Composite material that improves battery performance and method for manufacturing the same

Abstract

To improve the performance of electrical energy storage systems. [Solution] A composite material comprising a carbon-based core having a porous outer surface and a coating on at least a portion of the porous outer surface of the core. The coating is made from a material that is (i) substantially permeable to at least one metal ion or metal atom and (ii) substantially impermeable to liquids.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority and benefits thereof to U.S. Provisional Applications No. 63 / 287,600 (filed on 9 December 2021) and No. 63 / 385,845 (filed on 2 December 2022), both entitled “COMPOSITE MATERIALS PROVIDING IMPROVED BATTERY PERFORMANCE AND METHODS OF MANUFACTURE THEREOF.” The contents of both applications are incorporated herein by reference in their entirety.

[0002] This disclosure relates in general to compositions and methods for improving the performance of electrical energy storage systems. More specifically, the technology relates to composite materials suitable for use in high-capacity battery materials, for example, as electrode materials in lithium-ion batteries. More specifically, the disclosure relates to composite materials comprising a carbon-based core and a coating made of a material that is (i) substantially permeable to at least one metal ion or metal atom and (ii) substantially impermeable to liquids. [Background technology]

[0003] High-capacity battery materials, such as lithium-ion batteries, have a wide range of applications in power drive and energy storage systems. Compared to conventional batteries, lithium-ion batteries (LIBs) are widely used to power portable electronic devices, such as mobile phones, tablets, laptops, power tools, and other high-current devices, such as electric vehicles, due to their high operating voltage, low memory effect, and high energy density.

[0004] A lithium-ion battery (LIB) electrochemical cell mainly consists of a positive electrode, a negative electrode, an electrolyte capable of conducting lithium ions, a separator that electrically separates the positive and negative electrodes, and a current collector. LiCoO2 (LCO), LiFePO4 (LFP), LiMn2O4 (LMO), LiNi 0.8Co 0.15 Al 0.05 O2(NCA) and LiNi x Co y Mn z O2(NMC) is one of the five types of cathode materials widely used in lithium-ion batteries. These five types of batteries account for the majority of the market share in today's battery market. The electrolyte consists of a lithium salt dissolved in a specific solvent (mainly containing ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and propylene carbonate (PC)). The lithium salt is usually selected from LiClO4, LiPF6, LiBF4, and LiBOB. The separator material is generally a polyolefin resin material. Polypropylene (PP) and polyethylene (PE) microporous membranes are widely used as separators in commercially available lithium-ion batteries. Aluminum foil is usually used as a current collector for the positive electrode, and copper foil is used for the negative electrode. Carbon-based materials (including hard carbon and graphite) are currently the main choice for the active material in the negative electrode of most commercially available lithium-ion batteries. Other novel anode materials, such as titanium-based oxides, alloys / dealloying materials, and conversion materials, have also been investigated in detail and exhibit excellent electrochemical properties.

[0005] Under normal operation, lithium ions move from one electrode to the other through the electrolyte and separator via diffusion and migration. When a lithium-ion battery (LIB) is charged (delithiated), lithium ions in the electrolyte solution move from the cathode through the separator and are inserted into the anode. Charge-balancing electrons also move to the anode, but they also move through external circuits to supply power to devices (computers, mobile phones, electric vehicles, etc.). During discharge (lithiation), the reverse process occurs, and electrons flow through the powered device.

[0006] During the lithium-ion and delithiation processes, the anode and cathode undergo dimensional changes during charging and discharging, which can lead to cell expansion. Therefore, the materials used in the cell (e.g., electrode materials) typically undergo large volume changes during repeated cycles, potentially imposing significant stress on the cell. For example, silicon typically experiences a volume change of up to 300% during lithium-ion, while graphite undergoes approximately 10% volume expansion. The resulting stress can cause surface and intergranular cracking in the electrode material, leading to the pulverization of electrode particles and the formation of new surfaces for the formation and growth of the solid electrolyte interphase (SEI) layer. Consequently, these stresses, which destroy the integrity of the electrodes, result in capacity and power fade, causing insufficient battery cycle life and performance.

[0007] These mechanical degradation mechanisms are known to be strongly coupled with chemical degradation and significantly affect the cycle life of lithium-ion batteries. The effect of swelling becomes increasingly important as higher-capacity materials with greater volume expansion (e.g., silicon) are incorporated into battery electrodes. [Overview of the Initiative]

[0008] Embodiments disclosed herein address one or more of the problems and defects identified above by providing improved battery components, improved batteries fabricated therefrom, and methods for manufacturing and using them. However, it is likely that this disclosure may prove useful in addressing other problems and defects in many areas of the art. Therefore, the subject matter described in the claims should not necessarily be construed as being limited to addressing any of the specific problems or defects described herein.

[0009] The purpose of this disclosure is to eliminate or mitigate at least one drawback of prior methods and materials for improving performance (e.g., cycling stability, battery life of high-capacity batteries such as lithium-ion batteries).

[0010] In one general aspect, the present disclosure provides composite materials for use in electrical energy storage systems, such as lithium-ion batteries. The composite materials of the present disclosure are advantageous in that they suppress or reduce volume expansion (swelling) of electrode materials during charging and discharging, thereby improving the performance of the battery (e.g., capacity, lifespan, cycling stability, or a combination thereof).

