Silicon nanoparticles and methods for preparing silicon nanoparticles - Patent Application 20070122997

Abstract

Silicon nanoparticles and methods for preparing silicon nanoparticles are provided. Embodiments include a method for milling silicon. The method includes providing a silicon material, providing a milling liquid including a polar solvent, and milling the silicon material in the presence of the milling liquid to produce silicon nanoparticles. Milling the silicon in the presence of the milling liquid can chemically functionalize the silicon material as the nanoparticles are formed, providing stable, chemically functionalized nanoparticles.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 068,502, filed August 21, 2020, which is incorporated herein by reference in its entirety. [Background technology]

[0002] The present invention relates generally to silicon nanoparticles and methods for the preparation of silicon nanoparticles. More specifically, the present invention relates to materials and methods for producing nanoscale silicon materials for use in electrochemical applications such as lithium ion batteries.

[0003] Lithium-ion batteries (LIBs) are widely used in a variety of applications, from handheld electronic devices to automobiles. LIBs are a type of rechargeable battery in which lithium ions move from the anode to the cathode during discharge and from the cathode to the anode during charging. Traditionally, the cathode is formed from a lithium metal oxide (e.g., lithium cobalt oxide, lithium nickel dioxide, or lithium manganese oxide), and the anode is formed from graphite, where lithium ions intercalate within the graphite layers during charging (energy storage). Graphite is widely used because lithium intercalation is higher in graphite than in other known carbons.

[0004] The main drawback of conventional LIBs is the limited capacity of graphite. In other words, graphite can only accommodate a limited amount of lithium. Silicon has a higher affinity for lithium than graphite (carbon), allowing it to store much larger amounts of lithium than graphite, theoretically increasing the anode capacity of LIBs. By comparison, graphite combined with lithium has a theoretical capacity of 372 mAh / g, while silicon has a theoretical capacity of 4200 mAh / g. Therefore, it is desirable to incorporate as much silicon as possible into the anode. Silicon expands in volume by 3-4 times when fully lithiated. This expansion leads to high mechanical stress on the silicon particles, which can eventually lead to their fracture. The fractured silicon particles can lead to loss of electrical contact or separation of the active material within the electrode structure, resulting in increased resistivity, electrode destruction, and loss of capacity. The loss of capacity during charge and discharge cycles is called degradation or continuous capacity fade and is generally irreversible. The use of nanometer-sized silicon particles can reduce mechanical stress and prevent particle fracture caused by lithiation. A decrease in particle size leads to a corresponding increase in the surface area to volume ratio. For example, smaller particles, such as nanoparticles, have a larger surface area with a smaller volume. Without being bound by theory, particle volume is the driving mechanism for the expansion force. Therefore, a decrease in volume leads to a decrease in the expansion force and a corresponding decrease in the probability and rate of particle fracture due to volume expansion during lithiation.

[0005] Nano-sized silicon nanoparticles can be produced by grinding larger silicon particles. Grinding can be performed using two main techniques: dry and wet. Dry milling involves adding powdered silicon material to a container along with grinding media, typically zirconia (yttrium-stabilized), aluminum oxide, silicon carbide, silicon oxide, quartz, or stainless steel. Dry milling is known to be an inefficient and energy-consuming process. The particle size distribution in the dry milling process is controlled by matching the particle size of the starting material to the size of the grinding media. Wet milling consumes less energy to achieve a comparable grind size, e.g., approximately 15-50% less energy. Wet milling also produces finer particles, resulting in less particle agglomeration. However, the liquid or liquid mixture used in wet milling can affect the chemistry, surface properties, and morphology of the silicon particles, as well as their agglomeration and downstream processing. Furthermore, the chemistry, surface properties, and morphology of the silicon particles can affect their agglomeration, processing, and electrochemical properties.

[0006] Thus, there is a need for improved methods for controlling, selecting, modifying, or improving the surface properties and morphology of electroactive materials, such as silicon. However, in view of the state of the art as a whole at the time the present invention was made, it was not apparent to one skilled in the art how the shortcomings of the prior art could be overcome.

[0007] Although certain aspects of the prior art have been described to facilitate disclosure of the present invention, applicants do not in any way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects described herein, particularly in combination with the innovative aspects described herein.

[0008] The present invention may address one or more of the problems and deficiencies of the art described above. However, it is contemplated that the present invention may prove useful in addressing other problems and deficiencies in certain technical fields. Accordingly, the present invention as claimed should not necessarily be construed as limited to addressing any of the specific problems or deficiencies described herein.

