gel by a polymer system (e.g., polyimide or polyamic acid as described herein). At a certain point (defined as "gel point") in the polymerization or dehydration reaction as described herein, the sol loses fluidity. Without being intended to be bound by any particular theory, the gel point can be regarded as the point at which the gelled solution exhibits resistance to flow. In this context, gelling proceeds from the initial sol state (e.g., polyamic acid ammonium salt solution), through a high viscosity dispersed state, until the dispersed state solidifies and the sol gels (gel point), producing a wet gel (e.g., polyimide or polyamic acid gel). The amount of time required for the polymer in the solution (e.g., polyamic acid ammonium salt or polyimide) to be converted into a gel that is no longer able to flow is called "phenomenal gel time". Formally, gel time is measured using rheology. At the gel point, the elastic properties of the solid gel begin to dominate the viscous properties of the fluid sol. The formal gel time is the time when the real part and the imaginary part of the complex modulus of the gelled sol intersect. The change of these two moduli over time is monitored using a rheometer. The time is calculated from the moment when the last component of the sol is added to the solution. See, for example, the gelation discussion in the following literature: HH Winter "Can the Gel Point of a Cross-linking 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 oftetraethylorthosilane / 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.

[0154] In the context of the present disclosure, the term "voids" or "void space" as used throughout this specification refers to "empty" space, ie, space that is not utilized by silicon or a three-dimensional carbon network.

[0155] As used herein, the term "wet gel" or "wet organogel" refers to a gel in which the mobile interstitial phase within the network of interconnected pores is primarily composed of a liquid phase (such as a conventional solvent or water), a liquefied gas (such as liquid carbon dioxide), or a combination thereof. Aerogels typically require initial production of a wet gel, followed by processing and extraction to replace the mobile interstitial liquid phase in the gel with air or another gas. Examples of wet gels include, but are not limited to, alcohol gels, hydrogels, ketogels, carbon gels, and any other wet gels known to those skilled in the art.

[0156] As used herein, the term "alkyl" refers to a straight or branched chain saturated hydrocarbon group typically having 1 to 20 carbon atoms (i.e., C1 to C20). Representative alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl; while branched alkyl groups include, but are not limited to, isopropyl, sec-butyl, isobutyl, tert-butyl, isopentyl, and neopentyl. Alkyl groups may be unsubstituted or substituted. It should be understood that the carbon atom ranges described herein, such as "C1 to C20," explicitly include each integer falling within the end of the range as well as the end of the range itself, i.e., C1, C2, C3, C4, C5 to C20, and all subranges falling therein.

[0157] As used herein, the term "alkenyl" refers to a hydrocarbon group generally having 1 to 20 carbon atoms (i.e., C1 to C20) and having 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, isobutenyl, 1-pentenyl, 2-pentenyl, 3-methyl-1-butenyl, 2-methyl-2-butenyl, 2,3-dimethyl-2-butenyl, and the like. Alkenyl groups may be unsubstituted or substituted.

[0158] As used herein, the term "alkynyl" refers to a hydrocarbon group generally having 1 to 20 carbon atoms (i.e., C1 to C20) and having at least one carbon-carbon triple bond. Examples of alkynyl groups include, but are not limited to, ethynyl and propargyl. Alkynyl groups may be unsubstituted or substituted.

[0159] The term "aryl" as used herein refers to an aromatic carbocyclic group typically having 6 to 20 carbon atoms (i.e., C6 to C20). Examples of aryl groups include, but are not limited to, phenyl, naphthyl, and anthracenyl. Aryl groups may be unsubstituted or substituted.

[0160] The term "cycloalkyl" as used herein refers to a saturated carbocyclic group, which may be monocyclic or bicyclic. Cycloalkyl includes a ring having 3 to 7 carbon atoms (i.e., C3 to C7) as a monocyclic ring or a ring having 7 to 12 carbon atoms (i.e., C7 to C12) as a bicyclic ring. Examples of monocyclic cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Cycloalkyl may be unsubstituted or substituted.

[0161] As used herein, the term "substituted" applies to any of the above groups (alkyl, alkenyl, alkynyl, aryl, cycloalkyl, etc.), meaning that one or more hydrogen atoms of the group are independently replaced by a substituent. Typical substituents include, but are not limited to, -X, -R, -OH, -OR, -SH, -SR, NH2, -NHR, -N(R)2, -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, -SO3-, -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, -PO3H2, -C(=O)X, -C(=S)R, -CO2H, -CO2R, -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 is independently selected from F, Cl, Br, and I at each occurrence; and each R is independently selected from Cl-C 20 Alkyl and C6-C 20 Aryl. In any case where a group is described as "optionally substituted," the group may be substituted independently at each occurrence with one or more of the above substituents.

[0162] It should be understood that certain naming conventions can include various attachment scenarios, depending on the context. For example, where a substituent requires two points of attachment to the rest of the molecule, it can be understood that the substituent is bidentate. For example, substituents identified as alkyl but requiring two points of attachment include forms such as -CH2-, -CH2CH2-, -CH2CH(CH3)CH2-. Other naming conventions clearly indicate that the group is bidentate, such as "alkylene," "alkenylene," "arylene," etc. In any case where a substituent is bidentate, it should be understood that the substituent can be attached in any orientation configuration unless otherwise indicated.

[0163] Unless otherwise indicated, the term "substantially" as used herein means to a large extent, e.g., greater than about 95%, greater than about 99%, greater than about 99.9%, greater than 99.99%, or even 100% of the referenced feature, quantity, etc., as is relevant to the particular context (e.g., substantially pure, substantially identical, etc.).

[0164] Reference to an aqueous solution herein means that the solution is substantially free of any organic solvent. The term "substantially free" as used herein in the context of an organic solvent means that no organic solvent is intentionally added, and no organic solvent is present in excess of trace amounts. For example, in some aspects, an aqueous solution can be characterized as having less than 1% by volume of an organic solvent, or less than 0.1% by volume, or less than 0.01% by volume, or even 0% by volume of an organic solvent.

[0165] I. Methods of Forming Carbon Aerogels Containing Carbon Additives

[0166] In one aspect, a method for forming a carbon aerogel containing a carbon additive is provided. The method generally comprises: providing a solution containing an organogel precursor and a solvent; adding a carbon additive or a precursor thereof to the organogel precursor solution; initiating gelation of the organogel precursor to provide an organogel containing the carbon additive or a precursor thereof; drying the organogel to form an organic aerogel containing the carbon additive or a precursor thereof; and pyrolyzing the organic aerogel containing the carbon additive or a precursor thereof. Figure 1 A general non-limiting flow chart is provided that illustrates a method according to one aspect of the present disclosure. Figure 1 The method includes first providing a solution comprising an organogel precursor and a solvent. The organogel precursor, solvent, and method of providing the solution may vary.

[0167] Organogels and organogels precursors

[0168] In some aspects, the organogel comprises a resorcinol-formaldehyde (RF) polymer, a phloroglucinol-furfural (PF) polymer, polyacrylonitrile (PAN), polyurethane (PU), polyurea (PUA), polyamine (PA), polybutadiene, polydicyclopentadiene, or a combination thereof. In these aspects, the precursors are the corresponding monomers (e.g., phloroglucinol and furfural, acrylonitrile, a suitable alcohol and a suitable isocyanate, a suitable amine and a suitable isocyanate, a suitable amine and a suitable reactive species, butadiene, cyclopentadiene, or a combination thereof, respectively). One skilled in the art will recognize the appropriate reactants required to form the desired organogel.

[0169] In some aspects, the organogel comprises a polyimide, a polyamic acid, or a combination thereof. In some aspects, the organogel is a polyimide, and the organogel precursor is a polyamic acid salt. Polyimides, polyamic acids, and polyamic acid salts, and methods of providing solutions of any of them are further described below.

[0170] The solvent used to provide the organogel precursor solution can vary based on, for example, the desired properties of the particular organogel precursor and the organogel. For example, where the organogel precursor is water soluble, the solvent can be water. In certain aspects, the organogel is a polyimide, a polyamic acid, or a combination thereof, the organogel precursor is a polyamic acid salt, and the solvent is water. In some aspects, there may be advantages to using a process that is primarily or entirely water-based, for example, in avoiding the use of potentially toxic and expensive solvents and their associated processing costs.

[0171] In other aspects, the solvent is a polar aprotic organic solvent. Such organic solvents can be used to prepare any of the aforementioned organogels, including but not limited to polyimide and polyamic acid organogels. In some aspects, the solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone or a combination thereof.

[0172] Carbon additives and precursors

[0173] Continue to refer Figure 1 , the method includes adding a carbon additive or a precursor thereof to an organogel precursor solution. In some aspects, the carbon additive is graphene, graphene nanoribbons, graphene nanosheets, graphene oxide, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers or a combination thereof. In these aspects, the method includes adding a suitable carbon additive to an organogel precursor solution. As further described below, once the organogel precursor is caused to gel to form a corresponding organogel, the organogel will include the carbon additive dispersed in the organogel matrix. After subsequent drying and pyrolysis (further below), a corresponding carbon aerogel is obtained, wherein the carbon additive is dispersed in the carbon aerogel matrix.

[0174] In some aspects, the carbon additive is carbon black.

[0175] In some aspects, the carbon additive is a single-walled carbon nanotube, a multi-walled carbon nanotube, or a carbon nanofiber.

[0176] In some aspects, the carbon additive is graphene or graphene oxide. In some aspects, the carbon additive is graphene nanoribbons, graphene nanosheets, graphene ribbons are described, for example, in U.S. Pat. No. 10,640,384 to Nguyen, which is incorporated herein by reference.

[0177] In other aspects, the carbon additive is soft carbon. In these aspects, the method includes adding a soft carbon precursor to an organogel precursor solution. In some aspects, the soft carbon precursor comprises or is perylenetetracarboxylic dianhydride (PTCDA). In some aspects, the soft carbon precursor comprises or is pitch. As further described below, once the organogel precursor is caused to gel to form a corresponding organogel, the organogel will contain a carbon additive precursor dispersed in the organogel matrix. After subsequent drying and pyrolysis (further below), a corresponding carbon aerogel is obtained, wherein the carbon additive is dispersed in the carbon aerogel matrix. Specifically, it is found according to the present disclosure that the pyrolysis of an organogel material containing a suitable soft carbon precursor (such as PTCDA or pitch) surprisingly leads to carbonization of the carbon precursor material, thereby providing soft carbon dispersed throughout the carbon aerogel matrix. Depending on the pyrolysis temperature, the soft carbon precursor can also be graphitized (for example, by utilizing a high pyrolysis temperature, such as about 2000°C). Advantageously, the conversion of a soft carbon precursor to soft carbon can be achieved at a temperature below 1000°C (such as about 850°C). Such lower pyrolysis temperatures are desirable in terms of reducing the energy requirements associated with such pyrolysis.

[0178] As described above, the disclosed methods of forming carbon aerogels containing carbon additives have various advantages over other potential methods of incorporating carbon materials into carbon aerogels. In particular, the methods have a high degree of flexibility with respect to the type of carbon incorporated, the type of organogel that can be used, and the conditions under which gelation can be performed. In addition, the methods allow for fine tuning of the properties of the carbon aerogel, the carbon additive within the aerogel, and the associated physical and electrochemical properties of the carbon aerogel. The methods are also suitable for simultaneously incorporating carbon additives into electroactive materials such as silicon, as further described below.

[0179] Initiate gelation

[0180] Continue to refer Figure 1, the method includes initiating gelation of the organogel precursor to provide an organogel comprising the carbon additive or its precursor. The initiation of gelation can include exposing the organogel precursor solution to various conditions or reagents, depending on the specific organogel precursor used. In some aspects, the organogel comprises a resorcinol-formaldehyde (RF) polymer, a phloroglucinol-furfural (PF) polymer, a polyacrylonitrile (PAN), a polyurethane (PU), a polyurea (PUA), a polyamine (PA), a polybutadiene, a polydicyclopentadiene, or a combination thereof, and initiating gelation includes one or more of the following: contacting the corresponding reactive components with each other under appropriate conditions, heating the organogel precursor solution, exposing the organogel precursor solution to an appropriate polymerization catalyst, etc. Appropriate conditions for initiating gelation (e.g., polymerization) of one or more organogel precursors are known to those skilled in the art and can be easily selected.

[0181] In some aspects, the organogel comprises polyamic acid, the organogel precursor is a polyamic acid salt, and initiating gelation comprises inducing precipitation of the corresponding polyamic acid. In some aspects, the organogel comprises or is a polyimide, the organogel precursor is a polyamic acid salt, and initiating gelation comprises imidizing the polyamic acid salt. Organogels comprising polyimide or polyamic acid, corresponding organogel precursors, and methods of providing solutions thereof, as well as methods of initiating gelation of each thereof, are further described below.

[0182] Gels doped with electroactive materials

[0183] In some aspects, any organogel and aerogel as disclosed herein can be doped with an electroactive material, for example silicon, such as silicon particles, to provide a carbon aerogel doped with an electroactive material. Thus, in some aspects, the method further comprises adding silicon particles to the organogel precursor solution.

[0184] In the context of the present disclosure, the term "silicon particles" refers to silicon or silicon-based materials with a particle size range suitable for use with polyimides or carbon gels as disclosed herein. The silicon particles of the present disclosure can be nanoparticles, such as particles with two or three dimensions ranging from about 1 nm to about 150 nm. The silicon particles of the present disclosure can be fine particles, such as micron-sized particles with a maximum dimension (e.g., a diameter of a substantially spherical particle) ranging from about 150 nm to about 10 microns or more. For example, the maximum dimension (e.g., the diameter of a substantially spherical particle) of the silicon particles of the present disclosure can be 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 in a range between any two of these values. In some aspects, the particles are flat fragments, such as platelets, whose two dimensions (e.g., length and width) are about 10nm, 50nm, 100nm, 150nm, 200nm, 500nm, 1 micron, 1.5 microns, 2 microns, 3 microns, 5 microns, 10 microns, 20 microns, 40 microns, 50 microns, 100 microns, or in a range between any two of these values. In some aspects, the silicon particles can be monodisperse or substantially monodisperse. In other aspects, the silicon particles can have a particle size distribution. In the context of the present disclosure, the dimensions of the silicon particles are provided based on the median value (i.e., D50) of the particle size distribution. The silicon particles of the present disclosure can be silicon wire, crystalline silicon, amorphous silicon, silicon alloy, silicon oxide (SiO x ), coated silicon (e.g., carbon-coated silicon), and any combination of silicon particle materials disclosed herein. In some aspects, the silicon particles can be substantially planar flakes, i.e., have a flat fragment shape, which can also be referred to as a platelet shape. For example, the particle has two substantially flat major surfaces connected by a secondary surface, and the secondary surface defines the thickness between the major surfaces. In other aspects, the particles of silicon or other electroactive materials can be substantially spherical, cubic, oblong, elliptical, disc-shaped, or annular. Silicon can also be present in the form of a thin film, for example, a thin film containing silicon formed after vapor deposition (e.g., chemical vapor deposition) of silicon into a composite material.

[0185] Silicon particles can be produced by a variety of techniques, including electrochemical reduction and mechanical milling, i.e. grinding. Grinding can be performed using a wet or dry process. In a dry grinding process, the powder is added to a vessel together with a grinding medium. The grinding medium typically includes balls or rods of zirconium oxide (yttrium stabilized), silicon carbide, silicon oxide, quartz or stainless steel. The particle size distribution of the resulting ground material is controlled by the energy applied to the system and the matching of the starting material particle size with the grinding medium size. However, dry grinding is an inefficient and energy-consuming process. Wet grinding is similar to dry grinding, but a grinding fluid is added. One advantage of wet grinding is that the energy consumption to produce the same result is 15%-50% lower than that of dry grinding. Another advantage of wet grinding is that the grinding fluid can protect the grinding material from oxidation. It has also been found that wet grinding can produce finer particles and cause less particle agglomeration.

[0186] A wide variety of liquid components can be used for wet grinding. In exemplary aspects, the grinding liquid or the components contained in the grinding liquid are selected to reduce or eliminate chemical functionalization on the surface of the silicon particles during or after grinding. In other aspects, the grinding liquid or the components contained in the grinding liquid are selected to provide the desired surface chemical functionalization for the particles (e.g., silicon particles) during or after grinding. The grinding liquid or the components contained in the grinding liquid can also be selected to control the chemical reactivity or crystal morphology of the particles (e.g., silicon particles). In exemplary aspects, the grinding liquid or the components contained in the grinding liquid can be selected based on the compatibility or reactivity with downstream materials, processing steps or the uses of particles (e.g., silicon particles). For example, the grinding liquid or the components contained in the grinding liquid can be compatible with, can be used in, or are the same as the liquid or solvent used in the process for forming or manufacturing organic or inorganic aerogel materials. In yet another aspect, the slurry can be selected so that the slurry or a component contained in the slurry produces a coating on the surface of the silicon particles or an intermediate substance (such as an aliphatic or aromatic hydrocarbon), or by cross-linking or producing a cross-functional compound that reacts with the organic or inorganic aerogel material.

[0187] The solvent or solvent mixture for grinding can be selected to control the chemical functionalization of particles during or after grinding. Using silicon as an example and not bound by theory, grinding silicon in an alcohol-based solvent (such as isopropanol) can functionalize the silicon surface and covalently bond alkyl surface groups (e.g., isopropyl) to the surface of silicon particles. As demonstrated by FTIR-ATR analysis, when exposed to air, alkyl can be converted into corresponding alkoxides by oxidation. In exemplary aspects, grinding can be carried out in polar aprotic solvents such as DMSO, DMF, NMP, DMAC, THF, 1,4-dioxane, diglyme, acetonitrile, water or any combination thereof.

[0188] Typically, electroactive material (e.g., silicon) particles are added during the sol-gel process (i.e., the particles are added to the organogel precursor solution before or during gelation). In some aspects, the electroactive material (e.g., silicon) particles are dispersed in a solvent (e.g., water or a polar aprotic solvent) before merging with the organogel precursor solution. In one non-limiting aspect, the organogel precursor is a polyamic acid salt solution, and the electroactive material (e.g., silicon) particles are dispersed in the polyamic acid salt solution before or during imidization. In some aspects, the electroactive material is added to an aqueous solution of polyamic acid salt. In some aspects, the electroactive material is silicon.

[0189] In some aspects, the individual silicon particles are heterogeneously dispersed throughout the three-dimensional carbon network. In some aspects, the individual silicon particles are homogeneously dispersed throughout the three-dimensional carbon network. The expression "homogeneously dispersed" means that the Si particles are distributed throughout the three-dimensional carbon network without large changes in local concentration over the entire accessible network surface.

[0190] In some aspects, about 30 wt% to 70 wt%, about 20 wt% to about 50 wt% of the individual silicon particles dispersed within the plurality of silicon particles are in an agglomerated state. In some aspects, less than about 30 wt%, less than about 20 wt%, less than about 10 wt% of the individual silicon particles dispersed within the plurality of silicon particles are in an agglomerated state. In some aspects, homogeneously distributed Si particles may refer to the distribution of a plurality of Si particles throughout the porous polymer network, wherein less than about 30 wt%, less than about 20 wt%, less than about 10 wt% of the individual silicon particles dispersed within the plurality of silicon particles are in an agglomerated state.

[0191] Void Space

[0192] In some aspects, the carbon aerogel materials disclosed herein include void spaces within the aerogel matrix. Such void spaces can be produced by introducing sacrificial particles during its preparation. In some aspects, the carbon aerogel materials include sacrificial particles. In some aspects, the sacrificial particles of the present disclosure are made of sacrificial materials. In some aspects, the sacrificial particles of the present disclosure include sacrificial materials. In the context of the present disclosure, the term "sacrificial material" refers to a material that is intended to be sacrificed or at least partially removed in response to the mechanical, thermal, chemical and / or electromagnetic conditions experienced by the material. For example, when exposed to high temperatures or high and / or continuous stresses, the sacrificial material may decompose.