[0011] In one general embodiment, the composite material disclosed herein comprises a carbon-based core having a porous outer surface and a coating on at least a portion of the porous outer surface of the carbon-based core. The coating of the disclosure is made from a material that is (i) substantially permeable to at least one metal ion or metal atom and (ii) substantially impermeable to liquids. The coating disclosed herein can act as a barrier preventing the electrolyte of a battery cell (e.g., a lithium-ion battery cell) from penetrating into the carbon-based core. The carbon-based core can be used as an electrode component. The coating (substantially impermeable to liquids) suppresses or reduces swelling of the carbon-based core during the charge-discharge process. While not theoretically bound, suppressing or reducing core swelling improves battery performance.

[0012] In another embodiment, the coating of the present disclosure reduces the formation of solid electrolyte interphases (SEIs) on the porous outer surface of a carbon-based core.

[0013] The composite material of this technology can improve the performance of lithium-ion batteries compared to lithium-ion batteries having electrodes that do not have the composite material of this disclosure.

[0014] Carbon-based aerogels may have properties (e.g., pore volume, pore size distribution, morphology, etc.) that can be adjusted or modified depending on the precursor material and / or method used. In one embodiment, the disclosure uses a coated carbon-based aerogel as an electrode material with improved performance for applications in energy storage devices, such as lithium metal anodes for high-energy batteries.

[0015] Several advantages can be obtained by using the composite materials of this technology in high-capacity batteries such as lithium-ion batteries. For example, these include (i) providing volume for active material expansion without electrode swelling during the charge-discharge process, (ii) providing a conductive medium that facilitates electron transport between electrode active particles, (iii) improving stability and performance by changing the electrode surface chemistry properties that alter the electrochemical properties of the electrode surface, and (iv) providing a physical protective barrier that suppresses electrolyte reduction and forms an SEI on the core. Some of the composite materials disclosed herein can improve all aspects of performance. Others can improve one or more (but not all) aspects of performance.

[0016] In one embodiment, a composite material for use in an electrical energy storage system is provided herein. The composite material comprises a carbon-based core having a porous outer surface and a coating on at least a portion of the porous outer surface of the carbon-based core, the coating being (i) substantially permeable to at least one metal ion or metal atom, and (ii) substantially impermeable to liquid molecules.

[0017] In some examples, the liquid molecule contains an electrolyte solvent. In some examples, the electrolyte solvent is selected from ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), fluorinated ether (F-EPE), 1,3-dioxolane (DOL), dimethoxyethane (DME), ethyl methyl carbonate (EMC), propylene carbonate (PC), butylene carbonate (BC), ethylene sulfite (ES), propylene sulfite (PS), diethyl sulfite (DES), gamma-butyrolactone (BL), dimethyl sulfoxide (DMSO), ethyl acetate (EP), methyl acetate (MA), or a combination thereof.

[0018] In some cases, at least one metal ion is a lithium ion. In some cases, at least one metal atom is a lithium atom.

[0019] In some examples, the coating on at least a portion of the porous outer surface of the carbon core has thickness, and the thickness is approximately 2,500 nm or less. In some examples, the coating on at least a portion of the porous outer surface of the carbon core has a thickness of approximately 100 nm to approximately 2,000 nm, or a thickness of approximately 200 nm to 500 nm. In some examples, the coating extends into the porous outer surface of the carbon core. In some examples, the coating extends into the porous outer surface of the carbon core to a depth of approximately 2,500 nm or less, or approximately 100 nm to approximately 2,000 nm, or approximately 200 nm to 500 nm. In some examples, the coating is uniform on at least a portion of the porous outer surface of the core. In some examples, the coating is continuous on at least a portion of the porous outer surface of the core. In some examples, at least a portion of the porous outer surface of the core is at least 70%, at least 90%, or at least 95% of the outer surface. In some examples, the coating contains a conductive material. In some examples, the conductive material is formed from a precursor of a non-conductive material. In some examples, the conductive material is carbon. In some examples, the non-conductive material is a polymer. In some examples, the conductive material is formed from a precursor of a first conductive material. In some examples, the first conductive material is selected from metals or transition metals. In some examples, the first conductive material is selected from carbon materials. In some examples, the conductive material is carbon derived from pitch, such as soft carbon. In some examples, the precursor of the first conductive material includes pitch.

[0020] In some examples, the coating comprises a material selected from organic molecules, polymers, metals, transition metals, non-metals, metal-organic frameworks (MOFs), or combinations thereof. In some examples, the polymer is selected from the group of polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyimide, polyamide, or derivatives thereof. In a specific example, the coating comprises polyacrylonitrile (PAN). In some examples, the organic molecules, polymers, or combinations thereof are carbonized. In one example, the coating comprises carbonized polyacrylonitrile (PAN). In some examples, the coating is a carbon-based coating. In some examples, the carbon-based coating is derived from pitch. That is, in some examples, the coating is a carbon coating derived from pitch. In one example, the carbon coating derived from pitch comprises soft carbon.

[0021] In some examples, the coating penetrates into the pores of the carbon-based core. In some examples, the carbon-based core has a low bulk density, and the low bulk density ranges from about 0.25 g / cc to about 1.0 g / cc. In some examples, the carbon-based core has a pore volume of at least 0.3 cc / g. In some examples, the carbon-based core has a porosity of about 10% to about 90% of the volume of the core.

[0022] In some examples, the carbon-based core comprises a skeletal framework. For example, the skeletal framework can include carbon nanofibers. In some examples, the skeletal framework includes an array of interconnected pores.

[0023] In some examples, the carbon-based core is a monolith.

[0024] In some examples, the carbon-based core is in the form of particles. In some examples, the particles are substantially spherical and have a diameter of about 100 nm to about 4 mm, or about 5 μm to about 4 mm.