[0009] Where a document, act or article of knowledge is referenced or described in this specification, this reference or description does not constitute an admission that the document, act or article of knowledge, or any combination or derivative thereof, existed at the priority date, was publicly available, was generally known, was part of the common general knowledge, or otherwise constitutes prior art under any applicable legal provision or is known to be relevant to any attempt to solve any problem to which this specification pertains. Summary of the Invention

[0010] A long-standing but heretofore unmet need for improved methods of modifying or functionalizing the surfaces of electroactive materials such as silicon through various processes, including milling, is now met by a new, useful, and unobvious invention.

[0011] One aspect provides a silicon nanoparticle composition comprising silicon particles, the surfaces of which comprise attached functional groups, and a porous three-dimensional network, the silicon particles dispersed throughout the porous three-dimensional network. For example, the surfaces of the silicon particles can comprise covalently attached functional groups. In another example, the surfaces of the silicon particles can comprise hydrogen-bonded functional groups. In some embodiments, the surfaces of the silicon particles prior to functionalization can comprise silane groups. For example, the silane groups can comprise silicon hydrides. In some embodiments, the surfaces of the silicon particles prior to functionalization can comprise silicon oxide groups. In certain embodiments, the surfaces of the silicon particles prior to functionalization can comprise both silane groups (e.g., silicon hydrides) and silicon oxide groups. In some examples, at least some of the silane groups and silicon oxide groups are present in combination with attached functional groups, such as, for example, silane groups and attached functional groups, silicon oxide groups and attached functional groups, or both silane groups, silicon oxide groups, and attached functional groups.

[0012] In one example, the porous three-dimensional network can be a sol-gel, an aerogel precursor, a polyimide precursor, an aerogel, a carbon aerogel, and / or a polyimide-derived carbon aerogel. The functional groups on the surface of the silicon particles can be bonded to carbon atoms in the porous three-dimensional network. For example, the functional groups on the surface of the silicon particles can be covalently bonded to carbon atoms in the porous three-dimensional network. In another example, the functional groups on the surface of the silicon particles can be hydrogen-bonded to carbon atoms in the porous three-dimensional network.

[0013] In one example, the functional group can include at least one of -OH, -COOH, -COC-, -NH2, -NHR, or a combination thereof. The binding functional group can include isopropanol. The binding functional group can be selected from the group consisting of isopropanol, ethylene glycol methyl ether methacrylate, polyethylene glycol methyl ether methacrylate, unsaturated glycol, hydroxide groups, allylamine, vinylbenzylamine hydrochloride, or aminoethyl methacrylate hydrochloride. In one example, the binding functional group includes hydroxyl, unsaturated amine, unsaturated glycol, or a combination thereof. In an exemplary embodiment, the silicon particles can have a diameter of less than 150 nm.

[0014] One aspect provides a method for processing silicon. In an exemplary embodiment, the method includes providing a silicon material, providing a processing liquid, and processing the silicon material in the presence of the processing liquid to produce silicon nanoparticles. Before processing, the silicon material has a first particle size, e.g., a first particle size distribution. The first particle size, in some embodiments, can be the particle size or particle size distribution of individual particles of the silicon material. In other embodiments, the first particle size can be the particle size or particle size distribution of agglomerated particles of silicon. After processing, the silicon nanoparticles have a second particle size less than the first particle size, e.g., a second particle size distribution less than the first particle size distribution or lower than the first particle size distribution. In some embodiments, the second particle size can be the particle size or particle size distribution of deagglomerated particles of silicon.

[0015] The treatment liquid, in certain embodiments, comprises a polar solvent. In some embodiments, the treatment liquid is present at about 70 wt % to about 80 wt % of the total weight. Treating the silicon material in the presence of the treatment liquid functionalizes the surface of the silicon material as the nanoparticles are formed to provide stable functionalized nanoparticles.

[0016] For example, the treatment liquid may include a polar solvent selected from the group consisting of DMSO, DMF, NMP, DMAC, THF, 1,4-dioxane, diglyme, acetonitrile, isopropanol, and water. For example, the polar solvent may be water. In certain embodiments, the polar solvent may be a dipolar aprotic solvent. For example, the polar solvent may be DMAC. In another example, the polar solvent may be NMP. In certain embodiments, the treatment liquid may further include a polyimide precursor monomer.

[0017] In exemplary embodiments of the methods for processing silicon disclosed herein, the first particle size is in the range of about 1 um to about 10 um, and in certain embodiments, the second particle size is in the range of about 50 um to about 500 nm.