[0193] The sacrificial material can be selected from the group consisting of: siloxane, polyolefin, polyurethane, phenolic resin, melamine, cellulose acetate and polystyrene. In some cases, the material layer is in the form of a foam. In some aspects, the sacrificial material may wear due to exposure to mechanical (such as cyclic) loads. In some aspects, the sacrificial layer decomposes after exposure to a single mechanical, chemical and / or thermal event.

[0194] In some aspects, the onset temperature of chemical decomposition of the sacrificial material is in the range of about 100° C. to about 700° C., about 100° C. to about 500° C., about 200° C. to about 400° C. The sacrificial particles can be made of polymers, metals, natural and synthetic organics, salts, ceramic compounds, or combinations thereof.

[0195] The polymer used for the sacrificial material can be selected from a wide variety of thermoplastic resins, thermoplastic resin blends, or thermosetting resins. Examples of thermoplastic resins that can be used include polyacetals, polyacrylics, styrene acrylonitrile, polyolefins, acrylonitrile-butadiene-styrene, polycarbonates, polystyrenes, polyethylene terephthalate, polybutylene terephthalate, polyamides (such as but not limited to nylon 6, nylon 6,6, nylon 6,10, nylon 6,12, nylon 11 or nylon 12), polyamide-imides, polyarylates, polyurethanes, ethylene propylene rubber (EPR), polyarylsulfones, polyethersulfones, polyphenylene sulfide, polyvinyl chloride, polysulfones, polyetherimides, polytetrafluoroethylene, fluorinated ethylene propylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyetherketones, polyetheretherketones, polyetherketoneketones, or the like, or a combination comprising at least one of the foregoing thermoplastic resins.

[0196] Examples of thermoplastic resin blends that can be used for the sacrificial material include acrylonitrile-butadiene-styrene / nylon, polycarbonate / acrylonitrile-butadiene-styrene, acrylonitrile-butadiene styrene / polyvinyl chloride, polyphenylene oxide / polystyrene, polyphenylene oxide / nylon, polysulfone / acrylonitrile-butadiene-styrene, polycarbonate / thermoplastic urethane, polycarbonate / polyethylene terephthalate, polycarbonate / polybutylene terephthalate, thermoplastic elastomer alloy, polyethylene terephthalate / polybutylene terephthalate, styrene-maleic anhydride / acrylonitrile-butadiene-styrene, polyetheretherketone / polyethersulfone, styrene-butadiene rubber, polyethylene / nylon, polyethylene / polyacetal, ethylene-propylene rubber (EPR), etc., or a combination comprising at least one of the foregoing blends.

[0197] Examples of polymer thermosetting resins that can be used for the sacrificial material include polyurethanes, epoxies, phenolics, polyesters, polyamides, silicones, and the like, or a combination comprising at least one of the foregoing thermosetting resins. Blends of thermosetting resins and blends of thermoplastic resins with thermosetting resins can be used.

[0198] In some aspects, the sacrificial particles comprise a polymer having a pyrolysis yield of less than 30 wt%, less than 20 wt%, less than 18 wt%, less than 15 wt%, less than 10 wt%, less than 8.0 wt%, or less than 5.0 wt%.

[0199] In some aspects, the sacrificial particles are formed of a material selected from the group consisting of polymethyl methacrylate (PMMA), polyvinyl pyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethyleneimine (PEI), polyurethane, poly(3,4-ethylenedioxythiophene, PEDOT), polyvinyl butyral, polyethylene oxide copolymers, polypropylene oxide copolymers, polycarbonate (PC), polyvinyl chloride (PVC), polycaprolactone, polyvinylidene fluoride, polystyrene, or a combination thereof.

[0200] In some aspects, the sacrificial particles comprise poly(styrene), poly(ester), poly(methacrylate), poly(acrylate), poly(ethylene glycol), poly(amide), poly(norbornene), or a combination thereof. In one aspect, the sacrificial particles comprise poly(methyl methacrylate).

[0201] The sacrificial particles are typically provided by the same source and have a known, desired particle size, shape, porosity, and other substantially similar material properties. In some instances, the sacrificial particles have a diameter of less than 1000 nm, less than 800 nm, less than 500 nm, less than 300 nm, less than 250 nm, less than 200 nm, less than 150 nm, or less than 100 nm.

[0202] Thus, in some aspects, the method further comprises adding polymer particles to the organogel precursor solution prior to gelation. This sacrificial polymer particulate material forms voids in the corresponding carbon aerogel material during, for example, subsequent pyrolysis. In some aspects, the sacrificial polymer particulate material is poly(methyl methacrylate).

[0203] In some aspects, the carbon aerogel is included in the void space within the aerogel matrix, and the carbon aerogel further includes silicon, wherein at least a portion of the silicon is retained in the void space. In some aspects, the carbon aerogel material provided herein further includes silicon particles and a three-dimensional carbon network, wherein the void space is between the outer surface of the silicon particles and the three-dimensional carbon network. The void space between the outer surface of the silicon particles and the three-dimensional carbon network can cause the dispersion and anti-agglomeration of the silicon particles to be good. The void space fully adapted to the volume expansion of the silicon particles provides a free space for adapting to the volume expansion. The presence of the void can reserve space for the silicon particles during the volume expansion, and buffer the mechanical pressure of the three-dimensional carbon network, thereby significantly enhancing the structural integrity. Without wishing to be bound by theory, adapting to the volume expansion of the silicon particles can delay the fracture of the silicon particles caused by continuous charge and discharge battery cycles.

[0204] In some aspects, the void space is between the outer surface of the silicon particle and the three-dimensional carbon network. That is, the void space can at least partially surround or enclose the silicon particle and thus be able to accommodate volume changes in the silicon particle.

[0205] In some aspects, the volume of the void spaces is between 1% and 20%, between 3% and 15%, between 5% and 15%, between 3% and 10%, between 5% and 10% of the volume of the silicon particles.

[0206] Sacrificial layer

[0207] In some aspects, in order to produce a silicon-carbon composite material having a void space at least partially surrounding or surrounding a silicon particle, a sacrificial layer is first produced on at least a portion of the outer surface of the silicon particle. The sacrificial layer of the present technology provides the advantage of designing the void space, and its volume can be controlled. That is, the void space between the outer surface of the silicon particle and the three-dimensional carbon network can be produced by partially or completely removing the sacrificial layer. By adjusting the thickness of the sacrificial layer of the present technology, the volume of the void space can be controlled.

[0208] In another aspect, the volume of the void space can be adjusted by controlling the amount of the sacrificial layer that is removed (eg, decomposed) when exposed to an external stimulus / agent. Without wishing to be bound by theory, as the amount of sacrificial layer removed increases, the volume of the void space becomes larger.

[0209] In some aspects, the volume of the void space is customized or controlled by controlling the distribution of the silicon particles. In certain aspects, the volume of the void space is adjusted or controlled by designing the amount of silicon particles within the composite material (e.g., volume percentage of particles, volume percentage of sacrificial layer content).

[0210] Thus, in some aspects, the method further comprises adding a sacrificial material coated silicon to the organogel precursor solution, wherein the sacrificial material forms voids in the corresponding carbon aerogel during subsequent pyrolysis. Methods of providing a sacrificial material coated silicon material are further described below.

[0211] In some aspects, the surface of the silicon particles (e.g., silicon nanoparticles) can be modified with functional groups that can help the silicon particles disperse in the porous network before the sacrificial layer is formed. In another example, the formation of the sacrificial layer can further help the silicon particles disperse in the porous network. In one example, the porous network can be a sol-gel, an aerogel, a xerogel, a foam structure, etc.

[0212] For example, functional groups can be grafted onto the surface of silicon particles by covalent bonds. Before functionalization, the surface of silicon particles includes silane groups (such as silicon hydride) and / or silicon oxide groups. In some aspects, after the surface functionalization of silicon particles, at least a portion of these silane and silicon oxide groups can exist in combination with bonded functional groups, for example, the silicon particle surface can include silane groups and covalently attached functional groups, silicon oxide groups and covalently attached functional groups or silane and silicon oxide groups and covalently attached functional groups. The presence of functional groups on the surface of silicon particles can be detected by various techniques (for example, by infrared spectroscopy).

[0213] The surface of silicon particles can be functionalized with hydrophilic groups to help improve dispersion in the porous network. Without being bound by theory, functionalization with hydroxyl groups produces increased covalent bonding between the surface groups on silicon particles and the porous network. Therefore, functionalized silicon particles can be uniformly dispersed in the porous network. For example, hydrophilic hydroxyl groups can be grafted to the surface of particles by unsaturated diols to increase the hydrophilicity of the silicon particle surface. Increasing the hydrophilicity of silicon particles enables particles to be and remain more uniformly dispersed in the network and remain uniformly dispersed in the network during any additional processing (e.g., pyrolysis). In an example, functionalization via diols can improve the dispersion of silicon particles in polyimide sol-gel and / or aerogel or carbon aerogel. Any suitable diol can be used, including but not limited to ethylene glycol methyl ether methacrylate, poly (ethylene glycol) methyl ether methacrylate, etc.

[0214] In order to provide silicon particles comprising a sacrificial layer, silicon particles are first provided. Generally, silicon particles should be homogeneous. That is, silicon particles are typically provided by the same source and have known, desired particle size, shape, porosity and other substantially similar material properties. After obtaining silicon particles, the method includes oxidizing the particle surface to obtain hydroxyl functional groups on the surface. Oxidation of the silicon particle surface is necessary for further functionalization of the surface. Oxidation of the silicon particle surface may lead to complete or partial oxidation of surface Si-H groups. That is, after the oxidation process, all or a certain percentage of Si-H groups on the silicon particle surface are converted into Si-OH groups. Silicon particles can be oxidized in a single or multiple steps. Oxidation can be thermal oxidation (e.g., under air at elevated temperatures), chemical oxidation (e.g., acid and / or oxidant), electrochemical oxidation or a combination thereof.

[0215] The surface oxidation of multiple silicon particles may include an acid treatment step. In some aspects, the acid treatment step includes the use of thiochromic acid or H2O2 (hydrogen peroxide). In some instances, the acid treatment step includes the step of ultrasonically treating multiple silicon particles for a period of time (e.g., at least 5 minutes, at least 10 minutes, at least 20 minutes, at least 30 minutes, or at least 60 minutes). The surface oxidation of multiple silicon particles may include a step of pyrolysis at a temperature of about 300°C, about 400°C, or about 500°C to about 600°C, about 650°C, about 700°C, about 800°C, about 850°C, or about 900°C. In some aspects, the temperature is about 650°C.

[0216] The third step is to form a sacrificial layer on at least a portion of the surface of the silicon particles. The formation of the sacrificial layer is performed on the surface of the silicon particles before the silicon particles are introduced into the sol-gel solution containing the porous three-dimensional network precursor. The characteristics (e.g., thickness, material type) of the sacrificial layer formed in the third step can affect the dispersibility of the silicon particles in the sol-gel solution. The sacrificial layer can be made of polymers, metals, natural and synthetic organics, salts, ceramic compounds or combinations thereof.

[0217] In some aspects, the sacrificial layer is formed of a material selected from the group consisting of polymethyl methacrylate (PMMA), polyvinyl pyrrolidone (PVP), polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polypropylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide copolymers, polypropylene oxide copolymers, polycarbonate (PC), polyvinyl chloride (PVC), polycaprolactone, polyvinylidene fluoride, polystyrene, or a combination thereof. In some aspects, the sacrificial layer is formed of polymethyl methacrylate (PMMA).

[0218] In some aspects, the sacrificial layer has a thickness less than or equal to about 100 nm, or a thickness between about 100 nm and about 60 nm, or a thickness between about 60 nm and 0.3 nm. In some aspects, the sacrificial layer has a thickness in the range of about 20% to about 0.01% of the silicon particle diameter.

[0219] In some aspects, the sacrificial layer has a carbonization yield of less than about 20 wt%. In some aspects, the chemical decomposition temperature of the sacrificial material layer is in a range of about 130°C to about 850°C.

[0220] In some aspects, the formation of the sacrificial layer includes: i. grafting a polymer initiator onto the surface of silicon particles to react with the monomer; ii. polymerizing the monomer onto the surface of the silicon particles to form a sacrificial layer. In the first step, silicon particles having hydroxyl functional groups on their surfaces covalently react with functional silane groups. The step of covalently reacting the hydroxyl groups on the surface of the silicon particles includes using at least one functional group selected from the following: 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane (APTMS), N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPTES), and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS), and N-(6-aminohexyl)aminomethyltriethoxysilane (AHAMTES) or a combination thereof. In some aspects, 3-aminopropyltriethoxysilane (APTES) can be used as a functional silane group. The hydroxyl group reacts with the silane group in a polar solvent (e.g., ethanol). The polar solvent selected should be suitable for dissolving each component in the reaction, such as polymer initiator, silicon particles.

[0221] After covalently attaching at least one functional group (e.g., APTES) to the surface of the silicon particles to form silicon particles containing -NH2 groups on the surface, a polymer initiator is grafted onto the surface of the silicon particles to further react with the monomer. In some aspects, the polymer initiator comprises azobis(4-cyanovaleric acid) (ACPA), 2,2'-azobis(2-amidinopropane) hydrochloride (V50), ammonium persulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride (VA044), and ammonium persulfate / sodium metabisulfite. In some aspects, the polymer initiator comprises azobis(4-cyanovaleric acid) (ACPA).

[0222] The grafting of the polymer initiator onto the surface of the silicon particles occurs in a polar solvent (e.g., ethanol). The monomer initiator on the surface of the silicon particles undergoes a polymerization reaction with a monomer (e.g., methyl methacrylate). The monomer selected for the polymerization reaction depends on the type of sacrificial layer desired on the surface. The polymerization reaction can occur in a polar solvent (e.g., water). The polymerization reaction occurs at a temperature above 25°C.

[0223] In some aspects, the surface modification occurs before the silicon particles are added to the sol precursor solution. In other aspects, the surface modification is performed in the sol precursor solution during or after initiation of gelation. In some aspects, the surface modification is performed both before the silicon particles are dispersed in the sol precursor and after the sacrificial layer has been formed.

[0224] After forming the sacrificial layer (before dispersing the modified silicon particles in the sol precursor solution, after dispersing the modified silicon particles in the sol precursor solution, or both) and after processing the organogel material as described below, at least a portion of the sacrificial layer is removed.

[0225] The sacrificial layer of the present disclosure can be partially or completely removed by mechanical, thermal, chemical and / or electromagnetic forces and / or agents applied to the sacrificial layer. The manner of removing the sacrificial material depends primarily on the type of sacrificial material used. For example, when synthetic and natural organic matter is used as a sacrificial layer, it can be partially or completely removed by pyrolysis by applying a long heat treatment at a temperature between 130°C and 850°C. Due to the continuous mechanical and / or temperature and / or chemical changes experienced by the sacrificial layer, the sacrificial layer of the present technology can be partially or completely removed during the battery charge and discharge cycle. Partial or complete removal of the sacrificial layer during battery cycling may produce void space between the surface of the silicon particles and the three-dimensional network. Without wishing to be bound by theory, the void space produced allows for adaptation to the volume changes of the Si particles after the lithiation process.

[0226] In one aspect, the sacrificial layer of the present technology provides the advantage of designing void spaces of adjustable size. That is, by changing the thickness of the sacrificial layer provided herein, the size of the void space between the silicon particle surface and the three-dimensional network generated by removing the sacrificial layer can be customized.

[0227] In one aspect, the amount of the sacrificial layer removed depends on the duration of the heat treatment (e.g., pyrolysis) applied to the porous carbon network comprising silicon particles. In some aspects, the method further includes processing the porous carbon network comprising silicon particles to substantially remove the sacrificial layer, such as pyrolyzing the porous network. In one aspect, the processing includes heating the porous carbon network comprising silicon particles to the chemical decomposition temperature of the sacrificial layer. In some aspects, the chemical decomposition temperature of the sacrificial material layer is in the range of about 130°C to about 850°C. In some aspects, the composite material is processed to partially or completely remove the sacrificial layer so that a void space is provided around the silicon particles. In some aspects, the sacrificial layer is removed simultaneously during the pyrolysis of the organic aerogel material comprising a carbon additive or its precursor. In other aspects, before pyrolysis, the sacrificial layer is removed or partially removed in a separate step to convert the organic aerogel material and the carbon precursor (when present) into a corresponding carbon-silicon composite material comprising a carbon material.

[0228] Drying of organogel

[0229] Continue to refer Figure 1, the method comprising drying the organogel to form an organic aerogel comprising a carbon additive or a precursor thereof. In some aspects, drying the organogel comprises: optionally, washing or solvent exchanging the organogel; and subjecting the organogel to elevated temperature conditions, freeze-drying the organogel, or contacting the organogel with supercritical fluid carbon dioxide.

[0230] The wet organogel material obtained by gelling the organogel precursor material can be washed or solvent exchanged in a suitable second solvent to replace the main reaction solvent (i.e., water) present in the wet gel. Such a second solvent can be a straight-chain alcohol having 1 or more aliphatic carbon atoms; a diol having 2 or more carbon atoms; or a branched alcohol, a cyclic alcohol, an alicyclic alcohol, an aromatic alcohol, a polyol, an ether, a ketone, a cyclic ether, or a derivative thereof. In some aspects, the second solvent is water, a C1 to C3 alcohol (e.g., methanol, ethanol, propanol, isopropanol), acetone, tetrahydrofuran, ethyl acetate, acetonitrile, supercritical fluid carbon dioxide (CO2), or a combination thereof. In some aspects, the second solvent is ethanol.

[0231] After optional washing or solvent exchange, the liquid phase of the organogel material can then be at least partially extracted from the wet organogel material using an extraction method (including processing and extraction techniques) to form an aerogel material (i.e., "drying"). Liquid phase extraction plays an important role in engineering the characteristics of aerogels (such as porosity and density) and related properties (such as thermal conductivity), among other factors. Typically, an aerogel is obtained when the liquid phase is extracted from a wet gel in a manner that causes low shrinkage to the porous network and framework of the wet gel. Various techniques can be used to dry the wet gel to provide an aerogel or a xerogel. In exemplary aspects, the wet gel material can be dried at ambient pressure, under vacuum (e.g., by freeze drying), under subcritical conditions, or under supercritical conditions to form a corresponding dried gel (e.g., an aerogel, such as a xerogel).

[0232] In some aspects, it may be desirable to fine tune the surface area of ​​the dried gel. If it is desirable to fine tune the surface area, the aerogel can be converted in whole or in part into a xerogel having various porosities. The high surface area of ​​the aerogel can be reduced by forcing some of the pores to collapse. For example, this can be accomplished by immersing the aerogel in a solvent such as ethanol or acetone for a period of time or exposing it to solvent vapors. The solvent is then removed by drying at ambient pressure.

[0233] Aerogels are typically formed by removing a liquid mobile phase from a wet gel material at a temperature and pressure near or above the critical point of the liquid mobile phase. Once the critical point is reached (near critical) or exceeded (supercritical; that is, the pressure and temperature of the system are equal to or above the critical pressure and critical temperature, respectively), a new supercritical phase, distinct from the liquid or gas phase, emerges in the fluid. The solvent can then be removed without the introduction of liquid-gas interfaces, capillary forces, or any of the associated mass transfer limitations typically associated with the receding liquid-gas boundary. Additionally, the supercritical phase is typically more miscible with organic solvents and therefore has the ability to be better extracted. Cosolvents and solvent exchange are also commonly used to optimize supercritical fluid drying processes.