[0025] In some examples, the carbon-based core includes carbon-based aerogels, carbon-based xerogels, carbon-based ambigels, carbon-based aerogel xerogel hybrid materials, carbon-based aerogel ambigel hybrid materials, carbon-based aerogel ambigel xerogel hybrid materials, or combinations thereof. In some examples, the carbon-based core includes activated carbon, carbon black, carbon fibers, carbon nanotubes, pyrolytic carbon, graphite, graphene, or combinations thereof.

[0026] In some examples, the carbon core contains one or more additives, which are present at a level of at least about 0.1 to 80 weight percent of the carbon core. In some examples, the additives include one or more electrochemically active dopants. The one or more electrochemically active dopants are selected, without limitation, from the group consisting of lithium, sodium, potassium, calcium, magnesium, aluminum, iron, tin, lead, copper, mercury, manganese, vanadium, titanium, molybdenum, niobium, tungsten, zinc, silver, platinum, gold, carbon, boron, gallium, silicon, germanium, phosphorus, and antimony. In one example, the electrochemically active dopants are selected, without limitation, from the group consisting of silicon, germanium, tin, antimony, gold, silver, zinc, magnesium, platinum, and aluminum.

[0027] In some examples, the coating contains conductive additives. Conductive additives include carbon, carbon nanotubes, graphene, graphite, metals, metal oxides, silicon carbide, or combinations thereof.

[0028] In some cases, the carbon-based core has a capacity of approximately 200 mAh / g to approximately 3000 mAh / g. In some cases, the carbon-based core has an conductivity of at least approximately 1 S / cm. In some cases, the coating has an conductivity of at least approximately 1 S / cm.

[0029] In some examples, the energy storage system incorporating the composite materials of this technology is a battery. In some examples, the battery is a rechargeable battery. In some examples, the rechargeable battery is a lithium-ion battery.

[0030] In one embodiment, a rechargeable battery comprising a composite material of the technology disclosed herein is provided herein.

[0031] In another embodiment, a method for improving the performance of a rechargeable battery is provided herein, which includes incorporating the composite material disclosed herein into the rechargeable battery.

[0032] In another embodiment, a method for preparing the composite material of the present disclosure is provided herein. This method includes preparing a carbon-based core having a porous outer surface, and obtaining a composite material by coating at least a portion of the porous outer surface of the core.

[0033] In some examples, a method for preparing the composite material of the present disclosure further includes a subcritical or supercritical drying step prior to the step of coating at least a portion of the porous outer surface of the core. In some examples, the method further includes a carbonization step between the step of coating at least a portion of the porous outer surface of the core and the subcritical or supercritical drying step. In one example, the method further includes a second carbonization step after the step of coating at least a portion of the porous outer surface of the core.

[0034] In some examples, a method for preparing the composite material of the present disclosure further includes a step of subcritical or supercritical drying after a step of coating at least a portion of the porous outer surface of the core. In some examples, a carbonization step further includes after the subcritical or supercritical drying of the composite material.

[0035] In some examples, the step of coating at least a portion of the porous outer surface of the core includes a solidification process. In other examples, the step of coating at least a portion of the porous outer surface of the core includes a spray coating process. In some examples, the spray coating process includes a high-speed spray drying method using a spray feed. In some examples, the step of coating at least a portion of the porous outer surface of the core includes a dip coating process.

[0036] In some examples, the step includes coating at least a portion of the porous outer surface of the core.

[0037] This technology can be better understood from the following detailed explanation in conjunction with the attached drawings. [Brief explanation of the drawing]

[0038] [Figure 1] Figure 1 shows an exemplary bead coating process suitable for application to the carbon-based core of this disclosure. [Figure 2] Figure 2 shows a preparation scheme for coating C / Si beads with PAN using a solidification process. [Figure 3] Figure 3 shows two different paths for applying a PAN coating to the surface of C / Si beads. [Figure 4] Figures 4A and 4B are scanning electron microscope (SEM) images of sample A showing the carbon coating layer on the beads (from PAN solidification process 1, route 1). Figure 4A shows a portion of the coated beads, and Figure 4B is a higher magnification view of a portion of the coating on the surface of the beads shown in Figure 4A. [Figure 5A] Figure 5A is an SEM image of sample B (aerogel beads coated with PAN using process 1, route 2). This is an image of one of the coated beads (sample B). [Figure 5B]Figure 5B is an SEM image of sample B (PAN-coated aerogel beads using process 1 and route 2). It is a higher magnification image of a portion of the beads shown in Figure 5A. [Figure 5C] Figure 5C is an SEM image of sample B (PAN-coated aerogel beads using process 1, route 2). A higher magnification view of a portion of the beads is shown. [Figure 6] Figure 6 shows an SEM image of sample C (a carbon aerogel bead that was fully PAN-coated, with the coating formed using process 2, route 1). [Figure 7] Figures 7A and 7B are higher magnification images of sample C. Figure 7A shows two beads connected to each other by a coating, and Figure 7B is a higher magnification image of the coating at the neck / intersection of the beads. [Figure 8] Figure 8 shows an SEM image of sample D (a carbon aerogel bead that was fully PAN-coated, with the coating formed using process 2, route 2). [Figure 9] Figures 9A and 9B are higher magnification images of sample D. Figure 9A shows two beads connected to each other by a coating, and Figure 9B is a higher magnification of the coating at the neck / intersection of the beads. [Figure 10A] Figure 10A is a high-magnification SEM image of sample D, showing the PAN coating layer on a fibrous carbon aerogel structure. Figure 10A shows a portion of the coated surface. [Figure 10B] Figure 10B is a high-magnification SEM image of sample D, showing the PAN coating layer on a fibrous carbon aerogel structure. Figure 10B is a higher-magnification view of the coating. [Modes for carrying out the invention]

[0039] As mentioned above, for a specific active material (e.g., silicon), the storage and release of these ions (e.g., lithium ions in a lithium-ion battery) results in a substantial change in the volume of the active material. In conventional designs, this can lead to irreversible mechanical damage and ultimately to contact loss between individual electrode particles or between the electrode and the current collector beneath it. Furthermore, it can lead to the continuous growth of solid electrolyte phases (SEI) around such volume-changing particles.