[0018] In an exemplary embodiment, treating the silicon in the presence of a grinding liquid chemically functionalizes the silicon material as the nanoparticles are formed to provide stable, chemically functionalized nanoparticles. For example, the treatment liquid, or a component of the treatment liquid, can react with the silicon material. In another example, treating the silicon in the presence of a treatment liquid functionalizes the silicon material as the nanoparticles are formed to react with each other to produce an aliphatic or aromatic hydrocarbon or carbon precursor coating, photoluminescence, biocompatibility, or catalysis. In a further example, treating the silicon in the presence of a treatment liquid functionalizes the silicon material as the nanoparticles are formed to react with an aerogel precursor. In one example, the treatment liquid can include a polyimide precursor monomer. The treatment liquid can include isopropanol, ethylene glycol methyl ether methacrylate, polyethylene glycol methyl ether methacrylate, an unsaturated glycol, a hydroxide group, allylamine, vinylbenzylamine hydrochloride, aminoethyl methacrylate hydrochloride, or a combination thereof. In one example, the treatment liquid includes a hydroxyl, an unsaturated amine, an unsaturated glycol, or a combination thereof.

[0019] In exemplary embodiments, the step of processing the silicon includes milling the silicon. In such embodiments, the processing liquid may be referred to as a milling liquid. For example, processing such as milling is performed in a ball mill, a turbine mill, or a jet mill. In some embodiments, processing is performed as a batch process. In certain embodiments, processing is performed as a semi-batch process. In some embodiments, processing is performed as a continuous process.

[0020] A further aspect provides silicon nanoparticles produced by the methods disclosed herein. Another aspect provides a silicon nanoparticle composition comprising silicon nanoparticles and a polar solvent compatible with a process for producing an aerogel material. In an exemplary embodiment, the silicon nanoparticles can have a surface functionalized by interaction with a processing liquid, such as a polar solvent compatible with a process for producing an aerogel material.

[0021] For a full and clear understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a scanning electron micrograph (SEM) of milled nanoparticle silicon according to an embodiment disclosed herein. [Figure 2] FIG. 2 is a chart of silicon particle size distribution according to embodiments disclosed herein, measured using laser diffraction. [Figure 3] FIG. 3 is an infrared spectrum of isopropanol-grafted silicone. DETAILED DESCRIPTION OF THE INVENTION

[0023] In the following detailed description of the present invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

[0024] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used in this specification and the appended claims, the word "or" is generally used in its sense including "and / or" unless the context clearly dictates otherwise.

[0025] As used herein, "about" means approximately or nearly, and in the context of a stated numerical value or range, means ±15% of the numerical value. In one embodiment, the term "about" may include conventional rounding to the nearest significant figure. Furthermore, the phrase "about 'x' to 'y'" includes "about 'x' to about 'y'."

[0026] In exemplary embodiments, the systems and methods disclosed herein provide low-cost processing methods, such as processes for crushing electroactive materials, such as metals, metal oxides, and metalloids, or reducing their particle size to submicron particles suitable for incorporation into high-efficiency carbon materials for lithium-ion batteries (LIBs). In some embodiments, the processing method includes milling the electroactive material. In particular embodiments, the electroactive material can include metals, metal oxides, and metalloids, particularly silicon (Si), Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Cd, Se, Ag, Zn, Sn, Pb, Sb, Nb, Bi, Hf, Ba, Al, B, P, As, and other metals such as Al2O3, and any combination thereof. For example, silicon particles provided by the disclosed methods are useful for producing silicon-doped carbon materials, in which the silicon particles are at least partially contained within the carbon material.

[0027] Powders can be produced by a variety of techniques, including electrochemical reduction and mechanical milling, or comminution. Comminution can be carried out using wet or dry processes. In dry milling, powder is added to a vessel along with grinding media, which typically include zirconium oxide (stabilized yttrium), silicon carbide, silicon oxide, quartz, or stainless steel balls or rods. The particle size distribution of the resulting milled material is controlled by the energy applied to the system and by matching the particle size of the starting material to the size of the grinding media. However, dry milling is an inefficient and energy-consuming process. Wet milling is similar to dry milling, except that a grinding fluid is added. The advantage of wet milling is that it consumes 15–50% less energy than dry milling to produce the same results. An additional advantage of wet milling is that the grinding fluid protects the milled material from oxidation. Wet milling has also been found to produce finer particles, resulting in less particle agglomeration.

[0028] Wet milling can be carried out using a variety of liquid components. The milling of the present disclosure is not limited to altering particle size through fractionation; milling can include breaking down particles. In exemplary embodiments, the components contained in the milling liquid or solution are selected to reduce or eliminate surface chemical functionalization of silicon particles during or after milling. In other embodiments, the components contained in the milling liquid or solution are selected to provide desired surface chemical functionalization of particles, such as silicon particles, during or after milling. The components contained in the milling liquid or solution can also be selected to control the chemical reactivity or crystalline morphology of particles, such as silicon particles. In exemplary embodiments, the components contained in the milling liquid or solution can be selected based on compatibility or reactivity with downstream materials, such as processing steps or applications of particles, such as silicon particles. For example, the components contained in the milling liquid or solution can be compatible with, useful in, or identical to the liquids or solvents used in processes for forming or producing organic or inorganic aerogel materials. In yet another embodiment, the grinding liquid can be selected so that the grinding liquid or components contained therein produce a coating on the silicon particle surface or on intermediate species such as aliphatic or aromatic hydrocarbons, or by cross-linking or producing cross-functional compounds that react with organic or inorganic aerogel materials.

