Fibrous core-shell silicon-carbon structure

Abstract

The present disclosure relates to novel lithium-ion battery structures and methods of manufacture. One particular method involves coating a porous glass substrate. The method includes providing a porous glass substrate, flowing a gaseous hydrocarbon over the porous glass substrate in a reaction zone, and exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the porous substrate and the gas surrounding the porous substrate absorb the concentrated solar radiation and produce heat. The heat chemically reduces the glass fibers in the porous glass substrate to silicon fibers, and the heat decomposes the gaseous hydrocarbon into a carbon coating on the silicon fibers.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of and priority under 35 U.S.C. Section 119(e) to U.S. Provisional Patent Application No. 63 / 371,356, filed August 12, 2022, and entitled "Fibrous Core-Shell Silicon-Graphite," which is incorporated herein by reference in its entirety for all purposes.

[0002] FIELD OF THE DISCLOSURE The present invention relates generally to fibrous core silicon-carbon structures and methods for their production. [Background technology]

[0003] (background) High-rate charging is desirable for fast charging of electric vehicles and similar battery-powered devices. Rapid discharge may also be desirable in some applications, but the demand for fast charging can be technically much more challenging. Silicon-based anode materials have been previously utilized in battery technology. The primary advantage of silicon-based (including silica) anode materials is their high lithium uptake capacity (e.g., up to approximately 10 times that of graphite per unit weight). Silicon-based anodes can contain silicon-based particles with diameters of approximately 100 to 1,000 nanometers. However, the primary limitation and drawback of particulate silicon-based anode materials is their very low thermal conductivity. The primary limitation and drawback of silicon-based anode materials is their very low electrical conductivity. Therefore, increasing the thermal and electrical conductivity of silicon-based anodes in Li-ion batteries can be advantageous. Summary of the Invention [Means for solving the problem]

[0004] (Summary of Disclosure) In some aspects, techniques described herein relate to a method of coating a porous glass substrate, the method including providing a porous glass substrate; flowing a gaseous hydrocarbon over the porous glass substrate in a reaction zone; and exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the porous substrate and the gas surrounding the porous substrate absorb the concentrated solar radiation and produce heat, the heat chemically reducing glass fibers in the porous glass substrate to silicon fibers, and the heat decomposing the gaseous hydrocarbon into a carbon coating on the silicon fibers.

[0005] In some aspects, the techniques described herein relate to methods in which heat decomposes gaseous hydrocarbons into hydrogen gas and carbon.

[0006] In some aspects, the techniques described herein relate to methods in which concentrated solar irradiation triggers a photocatalytic process that accelerates the decomposition of gaseous hydrocarbons into hydrogen gas and carbon.

[0007] In some aspects, the techniques described herein relate to methods whereby the concentrated solar illumination has a concentration factor of 100 or greater.

[0008] In some aspects, the techniques described herein relate to methods in which the gaseous hydrocarbon is high-purity methane gas.

[0009] In some aspects, the techniques described herein relate to methods where the gaseous hydrocarbon is biogas.

[0010] In some aspects, the techniques described herein relate to methods involving a carrier gas in which gaseous hydrocarbons are mixed with methane or biogas.

[0011] In some aspects, the techniques described herein relate to methods in which the carrier gas is hydrogen gas, nitrogen gas, and / or argon gas.

[0012] In some aspects, the techniques described herein relate to methods in which carbon, including graphene, graphite, carbon nanotubes, or carbon black, is conformally deposited onto the surface of silicon fibers.

[0013] In some aspects, the techniques described herein relate to methods by which conformal carbon coatings from adjacent elements or ligaments of a porous substrate fuse together to form a continuous structure.

[0014] In some aspects, the techniques described herein relate to methods in which carbon is deposited onto a porous substrate, and the porous substrate is then used to fabricate an electrochemical energy storage device.

[0015] In some aspects, the techniques described herein relate to methods where concentrated solar illumination includes sunlight from the sun.

[0016] In some aspects, the techniques described herein relate to methods in which concentrated solar irradiation includes sunlight from the sun augmented with an artificial light source.

[0017] In some aspects, the techniques described herein relate to methods that further include optimizing the amount of enhanced artificial light from the artificial light source to maintain a constant irradiance.

[0018] In some aspects, the techniques described herein relate to methods in which the artificial light source includes a plasma arc lamp, a halogen bulb, an LED, a fluorescent bulb, a metal halide lamp, or an argon lamp.

[0019] In some aspects, the techniques described herein relate to methods in which the artificial light source includes a xenon arc lamp.

[0020] In some aspects, techniques described herein relate to methods in which the concentrated solar irradiation includes sunlight from the sun during times when the sun is shining light into a collector that concentrates the sun's light into the reaction zone, and the concentrated solar irradiation includes artificial light when the sun is not shining light into the collector.

[0021] In some aspects, the techniques described herein relate to methods in which the concentrated solar illumination includes light from an artificial light source.

[0022] In some aspects, the techniques described herein relate to methods in which the porous glass substrate comprises a roll-to-roll substrate.

[0023] In some aspects, the techniques described herein relate to methods that further include operating a roll-to-roll substrate to continuously maintain a virgin porous glass substrate.

[0024] In some aspects, the techniques described herein relate to methods in which the porous glass substrate comprises a silica cloth or felt.

[0025] In some aspects, the techniques described herein relate to methods that further include concentrating the solar light source using a reflector.

[0026] In some aspects, the techniques described herein relate to methods in which the reflector includes an array of elliptical reflectors, parabolic reflectors, compound reflectors, Fresnel lenses, and / or flat reflectors.

[0027] In some aspects, the techniques described herein relate to methods in which the reflector includes a variable reflector that adjusts the amount of solar irradiation concentrated within the reaction zone.

[0028] In some aspects, the techniques described herein relate to methods in which the reaction zone is contained within a reaction chamber.

[0029] In some aspects, the techniques described herein relate to methods in which exposing gaseous hydrocarbons to concentrated solar radiation occurs in multiple directions.