[0040] A composite material is provided to address the aforementioned problems, comprising a carbon-based core having an outer surface and a coating that is (i) substantially permeable to at least one metal ion or metal atom, and (ii) substantially impermeable to liquid. Although not bound by theory, the carbon-based core structurally supports the active material, electrically interconnects the active material, and adapts to the aforementioned volume changes of the active material. In general, composite particles may be able to adapt to volume changes of the active material during battery operation.

[0041] Such advantages are obtained for a wide range of high-capacity anode and cathode materials. In addition, advantages are particularly obtained for high-capacity anode and cathode materials (e.g., greater than about 250 mAh / g for Li-ion battery cathodes and greater than about 400 mAh / g for Li-ion battery anodes) that exhibit significant volume changes (e.g., greater than about 10%) upon insertion and extraction of ions (e.g., metal ions). With respect to the anode, the composite materials of the present disclosure can be used in metal ion (e.g., Li-ion) batteries. Examples include, without limitation, high-concentration doped, doped, and undoped Si, In, Sn, Sb, Ge, Mg, Pb, alloys with other metals and metalloids, other metals, metal oxides, metal fluorides, metal oxyfluorides, metal nitrides, metal phosphides, metal sulfides, and mixtures with semiconductor oxides, as well as mixtures with their hard carbon, graphite, graphene, and / or other carbon-based materials. With respect to the cathode, the composite materials of the present disclosure can be used in metal ion (e.g., Li-ion) batteries, and examples include, without limitation, LCO, LFP, LMO, NCA, NMC, metal sulfides, metal fluorides, metal oxyfluorides, and mixtures thereof. In the following description, due to the current prevalence and popularity of Li-ion technology, several examples are shown in the context of aqueous Li-ion batteries. However, such examples are provided merely to assist in the understanding and explanation of the techniques underlying them, and these techniques are applicable equally to various other metal ion batteries, such as Li + , Na + , Mg 2+ , Ca 2+ , and Al 3+ , and it should be understood that they can be similarly applied to other aqueous metal ion batteries. The composite materials of the present disclosure can be used, for example, in other battery chemistries (e.g., reversible redox reactions) in which the active particles undergo significant volume changes during their operation, including batteries containing aqueous electrolytes.

[0042] Definition As used herein, the term "about" means that the numbers are approximate and small variations will not significantly affect the implementation of the disclosed embodiments. When numerical limitations are used, unless otherwise specified in the context, "about" means that the numbers may vary by ±10% and remain within the scope of the disclosed embodiments.

[0043] As used herein, the terms “optional” or “optional” mean that the described event or situation may or may not occur, and the description includes both cases in which the event or situation occurs and cases in which it does not occur.

[0044] As used herein, the term “uniform” means that the variation in the thickness of the material (e.g., the coatings of this disclosure) is less than about 10%, less than about 5%, or less than about 1%.

[0045] As used herein, the term “continuous” refers to a layer that is free from gaps, holes, or any discontinuities. For example, a continuous layer that does not contain two (or more) physically separated (or spaced apart) component materials within that layer.

[0046] As used herein, in the context of particle size, the term "D50" means that half of the particles in a population have a particle size above this point, and the other half have a particle size below this point. A D90 particle size distribution indicates that 90% (by number) of particles have a Ferret diameter below a certain size as measured by scanning electron microscopy (SEM) or transmission electron microscopy. A D10 particle size distribution indicates that 10% (by number) of particles have a Ferret diameter below a certain size as measured by scanning electron microscopy (SEM) or transmission electron microscopy.

[0047] As used herein, the term “pitch” refers to a naturally occurring viscoelastic polymer, or a viscoelastic polymer that can be manufactured from petroleum, coal tar, or plants. Pitch is generally obtained as a result of heat treatment and subsequent distillation of coal tar or petroleum fractions. It is substantially composed of a mixture of aromatic hydrocarbons. Exemplary pitches include petroleum pitch, coat tar pitch, and chemically treated pitch. Preferred compounds include those with a high carbon content after thermal decomposition, for example, those with a carbon content ranging from about 1% to about 20%.

[0048] As used herein, the term "xerogel" refers to a gel dried under subcritical conditions, i.e., most solvents are not in a supercritical fluid state under these conditions.

[0049] As used herein, the term "Ambigel" refers to a gel dried at atmospheric pressure.

[0050] Carbon-based core In some examples, the carbon-based core includes carbon-based aerogels, carbon-based xerogels, carbon-based ambigels, carbon-based aerogel xerogel hybrid materials, carbon-based aerogel ambigel hybrid materials, carbon-based aerogel ambigel xerogel hybrid materials, or combinations thereof.

[0051] The aerogel used in this disclosure may be carbonized to obtain the carbon-based aerogel of the technology. Carbonization may be carried out by thermal decomposition at high temperatures in an inert atmosphere. The carbonized form of the aerogel used in this disclosure may have a nitrogen content of 0 to 20%. Typical thermal decomposition temperatures are in the range of 500°C to 2000°C. The temperature may be increased to reduce the nitrogen content of the resulting carbon aerogel. Thermal decomposition is usually carried out in an inert atmosphere (i.e., nitrogen, helium, neon, argon, or any combination thereof).