[0029] Aerogels and xerogels can be formed from inorganic and / or organic materials. When formed from organic materials, such as phenols, resorcinol-formaldehyde (RF), phloroglucinol furfuraldehyde (PF), polyacrylonitrile (PAN), polyimide (PI), polyurethane (PU), polybutadiene, polydicyclopentadiene, and their precursors or monomeric, oligomeric, or polymeric derivatives, the aerogel or xerogel can be carbonized (e.g., by pyrolysis) to form carbon aerogels that may have different or overlapping properties (e.g., pore volume, pore size distribution, morphology, etc.) depending on the precursor materials and the method used. Polyimide precursors, such as diamines and dianhydrides, each of which may contain aromatic and / or aliphatic groups, are mixed in a suitable solvent, such as a polar aprotic solvent. Polyimides are conventionally synthesized by forming polyamic acid prepolymers that may undergo ring closure with actinic, thermal, or electromagnetic radiation (e.g., photoinitiator-induced imidization to yield polyimides). The imidization reaction is typically carried out in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), or N,N-dimethylformamide (DMF), or a combination of tetrahydrofuran (THF) with methanol (MeOH) or water.

[0030] Prior to imidization, additive particles, e.g., electroactive materials such as silicon particles, are mixed with the imide precursor in a solvent. During imidization, a gel is formed in which the additive particles, e.g., silicon particles, are uniformly dispersed. The resulting mixture can then be cast as a coating, a three-dimensional monolithic structure, or dispersed into micron-sized particles, for example, by introducing a catalyzed precursor into a non-solvent mixed using a high-shear mixer. The silicon-containing polyimide is then dried to produce a porous polyimide-silicon composite; drying can be carried out using air, hot air, or subcritical and / or supercritical carbon dioxide. The polyimide-additive composite, e.g., polyimide-silicon composite, is then pyrolyzed to produce a continuous porous carbon composite. The resulting composite contains greater than 0 wt. % and less than about 95 wt. % additive, e.g., silicon, and has a porosity of about 5% to 99%. In certain embodiments, pyrolysis may be carried out at a maximum temperature of about 750° C. to about 1600° C., optionally with graphitization at about 1000° C. up to about 3000° C. Further details regarding polyimide compositions and processes are described in U.S. Patent Application No. 16 / 803,348, U.S. Patent Application No. 63 / 070,230, filed August 25, 2020, U.S. Patent Application No. 63 / 124,451, filed December 11, 2020, and U.S. Patent Application No. 63 / 124,454, filed December 11, 2020, each of which is incorporated herein by reference in its entirety.

[0031] In certain embodiments of the disclosed method, the material is processed, for example, by milling or grinding, to reduce agglomeration, particle size, and / or particle size distribution of the resulting particles or powder using a grinding fluid containing a solvent that is the same as or compatible with the solvent(s) used in the aerogel synthesis process. The material includes metals, metalloids, particularly silicon, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Ag, Zn, Sn, Pb, Sb, Nb, Bi, Hf, Ba, Al, B, P, As, other metals or metal oxides such as Al2O3, and combinations thereof. For example, the grinding fluid can include a suitable polar aprotic solvent, such as DMSO, DMF, NMP, DMAC, THF, 1,4-dioxane, diglyme, acetonitrile, isopropanol, water, or any combination thereof. In certain embodiments, the grinding fluid can include or consist essentially of DMAC. In some embodiments, the grinding liquid may comprise water, consist essentially of water, or a combination of water and any of the materials listed above.

[0032] By using a milling liquid that is the same as or compatible with the solvent(s) used to prepare the aerogel precursor material, the intermediate drying step (or other processing step, e.g., fractional distillation) to remove the milling solvent can be eliminated. Drying the milled additive particles can also result in particle agglomeration. Particle agglomerates typically must be broken down, e.g., by high-shear mixing, centrifugation, or sieving, before the additive particles can be further processed. By milling with a liquid that is the same as or compatible with the solvent used to form the aerogel precursor, both the drying and milling steps can be eliminated. Furthermore, the milling liquid can be chosen to chemically functionalize the particle surface so that the nanoparticles react, bond, or adsorb to the aerogel material or other nanoparticles, improving the size, mass, volume, or charge / discharge capacity of the LIB.