[0030] In some aspects, the techniques described herein relate to methods in which the gaseous hydrocarbons include natural gas.

[0031] In some aspects, the techniques described herein relate to methods that further include reflowing the output gas over a porous glass substrate in a reaction zone and exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the reflowed gas further decomposes into hydrogen gas and carbon.

[0032] In some aspects, the techniques described herein relate to methods that further include pretreating a porous glass substrate by adhering silicon or glass particles to glass fibers, wherein the silicon or glass particles become incorporated into a carbon coating on the silicon fibers after exposure to concentrated solar irradiation.

[0033] In some aspects, the techniques described herein relate to methods in which the silicon or glass particles are nanoparticles or microparticles.

[0034] In some aspects, the techniques described herein relate to methods in which the carbon coating comprises cylindrical concentric layers of carbon that are layered concentrically on top of each other in a repeating pattern.

[0035] In some aspects, the technology described herein relates to methods in which the silicon fibers comprise silicon dioxide and silicon.

[0036] In some aspects, the technology described herein relates to methods in which the silicon fibers comprise a silicon dioxide core with silicon rings surrounding the silicon dioxide core.

[0037] In some aspects, the techniques described herein relate to methods in which silicon rings form a shell around a silicon dioxide core.

[0038] In some aspects, the techniques described herein relate to methods in which the silicon fibers comprise solid silicon fibers.

[0039] In some aspects, techniques described herein relate to a method of coating a porous glass substrate, the method including: providing a porous glass substrate; flowing a carrier gas over the porous glass substrate in a reaction zone; exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the porous substrate and the gas surrounding the porous substrate absorb the concentrated solar radiation and produce heat, which chemically reduces glass fibers in the porous glass substrate to silicon fibers; and, as the reduction reaction ceases, flowing a gaseous hydrocarbon over the silicon fibers; and exposing the silicon fibers to concentrated solar radiation such that the silicon fibers and the gas surrounding the silicon fibers absorb the concentrated solar radiation and produce heat, which decomposes the gaseous hydrocarbon into a carbon coating on the silicon fibers.

[0040] In some aspects, the techniques described herein relate to methods in which heat decomposes gaseous hydrocarbons into hydrogen gas and carbon.

[0041] In some aspects, the techniques described herein relate to methods in which concentrated solar irradiation triggers a photocatalytic process that accelerates the decomposition of gaseous hydrocarbons into hydrogen gas and carbon.

[0042] In some aspects, the techniques described herein relate to methods whereby the concentrated solar illumination has a concentration factor of 100 or greater.

[0043] In some aspects, the techniques described herein relate to methods in which the gaseous hydrocarbon is high-purity methane gas.

[0044] In some aspects, the techniques described herein relate to methods where the gaseous hydrocarbon is biogas.

[0045] In some aspects, the techniques described herein relate to methods involving a carrier gas in which gaseous hydrocarbons are mixed with methane or biogas.

[0046] In some aspects, the techniques described herein relate to methods in which the carrier gas is hydrogen gas.

[0047] In some aspects, the techniques described herein relate to methods in which carbon, including graphene, graphite, carbon nanotubes, or carbon black, is conformally deposited onto the surface of silicon fibers.

[0048] In some aspects, the techniques described herein relate to methods by which conformal carbon coatings from adjacent elements or ligaments of a porous substrate fuse together to form a continuous structure.

[0049] In some aspects, the techniques described herein relate to methods in which carbon is deposited onto a porous substrate, and the porous substrate is then used to fabricate an electrochemical energy storage device.

[0050] In some aspects, the techniques described herein relate to methods in which the porous substrate is used to fabricate an anode for a lithium ion battery.

[0051] In some aspects, the techniques described herein relate to methods where concentrated solar illumination includes sunlight from the sun.

[0052] In some aspects, the techniques described herein relate to methods in which concentrated solar irradiation includes sunlight from the sun augmented with an artificial light source.

[0053] In some aspects, the techniques described herein relate to methods that further include optimizing the amount of enhanced artificial light from the artificial light source to maintain a constant irradiance.

[0054] In some aspects, the techniques described herein relate to methods in which the artificial light source includes a plasma arc lamp, a halogen bulb, an LED, a fluorescent bulb, a metal halide lamp, or an argon lamp.

[0055] In some aspects, the techniques described herein relate to methods in which the artificial light source includes a xenon arc lamp.

[0056] In some aspects, techniques described herein relate to methods in which the concentrated solar irradiation includes sunlight from the sun during times when the sun is shining light into a collector that concentrates the sun's light into the reaction zone, and the concentrated solar irradiation includes artificial light when the sun is not shining light into the collector.

[0057] In some aspects, the techniques described herein relate to methods in which the concentrated solar illumination includes light from an artificial light source.

[0058] In some aspects, the techniques described herein relate to methods in which the porous glass substrate comprises a roll-to-roll substrate.

[0059] In some aspects, the techniques described herein relate to methods that further include operating a roll-to-roll substrate to continuously maintain a virgin porous glass substrate.

[0060] In some aspects, the techniques described herein relate to methods in which the porous glass substrate comprises a silica cloth or felt.

[0061] In some aspects, the techniques described herein relate to methods that further include concentrating the solar light source using a reflector.

[0062] In some aspects, the techniques described herein relate to methods in which the reflector includes an array of elliptical reflectors, parabolic reflectors, compound reflectors, Fresnel lenses, and / or flat reflectors.

[0063] In some aspects, the techniques described herein relate to methods in which the reflector includes a variable reflector that adjusts the amount of solar irradiation concentrated within the reaction zone.

[0064] In some aspects, the techniques described herein relate to methods in which the reaction zone is contained within a reaction chamber.

[0065] In some aspects, the techniques described herein relate to methods in which exposing gaseous hydrocarbons to concentrated solar radiation occurs in multiple directions.

[0066] In some aspects, the techniques described herein relate to methods in which the gaseous hydrocarbons include natural gas.

[0067] In some aspects, the techniques described herein relate to methods that further include reflowing the output gas over a porous glass substrate in a reaction zone and exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the reflowed gas further decomposes into hydrogen gas and carbon.