[0052] The aerogel used in this disclosure may contain a silica component.

[0053] In some examples, the disclosure includes forming and using carbon-based cores, such as carbon aerogels, as electrode materials in energy storage devices, for example, as primary anode materials in LIBs. The pores of the porous core are designed, organized, and structured to accommodate, for example, silicon or other metalloid or metallic particles, and to accommodate the expansion of such particles during lithiation in the LIB. Alternatively, the pores of the porous core may be filled with sulfides, hydrides, any suitable polymer, or other additives, in which case it is beneficial to bring the additives into contact with the conductive material to obtain a more effective electrode.

[0054] Aerogels are solid materials containing a highly porous network of micro- and meso-sized pores. Depending on the precursor material used and the processing performed, when the density of the aerogel is approximately 0.05 g / cc, the pores can occupy more than 90% of the volume. Aerogels can be prepared by removing the solvent from the gel (the solid network containing the solvent) so that the shrinkage of the gel can be minimized or eliminated entirely by capillary forces on its surface. Methods of solvent removal include, but are not limited to, supercritical drying (or drying with a supercritical fluid so that the low surface tension of the supercritical fluid exchanges with the transient solvent in the gel), solvent exchange with a supercritical fluid, solvent exchange with a fluid that will later be converted to a supercritical state, subcritical or near-critical drying, and sublimation of the frozen solvent in a freeze-drying process.

[0055] When drying under ambient conditions, gel shrinkage may occur with solvent evaporation, potentially leading to the formation of an ambidel. Therefore, aerogel preparation by a sol-gel process or other polymerization method can proceed in the following series of steps: dissolution of solute in solvent, formation of a sol / solution / mixture, formation of a gel (which may include further crosslinking), and removal of the solvent by supercritical drying techniques or any other method of removing the solvent from the gel with controlled pore collapse.

[0056] Aerogels can be formed from inorganic and / or organic materials. When formed from organic materials (e.g., phenols, resorcinol formaldehyde (RF), phloroglucin flufuraldehyde (PF), polyacrylonitrile (PAN), polyimide (PI), polyurethane (PU), polybutadiene, polydicyclopentadiene, and their precursors or polymer derivatives), the aerogel may be carbonized (e.g., by thermal decomposition) to form a carbon aerogel.

[0057] Within the context of this disclosure, the terms “aerogel,” “aerogel material,” or “aerogel matrix” refer to a gel comprising a framework of interconnected structures, having a corresponding network of interconnected pores integrated within the framework, and containing a gas such as air as a dispersed gap medium, which exhibits the following physical and structural properties (as determined by nitrogen porosimetry testing) due to aerogel: (a) average pore diameter in the range of approximately 2 nm to approximately 100 nm, (b) porosity of at least 80%, and (c) surface area of ​​approximately 100 m². 2 Characterized by being greater than or equal to / g.

[0058] Therefore, the aerogel materials of this disclosure used as carbon-based cores include any aerogel or other open-cell material that satisfies the defining elements set forth in the previous paragraph, and otherwise include materials that can be classified as xerogels, cryogels, ambigels, microporous materials, etc.

[0059] Aerogel materials may be further characterized by further physical properties including (d) a pore volume of about 2.0 mL / g or more, particularly about 3.0 mL / g or more, (e) a density of about 0.50 g / cc or less, particularly about 0.3 g / cc or less, and more particularly about 0.25 g / cc or less, and (f) at least 50% of the total pore volume comprises pores having a pore diameter of 2 to 50 nm (however, as will be described in more detail below, embodiments disclosed herein include aerogel frameworks and compositions comprising pores having a pore diameter greater than 50 nm). However, satisfying these further properties is not necessary to characterize a compound as an aerogel material.

[0060] To further extend to exemplary applications within LIBs, when carbon aerogel material is used as the primary electrode material (e.g., the anode material as in the examples of this disclosure), the aerogel porous core has a narrow pore size distribution, as well as high conductivity, high mechanical strength, and morphology and sufficient pore volume (at final density) corresponding to the high weight percentage and expansion of silicon particles.

[0061] In some cases, the surface of the carbon aerogel may be modified by chemical, physical, or mechanical means to improve its performance by allowing electrochemically active species to be contained within the pores of the carbon aerogel.

[0062] While this disclosure describes several embodiments utilizing a carbon aerogel core, it should be understood that other carbon-based materials can be used instead. For example, other open-cell materials such as xerogels, cryogels, ambigels, and microporous materials can be used instead of aerogels or in conjunction with aerogels.

[0063] Carbon aerogel itself can function as a current collector due to its conductivity and mechanical strength, thus eliminating the need for a separate current collector on the cathode or anode side (when the cathode or anode is formed from carbon aerogel, respectively). In most LIBs, aluminum foil or copper foil needs to be bonded to the cathode or anode as its current collector, respectively. However, removing one or both of these components, depending on the application of the carbon aerogel, leads to more space for more electrode material, resulting in a larger capacity for the cell / individual electrodes and a greater overall energy density for the packaged battery system. However, in some examples, the existing current collector may be integrated with various other cathode and anode materials to increase the current collecting ability or capacity of the aluminum foil and copper foil.

[0064] In some examples, carbon-based cores, specifically carbon aerogels, can be used as a conductive network or current collector on the anode side of an energy storage device. Electrochemically active species are packed into a fully interconnected carbon aerogel network. The electrochemically active species are either in direct contact with or physically connected to the carbon network. The load of electrochemically active species is adjusted for pore volume and porosity for high and stable capacity and improved safety of the energy storage device. When used on the anode side, the electrochemically active species may include, for example, silicon, graphite, lithium, or other metalloids or metals. The anode can include a carbon-based core, and specifically carbon aerogel.