[0234] If evaporation or extraction occurs below the supercritical point, capillary forces generated by the evaporation of the liquid may cause shrinkage and pore collapse within the gel material. Maintaining the mobile phase at near or above the critical pressure and temperature during the solvent extraction process will reduce the negative effects of such capillary forces. In certain aspects of the present disclosure, the use of near-critical conditions just below the critical point of the solvent system can allow the production of aerogels or compositions with sufficiently low shrinkage to produce a commercially viable final product.

[0235] The wet organogel can be dried using various techniques to provide an aerogel. In exemplary aspects, the wet organogel material can be dried under ambient pressure, subcritical conditions, or supercritical conditions.

[0236] Both room temperature and high temperature processes can be used to dry the gel material at ambient pressure. In some aspects, a slow ambient pressure drying process can be used, wherein the wet organogel material is exposed to air in an open container for a period of time sufficient to remove the solvent, such as a period of time ranging from hours to weeks, depending on the solvent, the amount of wet organogel material, the exposed surface area, the size of the wet organogel material, etc.

[0237] In another aspect, the wet organogel material is dried by heating. For example, the wet organogel material can be heated in a convection oven for a period of time to evaporate most of the solvent (e.g., ethanol). After partial drying, the gel can be placed at ambient temperature for a period of time, such as several hours to several days, to completely dry. This drying method produces a xerogel.

[0238] In some aspects, the wet organogel material is dried by freeze drying. "Freeze drying" or "lyophilization" means a low temperature process for removing solvents, which involves freezing a material (e.g., a wet organogel material), reducing the pressure, and then removing the frozen solvent by sublimation. Since water represents an ideal solvent to be removed by freeze drying and water is a solvent in the methods disclosed herein, freeze drying is particularly suitable for forming aerogels from the disclosed polyimide wet organogel materials. This drying method produces a freeze-dried gel, which may be very similar to an aerogel.

[0239] Both supercritical and subcritical drying can be used to dry the wet organogel material. In some aspects, the wet organogel material is dried under subcritical or supercritical conditions. In exemplary aspects of supercritical drying, the gel material can be placed in a high pressure vessel to extract the solvent with supercritical CO2. After removing the solvent (e.g., ethanol), the vessel can be kept above the critical point of CO2 for a certain period of time, such as about 30 minutes. After supercritical drying, the vessel is depressurized to atmospheric pressure. Typically, an aerogel is obtained by this process.

[0240] In an exemplary aspect of subcritical drying, the gel material is dried at room temperature using liquid CO2 at a pressure in the range of about 800 psi to about 1200 psi. This operation is faster than supercritical drying; for example, the solvent (e.g., ethanol) can be extracted in about 15 minutes. Typically, an aerogel is obtained by this process.

[0241] Several additional aerogel extraction techniques are known in the art, including a range of different methods for drying aerogels using supercritical fluids, 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 evaporative 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 and then extracted under conditions in which the carbon dioxide is in a supercritical state. U.S. Patent No. 6,670,402 teaches the extraction of a liquid phase from a gel via rapid solvent exchange by injecting supercritical (rather than liquid) carbon dioxide into an extractor that has been preheated and pre-pressurized to substantially supercritical conditions or higher, thereby producing an aerogel. U.S. Patent No. 5,962,539 describes a process for obtaining an aerogel from a polymer material in the form of a sol-gel in an organic solvent, the process being performed by exchanging the organic solvent for a fluid having a critical temperature below the decomposition temperature of the polymer, and supercritically extracting the fluid from the sol-gel. U.S. Patent No. 6,315,971 discloses a process for producing a gel composition, the process comprising drying a wet gel comprising gel solids and a desiccant to remove the desiccant under drying conditions sufficient to reduce shrinkage of the gel during drying. U.S. Patent No. 5,420,168 describes a process in which a resorcinol / formaldehyde aerogel can be made 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 be stronger and more hydrophobic so that the gel framework and pores can resist collapse during ambient drying or subcritical extraction. Other examples of extracting a liquid phase from an aerogel material can be found in U.S. Patent Nos. 5,275,796 and 5,395,805.

[0242] In some aspects, the liquid phase is extracted from the wet organic gel material using supercritical conditions of carbon dioxide, including, for example: first substantially exchanging the main solvent present in the gel pore network with liquid carbon dioxide; and then heating the wet gel (typically in an autoclave) to a pressure exceeding the critical temperature of carbon dioxide (about 31.06°C) and increasing the system pressure to a pressure greater than the critical pressure of carbon dioxide (about 1070psig). The pressure around the gel material can fluctuate slightly to facilitate the removal of supercritical carbon dioxide fluid from the gel. Carbon dioxide can be recycled through the extraction system to facilitate the continuous removal of the main solvent from the wet gel. Finally, the temperature and pressure are slowly restored to ambient conditions to produce a dry aerogel material. Carbon dioxide can also be pre-processed into a supercritical state before being injected into the extraction chamber. In other aspects, any suitable mechanism can be used for extraction, such as changing the pressure, time and solvent discussed above.

[0243] Formation of carbon aerogels containing carbon additives

[0244] Continue to refer Figure 1 , the method includes converting the organic aerogel into a carbon aerogel containing a carbon additive. Typically, the conversion includes pyrolyzing (carbonizing) the organic aerogel, meaning heating the aerogel at a temperature and time sufficient to convert substantially all of the organic material into carbon. As used herein in the context of pyrolysis, "substantially all" means that more than 95% of the organic material is converted into carbon, such as 99%, or 99.9%, or 99.99%, or even 100% of the organic material is converted into carbon. Pyrolysis of the organic aerogel converts the organic aerogel into a homomorphic carbon aerogel, meaning that the physical properties (e.g., porosity, surface area, pore size, diameter, etc.) are substantially retained in the corresponding carbon aerogel, and the carbon additive or its precursor is retained or converted into the corresponding carbon additive, respectively. The time and temperature required for pyrolysis can vary. In some aspects, the organic aerogel is subjected to a treatment temperature of about 650°C or more, 800°C or more, 1000°C or more, 1200°C or more, 1400°C or more, 1600°C or more, 1800°C or more, 2000°C or more, 2200°C or more, 2400°C or more, 2600°C or more, 2800°C or more, or in a range between any two of these values, to carbonize the organic aerogel. Typically, pyrolysis is performed under an inert atmosphere to prevent combustion of the organic or carbon material. Suitable atmospheres include, but are not limited to, nitrogen, argon, or a combination thereof. In some aspects, pyrolysis is performed under nitrogen.

[0245] In some aspects, the organic aerogel is a polyimide, a polyamic acid or a combination thereof, and can be in the form of a monolith or a bead. In some aspects, the organic aerogel is a polyamic acid, which can be directly converted into a carbon aerogel (i.e., without first being imidized to provide a polyimide aerogel). In some aspects, the organic aerogel is a polyamic acid, which is thermally imidized as disclosed herein to first provide a polyimide aerogel, and then subsequently polyimide gas condensation is pyrolyzed to provide a carbon aerogel. In some aspects, the organic aerogel is a polyimide, which is pyrolyzed to provide a carbon aerogel. In some aspects, the organic aerogel is a polyamic acid metal salt aerogel, which is pyrolyzed to provide a carbon aerogel. In such aspects, when pyrolyzed, the ions of the soluble metal salt present can form a corresponding metal oxide or can be sintered and form a corresponding metal, depending on the metal species and pyrolysis conditions.

[0246] Carbon aerogels containing carbon additives prepared from polyamic acid salt solutions

[0247] In some aspects, the organogel is a polyimide, a polyamic acid, or a polyamic acid metal salt. Each of the polyimide, polyamic acid, or polyamic acid metal salt organogel can be obtained from an aqueous solution of a polyamic acid salt. Figure 2 A general non-limiting overview of three options for preparing polyimide aerogels, polyamic acid aerogels, polyamic acid metal salt aerogels containing carbon additives or precursors, and their corresponding carbon aerogels containing carbon additives (all prepared from aqueous solutions of polyamic acid salts) is provided.

[0248] In some aspects, the organogel is a polyimide. Figure 2 In Option 1, the polyamic acid aqueous solution is imidized and dried to provide a polyimide (PI) aerogel in the form of a monolith or beads. Optionally, the PI aerogel can be pyrolyzed to form the corresponding carbon aerogel.

[0249] Further references Figure 2 In option 2, the polyamic acid aqueous solution is acidified and dried to form a polyamic acid (PAA) aerogel as a monolith or beads. The PAA aerogel can be converted to a PI aerogel by thermal imidization, or it can be directly converted to the corresponding carbon aerogel by pyrolysis.

[0250] Further reference Figure 2 In option 3, the aqueous polyamic acid solution is subjected to metal ion exchange to form a PAA metal salt aerogel in the form of a monolith or bead. Such a PAA metal salt aerogel can be directly pyrolyzed to form the corresponding metal- or metal oxide-doped carbon aerogel.

[0251] Providing an aqueous solution of a polyamic acid salt

[0252] exist Figure 2 In each of the options presented, the commonality is an aqueous solution of a polyamic acid salt. Thus, in some aspects, a method of forming a carbon aerogel comprising a carbon additive comprises providing an aqueous solution of a polyamic acid salt, the polyamic acid salt comprising a polyamic acid containing a carboxylic acid group, wherein the carboxylic acid group is associated with a cationic species and exists substantially as a carboxylate anion; and adding a carbon additive as described above or a precursor thereof to the aqueous solution. Such polyamic acid salt solutions can be provided in a variety of different ways further described below.

[0253] In some aspects, polyamic acid is purchased or prepared in advance, and is dissolved in water in the presence of an alkali to provide a polyamic acid salt solution. In other aspects, the solution can be obtained by preparing in situ from a polyamic acid precursor (diamines and tetracarboxylic dianhydride) in the presence of an alkali under aqueous conditions. Each option is further described hereinafter.

[0254] Polyamic acid

[0255] In some respects, described method comprises providing polyamic acid or its salt.Polyamic acid is the polymer amide with repeating unit, and described repeating unit comprises carboxylic acid group, carboxamide group and aromatic or aliphatic part, and described carboxylic acid group, carboxamide group and aromatic or aliphatic part constitute diamine and tetracarboxylic acid that derive polyamic acid.As defined herein " repeating unit " is a part for polyamic acid (or corresponding polyimide), and its repetition will produce complete polymer chain (except terminal amino or unreacted anhydride end) by repeating unit being linked together along polymer chain successively.Those skilled in the art will recognize that polyamic acid repeating unit is produced by partial condensation of the amino group of tetracarboxylic dianhydride carboxyl and diamine.

[0256] In some respects, polyamic acid is any commercially available polyamic acid. In other respects, polyamic acid has been preformed (" preformed ") and separated, for example, prepared by reacting diamines with tetracarboxylic dianhydride in an organic solvent according to a conventional synthesis method. In either case, whether purchased or prepared and separated, suitable polyamic acid is in substantially pure form. Preformed and separated or commercially available polyamic acid can be, for example, in solid form (such as powder or crystalline form) or in liquid form.

[0257] The structure of suitable polyamic acid can vary. In some aspects, the polyamic acid has a structure represented by Formula I:

[0258]

[0259] in:

[0260] Z is a group connecting the two terminal amino groups of the diamine;

[0261] L is a group connecting to a carboxyl group; and

[0262] n is an integer indicating the number of polyamic acid repeating units and determining the molecular weight of the polyamic acid.

[0263] In some respects, Z is an aliphatic group (for example, alkyl, alkenyl, alkynyl or cycloalkyl) as described above. Therefore, in some respects, polyamic acid includes the amide of aliphatic diamine as repeating unit. In some respects, polyamic acid includes the amide of alkane diamine with 2 to 12 carbon atoms (that is, C2 to C12) as repeating unit. In some respects, polyamic acid includes the amide of C2 to C6 alkane diamine as repeating unit, and the alkane diamine is such as but not limited to ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane or 1,6-diaminohexane. In some respects, one or more carbon atoms of C2 to C6 alkane of diamine are replaced by one or more alkyl (such as methyl).

[0264] In some aspects, Z is an aryl group as described above. Therefore, in some aspects, polyamic acid comprises an amide of an aromatic diamine as a repeating unit. In some aspects, polyamic acid comprises an amide of a phenylenediamine, an ether diaminodiphenyl ether or an alkylenediamine as a repeating unit. In some aspects, polyamic acid comprises an amide of an aromatic diamine as a repeating unit, and the aromatic diamine is selected from the group consisting of: 1,3-phenylenediamine, 1,4-phenylenediamine, 4,4'-ether diaminodiphenyl ether, 4,4'-methylenedianiline and a combination thereof. In some aspects, polyamic acid comprises an amide of an aromatic diamine as a repeating unit, and the aromatic diamine is selected from the group consisting of: 1,4-phenylenediamine, 4,4'-methylenedianiline, 4,4'-ether diaminodiphenyl ether. In some aspects, polyamic acid comprises an amide of an aromatic diamine as a repeating unit, and the aromatic diamine is 1,4-phenylenediamine (PDA).

[0265] In some aspects, L comprises an alkyl group, a cycloalkyl group, an aryl group, or a combination thereof, each as described above. In some aspects, L comprises an aryl group. In some aspects, L comprises a phenyl group, a biphenyl group, or a diphenyl ether group. In some aspects, the polyamic acid comprises a tetracarboxylic acid as a repeating unit, the tetracarboxylic acid being 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, perylenetetracarboxylic acid, and combinations thereof. In some aspects, the polyamic acid comprises an amide of a tetracarboxylic acid as a repeating unit, the tetracarboxylic acid being benzene-1,2,4,5-tetracarboxylic acid,

[0266] Polyamic acid salt

[0267] Although polyamic acid is generally insoluble in water, it has been discovered in accordance with the present disclosure that certain polyamic acid salts have useful water solubility in which the carboxylic acid groups of the polyamic acid are associated with cationic species and exist substantially as carboxylate anions. "Present substantially as carboxylate anions" means that greater than about 95%, greater than about 99%, greater than about 99.9%, greater than about 99.99%, or even 100% of the free carboxylic acid groups present in the polyamic acid molecules are in their non-protonated (i.e., -CO2) - ) state. The cationic species may be, for example, an alkali metal cation or an ammonium cation. Figure 3A and Figure 3B Typically, the polyamic acid salt provided in solution comprises adding the polyamic acid to water to form an aqueous suspension of the polyamic acid, and adding a base to the aqueous suspension of the polyamic acid to form an aqueous solution of the polyamic acid salt. The polyamic acid is as described above and can be purchased or can be prepared as described herein.

[0268] The base can vary. For example, in some aspects, the base is an alkali metal hydroxide and the cation is an alkali metal ion. Figure 3A, polyamic acid is suspended in water, and alkali metal hydroxide is added to the suspension to produce a polyamic acid alkali metal salt aqueous solution. Suitable alkali metal hydroxides include, but are not limited to, lithium hydroxide, sodium hydroxide and potassium hydroxide. In some aspects, the alkali is a water-soluble carbonate or bicarbonate. Suitable carbonates and bicarbonates and methods for forming polyamic acid, polyimide and carbon materials (including aerogel materials) obtained therefrom using such salts are described in international patent application PCT / US2023 / 016821, and the patent application is incorporated herein by reference in its entirety. Those skilled in the art will recognize that some of the methods described therein can be applied to the disclosed method for preparing a porous carbon material comprising a carbon additive, and such methods are contemplated herein.

[0269] The amount of the alkali metal hydroxide added can vary, but is generally sufficient to react (for example, neutralize or deprotonate) with substantially all free carboxylic acid groups present in the polyamic acid, and makes substantially all polyamic acids dissolve.As used herein in the context of neutralizing carboxylic acid groups, "substantially all" means that the carboxylic acid groups greater than 95% are neutralized, such as 99%, or 99.9%, or 99.99%, or even 100% carboxylic acid groups are neutralized.As used herein in the context of polyamic acid dissolving, "substantially all" means that the polyamic acid greater than 95%, such as 99%, or 99.9%, or 99.99%, or even 100% polyamic acid dissolves.In some aspects, the mol ratio of alkali metal hydroxide to polyamic acid is about 0.1 to about 8, such as about 2 to about 8.In some aspects, the mol ratio of alkali metal hydroxide to polyamic acid is about 2 to about 4 or about 2.2 to about 2.5.

[0270] The amount of water used will vary depending on the desired concentration, the scale of solution formation, and the solubility of the polyamic acid salt in water. In some aspects, the concentration of the polyamic acid alkali metal salt in the solution ranges from about 0.01 to about 0.3 g / cm based on the weight of the polyamic acid. 3 .

[0271] In some aspects, the base is a non-nucleophilic amine base and the cation is an ammonium ion. Figure 3B, the polyamic acid is suspended in water, and a non-nucleophilic amine base is added to the suspension to produce an aqueous solution of polyamic acid ammonium salt. Typical non-nucleophilic amines are bulky, tertiary amines, or both, so that protons can be attached to basic centers, but alkylation, acylation, complexation, etc. are impossible or too slow to have any practical significance. Suitable non-nucleophilic amine bases include, but are not limited to, tertiary amines, such as alkyl, cycloalkyl, and aromatic tertiary amines. As used herein in the context of amines, "tertiary" means that the amine nitrogen atom has three bonds or an organic substituent attached thereto. Typically, suitable non-nucleophilic amines will have a solubility of at least about 4 grams per liter in water at 20°C. Particularly suitable non-nucleophilic amine bases are water-soluble lower trialkylamines, including cyclic trialkylamines. In some aspects, non-nucleophilic amine bases are selected from the group consisting of trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, diisopropylethylamine, and combinations thereof. In some aspects, the non-nucleophilic amine base is triethylamine. In some aspects, the non-nucleophilic amine base is diisopropylethylamine.

[0272] The amount of the non-nucleophilic amine base added can vary, but is usually enough to react (for example, neutralize or deprotonate) with substantially all free carboxylic acid groups present in the polyamic acid, and dissolve substantially all polyamic acids. In some aspects, the addition of the non-nucleophilic amine is enough to maintain substantially all polyamic acids in solution. In some aspects, the mol ratio of the non-nucleophilic amine base to the polyamic acid is about 0.1 to about 8, such as about 2 to about 8. In some aspects, the mol ratio of the non-nucleophilic amine base to the polyamic acid is about 2 to about 4 or about 2.2 to about 2.5.

[0273] The amount of water used will vary depending on the desired concentration, the scale of solution formation, and the solubility of the polyamic acid salt and / or non-nucleophilic amine base in water. In some aspects, the concentration of the polyamic acid ammonium salt in the solution ranges from about 0.01 to about 0.3 g / cm based on the weight of the polyamic acid (i.e., free acid weight). 3 .

[0274] In-situ preparation of polyamic acid ammonium salt

[0275] In some aspects, the aqueous solution of polyamic acid salt is prepared in situ by the following manner: for example, diamines are reacted with tetracarboxylic dianhydride in the presence of non-nucleophilic amines to provide polyamic acid ammonium salt aqueous solution. Typically, diamines are allowed to react with tetracarboxylic dianhydride in the presence of non-nucleophilic amines to form polyamic acid ammonium salts. In some aspects, a combination of more than one diamine can be used. A diamine combination can be used to optimize the properties of the gel material. In some aspects, a single diamine is used. Typically, diamines have considerable solubility in water. For example, suitable diamines can have a solubility of at least about 0.1 g per 100 ml, at least about 1 g per 100 ml, or at least about 10 g per 100 ml in water at 20°C.