[0068] In some aspects, the techniques described herein relate to methods that further include pretreating a porous glass substrate by adhering silicon or glass particles to glass fibers, wherein the silicon or glass particles become incorporated into a carbon coating on the silicon fibers after exposure to concentrated solar irradiation.

[0069] In some aspects, the techniques described herein relate to methods in which the silicon or glass particles are nanoparticles or microparticles.

[0070] In some aspects, the techniques described herein relate to methods in which the carbon coating comprises cylindrical concentric layers of carbon that are layered concentrically on top of each other in a repeating pattern.

[0071] In some aspects, the technology described herein relates to methods in which the silicon fibers comprise silicon dioxide and silicon.

[0072] In some aspects, the techniques described herein relate to methods in which the silicon fibers comprise a silicon dioxide core with a silicon shell.

[0073] In some aspects, the techniques described herein relate to methods in which the silicon fibers comprise solid silicon fibers.

[0074] In some aspects, the techniques described herein relate to an anode for a lithium-ion battery that includes a plurality of silicon fibers coated with a carbon coating.

[0075] In some aspects, the technology described herein relates to anodes in which the silicon fibers comprise silicon dioxide and silicon.

[0076] In some aspects, the technology described herein relates to anodes in which the silicon fibers include a silicon dioxide core with silicon rings surrounding the silicon dioxide core.

[0077] In some aspects, the techniques described herein relate to anodes in which silicon rings form a shell around a silicon dioxide core.

[0078] In some aspects, the techniques described herein relate to anodes in which the silicon carbide material is at the interface between the silicon fibers and the carbon coating.

[0079] In some aspects, the techniques described herein relate to anodes in which the carbon coating includes silicon or glass particles.

[0080] In some aspects, the techniques described herein relate to anodes in which the silicon or glass particles are nanoparticles or microparticles.

[0081] In some aspects, the techniques described herein relate to anodes in which the silicon fibers comprise solid silicon fibers.

[0082] In some aspects, the techniques described herein relate to anodes in which the carbon coating comprises cylindrical concentric layers of carbon that are layered concentrically on top of each other in a repeating pattern.

[0083] In some aspects, the techniques described herein relate to anodes in which the silicon fibers comprise amorphous silicon.

[0084] In some aspects, the techniques described herein relate to a lithium-ion battery that includes an anode and a cathode separate from the anode, the anode being an anode disclosed above. [Brief explanation of the drawings]

[0085] This description will be more fully understood with reference to the following figures and data graphs, which are presented as various embodiments of the present disclosure and should not be construed as a complete recitation of the scope of the disclosure.

[0086] [Figure 1] FIG. 1 illustrates a schematic process for graphite deposition onto a silicon core according to one embodiment of the present invention.

[0087] [Figure 2] FIG. 2 is a flow chart illustrating an exemplary process for producing graphite-coated silicon fibers, according to one embodiment of the present invention.

[0088] [Figure 3]FIG. 3 is a schematic cross-sectional view of an exemplary silicon fiber coated with graphite, according to one embodiment of the present invention.

[0089] [Figure 4] FIG. 4 is a scanning electron microscope (SEM) image of the treated porous glass substrate.

[0090] [Figure 5] 5A, 5B, and 5C illustrate various energy dispersive spectroscopy (EDS) images of the treated porous glass substrate illustrated in FIG.

[0091] [Figure 6] FIG. 6 is two exemplary X-ray diffraction (XRD) plots on the treated and untreated porous glass substrates illustrated in FIG.

[0092] [Figure 7] FIG. 7 illustrates an exemplary schematic diagram of glass fibers that have been pretreated with glass or silicon particles, prior to carbon deposition, according to an embodiment of the present invention.

[0093] [Figure 8] FIG. 8 diagrammatically illustrates an exemplary battery, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0094] (Detailed explanation) It has been discovered that the addition of carbon-based coatings to silicon-based anode materials in battery technology can provide increased thermal and electrical conductivity while also providing additional ion storage capacity. The carbon-based coating allows for fast charging without producing excess Joule heating, which can cause thermal runaway, which can lead to excessive temperatures and battery fires.

[0095] Various embodiments of the present disclosure include a cylindrical core-shell structure with a shell of graphite deposition and a protected core containing silicon. This structure can be highly advantageous for lithium-ion (Li-ion) battery anodes because silicon and graphite are known to have high lithium uptake capacities. In fact, the associated charge storage capacity of silicon can exceed that of graphite by up to 10 times. However, silicon suffers from poor mechanical stability and associated cycle storage limitations. The graphite shell can protect the silicon from much of this mechanical degradation.

[0096] Turning to the drawings, FIG. 1 schematically illustrates a process for graphite deposition onto a silicon core according to an embodiment of the present invention. Concentrated light 102 may be introduced into a gaseous hydrocarbon 104, which may dissociate into carbon and hydrogen 108. The concentrated light 102 may be concentrated sunlight. The carbon may be trapped within a porous silicon dioxide (SiO2) substrate 106, while the hydrogen 108 is allowed to escape as hydrogen gas. In some embodiments, the porous SiO2 substrate 106 may comprise a silica cloth or felt. The porous SiO2 substrate 106 may comprise a woven silica material with silica fibers. The silica fibers may be long, cylindrically shaped fibers that extend and are woven together. In some embodiments, the porous SiO2 substrate 106 may be configured in a roll-to-roll process, in which unused substrates may be continuously fed into a reaction chamber. The roll-to-roll process may be operated continuously.

[0097] In some examples, the starting porous SiO2 substrate 106 may be pretreated with glass or silicon particles before being coated with carbon. The particles may be nanoparticles or microparticles. The particles may be loosely attached to the fibers by van der Waals forces. Chemical reduction and high temperature may bond (e.g., cement) them to the fibers. During the carbon coating process, the particles may be conformally coated with graphene, graphite, carbon nanotubes, and / or carbon black. The conformal carbon coatings from adjacent elements or ligaments of the porous substrate may fuse and form a continuous structure.