[0065] Within the context of this disclosure, the term “collectorless” refers to the absence of a separate current collector directly connected to the electrode. As stated, in conventional LIBs, copper foil is coupled to the anode as its current collector. In the examples of this disclosure, electrodes formed from a carbon-based core (e.g., carbon aerogel) can be self-supporting or, if not, have the ability to be collectorless, because the scaffold or structure itself functions as a current collector due to its high conductivity. Within an electrochemical cell, collectorless electrodes can be connected to form circuits by embedding solids, meshes, or woven tabs during the solution step of creating continuous porous carbon, or by soldering, welding, or depositing leads onto a portion of the porous carbon surface. Other mechanisms for bringing carbon into contact with the rest of the system are also conceivable herein. In some examples, a carbon-based scaffold or structure, specifically carbon aerogel, may be placed on a dedicated current-collecting substrate (e.g., copper foil, aluminum foil, etc.) or otherwise in contact with it. In this scenario, carbon aerogel can be attached to a solid current collector using a conductive adhesive and applied at various pressure levels.

[0066] Furthermore, it is conceivable herein that carbon-based cores, specifically carbon aerogels, can take the form of a monolithic structure. When essentially monolithic, carbon aerogels eliminate the need for any binders. In other words, the anode can be binder-less. As used herein, the term “monolithic” refers to an aerogel material or composition in which the majority (by weight) of the aerogel is in the form of a single continuous interconnected aerogel nanostructure. Monolithic aerogel materials include those that, as aerogel materials, initially form a single interconnected gel or aerogel nanostructure but may subsequently be cracked, fractured, or segmented to become non-single aerogel nanostructures. Monolithic aerogels can take the form of self-supporting or reinforced (fiber or foam) materials. In comparison, using silicon lithification as an example, silicon incorporated into a monolithic aerogel can be utilized more effectively relative to its theoretical capacity than the same amount of silicon incorporated into a slurry using conventional processes.

[0067] Monolithic aerogel materials are distinguished from particulate aerogel materials. The term “particulate aerogel materials” refers to aerogel materials in which the majority (by weight) of the aerogel contained therein is in the form of fine particles, particles, granules, beads, or powder. These can be combined together (i.e., via a binder such as a polymer binder) or compressed together, but lack the interconnected aerogel nanostructures between individual particles. Collectively, this form of aerogel material is said to have the form of a powder or particles (as opposed to the monolithic form). Note that despite the individual particles of a powder having a single structure, the individual particles are not considered monoliths in this specification. Integrating aerogel powder into an electrochemical cell typically involves the preparation of a paste or slurry from the powder, casting and drying onto a substrate, and optionally, calendering.

[0068] Particulate aerogel materials, such as aerogel beads, offer specific advantages. For example, particulate materials can be used as a direct replacement for other materials, such as graphite, in LIB anodes and anode manufacturing processes. Particulate materials can also result in improved lithium ion diffusion rates due to shorter diffusion pathways within the particulate material. Particulate materials can also enable electrodes with increased packing density, for example, by adjusting particle size and packing arrangement. Particulate materials can also improve access to silicon due to interparticle and intraparticle porosity.

[0069] Carbon-based cores, such as carbon aerogels, according to this disclosure can be formed from any suitable organic precursor material. Examples of such materials, without limitation, include RF, PF, PI, polyamides, polyacrylates, polymethyl methacrylates, acrylate oligomers, polyoxyalkylenes, polyurethanes, polyphenols, polybutadienes, trialkylsilyl-terminated polydimethylsiloxanes, polystyrene, polyacrylonitriles, polyfurfural, melamine-formaldehyde, cresol-formaldehyde, phenol-furfural, polyethers, polyols, polyisocyanates, polyhydroxybenzenes, polyvinyl alcohol dialdehydes, polycyanurates, polyacrylamides, various epoxies, agaroses, chitosans, and combinations and derivatives thereof. Any precursor of these materials may be used to form and use the resulting material. In some examples, carbon aerogels are pyrolysis / carbonized polyimide aerogels, i.e., formed from the polymerization of polyimides. More specifically, polyimide aerogels can be produced using one or more methodologies described in U.S. Patents No. 7,071,287 and 7,074,880 (Rhine et al.), for example, by imidizing a poly(amidic) acid and drying the resulting gel using a supercritical fluid.Other suitable methods for producing polyimide aerogels (and carbon aerogels derived therefrom) are also considered herein, for example, U.S. Patent No. 6,399,669 (Suzuki et al.); U.S. Patent No. 9,745,198 (Leventiset al.); Leventis et al., Polyimide Aerogels by Ring-Opening Metathesis Polymerization (ROMP), Chem. Mater. 2011, 23, 8, 2250-2261; Leventiset al., Isocyanate-Derived Organic Aerogels: Polyureas, Polyimides, Polyamides, MRS Proceedings, 1306 (2011), Mrsf10-1306-bb03-01.doi:10.1557 / opl.2011.90; Chidambareswarapattar et al., One-step room-temperature synthesis of fibrous polyimide aerogels from anhydrides and isocyanates and conversion to isomorphic carbons, J. Mater.Chem.,2010,20,9666-9678;Guo et al.,Polyimide Aerogels Cross-Linked through Amine Functionalized Polyoligomeric Silsesquioxane,ACS Appl.Mater.Interfaces 2011,3,546-552;Nguyen et al.,Development of High Temperature,Flexible Polyimide Aerogels,American Chemical Society,proceedings published 2011;Meador et al.,Mechanically Strong,Flexible Polyimide Aerogels Cross-Linked with Aromatic Triamine,ACS Appl.Mater.Interfaces,2012,4(2),pp 536-544;Meador et al.,Polyimide Aerogels with Amide Cross-Links:A Low Cost Alternative for Mechanically Strong Polymer Aerogels,ACS Appl.Mater.Interfaces This is described in the literature 2015, 7, 1240-1249; Pei et al., Preparation and Characterization of Highly Cross-Linked Polyimide Aerogels Based on Polyimide Containing Trimethoxysilane Side Groups, Langmuir 2014, 30, 13375-13383. The resulting polyimide aerogel is then thermally decomposed to form a polyimide-derived carbon aerogel.