[0276] A non-limiting general reaction sequence is provided in Scheme 1. In some aspects, reactions are generally performed according to Scheme 1, and reagents and products have structures according to the formulas in Scheme 1.

[0277] Solution 1

[0278]

[0279] With reference to Scheme 1, each of Z, L and n is as defined above with reference to Formula I, and the non-nucleophilic amine is a non-nucleophilic amine base as described above (e.g., R1, R2 and R3 are alkyl, cycloalkylaryl or a combination thereof). Suitable diamines, tetracarboxylic dianhydrides and non-nucleophilic amines are further described below. The order of addition of the various reactants may vary, and the structure of the reactants may also vary. Suitable reactant structures and reaction conditions and the order of addition are further described below.

[0280] refer to Figure 3C According to General Scheme 1, there are three general options for providing an aqueous solution of a polyamic acid salt.

[0281] Option 1

[0282] In some aspects, the polyamic acid is prepared in situ. In some such aspects, providing an aqueous solution of a polyamic acid salt comprises:

[0283] dissolving a water-soluble diamine in water to form a diamine aqueous solution;

[0284] adding a non-nucleophilic amine to an aqueous diamine solution;

[0285] adding tetracarboxylic dianhydride to the aqueous diamine solution; and

[0286] The resulting solution is stirred at a temperature in the range of about 15°C to about 60°C for a period of time in the range of about 1 hour to about 24 hours.

[0287] refer to Figure 3C , Option 1 and Scheme 1, water-soluble diamine is dissolved in water. The structure of diamine can be varied. In some aspects, diamine has a structure according to Formula II, wherein Z is aliphatic (i.e., alkylene, alkenylene, alkynylene or cycloalkylene) or aryl, each as described above. In some aspects, Z is alkylene, such as C2 to C12 alkylene or C2 to C6 alkylene. In some aspects, diamine is C2 to C6 alkane diamine, such as but not limited to ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane or 1,6-diaminohexane. In some aspects, the C2 to C6 alkylene of alkane diamine is substituted by one or more alkyl (such as methyl).

[0288] In some aspects, Z is an aryl group. In some aspects, the aryl diamine is 1,3-phenylenediamine, 1,4-phenylenediamine, or a combination thereof. In some aspects, the diamine is 1,4-phenylenediamine (PDA).

[0289] Continue to refer Figure 3C , Option 1 and Scheme 1, non-nucleophilic amine is added to the aqueous diamine solution. Suitable non-nucleophilic amines are described above. In some aspects, the non-nucleophilic amine is selected from triethylamine, trimethylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, diisopropylethylamine and combinations thereof. In some aspects, the non-nucleophilic amine is triethylamine. In some aspects, the non-nucleophilic amine is diisopropylethylamine.

[0290] The amount of the non-nucleophilic amine added can vary. In some aspects, the molar ratio of non-nucleophilic amine to diamine is about 2 to about 4 or about 2 to about 3. In some aspects, the molar ratio is about 2.0, about 2.1, about 2.2, about 2.3, about 2.4 or about 2.5 to about 2.6, about 2.7, about 2.8, about 2.9 or about 3.0. In some aspects, the molar ratio of non-nucleophilic amine to diamine is about 2 to about 2.5. It is not desirable to be bound by any particular theory, it is believed that in some exemplary aspects, at least enough amines are needed to neutralize substantially all free carboxylic acid groups (that is, to form salts) of polyamic acid. According to the present disclosure, it has been observed that a molar ratio lower than 2.0 or lower than 2.2 may cause polyamic acid precipitation in some aspects. Therefore, the molar ratio may need to be optimized for each group of reactants and conditions. In some aspects, the molar ratio is selected to maintain the solubility of polyamic acid. In some aspects, the molar ratio is selected to avoid any precipitation of polyamic acid.

[0291] Continue to refer Figure 3C , Option 1 and Scheme 1, add tetracarboxylic dianhydride. In some aspects, add more than one tetracarboxylic dianhydride. Combinations of tetracarboxylic dianhydrides can be used to optimize the properties of the gel material. In some aspects, add a single tetracarboxylic dianhydride.

[0292] The structure of tetracarboxylic dianhydride can change.In some respects, tetracarboxylic dianhydride has the structure according to formula III, and wherein L comprises alkylene, cycloalkylene, arylene or its combination, each as described above.In some respects, L comprises arylene.In some respects, L comprises phenyl, biphenyl or diphenyl ether group.In some respects, the tetracarboxylic dianhydride of formula III has the structure selected from one or more structures provided in table 1.

[0293] Table 1. Non-limiting list of potential tetracarboxylic dianhydrides

[0294]

[0295] In some aspects, the tetracarboxylic dianhydride is selected from the group consisting of pyromellitic anhydride (PMDA), diphthalic anhydride (BPDA), oxydiphthalic anhydride (ODPA), benzophenonetetracarboxylic anhydride (BTDA), ethylenediaminetetraacetic anhydride (EDDA), 1,4,5,8-naphthalenetetracarboxylic anhydride and combinations thereof. In some aspects, the tetracarboxylic dianhydride is PMDA.

[0296] The mol ratio of diamines and dianhydride can change according to desired reaction time, reagent structure and desired material characteristic. In some respects, mol ratio is about 0.1 to about 10, such as about 0.1, about 0.5 or about 1 to about 2, about 3, about 5 or about 10. In some respects, ratio is about 0.5 to about 2. In some respects, ratio is about 1 (that is, stoichiometric), such as about 0.9 to about 1.1. In specific aspect, ratio is about 0.99 to about 1.01.

[0297] Referring to Scheme 1, diamine and dianhydride are allowed to react with each other in the presence of non-nucleophilic amine to form polyamic acid. Without wishing to be bound by theory, it is believed that polyamic acid forms a polyamic acid ammonium salt having a structure according to Formula IV in the presence of non-nucleophilic amine, and the water solubility of this salt allows the polyamic acid ammonium salt to remain in solution.

[0298] The molecular weight of polyamic acid can change based on reaction conditions (for example, concentration, temperature, reaction duration, the property of diamine and dianhydride, etc.).Molecular weight is based on the number of polyamic acid repeating units, as represented by the value of the integer "n" of the IV structure in Scheme 1.The specific molecular weight range of the polymer material produced by the disclosed method can change.Usually, the indicated reaction conditions can be changed to provide a gel with a desired physical property without specifically considering the molecular weight.In some aspects, the viscosity of the polyamic acid ammonium salt solution provides an index of alternative molecular weight, which is determined by variables such as temperature, concentration, the molar ratio of reactants, reaction time, etc.

[0299] The mol ratio of diamines and dianhydride can change according to desired reaction time, reagent structure and desired material characteristic. In some respects, mol ratio is about 0.1 to about 10, such as about 0.1, about 0.5 or about 1 to about 2, about 3, about 5 or about 10. In some respects, ratio is about 0.5 to about 2. In some respects, ratio is about 1 (that is, stoichiometric), such as about 0.9 to about 1.1. In specific aspect, ratio is about 0.99 to about 1.01.

[0300] The mol ratio of non-nucleophilic amine and diamine or dianhydride determines the solubility of polyamic acid.In some aspects, the mol ratio of non-nucleophilic amine and diamine is about 2 to about 4 or about 2 to about 3.In some aspects, the mol ratio is about 2.0, about 2.1, about 2.2, about 2.3, about 2.4 or about 2.5 to about 2.6, about 2.7, about 2.8, about 2.9 or about 3.0.It is not desirable to be bound by any particular theory, it is believed that in some exemplary aspects, at least enough amines are needed to neutralize substantially all free carboxylic acid groups (that is, to form salts) of polyamic acid.According to the present disclosure, it has been observed that the mol ratio lower than 2.0 or lower than 2.2 causes the precipitation of intermediate polyamic acid in some aspects (for example, due to the evaporation loss of non-nucleophilic amine).Therefore, the mol ratio may need to be optimized for each group of reactants and conditions.In some aspects, the mol ratio is selected to maintain the solubility of reaction components (for example, polyamic acid).In some aspects, the mol ratio is adjusted to avoid any precipitation.

[0301] The temperature for carrying out the reaction can vary. Suitable ranges are generally between about 10°C and about 100°C. In some aspects, the reaction temperature is about 15°C to about 60°C, such as about 20°C, about 25°C, about 30°C, about 35°C, about 40°C, about 45°C, about 50°C, about 55°C or about 60°C. In some aspects, the temperature is about 15°C to about 25°C. In some aspects, the temperature is about 50°C to about 60°C.

[0302] In some aspects, polyimide gels having different pore size distributions and different structural properties may be produced as the temperature increases. Without wishing to be bound by theory, it is believed that properties such as pore size distribution and structural rigidity may vary with temperature in some aspects, which may be a result of polyimide molecular weight, degree of chemical crosslinking (when possible), and other factors that may exhibit temperature dependence.

[0303] Allow reaction to proceed to a certain time period, and usually allow reaction to proceed until all available reactants (for example, diamines and dianhydride) have reacted with each other. The time required for complete reaction can change based on reagent structure, concentration and temperature. In some aspects, the reaction times is about 1 minute to about 1 week, for example, about 15 minutes to about 5 days, about 30 minutes to about 3 days or about 1 hour to about 1 day. In some aspects, the reaction times is about 1 hour to about 12 hours.

[0304] Option 2

[0305] In some aspects, the polyamic acid is prepared in situ, and providing an aqueous solution of a polyamic acid salt comprises:

[0306] dissolving a water-soluble diamine in water to form a diamine aqueous solution;

[0307] adding tetracarboxylic dianhydride to the aqueous diamine solution;

[0308] The resulting suspension is stirred at a temperature in the range of about 15°C to about 60°C for a period of time in the range of about 1 hour to about 24 hours.

[0309] adding a non-nucleophilic amine to the aqueous diamine solution; and

[0310] The resulting suspension is stirred at a temperature in the range of about 15°C to about 60°C for a period of time in the range of about 1 hour to about 24 hours.

[0311] refer to Figure 3C , Option 2 and Option 1, the water-soluble diamine is dissolved in water, as described above for Option 1. However, in this regard, the tetracarboxylic dianhydride (as described above for Option 1) is added to the aqueous diamine solution to form a suspension. The relative amounts of the reactants can vary as described above for Option 1.

[0312] In some aspects, the suspension is stirred for a period of time ranging from about 1 hour to about 1 day, such as from about 1 hour to about 12 hours.

[0313] The temperature of the stirred suspension can vary. Suitable ranges are generally between about 15°C and about 60°C, such as about 20°C, about 25°C, about 30°C, about 35°C, about 40°C, about 45°C, about 50°C, about 55°C, or about 60°C. In some aspects, the temperature is about 15°C to about 25°C. In some aspects, the temperature is about 50°C to about 60°C.

[0314] refer to Figure 3C , Option 2 and Scheme 1, add a non-nucleophilic amine. Suitable non-nucleophilic amines are those described above. In some aspects, the non-nucleophilic amine is selected from triethylamine, trimethylamine, tri-n-butylamine, N-methylpyrrolidine, N-methylpiperidine, diisopropylethylamine and combinations thereof. In some aspects, the non-nucleophilic amine is triethylamine. In some aspects, the non-nucleophilic amine is diisopropylethylamine.

[0315] The amount of non-nucleophilic amine added can vary as described above with respect to Option 1. In some aspects, the molar ratio of non-nucleophilic amine to diamine is from about 2 to about 2.5.

[0316] In some aspects, the resulting mixture is stirred for a period of time ranging from about 1 hour to about 1 day, such as from about 1 hour to about 12 hours.

[0317] The temperature of the stirred mixture can vary. Suitable ranges are generally between about 15°C and about 60°C, such as about 20°C, about 25°C, about 30°C, about 35°C, about 40°C, about 45°C, about 50°C, about 55°C, or about 60°C. In some aspects, the temperature is about 15°C to about 25°C. In some aspects, the temperature is about 50°C to about 60°C.

[0318] Option 3

[0319] In some aspects, the polyamic acid is prepared in situ, and providing an aqueous solution of a polyamic acid salt comprises:

[0320] adding a water-soluble diamine, a tetracarboxylic dianhydride, and a non-nucleophilic amine to water simultaneously or in rapid succession; and

[0321] The resulting solution is stirred at a temperature in the range of about 15°C to about 60°C for a period of time in the range of about 1 hour to about 24 hours.

[0322] refer to Figure 3C , Option 3 and Option 1, a water-soluble diamine, a tetracarboxylic dianhydride and a non-nucleophilic amine are added to water simultaneously or in rapid succession. Each of the water-soluble diamine, the tetracarboxylic dianhydride and the non-nucleophilic amine and their relative amounts are as described above for Options 1 and 2.

[0323] In some aspects, the resulting mixture is stirred for a period of time ranging from about 1 hour to about 1 day, such as from about 1 hour to about 12 hours.

[0324] The temperature of the stirred mixture can vary. Suitable ranges are generally between about 15°C and about 60°C, such as about 20°C, about 25°C, about 30°C, about 35°C, about 40°C, about 45°C, about 50°C, about 55°C, or about 60°C. In some aspects, the temperature is about 15°C to about 25°C. In some aspects, the temperature is about 50°C to about 60°C.

[0325] In each of the aforementioned options for preparing polyamic acid salt solutions and for preparing polyamic acid, it should be noted that although the use of aqueous solutions has been extensively mentioned, it is contemplated that organic solvents as described herein may also be used, and any disclosure regarding aqueous solutions should not be inferred to be so limited.

[0326] The polyamic acid salt is imidized to form a polyimide gel

[0327] Continue to refer Figure 2 Option I, in some aspects, the organogel is a polyimide, and the method includes imidizing the polyamic acid salt as described above to form a polyimide gel containing a carbon additive or a precursor thereof. The polyimide gel and the corresponding aerogel can be in the form of a monolith or in the form of beads. The polyamic acid salt can be an alkali metal salt or an ammonium salt as described above. Various methods for preparing polyimide aerogels from such polyamic acid salt solutions are further described below.

[0328] A. Monolithic polyimide aerogels obtained from aqueous solutions of polyamic acid salts by chemical imidization

[0329] In some aspects, the polyimide gel and corresponding aerogel are in the form of a monolith, and the polyamic acid salt in the aqueous solution is an ammonium salt, as described above with reference to Figure 3B or Figure 3C (Option 1, 2 or 3) described preparation. In these aspects, imidization can be chemical imidization, and the method can be Figure 4 The method generally described in .

[0330] refer to Figure 4 , polyamic acid salt is imidized including adding a dehydrating agent to an aqueous solution of polyamic acid salt to form a gelling mixture ("sol"), pouring the gelling mixture into a mold, and allowing the gelling mixture to gel. Adding a dehydrating agent to initiate and drive imidization, thereby forming a polyimide wet gel by polyamic acid ammonium salt. A non-restrictive general reaction sequence is provided in Scheme 2. In some aspects, polyimide has a structure according to Formula V, as shown in Scheme 2, wherein L, Z and n are each as described above for forming a polyamic acid ammonium salt of Formula IV.

[0331] Solution 2

[0332]

[0333] The structure of the dewatering agent can vary, but is generally at least partially dissolved in the reaction solution, reacts with the carboxylate groups of the ammonium salt and effectively drives the imidization of the polyamic acid carboxyl and amide groups while reacting with the minimum reagent of the aqueous solution. An example of a class of suitable dewatering agents is a carboxylic anhydride, such as acetic anhydride, propionic anhydride, etc. In some respects, the dewatering agent is acetic anhydride. Surprisingly, according to the disclosure, adding acetic anhydride to the ammonium salt aqueous solution causes the polyimide to gel quickly, and the acetic anhydride that is intuitively expected is not observed to be hydrolyzed by water in large quantities. Any hydrolysis that does occur is not enough to compete with the function of acetic anhydride in the polyimide formation.

[0334] In some respects, the amount of dewatering agent can change based on the amount of tetracarboxylic dianhydride.For example, in some respects, dewatering agent exists with the different mol ratios of tetracarboxylic dianhydride.The mol ratio of dewatering agent and tetracarboxylic dianhydride can change according to desired reaction time, reagent structure and desired material characteristic.In some respects, mol ratio is about 2 to about 10, such as about 2, about 3, about 4 or about 5 to about 6, about 7, about 8, about 9 or about 10.In some respects, ratio is about 4 to about 5.In some respects, ratio is 4.3.

[0335] The temperature at which the dehydration reaction is allowed to proceed can vary, but is typically below about 50°C, such as from about 10°C to about 50°C or from about 15°C to about 25°C.

[0336] Further references Figure 4, the gelling mixture is poured into a mold and the gelling mixture is allowed to gel. Typically, the resulting wet gel material is allowed to remain ("cast") in the mold for a certain period of time. The time required for the gelling mixture to completely gel to form a wet gel can vary. The time period can vary based on a variety of factors, such as the need for aging of the material, but will generally be between a few hours and a few days.

[0337] The process of converting the gelling mixture into a wet gel material can also include an aging step (also referred to as curing) before drying. Aging the wet gel material after it reaches its gel point can further strengthen the gel framework. For example, in some aspects, the framework can be strengthened during the aging process. The duration of gel aging can be adjusted to control various properties within the corresponding aerogel material. This aging procedure can be used to prevent potential volume loss and shrinkage during the liquid phase extraction of the wet gel material. Aging can involve: maintaining the gel (before extraction) in a static state for an extended period of time; maintaining the gel at an elevated temperature; or any combination thereof. The preferred temperature for aging is generally between about 10°C and about 200°C. Aging can also occur during a solvent exchange process, as described below. Aging of the wet gel material can also be referred to as "curing" and typically lasts until the liquid phase extraction of the wet gel material.

[0338] The size and shape of the resulting wet gel monolith can vary. In some aspects, the wet gel monolith has a thickness of about 5 to about 25 mm. In some aspects, the monolith is in the form of a film, such as a film with a thickness of about 50 microns to about 1 mm.

[0339] B. Monolithic polyimide aerogels obtained from aqueous solutions of polyamic acid salts by thermal imidization

[0340] In some aspects, the imidization may be thermal imidization, and the method may be Figure 5 Reference is made to the method generally described in Figure 5 In this aspect, imidizing the polyamic acid ammonium salt comprises:

[0341] adding delta-gluconolactone to an aqueous solution of a polyamic acid salt to form a gelled mixture;

[0342] pouring the gelling mixture into a mold and allowing the gelling mixture to gel;

[0343] washing the obtained polyamic acid gel with water; and

[0344] The polyamic acid gel is thermally imidized to form a polyimide gel, the thermal imidization comprising exposing the polyamic acid gel to microwave frequency irradiation.

[0345] In an aqueous environment, DGL reacts slowly with water to form delta-gluconic acid (DGA; Equation 1), which is used at least to initiate the acidification process for polyamic acid gelation.

[0346]

[0347] The gelled mixture is poured into a mould and the gelled mixture is allowed to gel. After acidification, polyamic acid becomes insoluble in aqueous environment, forms a polyamic acid wet gel. In some respects, the polyamic acid ammonium salt has the structure according to formula IV, and the polyamic acid gel has the structure (scheme 3) according to formula VI, wherein L, Z and n are each as described above, and acid is DGA.

[0348] Solution 3

[0349]

[0350] The time required for the gel-forming solution (sol; e.g., polyamic acid) to completely gel to form a wet gel can vary. Typically, gelation occurs in about 1.5 hours or less. Typically, the wet gel material is allowed to remain ("cast") in the mold for a certain period of time. The period of time can vary based on a variety of factors, such as the need for material aging as described above for chemical imidization.

[0351] refer to Figure 5 The resulting polyamic acid gel monolith is then washed with water. The washing is performed for a sufficient time and with sufficient water to remove any water-soluble by-products, such as ammonium salts, DGA or DGL, and other by-products generated when the polyamic acid ammonium salt solution is formed.