[0098] In some embodiments, the concentrated light 102 may be light from the sun, which may be concentrated through one or more concentrators (e.g., reflectors, refractors, mirrors). The concentrators may include an array of elliptical reflectors, parabolic reflectors, compound reflectors, Fresnel lenses, and / or flat reflectors. The concentrators may be variable concentrators (e.g., variable mirrors) that may vary the amount of light applied to the flow of gaseous hydrocarbons 104. The gaseous hydrocarbons 104 may be methane gas. The dissociation of the gaseous hydrocarbons 104 into carbon and hydrogen is an endothermic reaction. In some embodiments, the axis of the concentrated light 102 may be altered to modify the intensity of the light depending on the optimal amount of light for a particular situation.

[0099] In some embodiments, the concentrated light 102 may be produced by an artificial light source, such as a xenon light source, a metal halide light source, or an argon light source. In some embodiments, a combination of light from the sun and an artificial light source may be used to carry out the reaction. For example, the sun may produce light during the day, while a light source may be used at night to perpetuate the reaction. Furthermore, the reaction may be carried out strictly using light from an artificial light source. Light from an artificial light source may approach the porous SiO2 substrate 106 from one direction, while light from the sun may approach from another direction. The gaseous hydrocarbon 104 (e.g., methane) may be a permeable gas that cannot absorb significant amounts of the gaseous hydrocarbon 104. The porous SiO2 substrate 106 may absorb the concentrated light 102 within its solid web, producing localized heating of the gaseous hydrocarbon as it flows through the porous web and photocatalysis that accelerates its decomposition. The porous SiO2 substrate 106 and the gas surrounding the porous SiO2 substrate 106 may absorb the concentrated sunlight 102 and produce heat, which may decompose the gaseous hydrocarbons 104 into hydrogen gas and carbon. The gaseous hydrocarbons 104 and / or the porous SiO2 substrate 106 may not include any separate catalyst. The gaseous hydrocarbons 104 may also include a carrier gas, such as hydrogen, nitrogen, and / or argon. The gaseous hydrocarbons 104 may include natural gas. It has been discovered that carbon quality is improved with the addition of a carrier gas, such as hydrogen, to the gaseous hydrocarbons 104.

[0100] The process of dissociation of gaseous hydrocarbons 104 by heating may be referred to as cracking (e.g., hydrocarbon cracking or methane cracking). In some embodiments, the output gas may be reflowed over a porous SiO2 substrate in a reaction zone. The porous glass substrate may be further exposed to concentrated solar irradiation in the reaction zone such that the reflowed gas further decomposes into hydrogen gas and carbon.

[0101] A method and apparatus for the deposition of graphitic carbon on a porous substrate is described in International Publication No. WO 2022 / 236303, filed May 5, 2022, entitled "Apparatus and method for gaseous hydrocarbon self-catalyzation, reforming, and solid carbon deposition," which is incorporated herein by reference in its entirety for all purposes. This publication includes the disclosure of a unique composite material comprising a silicon rod-like core surrounded by a graphite tube-like shell. The disclosure further includes a light-emitting device producing a controllable radiant heat flux of up to 4,500 suns, which may be sufficient to bring reactor operating temperatures above 1,500 K. Similar conditions can be produced using a solar concentrator located outdoors in a natural solar radiation environment. In some embodiments, a gaseous hydrocarbon (e.g., methane or biogas) stream can be directed onto a porous SiO2 fiber substrate (e.g., glass felt or woven fabric) and decomposed. The use of a porous substrate also serves to significantly enhance heat transfer to the flowing medium as a result of the increased surface area, which therefore increases methane decomposition / conversion efficiency.

[0102] It has been discovered that at the beginning of the reaction, the glass fibers within the porous glass fiber substrate chemically reduce, producing primarily water vapor, unreacted gaseous hydrocarbons, other intermediate hydrocarbons, and hydrogen, as well as solid silicon fibers (e.g., deoxygenated glass fibers). Thus, the SiO fibers that make up the porous SiO fiber substrate are stripped of their oxygen, leaving primarily silicon fibers. The reduction reaction then stops due to the absence of accessible oxygen, and the overall reaction changes to methane decomposition, primarily producing hydrogen gas and solid carbon deposits on the surface of the resulting silicon fibers.

[0103] In some embodiments, the starting substrate can be a porous silicon substrate. The silicon substrate can be fibrous. Starting with a porous SiO2 substrate can provide advantages such as reduced cost and mechanical flexibility and / or durability. However, the starting substrate can also be porous silicon, which will not be exfoliated by oxygen, just like the porous SiO2 substrate.

[0104] FIG. 2 is a flow chart illustrating an exemplary process for producing graphite-coated silicon fibers according to an embodiment of the present invention. Process 200 includes providing a porous glass fiber substrate (202). The porous glass fiber substrate includes silica, silicon dioxide (SiO), or quartz. In some examples, the porous glass fiber substrate may be pretreated with glass or silicon particles before being coated with carbon. The particles may be nanoparticles or microparticles. The particles may be loosely attached to the fibers by van der Waals forces. Chemical reduction and high temperature may bond (e.g., cement) them to the fibers. During the carbon coating process, the particles may be conformally coated with graphite.

[0105] Process 200 further includes flowing a hydrocarbon gas over the porous glass fiber substrate (204). The hydrocarbon gas may be methane gas. The methane gas may have a chemical formula of CH4. Process 200 further includes exposing the porous glass fiber substrate to concentrated light irradiation (206). The concentrated light irradiation may be concentrated solar irradiation. The concentrated light irradiation may be produced by a solar concentrator, which may be capable of producing a controllable radiant heat flux of up to 4,500 suns, which may be sufficient to bring the reactor operating temperature above 1,500 K. This concentrated solar irradiation is described in more detail in WO 2022 / 236303 (previously incorporated by reference).