[0070] The carbon aerogels of this disclosure, for example, carbon aerogels derived from polyimide, can have a residual nitrogen content of at least about 4 wt%. For example, the carbon aerogels can have a residual nitrogen content of at least about 0.1 wt%, at least about 0.5 wt%, at least about 1 wt%, at least about 2 wt%, at least about 3 wt%, at least about 4 wt%, at least about 5 wt%, at least about 6 wt%, at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt%, or in the range between any two of these values.

[0071] In the examples of this disclosure, a dry polymer aerogel composition can be subjected to a treatment temperature of 200°C or higher, 400°C or higher, 600°C or higher, 800°C or higher, 1000°C or higher, 1200°C or higher, 1400°C or higher, 1600°C or higher, 1800°C or higher, 2000°C or higher, 2200°C or higher, 2400°C or higher, 2600°C or higher, 2800°C or higher, or in a range between any two of these values, for carbonization of an organic (e.g., polyimide) aerogel. In a typical embodiment, a dry polymer aerogel composition can be subjected to a treatment temperature in the range of about 1000°C to about 1100°C, for example, at about 1050°C. Although not bound by theory, it is considered herein that the conductivity of the aerogel composition increases with carbonization temperature.

[0072] Within the context of this disclosure, the term “conductivity” refers to a measure of a material’s ability to conduct electric current or enable the flow of electrons. Conductivity is specifically measured as the electrical conductivity / susceptance / admittance of a material per unit size. It is typically recorded as S / m (siemens per meter) or S / cm (siemens per centimeter). The conductivity or resistivity of a material may be determined by methods known in the art, including, for example, in-line four-point resistivity (using the dual-configuration test method of ASTM F84-99), without limitation. Within the context of this disclosure, unless otherwise specified, the conductivity measurement is obtained according to the ASTM F84 resistivity (R) measurement, which is obtained by measuring voltage (V) divided by current (I). Aerogel materials, such as the carbon aerogel or composition of the present disclosure, can have a conductivity of about 1 S / cm or more, about 5 S / cm or more, about 10 S / cm or more, 20 S / cm or more, 30 S / cm or more, 40 S / cm or more, 50 S / cm or more, 60 S / cm or more, 70 S / cm or more, 80 S / cm or more, or in the range between any two of these values.

[0073] Within the context of this disclosure, the term “electrochemically active species” refers to an additive that can be used in small amounts, for example, as a dopant, and which can accept and release ions within an energy storage device. Using a LIB as an example, an electrochemically active species in the anode accepts lithium ions during charging and releases lithium ions during discharge. The electrochemically active species can be stabilized in the anode by having direct / physical connections with a porous carbon core. The porous carbon network can form an interconnected structure around the electrochemically active species. The electrochemically active species is connected to the porous carbon at multiple points. An example of an electrochemically active species is silicon, which can expand and crack or fracture upon lithiation. However, because silicon has multiple connection points with porous carbon (aerogel), silicon can remain active by being retained within the porous structure (e.g., pores), or, in other cases, by being enveloped by the structure even upon fracture or cracking.

[0074] Electrochemically active species can be called electrically active additives and can be used to promote penetration and plating. For example, silicon doping can be used as a material for a Li metal anode to promote Li penetration and initiate lithium plating. In addition to silicon, other electrically active additives include gold, silver, zinc, magnesium, platinum, aluminum, tin, copper, nickel, and other dopants described herein. In some examples, electrochemically active materials can be used in small amounts as dopants to seed lithium plating within the porosity of carbon nanostructures.

[0075] Within the context of this disclosure, the terms “compressive strength,” “flexural strength,” and “tensile strength” refer to the resistance of a material to fracture or breakage under compressive, bending, or flexural forces, and tensile or tensile forces, respectively. These strengths are specifically measured as the amount of load / force per unit area resisting the load / force. This can be recorded as pounds per square inch (psi), megapascals (MPa), or gigapascals (GPa). Among other factors, the compressive, flexural, and tensile strengths of a material collectively contribute to the structural integrity of the material, which is useful, for example, to withstand the volume expansion of silicon particles during lithiation in a LIB. The modulus of elasticity may be determined by methods known in the art, with specific reference to Young's modulus, an indicator of mechanical strength, for example, without limitation, standard test practices for instrumented indentation testing (ASTM E2546, ASTM International, West Conshocken, PA); or standardized nanoindentation (ISO 14577, International Organization for Standardization, Switzerland). Within the context of this disclosure, Young's modulus measurements are obtained in accordance with ASTM E2546 and ISO 14577 unless otherwise specified. In specific examples, aerogel materials, such as the carbon aerogels or compositions of this disclosure, have a Young's modulus of about 0.2 GPa or greater, 0.4 GPa or greater, 0.6 GPa or greater, 1 GPa or greater, 2 GPa or greater, 4 GPa or greater, 6 GPa or greater, 8 GPa or greater, or in the range of any two of these values.