[0352] Continue to refer Figure 5 , after forming and washing the polyamic acid wet gel monolith, the polyamic acid gel is dehydrated (i.e., imidized) using thermal treatment (e.g., microwave exposure) to form a corresponding polyimide gel. A non-restrictive general reaction sequence is provided in Scheme 4. In some aspects, the polyimide has a structure according to Formula V, as shown in Scheme 4, wherein L, Z and n are each as described above.

[0353] Solution 4

[0354]

[0355] Irradiation of wet gel material with microwave frequency energy is a particularly suitable thermal treatment. Microwaves are low energy electromagnetic waves with wavelengths in the range of 0.001-0.3 meters and frequencies in the range of 1,000-300,000 MHz. Typical microwave devices operate with microwaves at a frequency of 2450 MHz. The electric field component of microwaves is primarily responsible for generating heat, interacting with molecules through dipole rotation and ionic conduction. In dipole rotation, molecules constantly rotate back and forth, trying to align their dipoles with the constantly oscillating electric field; the friction between the rotating molecules causes the generation of heat. In ionic conduction, free ions or ionic species translate in space, trying to align with the changing electric field. As with dipole rotation, the friction between these moving species causes the generation of heat. In both cases, the greater the polarity and / or ionicity of the molecular species, the more efficient the rate of heat generation. Microwave heating allows for rapid and efficient energy transfer compared to conventional heating that relies on slow thermal conduction. Therefore, microwave heating is particularly suitable for carrying out the thermal imidization reaction of the present disclosure. Typically, the power and duration of microwave frequency irradiation are enough to convert most of the amides and carboxyl groups of polyamic acid into imide groups. As used herein in the context of converting amides and carboxyl groups into imide groups, "most of" means greater than 90%, such as 95%, 99%, or 99.9%, or 99.99%, or even 100% of the amides and carboxyl groups are converted into imide groups.

[0356] Continue to refer Figure 5 After heating and forming the polyimide gel monolith, the polyimide gel monolith is washed (solvent exchanged) and dried as described above with respect to the chemically imidized polyimide monolith to form a polyimide aerogel monolith.

[0357] C. Polyamide obtained by chemical imidization (liquid drop method in aqueous solution) of polyamic acid ammonium salt aqueous solution Imine aerogel beads

[0358] In some aspects, the polyimide gel and corresponding aerogel are in the form of beads, and the polyamic acid salt in the aqueous solution is an ammonium salt, as described above with reference to Figure 3B or Figure 3C (Option 1, 2 or 3) described preparation. In these aspects, imidization can be chemical imidization, and the method can be Figure 5 As used herein, the term "bead" or "bead form" is intended to include discrete small units or fragments having a generally spherical shape. In some aspects, the gel beads are substantially spherical. The composition of the beads is generally uniform, so that each bead in a plurality of beads contains the same polyimide in approximately the same amount, within the normal range of variation expected in the preparation of such beads. The size of the beads can vary depending on the desired properties and the preparation method.

[0359] refer to Figure 6The polyamic acid ammonium salt is chemically imidized by adding a dehydrating agent to an aqueous solution of the polyamic acid ammonium salt to form a solution as described above. Figure 4 The gelled mixture. In some aspects, the dehydrating agent is acetic anhydride. However, in this respect, the method is not to pour the gelled mixture into a mold to form a monolith, but to be included in the gelled mixture before gelling and to add it to a solution of a water-soluble acid in water, or to add the gelled mixture to a water-immiscible solvent (optionally comprising acid) to form polyimide gel beads. Usually, the sol is added quickly so that dropwise addition is completed before the sol gels. Addition can be performed by a variety of different techniques, including dripping the gelled mixture into a solution of a water-soluble acid in water, spraying the gelled mixture under pressure to a solution of a water-soluble acid in water by one or more nozzles, or electrospraying the gelled mixture to a solution of a water-soluble acid in water by one or more needles.

[0360] refer to Figure 6 In some aspects, the method includes adding the gelling mixture to a solution of a water-soluble acid in water. The water-soluble acid can vary and can be, for example, an organic acid or a mineral acid. In some aspects, the acid is a mineral acid, such as hydrochloric acid, sulfuric acid, or phosphoric acid. In some aspects, the acid is an organic acid. The organic acid can vary, but typically is a lower carboxylic acid, including but not limited to formic acid, acetic acid, or propionic acid. In some aspects, the acid is acetic acid. The amount of acid present can vary, but typically is about 10% to about 20% by volume in water. In some aspects, the solution contains acetic acid in an amount of about 10% by volume or in an amount of about 20% by volume.

[0361] The size of the polyimide gel beads can vary based on the size of the drops added to the solution of the water-soluble acid in water. In some aspects, the gelled mixture is added as discrete droplets (e.g., dripped from a pipette or other suitable droplet forming device, manually or automatically). The diameter of the polyimide gel beads produced by such droplets is often relatively large, for example, with a diameter range of about 0.5 to about 10 millimeters, such as about 0.5, about 1, about 2, about 3, about 4 or about 5 to about 6, about 7, about 8, about 9 or about 10 mm. In some aspects, the diameter size range of the beads is about 0.5 to about 5 mm.

[0362] refer to Figure 6In some aspects, the gelled mixture is added by spraying to produce relatively small polyimide gel beads (for example, on the micron scale). A variety of aerosol formation techniques known in the art can be used for spraying, such as pressurized gas-assisted aerosol formation or electrospray. In a particular aspect, spraying is electrospray. Generally, electrospraying is performed in the following manner: a solution containing the gelled mixture is pumped to a bath of a solution of a water-soluble acid in water through one or more needles, while a voltage difference of about 5 to 60 kV is applied between the bath and the one or more needles. This method causes very fine gelled mixture droplets to be introduced into a solution of a water-soluble acid in water. After contact, micron-sized droplets are reacted with acid to form a polyamic acid skin around the droplets, and the skin gradually gels to form polyimide beads. Without wishing to be bound by theory, it is believed that the water-soluble acid protonates the carboxylate groups of the polyamic acid salt to form an initial skin, which is infiltrated by a dehydrating agent to imidize the polyamic acid salt in the droplets to form wet gel polyimide beads. In some aspects, the beads range in size from about 5 to about 200 microns in diameter, such as from about 5, about 10, about 20, about 30, about 40, or about 50 to about 60, about 70, about 80, about 90, about 100, or about 200 microns in diameter.

[0363] Continue to refer Figure 6 After the polyimide gel beads are formed by dropping or spraying, the polyimide gel beads are aged, washed (solvent exchanged), and dried as described above for the chemically imidized polyimide monolith to form the corresponding polyimide aerogel beads.

[0364] D. Polymer obtained by chemical imidization (liquid drop method; water-immiscible solvent) from aqueous solution of polyamic acid ammonium salt Imide aerogel beads

[0365] Continue to refer Figure 6 In another aspect, the gelling mixture is as described above for the aqueous droplet method. However, in this aspect, rather than adding the gelling mixture as drops to a solution of a water-soluble acid in water, the method comprises adding the gelling mixture to a water-immiscible solvent, optionally containing an acid, to form the polyimide gel beads. Typically, the sol is added rapidly so that the dropwise addition is completed before the sol gels.

[0366] Addition can be performed by a variety of different techniques, including dripping the gelled mixture into the water-immiscible solvent, spraying the gelled mixture under pressure into the water-immiscible solvent through one or more nozzles, or electrospraying the gelled mixture into the water-immiscible solvent through one or more needles, each as described above.

[0367] Water-immiscible solvents can vary. Suitable solvents include, but are not limited to, oils (such as silicone oil or mineral oil), aliphatic hydrocarbons, aromatic hydrocarbons, and chlorinated hydrocarbons. In some aspects, the solvent is an aliphatic or aromatic hydrocarbon of five to twelve carbon atoms (C5-C12). In some aspects, the solvent is hexane. In particular aspects, the solvent is mineral spirits.

[0368] The optional acid can vary, but is typically a lower carboxylic acid, including but not limited to formic acid, acetic acid, or propionic acid. In some aspects, the acid is acetic acid. The amount of acid present can vary, but when present is typically about 10% to about 20% by volume of the water-immiscible solvent. Without wishing to be bound by theory, it is believed that the presence of the acid during the gelation process can form an outer surface of the beads with carboxyl groups that do not react to form imide groups, and the presence of such acid groups on the outer surface can avoid agglomeration of the beads.

[0369] In some aspects, the gelling mixture is added as discrete droplets (e.g., dripped from a pipette or other suitable drop-forming device, either manually or automatically). The diameter of the polyimide gel beads produced by such droplets tends to be relatively large, e.g., ranging from about 0.5 to about 10 millimeters in diameter, e.g., about 0.5, about 1, about 2, about 3, about 4, or about 5 to about 6, about 7, about 8, about 9, or about 10 mm in diameter. In some aspects, the diameter size of the beads ranges from about 0.5 to about 5 mm.

[0370] In some aspects, the gelled mixture is added by spraying to produce relatively small polyimide gel beads (for example, on the micron scale). A variety of aerosol formation techniques known in the art can be used for spraying, such as pressurized gas-assisted aerosol formation or electrospray. In particular aspects, spraying is electrospray. Generally, electrospray is performed in the following manner: the solution comprising the gelled mixture is pumped to a bath of a solution of a water-soluble acid in water by one or more needles, while a voltage difference of about 5 to 60 kV is applied between the bath and the one or more needles. This method causes very fine gelled mixture droplets to be introduced into a solution of a water-soluble acid in water. After contact, micron-sized droplets are reacted with acid to form a polyamic acid skin around the droplets, and the skin is gradually gelled to form polyimide beads. Without wishing to be bound by theory, it is believed that water-soluble acid protonates the carboxylate groups of polyamic acid salts to form an initial skin, which is infiltrated by a dehydrating agent to imidize the polyamic acid salts in the droplets to form wet gel polyimide beads. In some aspects, the beads range in size from about 5 to about 200 microns in diameter, such as from about 5, about 10, about 20, about 30, about 40, or about 50 to about 60, about 70, about 80, about 90, about 100, or about 200 microns in diameter.

[0371] Continue to refer Figure 6After the polyimide gel beads are formed by dropping or spraying, the polyimide gel beads are aged, washed (solvent exchanged), and dried as described above for the chemically imidized polyimide monolith to form the corresponding polyimide aerogel beads.

[0372] E. Polyimide aerogel beads obtained by chemical imidization of polyamic acid ammonium salt aqueous solution (emulsion method 1)

[0373] In some aspects, the polyimide gel and corresponding aerogel are in the form of beads, and the polyamic acid salt in the aqueous solution is an ammonium salt, as described above with reference to Figure 3B or Figure 3C (Option 1, 2 or 3) described preparation. In these aspects, imidization can be chemical imidization, and the method can be Figure 7 Reference is made to the method generally described in Figure 7 The imidization of the polyamic acid salt comprises adding a dehydrating agent to an aqueous solution of the polyamic acid salt to form a gelled mixture as described above. The method further comprises combining the gelled mixture with a water-immiscible solvent containing a surfactant; and mixing the resulting mixture under high shear conditions.

[0374] Mixing the biphasic mixture under high shear conditions generally provides micrometer-sized polyimide beads. In some aspects, a water-immiscible solvent and a surfactant are added to the aqueous gelling mixture. In some aspects, the aqueous gelling mixture is added to the water-immiscible solvent and the surfactant.

[0375] The water-immiscible solvent can vary. Suitable solvents include, but are not limited to, oils (such as silicone oil or mineral oil), aliphatic hydrocarbons, aromatic hydrocarbons, and chlorinated hydrocarbons. In some aspects, the solvent is a C5-C12 aliphatic or aromatic hydrocarbon. In some aspects, the solvent is hexane. In particular aspects, the solvent is mineral spirits.

[0376] Surfactant can vary. As used herein, the term "surfactant" refers to a substance that helps the formation and stability of an emulsion by promoting the dispersion of hydrophobic and hydrophilic (e.g., oil and water) components. Suitable surfactants are typically nonionic and include, but are not limited to, fatty acid polyethylene glycol esters, fatty acid propylene glycol esters, polysorbates, fatty acid polyglycerol esters, fatty acid sorbitan esters, etc. Suitable surfactants have an HLB number in the range of about 0 to about 20. In some aspects, the HLB number is about 3.5 to about 6. As will be appreciated by those skilled in the art, HLB is the hydrophilic-lipophilic balance of an emulsifier or surfactant, a measure of its hydrophilic or lipophilic degree. The HLB value can be determined by calculating the values ​​for different regions of the molecule as described by 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 by 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. The HLB value can be determined according to the industry standard textbook, "The HLB SYSTEM, a time-saving guide to emulsifier selection" ICI Americas Inc., published in 1976 and revised in March 1980.

[0377] Examples of suitable surfactants generally include, but are not limited to, polyoxyethylene-sorbitan-fatty acid esters; such as mono- and tri-lauryl, palmityl, stearyl and oleyl esters; such as the type known as polysorbates and marketed under the trade name Products commercially available under the trade names of Polyoxyethylene stearates commercially available under the trade names those available under the trade names of polyoxyethylene castor oil derivatives, such as those of the type known and marketed under the trade names of Sorbitan fatty acid esters, such as those of the type known and available under the trade name commercially available under the trade name Span 80; polyoxyethylene-polyoxypropylene copolymers, such as those of the type known and marketed under the trade name or commercially available products; triacetin; and monoglycerides and acetylated monoglycerides, such as mono-dicocoylglycerol ( 928), monocaprylic acid glyceryl ( 308) and monoacetylated and diacetylated monoglycerides. In some aspects, the one or more surfactants include a polymeric surfactant of the type known commercially available under the trade name (CrodaIndustrial Chemicals; Edison, NJ, USA).

[0378] In some aspects, the one or more surfactants comprise Tween 20, Tween 80, Span 20, Span 40, Span 60, Span 80, or a combination thereof. In some aspects, the surfactant is Span 20, Tween 80, or a mixture thereof. In some aspects, the one or more surfactants are B246SF. In some aspects, the one or more surfactants are A70.

[0379] The concentration of the surfactant can vary. In some aspects, the surfactant or surfactant mixture is present in the water-immiscible solvent in an amount from about 1 to about 5%, such as about 1, about 2, about 3, about 4, or about 5% by weight.

[0380] The spherical droplets of aqueous sols are formed in water-immiscible solvents due to interfacial tension. In the time in water-immiscible solvents (e.g., mineral spirits), the droplets gel and strengthen. Agitated mixtures are typically used to form emulsions and / or prevent droplet agglomeration. For example, a mixture of an aqueous gelled mixture and a water-immiscible solvent can be stirred (e.g., stirred) to form an emulsion, which can be stable or temporary. Stirring to provide exemplary aspects of gel beads by sol mixtures and water-immiscible solvents includes magnetic stirring (up to about 600rpm), mechanical mixing (up to about 1500rpm) and homogenization (i.e., mixing at up to about 9000rpm). In some aspects, mixing is performed under high shear conditions, such as using a high shear mixer or homogenizer. When the fluid in one region flows at different speeds relative to an adjacent region, the fluid is subjected to shear. A high shear mixer (homogenizer) uses a rotating impeller or high-speed rotor, or a series of such impellers or in-line rotors to "process" the fluid, generating flow and shear. The tip speed (i.e., the speed encountered by the fluid at the outer diameter of the rotor) will be higher than the speed encountered at the center of the rotor, and this speed difference will produce shear. Generally, higher shear results in smaller beads.

[0381] In some aspects, additional solvent, such as water or ethanol, can be added after gelation to produce smaller beads and reduce agglomeration of large clusters of beads.

[0382] The size of the wet gel beads can vary. In some aspects, the diameter size range of the wet gel beads is about 5 to about 500 microns, for example, a diameter of about 5, about 10, about 20, about 30, about 40 or about 50 to about 60, about 70, about 80, about 90, about 100, about 200, about 300, about 400 or about 500 microns.

[0383] Continue to refer Figure 7 After the polyimide gel beads are formed, the polyimide gel beads are aged, washed (solvent exchanged), and dried as described above with respect to chemical imidization of polyimide beads by a droplet method to form corresponding polyimide aerogel beads.

[0384] F. Polyimide aerogel beads obtained by chemical imidization of polyamic acid ammonium salt aqueous solution (emulsion method 2)

[0385] In some aspects, the polyimide gel and corresponding aerogel are in the form of beads, and the polyamic acid salt in the aqueous solution is an ammonium salt, as described above with reference to Figure 3B or Figure 3C (Option 1, 2 or 3) described preparation. In these aspects, imidization can be chemical imidization, and the method can be Figure 8 Reference is made to the method generally described in Figure 8The method comprises: mixing a gelled mixture with a water-immiscible solvent containing a surfactant; mixing the resulting mixture under high shear conditions to form a quasi-stable emulsion; and adding a dehydrating agent to the quasi-stable emulsion. The method is different from the emulsion method 1 described above only in that a quasi-stable emulsion of an aqueous polyamic acid ammonium salt and a water-immiscible solvent is first formed, and then a dehydrating agent is added.

[0386] Surfactants, water-immiscible solvents, and mixing conditions are as described above for emulsion method 1. In some aspects, the water-immiscible organic solvent is a C5-C12 hydrocarbon. In some aspects, the water-immiscible organic solvent is mineral spirits. In some aspects, the dehydrating agent is acetic anhydride.

[0387] Monolithic polyamic acid and polyimide aerogels obtained from aqueous solutions of polyamic acid salts

[0388] In another aspect, a method of forming a polyamic acid aerogel in the form of a monolith is provided. The method generally comprises: providing an aqueous solution of a polyamic acid salt; acidifying the polyamic acid salt solution to form a polyamic acid gel; and drying the polyamic acid gel to form a polyamic acid aerogel. In some aspects, the acidification of the polyamic acid salt comprises adding delta-gluconolactone to the aqueous solution of the polyamic acid salt to form a gelling mixture and pouring the gelling mixture into a mold and allowing the gelling mixture to gel, each as described with respect to Figure 5 Therefore, as mentioned in reference Figure 5 The polyamic acid gel monolith can be used as a starting point to provide a polyamic acid aerogel monolith. In some aspects, the polyamic acid aerogel monolith can be based on Fig. 9 Prepared from the corresponding polyamic acid gel monolith. Fig. 9 , the polyamic acid gel monolith was washed with water, solvent exchanged and dried (each as described above) to provide a polyamic acid aerogel monolith.

[0389] In some aspects, the method further comprises preparing a polyimide gel monolith from the polyamic acid gel monolith. Fig. 9 , thermal imidization (eg, by subjecting the polyamic acid gel monolith to a temperature of about 300° C. for a certain period of time) converts the polyamic acid gel monolith into the corresponding polyimide gel monolith.

[0390] In some aspects, the method further comprises preparing a polyimide aerogel monolith from a polyamic acid aerogel monolith. Fig. 9 The polyamic acid aerogel monolith is converted into the corresponding polyimide aerogel monolith by thermal imidization (eg, by subjecting the polyamic acid gel monolith to a temperature of about 300° C. for a certain period of time).

[0391] In some aspects, the method further comprises preparing a polyimide aerogel monolith from the polyimide aerogel monolith. Figure 8 , the polyimide gel monolith was washed with water, solvent exchanged and dried (each as described above) to provide a polyimide aerogel monolith.