[0106] Concentrated solar irradiation may chemically reduce at least a portion of the glass fibers within the porous glass fiber substrate to silicon fibers (208). The glass fibers within the porous glass fiber substrate chemically reduce, producing product streams primarily consisting of water vapor, unreacted methane, other intermediate hydrocarbons, and solid silicon fibers (e.g., deoxygenated glass fibers). As the reduction reaction ceases, the methane gas may decompose into solid carbon, which coats the silicon fibers (210). In some embodiments, the coated silicon fibers may be advantageously utilized to produce fibrous core-shell silicon-graphite battery anodes.

[0107] In some embodiments, concentrated solar radiation (e.g., concentration factor 100 or greater) may be used in a process to convert inexpensive glass fibers into silicon fibers, which are then seamlessly coated to protect them. The silicon fibers may be coated with graphite.

[0108] In some embodiments, pure methane or methane-carrier gas mixtures (eg, hydrogen as the carrier gas) may be converted into graphite coatings on silicon.

[0109] In some embodiments, a gaseous hydrocarbon may be flowed over the substrate. The gaseous substrate may be methane or biogas.

[0110] In some embodiments, a carrier gas (eg, hydrogen) may be the only gas present during the reduction reaction, followed by the introduction of methane for carbon deposition onto the silicon fibers.

[0111] In some embodiments, the porous glass fiber substrate may comprise glass felt, woven, and / or perforated. As discussed above, the starting substrate may be a porous silicon substrate.

[0112] In some embodiments, the light source may augment actual solar incidence (e.g., in an outdoor setting) with a complementary artificial light source (e.g., a xenon arc lamp) to maintain near-constant irradiance while controlling for normal variations in solar flux. For example, a secondary concentrated solar power source may be utilized.

[0113] In some embodiments, the heating from the light source may be augmented with a secondary non-optical heater. For example, a joule heater may be utilized to supplement the heat from the light source. The heating from the light source may also be augmented with heating from another light source.

[0114] In some embodiments, the porous glass fiber substrate may be a roll-to-roll substrate, where virgin porous substrate can be continuously introduced into the process and allow the solid reaction product to be extracted onto the roll-to-roll substrate. The treated substrate may be used in the manufacture of electrochemical energy storage devices.

[0115] Concentrated solar irradiation may be produced using a concentrator, which may include one or more types of reflectors (e.g., elliptical, parabolic, compound). The artificial light source may include one or more types of light bulbs (e.g., plasma arc, halogen, LED, fluorescent). The reaction may be carried out in a reaction chamber. The reaction zone may be contained within the reaction chamber.

[0116] 3 is a schematic cross-sectional view of an exemplary silicon fiber coated with graphite according to an embodiment of the present invention. As discussed above, the SiO2 fiber is exfoliated from oxygen and thus converted into a Si fiber. The SiO2 portion 301 may still remain as the core of the Si fiber. Thus, the Si portion 302 may be an annular coating surrounding the remaining SiO2 portion 301. Although the SiO2 portion 301 is illustrated as a remaining cylindrical member, the SiO2 portion 301 may have other shapes, such as an oval shape. Furthermore, the Si portion 302 may be interspersed within the SiO2 portion 301.

[0117] The illustrated silicon portion 302 is a cylindrical, annular shaped member coated with an annular coating of carbon 304. The carbon 304 may be graphitic carbon or may be formed in layers, which may be seen in the images included and discussed below. The interface of the carbon coating 304 and the silicon portion 302 may be a silicon carbide (SiC) layer 306. The SiC layer 306 may mediate changes in thermal and mechanical behavior during operation as a battery anode. During carbon deposition, the outer silicon portion of the silicon portion 302 may combine with the carbon to form the SiC layer 306 at the interface between the carbon 304 and the silicon portion 302.

[0118] While the presence of residual SiO2 fibers 301 is shown, it has also been discovered that the process can be modified to produce complete conversion of the SiO2 fibers to silicon, and thus the residual SiO2 fibers 301 are exemplary of a process that includes residual SiO2 fibers. Although the residual SiO2 fibers 301 are shown as being large relative to the silicon portion 302, the process may make the residual SiO2 fibers 301 larger or smaller compared to the silicon portion 302.

[0119] The present structure may be utilized in battery technology, including as a battery anode. As discussed above, batteries including anodes including a carbon-based coatings may be advantageous. The carbon-based coating may be implemented on silicon fibers, which may improve Li-ion storage because silicon has demonstrated increased Li-ion storage capacity compared to carbon. In embodiments with residual SiO2 fibers 301, the SiO2 fibers 301 also have increased Li-ion storage capacity compared to pure carbon. The carbon-based coating may provide increased thermal and electrical conductivity compared to silicon-only anodes. The carbon-based coating may be high-quality graphitic carbon, which has been shown to have increased Li-ion storage capacity, thermal conductivity, and electrical conductivity compared to regular carbon.

[0120] FIG. 4 is a scanning electron microscope (SEM) image of a processed porous glass substrate. The processed substrate includes a core 402. The core 402 may include a combination of silicon and SiO. As illustrated in FIG. 3, the core 402 may include residual SiO and a silicon portion. The core 402 may be surrounded by a carbon coating 404. As shown, the carbon coating 404 may be layered on the core 402. The produced carbon coating 404 has been observed to be cylindrical and graphite. The carbon coating 404 may be graphene layers formed concentrically around the core 404 (e.g., fiber). This type of graphite layer has not been observed previously, except in multi-walled carbon nanotubes, which contain hollow cores and are generally much smaller in diameter. Such layered graphite structures are particularly advantageous in the production of and use in Li-ion battery anodes.

[0121] 5A, 5B, and 5C illustrate various energy dispersive spectroscopy (EDS) images of the treated porous glass substrate illustrated in FIG. 4. The EDS images analyze the treated porous glass substrate for different chemical compositions. FIG. 5A illustrates an analysis for carbon. As illustrated, carbon is spread throughout the treated porous glass substrate. FIG. 5B illustrates an analysis for silicon. As illustrated, silicon is present within the core area 502. FIG. 5C illustrates an analysis for SiO. As illustrated, SiO is present within the core area 502.