[0033] After processing according to embodiments disclosed herein, e.g., by milling, particles, e.g., particles of electroactive material such as silicon particles, can have a maximum dimension ranging from about 1 nm to about 150 nm. The particles of the present disclosure can be fine particles, e.g., micron-sized particles, having a maximum dimension, e.g., diameter in the case of substantially spherical particles, ranging from about 150 nm to about 10 micrometers or more. For example, particles of the present disclosure can have a maximum dimension, e.g., diameter in the case of substantially spherical particles, of about 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 500 nm, 1 micrometer, 1.5 micrometers, 2 micrometers, 3 micrometers, 5 micrometers, 10 micrometers, 20 micrometers, 40 micrometers, 50 micrometers, 100 micrometers, or a range between any two of these values. In some embodiments, the particles are flat, piecemeal in shape, e.g., platelets, having two dimensions, e.g., length and width, of about 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 500 nm, 1 micron, 1.5 microns, 2 microns, 3 microns, 5 microns, 10 microns, 20 microns, 40 microns, 50 microns, 100 microns, or a range between any two of these values. Figure 2 is a chart of silicon particle sizes according to embodiments disclosed herein measured using laser diffraction. Particle size can be measured using a laser diffraction / scattering particle size distribution analyzer (LA-960 Laser Diffraction Analyzer, manufactured by HORIBA, Ltd.). Silicon nanoparticles have a D of less than 500 μm, less than 400 μm, or less than 300 μm. 50 The particle size distribution may be:

[0034] In some embodiments, the particles may be monodisperse or substantially monodisperse. In other embodiments, the silicon particles may have a particle size distribution. Within the context of this disclosure, the size of the silicon particles is determined by the median of the particle size distribution, i.e., D 50The present invention provides a method for producing a silicon particle having a thickness of 1000 Å (0.1 Å) based on the principles of the present invention. Particles, such as particles of electroactive material, e.g., silicon particles, can have a variety of shapes after processing according to embodiments disclosed herein. In some embodiments, silicon particles milled according to the processes disclosed herein can have a flat, piecemeal shape, sometimes referred to as a substantially planar flake, i.e., a platelet shape, as shown in FIG. 1 . For example, the particles have two substantially flat major surfaces connected by a minor surface that defines a thickness between the major surfaces. In other embodiments, the particles of electroactive material can be substantially spherical, cubic, ellipsoidal, oval, discoidal, or toroidal.

[0035] As mentioned above, the solvent or mixture of solvents used for milling can be selected to control the chemical functionalization of the particles during or after milling. Using silicon as an example, without being bound by theory, milling silicon in an alcoholic solvent such as isopropanol can functionalize the silicon surface and attach alkoxide surface groups, such as isopropoxide, to the surface of the silicon particles through hydrogen or covalent bonds. In an exemplary embodiment, milling can be carried out in a polar aprotic solvent such as DMSO, DMF, NMP, DMAC, THF, 1,4-dioxane, diglyme, acetonitrile, isopropanol, water, or any combination thereof, which has numerous advantages. Reactive chemicals can be used as solvents during the milling process. For example, the reactive chemicals can include one or more alkenes, alkynes, alcohols, carboxylic acids, and aldehydes, each having a functional group including, but not limited to, -OH, -COOH, -COC-, -NH, -NHR, or combinations thereof.

[0036] Milling in a process-compatible solvent for producing aerogel materials, such as the polar aprotic solvents described above, can eliminate the need to remove the grinding liquid from the particles prior to addition to the aerogel production process, since the grinding liquid is the same as or compatible with the solvent used in the aerogel process. In other embodiments, the grinding liquid can include a precursor to a monomer, oligomer, or polymer. For example, the grinding liquid can include a polyimide precursor monomer, such as polyacrylic acid (PAA). In another example, the grinding liquid can include a sol-gel liquid. In these embodiments, the grinding liquid containing the precursor components (e.g., aerogel precursors) or the sol-gel liquid can impart sol-gel functionality to the surfaces of particles, such as silicon particles. In further embodiments, the grinding liquid can be selected to impart functionality to the surfaces of particles, such as silicon particles, so that the functionalized particles react or interact with each other during or after the milling process.

[0037] In one example, the surface of silicon particles (e.g., silicon nanoparticles) can be modified with functional groups that can help disperse the silicon particles in a porous three-dimensional network. In one example, the porous three-dimensional network can be a sol-gel, aerogel, xerogel, foam structure, among others. The functional groups grafted onto the surface of the silicon particles can be selected to help form a uniform distribution of the silicon particles within the three-dimensional network.