[0392] Polyamic acid and polyimide aerogel beads obtained from aqueous solutions of polyamic acid salts

[0393] A. Droplet Method

[0394] In another aspect, a method of forming a polyamic acid aerogel in the form of beads is provided. In some aspects, the method can be Fig. 10A Reference is made to the method generally described in Fig. 10A , the method generally includes: providing an aqueous solution of a polyamic acid salt; acidifying the polyamic acid salt solution to form a polyamic acid gel; and drying the polyamic acid gel to form a polyamic acid aerogel. In some aspects, the acidification of the polyamic acid salt includes adding an aqueous solution of a polyamic acid salt to a solution of a water-soluble acid in water to form polyamic acid gel beads, wherein the adding includes dripping the aqueous solution of a polyamic acid salt into a solution of a water-soluble acid in water, spraying the aqueous solution of a polyamic acid salt under pressure through one or more nozzles into the solution of a water-soluble acid in water using pressure; or electrospraying the aqueous solution of a polyamic acid salt into the solution of a water-soluble acid in water, each as described with respect to Figure 6 described. Fig. 10B A non-limiting cartoon illustration of the processes believed to occur during bead formation is provided in. Without wishing to be bound by theory, it is believed that the water-soluble acid (e.g., acetic acid) protonates the carboxylate groups of the polyamic acid ester, forming an initial skin, which is penetrated by the water-soluble acid, protonating the carboxylate groups of the polyamic acid ammonium salt within the droplets, forming wet gel polyamic acid beads.

[0395] In some aspects, such as reference Figure 6 The polyamic acid gel beads are provided Fig. 10A The starting point of the polyamic acid aerogel beads. Fig. 10A , the polyamic acid gel beads are washed with water, solvent exchanged and dried (each as described above) to provide polyamic acid aerogel beads.

[0396] In some aspects, the method further comprises preparing polyimide gel beads from polyamic acid gel beads. Fig. 10A The polyamic acid gel beads are converted to corresponding polyimide gel beads by thermal imidization (eg, by subjecting the polyamic acid gel beads to a temperature of about 300° C. for a certain period of time).

[0397] In some aspects, the method further comprises preparing polyimide aerogel beads from polyamic acid aerogel beads. Fig. 10AThe polyamic acid aerogel beads are converted to the corresponding polyimide aerogel beads by thermal imidization (eg, by subjecting the polyamic acid gel beads to a temperature of about 300° C. for a certain period of time).

[0398] In some aspects, the method further comprises preparing polyimide aerogel beads from polyimide aerogel beads. Fig. 10A , the polyimide gel beads are washed with water, solvent exchanged and dried (each as described above) to provide polyimide aerogel beads.

[0399] B. Emulsion method

[0400] In another aspect, a method of forming a polyamic acid aerogel in the form of beads is provided. In some aspects, the method can be Fig.11 Reference is made to the method generally described in Fig.11 The method generally comprises: providing an aqueous solution of a polyamic acid salt; combining the aqueous solution of the polyamic acid salt with a water-immiscible solvent comprising a surfactant; mixing the resulting mixture under high shear conditions to form an emulsion; and adding an organic acid to the emulsion.

[0401] The water-immiscible solvent can vary. Suitable solvents include, but are not limited to, oils (such as silicone oil or mineral oil), aliphatic hydrocarbons, aromatic hydrocarbons, and chlorinated hydrocarbons. In some aspects, the solvent is a C5-C12 aliphatic or aromatic hydrocarbon. In particular aspects, the solvent is mineral spirits.

[0402] The water-immiscible solvent comprises a surfactant as described above. In some aspects, the surfactant comprises or a combination thereof. In some aspects, the surfactant is or mixtures thereof. In some aspects, the surfactant is B246SF. In some aspects, the surfactant is A70.

[0403] The concentration of the surfactant can vary. In some aspects, the surfactant or surfactant mixture is present in the water-immiscible solvent in an amount from about 1 to about 5%, such as about 1, about 2, about 3, about 4, or about 5% by weight.

[0404] In some aspects, combining comprises adding an aqueous solution of polyamic acid ammonium salt to a water-immiscible solvent comprising a surfactant. In some aspects, combining comprises adding an aqueous solution of polyamic acid ammonium salt to a water-immiscible solvent comprising a surfactant.

[0405] Mixing two-phase mixture under high shear condition generally provides the polyamic acid beads of micron size.The size of polyamic acid wet gel beads can change.In some aspects, the diameter size range of wet gel beads is about 5 to about 500 microns, for example diameter is about 5, about 10, about 20, about 30, about 40 or about 50 to about 60, about 70, about 80, about 90, about 100, about 200, about 300, about 400 or about 500 microns.

[0406] Continue to refer Fig.11 , the polyamic acid gel beads are washed with water, solvent exchanged and dried (each as described above) to provide polyamic acid aerogel beads.

[0407] In some aspects, the method further comprises preparing polyimide gel beads from polyamic acid gel beads. Fig.11 The polyamic acid gel beads are converted to corresponding polyimide gel beads by thermal imidization (eg, by subjecting the polyamic acid gel beads to a temperature of about 300° C. for a certain period of time).

[0408] In some aspects, the method further comprises preparing polyimide aerogel beads from polyamic acid aerogel beads. Fig.11 The polyamic acid aerogel beads are converted to corresponding polyimide aerogel beads by thermal imidization (eg, by subjecting the polyamic acid aerogel beads to a temperature of about 300° C. for a certain period of time).

[0409] In some aspects, the method further comprises preparing polyimide gel beads from polyimide aerogel beads. Fig.11 , the polyimide gel beads are washed with water, solvent exchanged and dried (each as described above) to provide polyimide aerogel beads.

[0410] Polyamic acid metal salt aerogel beads obtained from aqueous solution of polyamic acid salt

[0411] In another aspect, a method of forming a polyamic acid metal salt aerogel in the form of beads is provided. In some aspects, the method can be Fig.12 Reference is made to the method generally described in Fig.12 , the method generally comprises:

[0412] Providing an aqueous solution of polyamic acid ammonium salt or alkali metal salt;

[0413] performing a metal ion exchange, comprising adding a solution of a polyamic acid salt to a solution comprising a soluble metal salt to form polyamic acid metal salt gel beads; and

[0414] The polyamic acid metal salt gel beads are dried to form polyamic acid metal salt aerogel beads.

[0415] In some aspects, the salt is as described above with reference to Figure 3A , Figure 3B or Figure 3C In some aspects, the salt is an ammonium salt. In some aspects, the salt is an alkali metal salt. The method includes performing metal ion exchange. Fig.12 , metal ion exchange includes adding a solution of polyamic acid salt to a solution comprising a soluble metal salt. In some aspects, adding includes dripping an aqueous solution of polyamic acid salt into a soluble metal salt solution, spraying an aqueous solution of polyamic acid salt into a soluble metal salt solution under pressure through one or more nozzles, or electrospraying an aqueous solution of polyamic acid salt into a soluble metal salt solution, wherein each of dripping, spraying, and electrospraying is as described above. In particular aspects, the method includes electrospraying a polyamic acid salt solution through one or more needles at a voltage in the range of about 5 to about 60 kV.

[0416] In some aspects, the soluble metal salt comprises a main group transition metal, a rare earth metal, an alkaline earth metal, or a combination thereof. In some aspects, the soluble metal salt comprises copper, iron, nickel, silver, calcium, magnesium, yttrium, or a combination thereof. In some aspects, the soluble metal salt comprises lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or a combination thereof.

[0417] Without wishing to be bound by theory, it is believed that droplets of an aqueous solution of polyamic acid ammonium salt or alkali metal salt, when in contact with metal ions in a solution containing a soluble metal salt, form an outer shell of insoluble polyamic acid metal salt, and then the soluble metal salt ions migrate to the interior of the droplets, thereby forming polyamic acid metal salt gel beads, in which most of the polyamic acid carboxylate groups are associated with the anions of the soluble metal salt.

[0418] Continue to refer Fig.12 The resulting polyamic acid metal salt gel beads are aged, washed with water, solvent exchanged and dried (each as described above) to provide polyamic acid metal salt (polyamic acid salt) aerogel beads.

[0419] As noted above with respect to the formation of polyamic acid and its salts, the imidization options discussed above, while generally with reference to water-based methods, should not be construed as being so limited. One skilled in the art will recognize that there are many opportunities to substitute organic solvent solutions for aqueous solutions, and such substitutions are contemplated herein.

[0420] Carbon aerogels containing carbon additives obtained from polyimide, polyamic acid and metal polyamic acid salt aerogels

[0421] As described above, the method generally comprises converting an organic aerogel comprising a carbon additive or a precursor thereof into a carbon aerogel comprising a carbon additive, the conversion comprising pyrolyzing (carbonizing) the organic aerogel. In some aspects, the organic aerogel is a polyimide, a polyamic acid, or a combination thereof, which may be in the form of a monolith or beads.

[0422] In some aspects, the organic aerogel is a polyimide that is pyrolyzed to provide a carbon aerogel comprising a carbon additive. Fig.13 A non-limiting illustration in this regard is provided in .

[0423] In some aspects, the organic aerogel is a polyamic acid that can be directly converted to a carbon aerogel comprising a carbon additive (i.e., without first being imidized to provide a polyimide aerogel). In some aspects, the organic aerogel is a polyamic acid that is thermally imidized as disclosed herein to first provide a polyimide aerogel, and then the polyimide aerogel is subsequently pyrolyzed to provide a carbon aerogel comprising a carbon additive. Fig.14 A non-limiting illustration of these aspects is provided in .

[0424] In some aspects, the organic aerogel is a polyamic acid metal salt aerogel that is pyrolyzed to provide a carbon aerogel containing a carbon additive. In such aspects, upon pyrolysis, the ions of the soluble metal salt present can form the corresponding metal oxide or can sinter and form the corresponding metal, depending on the metal species and the pyrolysis conditions. Fig.15 A non-limiting illustration in this regard is provided in .

[0425] II. Physical properties of carbon aerogels containing carbon additives

[0426] In some aspects, the carbon aerogels including carbon additives as disclosed herein can be in the form of monoliths. As used herein, the term "monolith" refers to an aerogel material in which a majority (by weight) of the aerogel contained in the aerogel material is in the form of a macroscopic, single, continuous, self-supporting object. Monolithic aerogel materials include aerogel materials that are initially formed to have a well-defined shape but can subsequently be broken, fractured, or split into non-self-repeating objects. For example, irregular blocks can be considered monoliths. Monolithic aerogels can be in the form of free-standing structures or in the form of reinforcement materials having fibers or interpenetrating foams.

[0427] In other aspects, the carbon aerogel containing carbon additives of the present disclosure can be in particulate form, for example, beads or particles obtained by, for example, crushing monolithic materials or by a preparation method for bead formation. Aerogels in particulate form can have various particle sizes. In the case of spherical particles (e.g., beads), the particle size is the diameter of the particle. In the case of irregular particles, the term particle size refers to the maximum dimension (e.g., length, width or height). The particle size can vary, depending on the physical form, preparation method and any subsequent physical steps performed. In some aspects, aerogels in particulate form can have a particle size of about 1 micron to about 10 millimeters. For example, the aerogel in the form of microparticles can have a particle size of about 1 micron, about 2 microns, about 3 microns, about 4 microns, about 5 microns, about 6 microns, about 7 microns, about 8 microns, about 9 microns, about 10 microns, about 15 microns, about 20 microns, about 25 microns, about 30 microns, about 35 microns, about 40 microns, about 45 microns, about 50 microns, about 60 microns, about 70 microns, about 80 microns, about 90 microns, about 100 microns, about 200 microns, about 300 microns, about 400 microns, about 500 microns, about 600 microns, about 700 microns, about 800 microns, about 900 microns, about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, or in the range of any two of these values. In some aspects, the aerogel can have a particle size in the range of about 5 microns to about 100 microns or about 5 to about 50 microns. In some aspects, the aerogel can have a particle size in the range of about 1 to about 4 millimeters.

[0428] The amount of carbon additive present in the carbon aerogel can vary, depending on, for example, the initial load of the additive or precursor, the efficiency of incorporation, and the efficiency of the precursor conversion to the additive. In some aspects, the carbon aerogel comprises about 0.1% to about 20% carbon black by weight, such as about 0.1%, about 0.5%, or about 1% to about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9% or about 10% carbon black by weight. In some aspects, the carbon aerogel comprises about 0.1% to about 20% soft carbon by weight, such as about 0.1%, about 0.5%, about 1% to about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9% or about 10% soft carbon by weight. In some aspects, the carbon aerogel comprises about 0.1% to about 5% graphene or graphene oxide by weight, such as about 0.1%, about 0.5%, or about 1% to about 2%, about 3%, about 4%, or about 5% graphene or graphene oxide by weight.

[0429] In some aspects, the carbon aerogel comprises about 0.1% to about 10% by weight single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or a combination thereof, such as about 0.1%, about 0.5%, or about 1% to about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, or about 10% by weight single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or a combination thereof.

[0430] In some aspects, the carbon aerogel further comprises silicon. The amount of silicon present in the aerogel can vary. In some aspects, at least a portion of the silicon is present in the voids of the carbon aerogel.

[0431] In some aspects of the present disclosure, the carbon aerogel (aerogel or xerogel, monolith or bead) may include a fibril morphology. In the context of the present disclosure, the term "fibril morphology" refers to the structural morphology of a nanoporous material (e.g., a carbon aerogel), including struts, rods, fibers or filaments.

[0432] Measurement of carbon aerogel properties

[0433] Carbon aerogels can be characterized by properties such as pore volume, porosity, surface area, and pore size distribution. These properties and related terms, as well as methods of measuring and / or calculating such properties, are defined below.

[0434] In the context of the present disclosure, the term "pore volume" refers to the total volume of pores in a porous material sample. Pore volume is specifically measured as the volume of void space within a porous material, where the void space may be measurable and / or accessible to another material (e.g., an electrochemically active material such as silicon particles). It is typically reported as cubic centimeters per gram (cm 3 / g or cc / g).

[0435] In the context of the present disclosure, when used with respect to the polymer networks or carbon aerogels disclosed herein, the term "porosity" refers to the volume fraction of pores that do not contain another material (e.g., an electrochemically active material, such as silicon particles) bonded to the pore walls. For the purposes of clarification and illustration, it should be noted that in a specific implementation of a silicon-doped polymer network (e.g., an aerogel as the primary anode material in a LIB), the porosity refers to the void space after the silicon particles are included. Thus, when the anode is in a pre-lithiated state (to accommodate ion transport and silicon expansion), the porosity can be, for example, about 10%-70%, and when the anode is in a post-lithiated state, the porosity can be about 1%-50%. It should be noted that pore volume and porosity are different measures of the same property of the pore structure (i.e., the "empty space" within the pore structure). For example, when silicon is used as the electrochemically active material contained within the pores of the network (e.g., a carbon aerogel as described herein), the pore volume and porosity refer to the "empty" space, i.e., the space not utilized by silicon or carbon.

[0436] In the context of the present 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 means that a relatively large proportion of pores are within a narrow pore size range, thereby optimizing the amount of pores that can surround the electrochemically active material and maximizing the use of the pore volume. Conversely, a wider pore size distribution means that a relatively small proportion of pores are within a narrow pore size range. Therefore, the pore size distribution is typically measured as a function of pore volume and recorded as the unit size of the half-maximum full width of the dominant peak in the pore size distribution graph.

[0437] In the context of the present disclosure, the term "pore size at the maximum peak in the distribution" refers to the value at the discernible peak on a graph showing the pore size distribution. The pore size at the maximum peak in the distribution is specifically measured as the pore size at which the maximum percentage of pores is formed. It is typically reported as any unit length of pore size, such as micrometers or nanometers (nm).

[0438] In the context of the present disclosure, the term "BET surface area" has the general meaning of the Brunauer-Emmett-Teller method for determining surface area by N2 adsorption measurement. 2 The BET surface area, expressed as 100 μm / g, is a measure of the total surface area per unit mass of a porous material. Unless otherwise specified, "surface area" refers to the BET surface area. As an alternative to the BET surface area, the geometric external surface area of, for example, a polyimide or carbon bead can be calculated based on the diameter of the bead. Typically, such geometric external surface areas of beads of the present disclosure are in the range of about 3 to about 700 μm. 2 within the range.

[0439] As used herein, the term "particle size D50" is the cumulative 50% size based on volume, which is the particle size at the 50% point on the cumulative curve when the cumulative curve is plotted so that the particle size distribution is obtained based on volume and the entire volume is 100% (i.e., the particle diameter located at the 50th percentile (median) of the particle volume).

[0440] In the context of the present disclosure, the term "density" refers to the measurement of the mass of a material (e.g., a carbon aerogel as described herein) per unit volume. The term "density" generally refers to the true density or skeletal density of a material as well as the bulk density of a material or composition. Density is typically reported as g / cm 3 , g / cc or g / mL.

[0441] Mercury intrusion porosity and helium pycnometer experiments can be used to determine the properties of carbon aerogels. Mercury intrusion porosity can be used to determine the porosity, pore size distribution, and pore volume of solid particles. During a typical mercury intrusion porosity method, a pressurized chamber is used to force mercury into the voids in a porous substrate. When pressure is applied, mercury first fills larger pores. As pressure increases, mercury can enter smaller pores. Mercury pycnometer can reach and measure pores greater than about 3nm. Mercury intrusion porosity can be used to measure bulk density, skeletal density, and porosity. By changing the test parameters (e.g., pressure range), pores with different sizes can be excluded. In the case of mercury intrusion porosity, the lower limit pore size is about 3nm.

[0442] Helium pycnometry uses helium to measure the volume of the pores of a solid material. During helium pycnometry, the sample is sealed in a compartment and helium is added to the compartment. The helium penetrates into the small pores in the material. After the system has reached equilibrium, the change in pressure can be used to determine the skeletal density of the solid material. Helium pycnometry can reach and measure pores greater than about 0.3 nm, for example, pores with a size of about 3 nm to about 300 nm.

[0443] “Hg skeleton density” (g / cm 3 ) is calculated by dividing the mass of the composite particle (g) by the volume of the particle (cm 3 ), where the volume is measured by controlling (e.g., by pressure control) the mercury that accesses the pores of the particles larger than 3 nm during the measurement. This volume does not include the volume of the pores of the composite material that are accessible to mercury larger than 3 nm. Instead, the volume includes only the volume of the "skeleton" of the composite material particles. The volume of pores smaller than 3 nm is considered part of the skeleton and is included in the skeleton density calculation.

[0444] The Hg volume density is calculated by dividing the mass of the carbon aerogel particles (g) by the volume of the particles (cm 3 ), wherein the volume is measured by controlling (e.g., by pressure control) the mercury from reaching the particle pores during the measurement. This volume includes the volume of the pores of the carbon aerogel (including pores larger than 3 nm and smaller than 3 nm).

[0445] The “He skeletal density” is calculated by dividing the mass (g) of the carbon aerogel particle by the particle volume (cm 3 ), where the volume is measured by controlling (e.g., by pressure control) the helium that accesses the particle pores larger than 0.3 nm during the measurement. This volume does not include the volume of the helium-accessible pores of the carbon aerogel larger than 0.3 nm. Instead, the volume includes only the volume of the "skeleton" of the carbon aerogel particle. The volume of pores smaller than 0.3 nm is considered part of the skeleton and is included in the skeleton density calculation.

[0446] Carbon aerogels may also contain pores that are inaccessible to both helium and mercury during helium pycnometer or mercury pycnometer testing. For example, some pores formed by removing sacrificial particles may be enclosed in a three-dimensional network and are therefore inaccessible to both helium pycnometer and mercury pycnometer. These inaccessible pores are typically very small in the composite materials disclosed herein. The inaccessible pores are considered part of the skeleton volume without introducing significant changes.

[0447] Using the mercury (Hg) intrusion skeletal density measurements measured by mercury pycnometer (Hg skeletal density), the mercury intrusion bulk density measured by mercury pycnometer (Hg bulk density), and the helium (He) skeletal density tested by helium pycnometer (He skeletal density), various physical properties can be calculated according to the following formulas.