[0122] FIG. 6 shows two exemplary X-ray diffraction (XRD) plots of the treated and untreated porous glass substrates shown in FIG. 4. The bottom plot 602 is the XRD plot of the untreated porous glass substrate. A single peak 604, corresponding to the level of SiO, is present. The bottom XRD plot shows a high content of SiO and does not show any other peaks corresponding to the presence of other elements. The top plot 606 is the XRD plot of the treated porous glass substrate. The top plot 606 includes a high peak 608 and two smaller peaks 610, 612, corresponding to a large amount of crystalline carbon. The top plot 606 also includes a small peak 614, corresponding to the amount of SiC. The top plot 606 also includes a small peak 616, corresponding to the amount of SiO. The top plot 606 does not have a sharp XRD peak corresponding to silicon due to the presence of amorphous silicon rather than crystalline silicon, but rather it has a broad shoulder centered at about 25 degrees. The background of the XRD spectrum is subtracted, which reduces the presence of this broad shoulder corresponding to amorphous silicon from the top plot 606.

[0123] Thus, the bottom plot 602 shows that the untreated porous glass substrate initially contains a large amount of SiO. The top plot 606 shows that the treated porous glass substrate contains a large amount of crystalline carbon.

[0124] In some examples, porous substrates (e.g., porous glass substrates or porous silicon substrates) may be pretreated with glass or silicon particles before being coated with carbon. The particles may be nanoparticles or microparticles. The particles may be loosely attached to the fibers by van der Waals forces. Chemical reduction and high temperatures may bond (e.g., cement) them to the fibers. During the carbon coating process, the particles may be conformally coated with graphite.

[0125] 7 illustrates an exemplary schematic diagram of glass fibers pretreated with glass or silicon particles prior to carbon deposition, according to an embodiment of the present invention. As shown, glass or silicon particles 702 may be adhered to glass fibers 704. During carbon deposition, the glass or silicon particles 702 may be incorporated into the carbon coating. The glass or silicon particles 702 may increase the Li-ion capacity of the anode when the resulting structure is incorporated into a battery. The inclusion of glass or silicon particles 702 within the carbon coating may provide increased Li-ion capacity, as discussed above, while still incorporating the advantageous high electrical and thermal conductivity of the carbon coating.

[0126] 8 schematically illustrates an exemplary battery according to an embodiment of the present invention. The battery 806 includes an anode 802 and a cathode 804, which is electrically isolated from the anode. The anode 802 stores Li ions 808. In operation, the Li ions 808 flow from the anode 802 to the cathode 804, producing an electric current. The anode 802 may include treated carbon-coated silicon fibers, as discussed above. The treated carbon-coated silicon fibers may provide advantages such as higher Li ion uptake and increased electrical and thermal conductivity, as discussed above.

[0127] Although only a few embodiments of the present invention have been described in detail, it should be understood that the present invention may be embodied in many other forms without departing from the spirit or scope of the present invention. For example, embodiments such as those listed below are contemplated.

[0128] Appendix 1. A method of coating a porous glass substrate, the method including: providing a porous glass substrate; flowing a gaseous hydrocarbon over the porous glass substrate in a reaction zone; and exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the porous substrate and the gas surrounding the porous substrate absorb the concentrated solar radiation and produce heat, wherein the heat chemically reduces glass fibers in the porous glass substrate to silicon fibers, and the heat decomposes the gaseous hydrocarbon into a carbon coating on the silicon fibers.

[0129] Clause 2. The method of clause 1, wherein heat decomposes gaseous hydrocarbons into hydrogen gas and carbon.

[0130] Appendix 3. The method of Appendix 2, wherein concentrated solar irradiation induces photocatalysis that accelerates the decomposition of gaseous hydrocarbons into hydrogen gas and carbon.

[0131] Item 4. The method of item 1, wherein the concentrated solar radiation has a concentration factor of 100 or greater.

[0132] Appendix 5. The method of Appendix 1, wherein the gaseous hydrocarbon is high-purity methane gas.

[0133] Appendix 6. The method of Appendix 1, wherein the gaseous hydrocarbon is biogas.

[0134] Item 7. The method of item 1, wherein the gaseous hydrocarbon comprises a carrier gas that is mixed with methane or biogas.

[0135] Appendix 8. The method of Appendix 7, wherein the carrier gas is hydrogen gas, nitrogen gas, and / or argon gas.

[0136] Item 9. The method of item 1, wherein the carbon comprises graphene, graphite, carbon nanotubes, or carbon black that is conformally deposited on the surface of the silicon fibers.

[0137] Clause 10. The method of clause 9, wherein the conformal carbon coating from adjacent elements or ligaments of the porous substrate fuses together to form a continuous structure.

[0138] Item 11. The method of item 9, wherein after the carbon is deposited on the porous substrate, the porous substrate is used to fabricate an electrochemical energy storage device.

[0139] Clause 12. The method of clause 1, wherein the concentrated solar radiation comprises sunlight from the sun.

[0140] Appendix 13. The method of Appendix 1, wherein the concentrated solar radiation comprises sunlight from the sun augmented with an artificial light source.

[0141] Clause 14. The method of clause 13, further comprising optimizing the amount of enhanced artificial light from the artificial light source to maintain a constant irradiance.

[0142] Item 15. The method of item 13, wherein the artificial light source comprises a plasma arc lamp, a halogen bulb, an LED, a fluorescent bulb, a metal halide lamp, or an argon lamp.

[0143] Clause 16. The method of clause 13, wherein the artificial light source comprises a xenon arc lamp.

[0144] Item 17. The method of item 13, wherein concentrated solar irradiation includes sunlight from the sun during times when the sun is shining light into a collector that concentrates the sun's light into the reaction zone, and concentrated solar irradiation includes artificial light when the sun is not shining light into the collector.

[0145] Item 18. The method of item 1, wherein the concentrated solar radiation includes light from an artificial light source.

[0146] Clause 19. The method of clause 1, wherein the porous glass substrate comprises a roll-to-roll substrate.