[0038] For example, functional groups can be grafted onto the surface of silicon particles by covalent and / or hydrogen bonding. Prior to functionalization, the surface of the silicon particles contains silane groups, such as silicon hydride groups, and / or silicon oxide groups. In some embodiments, at least a portion of these silane and silicon oxide groups can be present in combination with binding functional groups after functionalization of the surface of the silicon particles. For example, the silicon particle surface can contain both silane and binding functional groups, silicon oxide and binding functional groups, or both silane and silicon oxide groups and binding functional groups. The presence of functionality on the surface of silicon particles can be detected by various techniques, such as infrared spectroscopy. An exemplary spectrum of functionalized silicon particles is from 800 to 900 cm. -1 The characteristic peaks of the Si-OC bond in the range of 1370-1460 cm -1 and 2870-2980cm -1 Figure 3 shows characteristic peaks of C-H bonds in the range of 100 to 1500 nm. These characteristic peaks indicate successful grafting of functional groups to the surface of the silicon particles. As a specific example, Figure 3 shows the infrared spectrum of silicon nanoparticles functionalized with isopropanol, as described in Example 1 below.

[0039] The surfaces of silicon particles can be functionalized with hydrophilic groups to help improve dispersion within the porous three-dimensional network. Without being bound by theory, functionalization with hydroxide groups creates stronger hydrogen and / or covalent bonds between the surface groups on the silicon particles and the porous three-dimensional network. As a result, the functionalized silicon particles can be uniformly dispersed within the porous three-dimensional network. For example, to increase the hydrophilicity of the silicon particle surface, hydrophilic hydroxide groups can be grafted onto the particle surface using an unsaturated glycol. Increasing the hydrophilicity of silicon nanoparticles can allow them to be more uniformly dispersed and remain dispersed within the three-dimensional network, even during any additional processing (e.g., pyrolysis). In one example, glycol functionalization can improve the dispersion of silicon particles within polyimide sol-gels and / or aerogels. Any suitable glycol can be used, including, but not limited to, ethylene glycol methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, among others.

[0040] In another example, the functional group can be a reactive amino group. For example, an amino group can be grafted onto the surface of a silicon nanoparticle using an unsaturated amine. The reactive amino group can be covalently bonded to the surface of the silicon particle. The reactive amino group can be bonded to the surface of the silicon particle through hydrogen bonding. In one example, the reactive amino group grafted onto the silicon particle can participate in a polyimide synthesis reaction. In such an example, the grafted amino group can be used to covalently bond the particle to a polyimide matrix. In some examples, the grafted amino group can be used to bond the particle to a polyimide matrix through hydrogen bonding. Examples of reactive amino groups include, but are not limited to, allylamine, vinylbenzylamine hydrochloride, aminoethyl methacrylate hydrochloride, or a combination thereof.

[0041] The functional groups can be selected to participate in the reaction of aerogel formation, for example, the surface functionalization of the nanoparticles can be selected so that the functional groups can participate in the reaction of polyimide synthesis. [Example]

[0042] Example 1 Silicon powder with particle sizes between 1 and 5 microns was milled for 5 hours in a Buhler MMX-1 ball mill using isopropanol as the solvent. The resulting silicon nanoparticles had a size of 130 nm. The silicon powder was dried at 80 °C for 24 hours to remove residual isopropanol. The infrared spectrum of the resulting silicon nanoparticles can be seen in Figure 3. The characteristic peak of the Si-O-C bond was observed between 800 and 900 cm. -1 The characteristic peak of the C-H bond is seen in the range of 1370-1460 cm -1 and 2870-2980cm -1 This indicates the successful grafting of isopropanol to the silicon surface. The isopropanol-grafted silicon nanoparticles are more hydrophilic than the unmodified silicon particles and can be uniformly dispersed in water.

[0043] All referenced publications are incorporated by reference in their entirety into this disclosure. Furthermore, if the definition or use of a term in a reference incorporated herein by reference contradicts or is inconsistent with the definition of that term provided herein, the definition of that term provided herein shall apply and the definition of that term in the reference shall be disregarded.