[0448]

[0449] Micropore volume percentage (%, relative to total pore volume)

[0450] Micropore volume / total pore volume (4)

[0451] The mesopore volume percentage (% relative to the total pore volume) can be obtained by mercury intrusion porosimetry by excluding all pores >50 nm.

[0452] Macropore volume percentage (%, relative to total pore volume)

[0453] 1 Micropore volume percentage Mesopore volume percentage (5)

[0454] "Total bead porosity" (%) refers to the ratio of the pore volume in the carbon aerogel particle to the volume of the composite particle. The total bead porosity is calculated by equation (1). The total bead porosity includes pores larger than 0.3 nm that are accessible to helium and mercury.

[0455] “Total pore volume” (cm 3 / g) refers to the total pore volume per unit weight of carbon aerogel particles. The total pore volume is calculated by equation (2). The total pore volume includes pores larger than 0.3 nm that can be reached by helium and mercury.

[0456] “Micropore volume” (cm 3 / g) refers to the micropore volume per unit weight of carbon aerogel particles. According to equation (3), the micropore volume of the composite material (cm 3 / g) is the skeletal density of mercury (g / cm 3 ) (cm 3 / g) and helium skeletal density (g / cm 3 ) (cm 3 The micropore volume includes pores larger than 0.3 nm but smaller than 3 nm. Micropores are accessible to helium but not to mercury.

[0457] "Micropore volume percentage" (%) refers to the volume ratio between the micropore volume and the total pore volume. The micropore volume percentage is calculated by equation (4).

[0458] "Mesopore volume percentage" (%) refers to the volume ratio between the mesopore volume and the total pore volume. Mesopores refer to pores between about 3 nm and about 50 nm that are accessible to mercury. Pores below 3 nm are inaccessible to mercury. By excluding pores larger than 50 nm, the mesopore volume percentage can be directly measured using mercury pycnometer determination. The mesopore volume percentage can also be obtained by subtracting the micropore volume percentage (calculated by equation (4)) and the mesopore volume percentage (measured by mercury pycnometer determination) from the total pore volume percentage (100%).

[0459] "Macropore volume percentage" (%) refers to the volume ratio between the macropore volume and the total pore volume. Macropores are larger than about 50 nm and are accessible to mercury. By excluding pores smaller than 50 nm, the macropore volume percentage can be directly measured using mercury pycnometer determination. The macropore volume percentage can also be obtained by subtracting the micropore volume percentage (calculated by equation (4)) and the macropore volume percentage (measured by mercury pycnometer determination) from the total pore volume percentage (100%).

[0460] Carbon Aerogel Properties

[0461] Total porosity

[0462] The carbon aerogels described herein generally comprise micropores (<3nm), mesopores (3nm-50nm) and macropores (>50nm). The carbon aerogels described herein comprise a three-dimensional carbon network having a large number of macropores. In some aspects, the total porosity level of the three-dimensional carbon network is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, or greater than 70%. In some aspects, the total porosity level of the three-dimensional carbon network is 25% to 35%, 30% to 40%, 35% to 45%, 40% to 50%, 55% to 65%, or 60% to 70%.

[0463] Total pore volume

[0464] In certain aspects, the carbon aerogels of the present disclosure (not incorporated with electrochemically active materials, such as silicon) have a relatively large total pore volume of about 1 cc / g or greater, 1.5 cc / g or greater, 2 cc / g or greater, 2.5 cc / g or greater, 3 cc / g or greater, 3.5 cc / g or greater, 4 cc / g or greater, or in a range between any two of these values. In other aspects, the carbon aerogels of the present disclosure (incorporated with electrochemically active materials, such as silicon) have a total pore volume of about 0.03cc / g or more, about 0.1cc / g or more, about 0.3cc / g or more, 0.6cc / g or more, 0.9cc / g or more, 1.2cc / g or more, 1.5cc / g or more, 1.8cc / g or more, 2.1cc / g or more, 2.4cc / g or more, 2.7cc / g or more, 3.0cc / g or more, 3.3cc / g or more, 3.6cc / g or more, or in a range between any two of these values. In still other aspects, the total pore volume of the carbon aerogels (incorporated with electrochemically active materials, such as silicon) is about 0.1cm 3 / g to about 1.5cm 3 / g, about 0.1cm 3 / g to about 1.0cm 3 / g, about 0.1cm 3 / g to about 0.5cm 3 / g, about 0.1cm 3 / g to about 0.4cm 3 / g, about 0.4cm 3 / g to about 1.0cm 3 / g, or about 0.9cm 3 / g to about 1.4cm 3 / g.

[0465] Pore ​​size distribution

[0466] In certain embodiments, the aerogel materials of the present disclosure have 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 in a range between any two of these values.

[0467] Macropores, mesopores and micropores

[0468] In some aspects, macropores constitute a volume fraction greater than about 5%, greater than about 10%, greater than about 20%, greater than about 30%, greater than about 40%, greater than about 50%, greater than about 60%, greater than about 70% or greater than about 80% of the total pore volume of the three-dimensional carbon network. In some aspects, macropores constitute a volume fraction of 45% to 55%, 55% to 65%, 65% to 75%, or 70% to 80% of the total pore volume of the three-dimensional carbon network. The carbon aerogel described herein generally has a low volume fraction of mesopores. In some aspects, mesopores constitute a volume fraction of less than 20%, less than 10%, less than 5%, less than 2%, or less than 1% of the total pore volume of the three-dimensional carbon network. In some aspects, mesopores constitute a volume fraction of 10% to 20%, 5% to 10%, or 1% to 5% of the total pore volume of the three-dimensional carbon network.

[0469] Compared with mesopore, carbon aerogel described herein comprises higher percentage of micropore.In some aspects, micropore constitutes the total pore volume of three-dimensional carbon network less than 80%, less than 70%, less than 65%, less than 55%, less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15% or less than 10% volume fraction.In some aspects, micropore constitutes the total pore volume of three-dimensional carbon network about 10% to about 50%, about 10% to about 45%, about 10% to about 40%, about 10% to about 35%, about 10% to about 30%, about 10% to about 25%, about 10% to about 20%, about 10% to about 15%, about 15% to about 25%, about 25% to about 35%, about 35% to about 45% or about 45% to about 55% volume fraction.

[0470] Skeletal density

[0471] In some aspects, the carbon aerogel has a skeletal density of about 1.0 g / mL to about 2.5 g / mL, about 1.5 g / mL to about 2.5 g / mL, about 1.0 g / mL to about 2.0 g / mL, or 1.0 g / mL to about 1.5 g / mL measured using a helium pycnometer. In some aspects, the carbon aerogel has a skeletal density of about 0.5 g / mL to about 2.5 g / mL, about 1.5 g / mL to about 2.5 g / mL, about 1.5 g / mL to about 2.0 g / mL, about 0.5 g / mL to about 2.0 g / mL, about 0.5 g / mL to about 1.5 g / mL, or about 0.5 g / mL to about 1.0 g / mL measured using mercury intrusion porosimetry. In some aspects, the carbon aerogel has a bulk density of 0.5 g / mL to about 2.5 g / mL, 0.5 g / mL to about 2.0 g / mL, about 0.5 g / mL to about 1.5 g / mL, or about 0.5 g / mL to about 1.0 g / mL as measured using mercury pycnometry.

[0472] III. Electrochemical properties of carbon aerogels containing carbon additives

[0473] In some aspects, the carbon aerogel beads comprising carbon additives as disclosed herein have improved first cycle coulombic efficiency relative to carbon aerogel beads having only carbon (i.e., without carbon additives). In some aspects, the low surface area (<20 m2) aerogel beads comprising carbon additives as disclosed herein have improved first cycle coulombic efficiency relative to carbon aerogel beads having only carbon (i.e., without carbon additives). 2 / g) carbon aerogel beads have a first cycle coulombic efficiency in the range of about 60%-68%. Surprisingly, in contrast, carbon beads without carbon additives have a first cycle coulombic efficiency of about 50%-58%.

[0474] In some aspects, the carbon-silicon composite aerogel beads comprising carbon additives as disclosed herein have improved rate performance relative to Si / C beads without carbon additives. In particular, it was surprisingly found that Si / C beads containing soft carbon and carbon black as additives exhibited higher capacity at higher current rates relative to Si / C beads without carbon additives.

[0475] The conductivity of the disclosed materials may vary. In the context of the present disclosure, the term "conductivity" refers to a measurement of the ability of a material to conduct an electric current or otherwise allow electrons to pass through or flow therein. Conductivity is specifically measured as the conductivity / susceptance / admittance / unit size of a material. It is typically recorded as S / m (Siemens / meter) or S / cm (Siemens / centimeter). The conductivity or resistivity of a material can be determined by methods known in the art, such as, but not limited to: online four-point resistivity (using the dual configuration test method of ASTM F84-99). In the context of the present disclosure, the measured value of conductivity is obtained according to ASTM F84-resistivity (R) measurement obtained by measuring voltage (V) divided by current (I), unless otherwise stated. In certain aspects, the materials of the present disclosure (e.g., carbon aerogels comprising carbon additives (alone or with silicon particles)) have an electrical 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 in a range between any two of these values.

[0476] Unless otherwise noted herein or clearly contradicted by context, all methods described herein can be performed in any suitable order. Unless otherwise claimed, the use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better illustrate the materials and methods, rather than to impose limitations on the scope. The language in the specification should not be interpreted as indicating that any unclaimed element is necessary to practice the disclosed materials and methods.

[0477] It will be apparent to those of ordinary skill in the relevant art that the compositions, methods and applications described herein may be appropriately modified and adjusted without departing from the scope of any aspect or aspect thereof. The methods provided are exemplary and are not intended to limit the scope of the claimed aspects. The various aspects, aspects and options disclosed herein may be combined in all variations. The scope of the compositions, preparations, methods and processes described herein includes all actual or potential combinations of aspects, aspects, options, embodiments and preferences herein.

[0478] Although the technology of this article has been described herein with reference to specific aspects, it should be understood that these aspects are only illustrative of the principles and applications of the present technology. It will be apparent to those skilled in the art that various modifications and variations can be made in the methods and devices of the present technology without departing from the spirit and scope of the present technology. Therefore, the present technology is intended to include modifications and variations within the scope of the appended claims and their equivalents.

[0479] References throughout the specification to "an aspect," "certain aspects," "one or more aspects," or "aspects" mean that the particular features, structures, materials, or characteristics described with respect to the aspects are included in at least one aspect of the present technology. Therefore, phrases such as "in one or more aspects," "in certain aspects," "in an aspect," or "in an aspect" that appear throughout this specification do not necessarily refer to the same aspect of the present technology. In addition, in one or more aspects, particular features, structures, materials, or characteristics may be combined in any suitable manner. Any ranges cited herein are included.

[0480] Various aspects of the present technology will be more fully described with reference to the following examples. Before describing several exemplary aspects of the present technology, it should be understood that the present technology is not limited to the details of the construction or process steps described in the following description. The present technology can have other aspects and can be practiced or carried out in various ways. The following examples are described to illustrate certain aspects of the present technology, but should not be construed as limiting thereof.

[0481] Example

[0482] The invention is further illustrated by the following non-limiting examples which describe the process.

[0483] Example 1. Carbon aerogel microbeads containing 3% graphene oxide

[0484] Carbon aerogel beads containing 3% by weight of graphene oxide were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of graphene oxide, followed by pyrolysis of the resulting polyimide gel beads.

[0485] Preparation of polyimide gel beads containing graphene oxide with a target density of about 0.073 g / cm 3. A solution of 1,4-phenylenediamine in water was prepared by mixing PDA (3.51 g; 32.5 mmol) with water (73 g) and then heating at 60°C until complete dissolution occurred (approximately 8 minutes). The solution was cooled to room temperature and stirred while adding a dispersion of graphene oxide in water (33 ml of a 4 mg / ml dispersion). Triethylamine (10.9 ml; 2.4:1 mol / mol ratio with PMDA) was added and then stirred for 3 minutes. To this mixture was added pyromellitic dianhydride (PMDA; 7.09 g; 1:1 mol / mol ratio relative to PDA) and then stirred at room temperature for 3 hours to form a polyamic acid triethylammonium salt solution. Then, 32.55 g of a graphene oxide suspension having a mass concentration of 0.4 wt% was added to the polyamic acid triethylammonium salt solution. After adding the graphene oxide suspension, acetic anhydride (13.2 ml; 4.3 mol / mol molar ratio to PMDA) was added and the mixture was stirred for 50 seconds. At the end of this period, the sol was poured into the immiscible phase under high shear conditions using a Ross mixer. 9.75 g of surfactant was added. B246SF (HLB of 6) was dissolved in 650 mL of mineral spirits (the ratio of mineral spirits to PI sol was 5:1) to prepare the immiscible phase. The sol-immiscible phase mixture was emulsified by stirring at 4000 rpm for 2.5 minutes with a Ross mixer. After standing for 1 hour, the emulsified mixture was removed from the Ross mixer and the mineral spirits phase was decanted. The beads were washed with ethanol and collected by filtration. The beads were washed several times with ethanol to fully remove residual water and mineral spirits and then dried at 68°C. Fig.16A Micrographs of dried polyimide beads are provided in . Fig.16A The image of the beads is very similar to that of polyimide beads prepared in the absence of graphene oxide, and indicates that the dispersion of graphene oxide is very good. The dried polyimide beads were pyrolyzed at 1050 °C for 2 h under nitrogen to provide the corresponding carbon aerogel beads. Fig. 16B Micrographs of carbonized beads are provided.

[0486] Example 2. Carbon aerogel microbeads containing 20% ​​soft carbon

[0487] Carbon aerogel beads including 20% ​​by weight of soft carbon were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of perylenetetracarboxylic dianhydride (PTCDA), followed by thermally decomposing the resulting polyimide gel beads.

[0488] Polyimide gel beads containing PTCDA were prepared with a target density of about 0.073 g / cm 3. A solution of 1,4-phenylenediamine in water was prepared by mixing PDA (7.02 g; 65 mmol) with water (211 g) and then heating at 60°C until complete dissolution occurred (approximately 8 minutes). The solution was cooled to room temperature and stirred. Triethylamine (21.8 ml; 2.4:1 mol / mol ratio with PMDA) was added and then stirred for 3 minutes. To this mixture was added pyromellitic dianhydride (PMDA; 14.2 g; 1:1 mol / mol ratio relative to PDA) and then stirred at room temperature for 3 hours. Perylenetetracarboxylic dianhydride (PTCDA; 4.34 g; 11 mmol) was added to the resulting polyamic acid triethylammonium salt solution and stirred for 10 min, and then acetic anhydride (26.4 ml; 4.3 mol / mol ratio relative to PMDA) was added, and the mixture was stirred for 50 seconds. At the end of this period, the sol was poured into the immiscible phase under high shear using a Ross mixer at 4000 rpm. B246SF (HLB of 6) was dissolved in 650 mL of mineral spirits (ratio of mineral spirits to PI sol was 5:1) to prepare an immiscible phase. The mixture was stirred at 4000 rpm for 3 minutes using a Ross mixer. After standing for 1 hour, the mixture was removed from the Ross mixer and the mineral spirits phase was decanted. The beads were washed with ethanol and collected by filtration. The beads were washed several times with ethanol to fully remove residual water and mineral spirits and then dried at 68°C. Fig.17A A micrograph of the dried polyimide beads is provided in . The dried polyimide beads were pyrolyzed at 1050°C for 2 hours under nitrogen to provide the corresponding carbon aerogel beads. Fig. 17B Micrographs of carbonized beads are provided.

[0489] Example 3. Carbon aerogel microbeads containing 10% soft carbon

[0490] Carbon aerogel beads containing 10% by weight of soft carbon were prepared according to the procedure of Example 2 but using half the amount of PTCDA.

[0491] Example 4. Carbon aerogel microbeads containing 10% carbon black

[0492] Carbon aerogel beads containing 10% by weight of carbon black were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of carbon black, followed by pyrolysis of the resulting polyimide gel beads.

[0493] Polyimide gel beads containing carbon black were prepared with a target density of about 0.073 g / cm 3. A solution of 1,4-phenylenediamine in water was prepared by mixing PDA (7.02 g; 65 mmol) with water (211 g) and then heating at 60 ° C until complete dissolution occurred (approximately 8 minutes). The solution was cooled to room temperature and stirred. Triethylamine (21.8 ml; mol / mol ratio with PMDA was 2.4: 1) was added and then stirred for 3 minutes. To this mixture was added pyromellitic dianhydride (PMDA; 14.2 g; mol / mol ratio relative to PDA was 1: 1) and then stirred at room temperature for 3 hours. Carbon black (0.96 g) was added to the resulting polyamic acid triethylammonium salt solution and stirred for 10 min, and then acetic anhydride (26.4 ml; 4.3 mol / mol relative to PMDA) was added, and the mixture was stirred for 50 seconds. At the end of this period, the sol was poured into the immiscible phase at 4000 rpm under high shear using a Ross mixer. By adding 9.75 g of surfactant B246SF (HLB of 6) was dissolved in 650 mL of mineral spirits (the ratio of mineral spirits to PI sol was 5:1) to prepare an immiscible phase. The mixture was stirred at 4000 rpm for 3 minutes using a Ross mixer. After standing for 1 hour, the mixture was taken out of the Ross mixer and the mineral spirits phase was decanted. The beads were washed several times with ethanol to fully remove residual water and mineral spirits and then dried at 68°C. Fig.18A A micrograph of the dried polyimide beads is provided in . The dried polyimide beads were pyrolyzed at 1050°C for 2 hours under nitrogen to provide the corresponding carbon aerogel beads. Fig.18B Micrographs of carbonized beads are provided.

[0494] Example 5. Carbon aerogel microbeads containing carbon black and silicon

[0495] Carbon aerogel beads comprising carbon black (about 10% by weight) and silicon (about 50% by weight) were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of carbon black and silicon, followed by pyrolysis of the resulting polyimide gel beads.

[0496] Polyimide gel beads containing carbon black were prepared with a target density of about 0.085 g / cm 3. A solution of 1,4-phenylenediamine in water was prepared by mixing PDA (12.7 g; 118 mmol) with water (313 g) and then heating at 120°C until complete dissolution occurred (approximately 8 minutes). The solution was cooled to near room temperature and stirred. Triethylamine (39.3 ml; 2.4:1 mol / mol ratio with PMDA) was added and then stirred for 4 minutes. To this mixture was added pyromellitic dianhydride (PMDA; 25.5 g; 1:1 mol / mol ratio relative to PDA) and then stirred at room temperature for 4 hours. Carbon black (1.7 g) and powdered silicon (15.1 g; modified Evonik AE-APTMS) were added to the resulting polyamic acid triethylammonium salt solution and stirred for 10 min, then acetic anhydride (47.6 ml; 4.3 mol / mol molar ratio relative to PMDA) was added, and the mixture was stirred for 50 seconds. At the end of this period, the sol was poured into the immiscible phase under high shear using a Ross mixer at 3880 rpm. B246SF (HLB of 6) was dissolved in 1200 mL of mineral spirits (the ratio of mineral spirits to PI sol was 3:1) to prepare an immiscible phase. The mixture was stirred for 3 minutes using a Ross mixer. After standing for 2 hours, the mixture was removed from the Ross mixer, and about 300 ml of the mineral spirits phase was decanted, and the beads were allowed to remain in suspension overnight. The next day, the mineral spirits layer was removed by decantation, and ethanol (600 ml) was added, followed by stirring for 1 hour. The mixture was allowed to stand for 48 hours and then decanted. Ethanol (600 ml) was added, followed by stirring for 2 hours. The suspension was filtered and the beads were stirred with ethanol (400 ml) for 2 hours. The suspension was filtered again and the collected beads were dried at 68°C. As Fig.19A Provides a micrograph of polyimide beads with silica and carbon black particles dispersed inside the beads. Fig.19A , the image shows that the two different particles are well dispersed inside the beads.After drying, the beads were ground with a mortar and pestle and then pyrolyzed at 1050°C for 2 hours. Fig.19B is a SEM image of carbonized Si / C carbon beads, which shows the presence of two types of carbon (carbon black added to the sol and carbon provided by carbonization of the polyimide, but the two carbon types cannot be distinguished in the image).