[0147] Clause 20. The method of clause 19, further comprising operating a roll-to-roll substrate to continuously maintain a virgin porous glass substrate.

[0148] Clause 21. The method of clause 1, wherein the porous glass substrate comprises silica cloth or felt.

[0149] Clause 22. The method of clause 1, further comprising concentrating the solar light source using a reflector.

[0150] Clause 23. The method of clause 22, wherein the reflector comprises an array of elliptical reflectors, parabolic reflectors, compound reflectors, Fresnel lenses, and / or flat reflectors.

[0151] Clause 24. The method of clause 22, wherein the reflector comprises a variable reflector that adjusts the amount of solar radiation concentrated within the reaction zone.

[0152] Clause 25. The method of clause 1, wherein the reaction zone is contained within a reaction chamber.

[0153] Appendix 26. The method of Appendix 1, wherein exposing the gaseous hydrocarbon to concentrated solar radiation occurs in multiple directions.

[0154] Addendum 27. The method of Addendum 1, wherein the gaseous hydrocarbon comprises natural gas.

[0155] Clause 28. The method of clause 1, further comprising reflowing the output gas over a porous glass substrate in a reaction zone; and exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the reflowed gas further decomposes into hydrogen gas and carbon.

[0156] Appendix 29. The method of Appendix 1, further comprising pretreating the porous glass substrate by adhering silicon or glass particles to the glass fibers, wherein the silicon or glass particles become incorporated into a carbon coating on the silicon fibers after exposure to concentrated solar irradiation.

[0157] Item 30. The method of item 29, wherein the silicon or glass particles are nanoparticles or microparticles.

[0158] Clause 31. The method of clause 1, wherein the carbon coating comprises cylindrical concentric layers of carbon that are concentrically layered on top of each other in a repeating pattern.

[0159] Addendum 32. The method of Addendum 1, wherein the silicon fibers comprise silicon dioxide and silicon.

[0160] Clause 33. The method of clause 32, wherein the silicon fiber comprises a silicon dioxide core with a silicon ring surrounding the silicon dioxide core.

[0161] Item 34. The method of item 33, wherein the silicon rings form a shell around the silicon dioxide core.

[0162] Item 35. The method of item 1, wherein the silicon fibers comprise solid silicon fibers.

[0163] Addendum 36. A method for coating a porous glass substrate, the method including: providing a porous glass substrate; flowing a carrier gas over the porous glass substrate in a reaction zone; exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the porous substrate and the gas surrounding the porous substrate absorb the concentrated solar radiation and produce heat, which chemically reduces glass fibers in the porous glass substrate to silicon fibers; and, as the reduction reaction ceases, flowing a gaseous hydrocarbon over the silicon fibers; and exposing the silicon fibers to concentrated solar radiation such that the silicon fibers and the gas surrounding the silicon fibers absorb the concentrated solar radiation and produce heat, which decomposes the gaseous hydrocarbon into a carbon coating on the silicon fibers.

[0164] 37. The method of claim 36, wherein the heat decomposes the gaseous hydrocarbons into hydrogen gas and carbon.

[0165] Item 38. The method of item 37, wherein concentrated solar irradiation induces photocatalysis that accelerates the decomposition of gaseous hydrocarbons into hydrogen gas and carbon.

[0166] Item 39. The method of item 36, wherein the concentrated solar radiation has a concentration factor of 100 or greater.

[0167] Item 40. The method of item 36, wherein the gaseous hydrocarbon is high-purity methane gas.

[0168] Addendum 41. The method of Addendum 36, wherein the gaseous hydrocarbon is biogas.

[0169] Item 42. The method of item 36, wherein the gaseous hydrocarbon comprises a carrier gas that is mixed with methane or biogas.

[0170] Item 43. The method of item 42, wherein the carrier gas is hydrogen gas.

[0171] Clause 44. The method of clause 36, wherein the carbon comprises graphene, graphite, carbon nanotubes, or carbon black that is conformally deposited on the surface of the silicon fibers.

[0172] Clause 45. The method of clause 44, wherein the conformal carbon coating from adjacent elements or ligaments of the porous substrate fuses together to form a continuous structure.

[0173] 46. ​​The method of claim 44, wherein after the carbon is deposited on the porous substrate, the porous substrate is used to fabricate an electrochemical energy storage device.

[0174] Item 47. The method of item 46, wherein the porous substrate is used to manufacture an anode for a lithium ion battery.

[0175] Item 48. The method of item 36, wherein the concentrated solar radiation comprises sunlight from the sun.

[0176] Item 49. The method of item 36, wherein the concentrated solar radiation comprises sunlight from the sun augmented with an artificial light source.

[0177] Item 50. The method of item 49, further comprising optimizing the amount of enhanced artificial light from the artificial light source to maintain a constant irradiance.

[0178] Addendum 51. The method of Addendum 49, wherein the artificial light source comprises a plasma arc lamp, a halogen bulb, an LED, a fluorescent bulb, a metal halide lamp, or an argon lamp.

[0179] Item 52. The method of item 49, wherein the artificial light source comprises a xenon arc lamp.

[0180] Item 53. The method of item 49, wherein the concentrated solar irradiation includes sunlight from the sun during times when the sun is shining light into a collector that concentrates the sun's light into the reaction zone, and the concentrated solar irradiation includes artificial light when the sun is not shining light into the collector.

[0181] Item 54. The method of item 36, wherein the concentrated solar radiation includes light from an artificial light source.

[0182] Clause 55. The method of clause 36, wherein the porous glass substrate comprises a roll-to-roll substrate.

[0183] Clause 56. The method of clause 55, further comprising operating a roll-to-roll substrate to continuously maintain a virgin porous glass substrate.

[0184] Clause 57. The method of clause 36, wherein the porous glass substrate comprises silica cloth or felt.

[0185] Clause 58. The method of clause 36, further comprising concentrating the solar light source using a reflector.

[0186] Clause 59. The method of clause 58, wherein the reflector comprises an array of elliptical reflectors, parabolic reflectors, compound reflectors, Fresnel lenses, and / or flat reflectors.