[0044] The advantages set forth above and those made apparent from the foregoing description are efficiently attained. Since certain changes may be made in the above-described constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

[0045] It is also to be understood that the following claims are intended to cover all of the general and specific features of the invention described herein, and to cover all statements of the scope of the invention that, as a matter of terminology, may be found therebetween. Some of the embodiments of the invention related to the present invention are shown below. [Embodiment 1] 1. A composition comprising: silicon particles having a diameter of less than 200 nm, wherein the surface of the silicon particles comprises attached functional groups; a porous three-dimensional network; wherein said silicon particles are dispersed throughout said porous three-dimensional network. [Embodiment 2] 2. The composition of embodiment 1, wherein the porous three-dimensional network is a sol-gel solution. [Embodiment 3] 3. The composition of embodiment 2, wherein the sol-gel solution comprises an aerogel precursor. [Embodiment 4] 3. The composition of embodiment 2, wherein the sol-gel solution comprises a polyimide precursor. [Embodiment 5] 2. The composition of any preceding claim, wherein the porous three-dimensional network comprises an aerogel. [Embodiment 6] 6. The composition of any one of claims 1 or 5, wherein the porous three-dimensional network comprises a carbon aerogel. [Embodiment 7] 6. The composition of any one of claims 1 or 5, wherein the porous three-dimensional network comprises a polyimide-derived carbon aerogel. [Embodiment 8] 8. The composition of any one of the preceding claims, wherein the functional groups on the surface of the silicon particles are bonded to carbon atoms within the porous three-dimensional network. [Embodiment 9] The functional group is -OH, -COOH, -COC-, -NH 2 9. The composition of any one of embodiments 1-8, comprising at least one of: -NHR, -NCH, or a combination thereof. [Embodiment 10] 10. The composition of any one of the preceding embodiments, wherein the attached functional group comprises isopropanol. [Embodiment 11] 11. The composition of any one of the preceding claims, wherein the attached functional group is selected from the group consisting of isopropanol, ethylene glycol methyl ether methacrylate, polyethylene glycol methyl ether methacrylate, unsaturated glycol, hydroxide group, allylamine, vinylbenzylamine hydrochloride, or aminoethyl methacrylate hydrochloride. [Embodiment 12] 12. The composition of any one of the preceding embodiments, wherein the attached functional groups comprise hydroxyl, unsaturated amine, unsaturated glycol, or a combination thereof. [Embodiment 13] 13. The composition of any one of the preceding claims, wherein the surface of the silicon particles comprises covalently bound functional groups. [Embodiment 14] 13. The composition of any one of the preceding claims, wherein the surface of the silicon particles comprises hydrogen-bonded functional groups. [Embodiment 15] 15. The composition of any one of the preceding claims, wherein the functional groups on the surface of the silicon particles are covalently bonded to carbon atoms within the porous three-dimensional network. [Embodiment 16] 15. The composition of any one of the preceding claims, wherein the functional groups on the surface of the silicon particles are hydrogen bonded to carbon atoms within the porous three-dimensional network. [Embodiment 17] 17. The composition of any one of the preceding embodiments, wherein the surface of the silicon particles comprises silane groups. [Embodiment 18] 18. The composition of embodiment 17, wherein the silane group comprises a silicon hydride. [Embodiment 19] 19. The composition of any one of the preceding embodiments, wherein the surface of the silicon particles comprises silicon oxide groups. [Embodiment 20] 20. The composition of any one of the preceding embodiments, wherein the silicon particles have a diameter of less than 150 nm. [Embodiment 21] 21. The composition of any one of the preceding embodiments, further comprising a polar solvent that is compatible with the process for producing the aerogel material. [Embodiment 22] 1. A method for functionalizing the surface of silicon nanoparticles, comprising: providing a silicon material having a first particle size; providing a treatment liquid comprising a polar solvent; treating the silicon material in the presence of the treatment liquid to produce silicon nanoparticles having a second particle size less than the first particle size; Including, treating the silicon material in the presence of the treatment liquid functionalizes the surface of the silicon material as the nanoparticles are formed to provide stable functionalized nanoparticles. method. [Embodiment 23] 23. The method of embodiment 22, wherein the polar solvent is compatible with a process for producing an aerogel material. [Embodiment 24] 24. The method of any one of embodiments 22-23, wherein the polar solvent is selected from the group consisting of DMSO, DMF, NMP, DMAC, THF, 1,4-dioxane, diglyme, acetonitrile, isopropanol, and water. [Embodiment 25] 25. The method of any one of claims 22-24, wherein the treatment solution comprises at least one of isopropanol, ethylene glycol methyl ether methacrylate, polyethylene glycol methyl ether methacrylate, an unsaturated glycol, a hydroxide group, allylamine, vinylbenzylamine hydrochloride, or aminoethyl methacrylate hydrochloride. [Embodiment 26] 26. The method of any one of embodiments 22 to 25, wherein the first particle size is in the range of about 1 um to about 10 um. [Embodiment 27] 27. The method of any one of embodiments 22-26, wherein the second particle size is in the range of about 50 nm to about 500 nm. [Embodiment 28] 28. The method of any one of embodiments 22-27, wherein the treatment solution is present at about 70% to about 80% by weight of the total weight. [Embodiment 29] 29. The method of any one of embodiments 22-28, wherein the treatment solution further comprises an aerogel precursor monomer. [Embodiment 30] 30. The method of any one of embodiments 22 to 29, wherein the treatment solution further comprises a polyimide precursor monomer. [Embodiment 31] 31. The method of any one of claims 22-30, wherein the treatment solution comprises isopropanol, ethylene glycol methyl ether ether methacrylate, polyethylene glycol methyl ether methacrylate, an unsaturated glycol, a hydroxide group, allylamine, vinylbenzylamine hydrochloride, aminoethyl methacrylate hydrochloride, or a combination thereof. [Embodiment 32] 32. The method of any one of claims 22-31, wherein the treatment solution comprises a hydroxyl, an unsaturated amine, an unsaturated glycol, or a combination thereof. [Embodiment 33] 33. The method of any one of claims 22-32, wherein the step of treating the silicon comprises grinding the silicon. [Embodiment 34] 34. The method of any one of embodiments 22 to 33, wherein the treating is carried out in a ball mill, a jet mill, or a turbine mill. [Embodiment 35] 35. The method of any one of embodiments 22 to 34, wherein the treatment is carried out as a batch process. [Embodiment 36] 36. The method of any one of embodiments 22 to 35, wherein the treatment is carried out as a semi-batch process. [Embodiment 37] 37. The method of any one of embodiments 22 to 36, wherein the treatment is carried out as a continuous process.