[0497] Example 6. Carbon aerogel microbeads containing soft carbon and silicon

[0498] Carbon aerogel beads comprising soft carbon (about 10% by weight) and silicon (about 50% by weight) were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of PTCDA and silicon, followed by pyrolysis of the resulting polyimide gel beads.

[0499] Polyimide beads containing PTCDA and silicon were prepared by gelling an emulsion of an aqueous solution of polyamic acid triethylammonium salt, with a target density of about 0.085 g / cm 3 . A solution of 1,4-phenylenediamine in water was prepared by mixing PDA (12.7 g; 118 mmol) with water (313 g) and then heating at 120°C until complete dissolution occurred (approximately 8 minutes). The solution was cooled to room temperature and stirred. Triethylamine (39.2 ml; 2.4:1 mol / mol ratio with PMDA) was added and then stirred for 3 minutes. To this mixture was added pyromellitic dianhydride (PMDA; 25.5 g; 1:1 mol / mol ratio relative to PDA) and then stirred at room temperature for 4 hours. Perylenetetracarboxylic dianhydride (PTCDA; 3.4 g; 8.6 mmol) was added to the resulting polyamic acid triethylammonium salt solution and stirred for 10 min, then acetic anhydride (47.6 ml; 4.3 mol / mol molar ratio relative to PMDA) was added, and the mixture was stirred for 50 seconds. At the end of this period, the sol was poured into the immiscible phase under high shear using a Ross mixer at 3880 rpm. B246SF (HLB of 6) was dissolved in 1200 mL of mineral spirits (the ratio of mineral spirits to PI sol was 3:1) to prepare an immiscible phase. The mixture was stirred for 3 minutes using a Ross mixer. After standing for 2 hours, the mixture was removed from the Ross mixer, and about 300 ml of the mineral spirits phase was decanted, and the beads were allowed to remain in suspension overnight. The next day, the mineral spirits layer was removed by decantation, and ethanol (600 ml) was added, followed by stirring for 1 hour. The mixture was allowed to stand for 48 hours and then decanted. Ethanol (600 ml) was added, followed by stirring for 2 hours. The suspension was filtered and the beads were stirred with ethanol (400 ml) for 2 hours. The suspension was filtered again and the collected beads were dried at 68°C. As Fig. 20A A micrograph of polyimide beads is provided, with silicon and PTCDA particles dispersed inside the beads. After drying, the beads were ground with a mortar and pestle and then pyrolyzed at 1050°C for 2 hours. Fig. 20B is a SEM image of carbonized Si / C beads.

[0500] Example 7: Carbon Aerogel Microbeads (Reference)

[0501] Reference carbon aerogel beads were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt and subsequently pyrolyzing the resulting polyimide gel beads.

[0502] Preparation of polyimide gel beads with a target density of approximately 0.073 g / cm 3. A solution of 1,4-phenylenediamine in water was prepared by mixing PDA (7.02 g; 65 mmol) with water (211 g) and then heating at 60°C until complete dissolution occurred (approximately 8 minutes). The solution was cooled to room temperature and stirred. Triethylamine (21.8 ml; mol / mol ratio with PMDA was 2.4:1) was added and then stirred for 3 minutes. To this mixture was added pyromellitic dianhydride (PMDA; 14.2 g; mol / mol ratio relative to PDA was 1:1) and then stirred at room temperature for 3 hours. Acetic anhydride (26.4 ml, mol / mol ratio relative to PMDA was 4.3 mol / mol) was added to the resulting polyamic acid triethylammonium salt solution, and the mixture was stirred for 50 seconds. At the end of this period, the sol was poured into the immiscible phase at 4000 rpm under high shear using a Ross mixer. By adding 9.75 g of surfactant B246SF (HLB of 6) was dissolved in 650 mL of mineral spirits (the ratio of mineral spirits to PI sol was 5:1) to prepare the immiscible phase. The mixture was stirred at 4000 rpm using a Ross mixer for 3 minutes. After standing for 1 hour, the mixture was taken out of the Ross mixer and the mineral spirits phase was decanted. The beads were washed with ethanol and collected by filtration. The beads were washed with ethanol several times to fully remove residual water and mineral spirits and then dried at 68°C. The dried polyimide beads were pyrolyzed at 1050°C under nitrogen for 2 hours.

[0503] Example 8. Carbon aerogel microbeads containing carbon black

[0504] Carbon aerogel beads containing carbon black are prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of carbon black, followed by thermal decomposition of the obtained polyimide gel beads.

[0505] A solution of 1,4-phenylenediamine (PDA) in water was prepared by stirring a mixture of PDA (9.78 g) and water (182.93 g) for 30 min. Triethylamine (22 g) was added to the solution and then stirred for 10 minutes. Benzene-1,2,4,5-tetracarboxylic anhydride (19.726 g) was then added and stirred for 4 h. Carbon black (1.167 g) was added to the solution and then stirred for 10 minutes. Acetic anhydride (39.7 g) was then poured into the suspension, and the mixture was stirred for 50 s, and then the combined mixture was poured into 750 mL of mineral spirits containing a surfactant while mixing at 2800 rpm. The obtained emulsion was then aged overnight, and then the polyimide beads were collected by filtration. The collected beads were rinsed several times with ethanol and then dried in an oven at 70 ° C. The dried polyimide beads were pyrolyzed at 1050 ° C for 2 hours under nitrogen.

[0506] Example 9. Carbon aerogel microbeads containing carbon black and silicon

[0507] Carbon aerogel beads comprising carbon black and silicon particles were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of carbon black and silicon particles, followed by pyrolysis of the resulting polyimide gel beads. Beads were prepared as in Example 8 but with further addition of silicon particles (4.613 g) along with the carbon black.

[0508] Example 10. Carbon aerogel microbeads containing carbon nanotubes

[0509] Carbon aerogel beads containing carbon nanotubes were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of carbon nanotubes and then pyrolyzing the resulting polyimide gel beads. Beads were prepared as in Example 8 but using carbon nanotubes (0.106 g) instead of carbon black.

[0510] Example 11. Carbon aerogel microbeads containing graphene ribbons

[0511] Carbon aerogel beads comprising graphene ribbons were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of graphene ribbons followed by pyrolysis of the resulting polyimide gel beads. Beads were prepared as in Example 8 but using graphene ribbons (0.053 g) instead of carbon black.

[0512] Example 12. Carbon aerogel microbeads containing soft carbon

[0513] Carbon aerogel beads including soft carbon were prepared by imidizing an emulsified aqueous solution of polyamic acid triethylammonium salt in the presence of PTCDA, followed by pyrolysis of the obtained polyimide gel beads.

[0514] A solution of 1,4-phenylenediamine (PDA) in water was prepared by stirring a mixture of PDA (9.78 g) and water (182.93 g) for 30 min. Triethylamine (22 g) was added to the solution and then stirred for 10 minutes. Benzene-1,2,4,5-tetracarboxylic anhydride (19.726 g) was then added and stirred for 4 h. Perylene tetracarboxylic dianhydride (PTCDA, 2.917 g) was added to the solution and then stirred for 10 minutes. Acetic anhydride (39.7 g) was then poured into the suspension, and the mixture was stirred for 50 s, and then the combined mixture was poured into 750 mL of mineral spirits containing a surfactant while mixing at 2800 rpm. The obtained emulsion was then aged overnight, and then the polyimide beads were collected by filtration. The collected beads were rinsed several times with ethanol and then dried in an oven at 70 ° C. The dried polyimide beads were pyrolyzed at 1050 ° C for 2 hours under nitrogen.

[0515] Example 13. Evaluation of specific capacity

[0516] The prepared carbon bead materials containing different carbon additives (e.g., soft carbon and hard carbon, Examples 1, 2 and 4 and Reference Example 7) were tested using a lithium metal half-cell with a 2032 stainless steel button cell. The carbon sample was first blended with 2wt% sodium carboxymethylcellulose (CMC), 3wt% styrene-butadiene rubber (SBR) aqueous binder, and 10% carbon black to make a slurry, and the slurry was then coated on a copper foil. The copper foil was dried at 100°C under vacuum, and the dried foil was punched into small discs (16 mm in diameter). The electrolyte used was 1.2M LiPF6 in 3 / 7v / v ethylene carbonate:ethyl methyl carbonate (EC:EMC). The battery cell was tested with a current of 150μA in a potential range of 10mV to 1.5V.

[0517] Results are provided in Fig.21 Reference Fig.21 , carbon aerogel microbeads containing graphene oxide, soft carbon, and carbon black (Examples 1, 2, and 4, respectively) show improved FCE and reversible capacity relative to the reference carbon aerogel microbeads (Example 7). In addition, the lithiation potential of the modified carbon beads is higher than that of the carbon beads without carbon additives. All of these carbon bead samples have similar low surface areas (<10 m 2 / g) and were tested under the same conditions. Therefore, the improved FCE and reversible capacity and their differences in lithiation potential are believed to be due to changes in the inherent properties of the obtained carbon material. Without wishing to be bound by theory, it is believed that this may be caused by changes in the introduced carbon additive itself as well as changes in the polyimide-derived carbon induced by the carbon additive.

[0518] Example 14. Evaluation of lithium removal capacity

[0519] The protocol of Example 8 was used to determine the delithiation capacity of the prepared carbon bead materials containing different carbon additives (eg, soft carbon and hard carbon, Examples 1, 2 and 4 and Reference Example 7).

[0520] Results are provided in Fig. 22 The figure shows that the addition of carbon additives to Si / C composites improves the rate performance of the obtained material. Fig. 22 , Si / C beads containing different carbon additives (Examples 1, 2 and 4) show improved capacity at higher current rates. These results demonstrate that the addition of carbon additives not only changes the carbon structure and improves the FCE of the carbon material, but also improves the high rate performance, which is very important for fast charging behavior. Without wishing to be bound by theory, it is believed that this improved high rate performance is due to the improved conductivity of the resulting carbon material in the presence of the carbon additive.

[0521] Example 15. Synthesis of non-crosslinked sacrificial particles (PMMA nanospheres)

[0522] Water (80 grams) and monomer methyl methacrylate (20 grams) are added to a beaker and stirred at 500RPM for 15 minutes on a hot plate, wherein the solution temperature is controlled at 80°C. 1.8 grams of ammonium persulfate are added to the solution as an initiator. Then after 60 minutes, the stirring speed is reduced to 300RPM. When the solution color changes from transparent to milky white, the stirring speed is increased to 500RPM again. The solution is stirred for another 180 minutes, and then 2.1 grams of polymer modifier (hydroxyethyl) methacrylate are added. The solution temperature is changed to 60°C and the solution is stirred overnight. By the next morning, the synthesis of PMMA nanospheres in the emulsion is complete.

[0523] Example 16. Synthesis of cross-linked sacrificial particles (PMMA nanospheres)

[0524] Water (80 g) and monomer methyl methacrylate (20 g) were added to a beaker and stirred at 500 RPM for 15 minutes on a hot plate, with the solution temperature controlled at 80°C. Ammonium persulfate (1.8 g) was added to the solution as an initiator. Then after 60 minutes, the stirring speed was reduced to 300 RPM. When the solution color changed from transparent to milky white, the stirring speed was increased to 500 RPM again. 1,3-Butanediol dimethacrylate (1.8 g) was immediately added to the solution as a crosslinking agent. The solution was stirred for another 180 minutes, and then a polymer modifier ((hydroxyethyl) methacrylate; 2.1 g) was added. The solution temperature was changed to 60°C and stirred overnight. By the next morning, the synthesis of PMMA nanospheres in the emulsion was completed.

[0525] Example 17. Synthesis of Si particles coated with a sacrificial layer

[0526] Commercially available silicon particles may or may not include oxidized (partially or fully oxidized) silicon particles. Thus, depending on the surface functional groups of the silicon particles provided by the commercial supplier, the oxidation step provided herein is optional.

[0527] Silicon particles (10-100 g; 100-3000 nm; available from Evonik) were heated in a temperature range of 400°C-800°C for 1-5 h under humid conditions, or dispersed in 0.1-5 M of 10-1000 mL of sulfochromic acid or 1-10 M of H2O2 (hydrogen peroxide; 10-1000 mL). For the Si dispersion, it was heated to 50-120°C for 1-10 hours under constant stirring in order to obtain hydroxyl functional groups (or silanol groups) on the surface of the silicon particles. In principle, other oxidizing agents can also be used for this purpose. After stirring the solution for 1-10 hours, the solution was cooled to room temperature and centrifuged to obtain oxidized silicon particles. The obtained silicon particles were washed 3-5 times with 100-3000 mL volumes of water to remove any residual acid and dried under ambient conditions for 3-10 hours. IR spectroscopy confirmed the surface oxidation, as shown by the presence of IR at 2105 and 1993 cm -1 The intensity of the band at 1052 cm -1 Oxidation by heating the dry powder can also be confirmed by the increase in mass after treatment.

[0528] Oxidized silicon particles (10 g) were dispersed in 50 mL of ethanol. The dispersion was sonicated for 30 minutes to prevent agglomeration of the silicon particles. Then, 1 g of AEAPTMS was added to the dispersion and stirred on a hot plate for 240 minutes, with the dispersion temperature controlled at 70°C. After the dispersion was cooled to room temperature, the initiator (4,4'-azobis(4-cyanovaleric acid; 0.5 g) was added to the dispersion and the dispersion was stirred for another 240 minutes. The dispersion was then left to settle overnight to allow the silicon particles to settle, after which the top clear solvent was poured off and the remaining silicon slurry was dispersed in 67 mL of water by stirring at 600 RPM for 5 minutes. The monomer methyl methacrylate (25.3 g) was added to the dispersion and stirred at 500 RPM on a hot plate for 60 minutes, with the dispersion temperature controlled at 80°C. The stirring speed was then reduced to 300 RPM for 60 minutes and then increased to 500 RPM. The dispersion was stirred for another 180 minutes and then the polymer modifier ((hydroxyethyl) methacrylate; 2.6 g) was added to the dispersion. The solution temperature was changed to 70°C and stirred overnight. By the next morning, the synthesis of silicon particles with a sacrificial polymer coating was complete. The PPMA coated silicon particles were analyzed by IR and found to have a peak at 1950 and 2200 cm -1 The characteristic peak of the Si-H bond between the two layers disappears, indicating that the PMMA layer has a good coverage effect on the silicon surface.

[0529] When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms should not be interpreted to exclude the presence of other features, steps or components.

[0530] The present invention may also broadly include the parts, elements, steps, examples and / or features mentioned or indicated in the specification individually or collectively in any and all combinations of two or more of the parts, elements, steps, examples and / or features. In particular, one or more features in any embodiment described herein may be combined with one or more features in any other one or more embodiments described herein.

[0531] Protection may be sought for any feature disclosed in any one or more of the published documents cited herein in combination with the present disclosure.

[0532] Although certain exemplary embodiments of the invention have been described, the scope of the appended claims is not intended to be limited to only these embodiments. The claims should be interpreted literally, intentionally, and / or encompass equivalents.

Claims

1. A method of forming a carbon aerogel containing a carbon additive, the method comprising: providing a solution comprising an organogel precursor and a solvent; adding a carbon additive or a precursor thereof to the organogel precursor solution; initiating gelation of the organogel precursor to provide an organogel comprising the carbon additive or a precursor thereof; drying the organogel to form an organic aerogel comprising the carbon additive or a precursor thereof; as well as The organic aerogel isomorphously converted into a carbon aerogel comprising the carbon additive, the conversion comprising pyrolyzing the organic aerogel at a temperature of at least about 650° C. under an inert atmosphere.

2. The method of claim 1, wherein the carbon additive is graphene, graphene nanoribbons, graphene nanosheets, graphene oxide, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or a combination thereof, and the method comprises adding the carbon additive to the organogel precursor solution.

3. The method of claim 1, wherein the carbon additive is a soft carbon, the method comprising adding a soft carbon precursor to the organogel precursor solution, wherein the soft carbon precursor comprises or is perylenetetracarboxylic dianhydride (PTCDA).

4. The method of claim 1, wherein the carbon additive is soft carbon, the method comprising adding a soft carbon precursor to the organogel precursor solution, wherein the soft carbon precursor comprises or is pitch.

5. The method of any one of claims 1 to 4, wherein the carbon aerogel further comprises silicon or sacrificial polymer (PMMA) coated silicon particles, the method further comprising adding silicon or sacrificial polymer (PMMA) coated silicon particles to the organogel precursor solution.

6. The method of claim 5, wherein the method further comprises adding poly(methyl methacrylate) particles to the organogel precursor solution.

7. The method of any one of claims 1 to 6, wherein drying the organogel comprises: Optionally, washing or solvent exchanging the organogel; as well as The organogel is subjected to elevated temperature conditions, freeze-dried, or contacted with supercritical fluid carbon dioxide.

8. The method of claim 7, wherein the washing or solvent exchange is performed with water, a C1 to C3 alcohol, acetone, acetonitrile, ether, tetrahydrofuran, toluene, liquid carbon dioxide, or a combination thereof.

9. The method of any one of claims 1 to 8, wherein the organogel comprises resorcinol-formaldehyde (RF) polymer, phloroglucinol-furfural (PF) polymer, polyacrylonitrile (PAN), polyurethane (PU), polyurea (PUA), polyamine (PA), polybutadiene, polydicyclopentadiene, or a combination thereof.

10. The method of any one of claims 1-8, wherein the organogel comprises polyimide, polyamic acid, or a combination thereof.

11. The method of claim 10, wherein the organogel is a polyimide, and wherein the organogel precursor is a polyamic acid salt.

12. The method of claim 11, wherein initiating gelation comprises imidizing the polyamic acid salt.

13. The method of claim 12, wherein imidization comprises adding a dehydrating agent to the solution of the polyamic acid salt.

14. The method of claim 13, wherein the dehydrating agent is acetic anhydride.

15. The method of any one of claims 1-14, wherein the solvent is water.

16. The method of any one of claims 1 to 14, wherein the solvent is a polar aprotic organic solvent.

17. The method of claim 16, wherein the solvent is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, or a combination thereof.

18. A carbon aerogel comprising a carbon additive, wherein the carbon aerogel is prepared by the method according to any one of claims 1 to 17.

19. The carbon aerogel of claim 18, comprising from about 0.1% to about 20% by weight carbon black.

20. The carbon aerogel of claim 18, comprising from about 0.01% to about 5% by weight of graphene or graphene oxide.

21. The carbon aerogel of claim 18, comprising about 0.1% to about 20% by weight of soft carbon.

22. The carbon aerogel of claim 18, comprising from about 0.01% to about 10% by weight of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or combinations thereof.

23. The carbon aerogel according to any one of claims 16 to 22, which is in the form of a monolith.

24. The carbon aerogel of any one of claims 18 to 22 in the form of beads.

25. The carbon aerogel of any one of claims 18 to 24, further comprising silicon.

26. The carbon aerogel of any one of claims 18-24, further comprising void space.

27. The carbon aerogel of any one of claims 18-24, further comprising silicon and void space, wherein at least a portion of the silicon is present within the void space.

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