[0187] Clause 60. The method of clause 58, wherein the reflector comprises a variable reflector that adjusts the amount of solar irradiation concentrated within the reaction zone.

[0188] Clause 61. The method of clause 36, wherein the reaction zone is contained within a reaction chamber.

[0189] Item 62. The method of item 36, wherein exposing the gaseous hydrocarbon to concentrated solar radiation occurs in multiple directions.

[0190] Addendum 63. The method of Addendum 36, wherein the gaseous hydrocarbon comprises natural gas.

[0191] Clause 64. The method of clause 36, further comprising reflowing the output gas over a porous glass substrate in a reaction zone; and exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the reflowed gas further decomposes into hydrogen gas and carbon.

[0192] Item 65. The method of item 36, further comprising pretreating the porous glass substrate by adhering silicon or glass particles to glass fibers, wherein the silicon or glass particles are incorporated into a carbon coating on the silicon fibers after exposure to concentrated solar irradiation.

[0193] Item 66. The method of item 65, wherein the silicon or glass particles are nanoparticles or microparticles.

[0194] Clause 67. The method of clause 36, wherein the carbon coating comprises cylindrical concentric layers of carbon that are concentrically layered on top of each other in a repeating pattern.

[0195] Addendum 68. The method of Addendum 36, wherein the silicon fibers comprise silicon dioxide and silicon.

[0196] Item 69. The method of item 68, wherein the silicon fiber comprises a silicon dioxide core with a silicon shell.

[0197] Clause 70. The method of clause 36, wherein the silicon fibers comprise solid silicon fibers.

[0198] Addendum 71. An anode for a lithium ion battery comprising a plurality of silicon fibers coated with a carbon coating.

[0199] Clause 72. The anode of clause 71, wherein the silicon fibers comprise silicon dioxide and silicon.

[0200] Clause 73. The anode of clause 72, wherein the silicon fiber comprises a silicon dioxide core with a silicon ring surrounding the silicon dioxide core.

[0201] Item 74. The anode of item 73, wherein the silicon rings form a shell around the silicon dioxide core.

[0202] Item 75. The anode of item 71, wherein the silicon carbide material is at an interface between the silicon fibers and the carbon coating.

[0203] Item 76. The anode of item 71, wherein the carbon coating comprises silicon or glass particles.

[0204] Item 77. The anode of item 76, wherein the silicon or glass particles are nanoparticles or microparticles.

[0205] Clause 78. The anode of clause 71, wherein the silicon fibers comprise solid silicon fibers.

[0206] Clause 79. The anode of clause 71, wherein the carbon coating comprises cylindrical concentric layers of carbon layered concentrically on top of each other in a repeating pattern.

[0207] Clause 80. The anode of clause 71, wherein the silicon fibers comprise amorphous silicon.

[0208] Clause 81. The anode of clause 71, wherein the anode is combined with a cathode separate from the anode to form a lithium ion battery.

[0209] (Doctrine of Equivalents) While the above description contains many specific embodiments of the present invention, these should be construed as an example of one embodiment thereof, rather than as limitations on the scope of the invention. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope and spirit of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive. The scope of the invention should, therefore, be determined not by the embodiments exemplified, but by the appended claims and their equivalents.

Claims

1. 1. A method for coating a porous glass substrate, the method comprising: Providing a porous glass substrate; flowing a gaseous hydrocarbon over a porous glass substrate in a reaction zone; exposing the porous glass substrate to concentrated solar radiation in the reaction zone such that the porous substrate and a gas surrounding the porous substrate absorb the concentrated solar radiation and produce heat; Including, the heat chemically reduces the glass fibers within the porous glass substrate to silicon fibers; The method wherein the heat decomposes the gaseous hydrocarbons into a carbon coating on the silicon fibers.

2. The method of claim 1 , wherein the heat decomposes the gaseous hydrocarbons into hydrogen gas and carbon.

3. 3. The method of claim 2, wherein the concentrated solar irradiation causes a photocatalytic reaction that accelerates the decomposition of the gaseous hydrocarbons into hydrogen gas and carbon.

4. The method of claim 1 , wherein the porous glass substrate comprises a roll-to-roll substrate.

5. The method of claim 1 , wherein the porous glass substrate comprises silica cloth or felt.

6. The method of claim 1 , wherein the gaseous hydrocarbon is high-purity methane gas.

7. 10. The method of claim 1, wherein the carbon comprises graphene, graphite, carbon nanotubes, or carbon black conformally deposited on the surface of the silicon fibers.

8. The method of claim 7 , wherein the conformal carbon coating from adjacent elements or ligaments of the porous substrate fuses together to form a continuous structure.

9. 10. The method of claim 1, wherein after the carbon is deposited on the porous substrate, the porous substrate is used to fabricate an electrochemical energy storage device.

10. An anode for a lithium ion battery comprising a plurality of silicon fibers coated with a carbon coating.

11. 11. The anode of claim 10, wherein the silicon fibers comprise silicon dioxide and silicon.

12. 12. The anode of claim 11, wherein the silicon fiber comprises a silicon dioxide core with a silicon ring surrounding the silicon dioxide core.

13. 13. The anode of claim 12, wherein the silicon rings form a shell around the silicon dioxide core.

14. 11. The anode of claim 10, wherein silicon carbide material is at the interface between the silicon fibers and the carbon coating.

15. 11. The anode of claim 10, wherein the carbon coating comprises silicon or glass particles.

16. 16. The anode of claim 15, wherein the silicon or glass particles are nanoparticles or microparticles.

17. The anode of claim 10 , wherein the silicon fibers comprise solid silicon fibers.

18. 11. The anode of claim 10, wherein the carbon coating comprises cylindrical concentric layers of carbon layered concentrically on top of each other in a repeating pattern.

19. The anode of claim 10 , wherein the silicon fibers comprise amorphous silicon.

20. 11. The anode of claim 10, wherein the anode is combined with a cathode separate from the anode to form a lithium ion battery.

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