Claims

1. 1. A composition comprising: silicon particles having a diameter of less than 200 nm, the surface of the silicon particles being functionalized with an unsaturated glycol; a porous three-dimensional network; wherein the silicon particles are dispersed throughout the porous three-dimensional network; the porous three-dimensional network comprises carbon aerogel; the unsaturated glycol is covalently bonded to the surface of the silicon particle; The composition wherein the unsaturated glycol is selected from the group consisting of ethylene glycol methyl ether methacrylate, polyethylene glycol methyl ether methacrylate, and combinations thereof.

2. 10. The composition of claim 1, wherein the porous three-dimensional network comprises a polyimide-derived carbon aerogel.

3. 10. The composition of claim 1, wherein the unsaturated glycol on the surface of the silicon particles is covalently bonded to a carbon atom within the porous three-dimensional network.

4. 10. The composition of claim 1, wherein the unsaturated glycols on the surface of the silicon particles are hydrogen bonded to carbon atoms within the porous three-dimensional network.

5. The composition of claim 1 , wherein the surface of the silicon particles comprises silane groups.

6. The composition of claim 5 wherein the silane group comprises a silicon hydride.

7. The composition of claim 1 , wherein the surface of the silicon particles comprises silicon oxide groups.

8. The composition of claim 1 , wherein the silicon particles have a diameter of less than 150 nm.

9. 10. The composition of claim 1, further comprising a polar solvent that is compatible with a process for producing an aerogel material.

10. 1. A method for functionalizing the surface of silicon nanoparticles, comprising: providing a silicon material having a first particle size; providing a treatment liquid comprising a polar solvent; treating the silicon material in the presence of the treatment liquid to produce silicon nanoparticles having a second particle size less than the first particle size; Including, treating the silicon material in the presence of the treatment liquid functionalizes the surface of the silicon material as the nanoparticles are formed to provide stable functionalized nanoparticles; The method, wherein the treatment liquid comprises ethylene glycol methyl ether methacrylate, polyethylene glycol methyl ether methacrylate, or a combination thereof.

11. 11. The method of claim 10, wherein the polar solvent is compatible with a process for producing an aerogel material.

12. 12. The method of claim 11, wherein the polar solvent is selected from the group consisting of DMSO, DMF, NMP, DMAC, THF, 1,4-dioxane, diglyme, acetonitrile, isopropanol, and water.

13. The method of claim 10, wherein the first particle size is in the range of 1 μm to 10 μm.

14. The method of claim 10, wherein the second particle size is in the range of 50 nm to 500 nm.

15. The method of claim 10, wherein the treatment liquid is present at 70% to 80% by weight of the total weight.

16. The method of claim 10 , wherein the treatment liquid further comprises an aerogel precursor monomer.

17. The method of claim 10 , wherein the treatment solution further comprises a polyimide precursor monomer.

18. The method of claim 10 , wherein the step of treating the silicon material comprises milling the silicon material.

19. 11. The method of claim 10, wherein the processing is carried out in a ball mill, a jet mill, or a turbine mill.

20. The method of claim 10 wherein the treatment is carried out as a batch process.

21. The method of claim 10 wherein the treatment is carried out as a semi-batch process.

22. The method of claim 10, wherein the treatment is carried out as a continuous process.

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