[0076] Within the context of this disclosure, the term “pore size distribution” refers to the statistical distribution or relative quantity of each pore size within a sample volume of a porous material. A narrower pore size distribution refers to a relatively large proportion of pores within a narrow range of pore sizes, thus increasing the amount of pores that can enclose electrochemically active species and maximizing the use of pore volume. Conversely, a wider pore size distribution refers to a relatively small proportion of pores within a narrow range of pore sizes. Thus, the pore size distribution can be measured as a function of pore volume and recorded as the unit size of the full width at half maximum of the main peak in a pore size distribution chart. The pore size distribution of a porous material may also be determined by methods known in the art, such as, without limitation, nitrogen adsorption / desorption surface area and porosity analyzers capable of calculating the pore size distribution. Within the context of this disclosure, measurements of the pore size distribution are obtained according to these methods unless otherwise specified. In some examples, aerogel materials, such as the carbon aerogel or composition of this disclosure, have a relatively narrow pore size distribution (full width at half maximum) in the range of about 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, 30 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, 5 nm or less, or between any two of these values.

[0077] Within the context of this disclosure, the term “pore volume” refers to the total volume of pores in a sample of porous material. Pore volume is specifically measured as the volume of voids within the porous material. These voids may be measurable and / or accessible by other materials, such as electrochemically active species, including silicon particles. It is measured in cubic centimeters / gram (cm³). 3It can be recorded as ( / g or cc / g). The pore volume of porous materials may be determined by methods known in the art, such as, for example, nitrogen adsorption / desorption surface area and porosity analyzers that can calculate pore volume. Within the context of this disclosure, pore volume measurements are obtained according to this method unless otherwise specified. In certain examples, the aerogel materials or compositions of this disclosure (without incorporating electrochemically active species, e.g., silicon particles) have relatively large pore volumes in the range of about 0.5 cc / g or more, 1 cc / g or more, 1.5 cc / g or more, 2 cc / g or more, 2.5 cc / g or more, 3 cc / g or more, 3.5 cc / g or more, 4 cc / g or more, or any two of these values. In other examples, aerogel materials, such as the carbon aerogel or composition of the present disclosure (incorporating electrochemically active species, such as silicon particles), have pore volumes of approximately 0.10 cc / g or more, 0.3 cc / g or more, 0.6 cc / g or more, 0.9 cc / g or more, 1.2 cc / g or more, 1.5 cc / g or more, 1.8 cc / g or more, 2.1 cc / g or more, 2.4 cc / g or more, 2.7 cc / g or more, 3.0 cc / g or more, 3.3 cc / g or more, 3.6 cc / g or more, or in the range between any two of these values.

[0078] Within the context of this disclosure, the term “porosity” refers to the volume ratio of pores that do not contain other materials bonded to the pore walls (e.g., electrochemically active species such as silicon particles). For clarification and explanatory purposes, it should be noted that within a specific implementation of silicon-doped carbon aerogel as the primary anode material in a LIB, porosity refers to the voids after the inclusion of silicon particles. Porosity may also be determined by methods known in the art, including, for example, the ratio of the pore volume of an aerogel material to its bulk density, without limitation. Within the context of this disclosure, porosity measurements are obtained according to this method unless otherwise specified. In specific examples, aerogel materials, e.g., carbon aerogels or compositions of this disclosure, have porosity in the range of about 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or any two of these values.

[0079] It should be noted that pore volume and porosity are different measures of the same property of the pore structure, namely the "empty space" within the pore structure. For example, when silicon is used as an electrochemically active species surrounded within the pores of a nanoporous carbon material, pore volume and porosity refer to the "empty" space, i.e., the space not utilized by the carbon or electrochemically active species. As is understood, densification (e.g., by compression) of pre-carbonized porous materials can affect pore volume and porosity, among other properties.

[0080] Within the context of this disclosure, the term “pore size at the maximum peak from the distribution” refers to the value at a recognizable peak on a graph illustrating a pore size distribution. The pore size at the maximum peak from the distribution is specifically measured as the pore size in which the largest proportion of pores are formed. It can be recorded as any unit length of pore size, e.g., μm or nm. The pore size at the maximum peak from the distribution may also be determined by methods known in the art, including, but not limited to, nitrogen adsorption / desorption surface area and porosity analyzers that can calculate the pore size distribution and determine the pore size at the maximum peak. Within the context of this disclosure, measurements of the pore size at the maximum peak from the distribution are obtained according to these methods unless otherwise specified. Aerogel materials, such as the carbon aerogel or composition of the present disclosure, can have a pore size at the maximum peak from the distribution of about 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 5 nm or less, 2 nm or less, or in the range between any two of these values.

[0081] Within the context of this disclosure, the term “capacity” refers to a specific amount of energy or charge that a battery can store. In some examples, capacity refers to reversible capacity. Capacity is specifically measured as the discharge current that a battery can deliver per unit mass over time. It can be recorded as ampere-hours or milliampere-hours per gram, Ah / g or mAh / g, of the total electrode mass. The capacity of a battery (particularly the anode) may also be determined by methods known in the art, including, for example, without limitation: applying a constant current load to a fully charged cell until the cell voltage reaches the end of the discharge voltage value; the discharge capacity is the constant current multiplied by the time to reach the end of the discharge voltage; specific capacity and volumetric capacity can be determined by dividing the discharge capacity by the weight of the electrode material or volume. Within the context of this disclosure, capacity measurements are obtained by this method unless otherwise specified. Aerogel materials, for example, the carbon aerogel or composition of this disclosure, have an anode capacity of approximately 100 mAh / g or more, 150 mAh / g or more, 200 mAh / g or more, 300 mAh / g or more, 400 mAh / g or more, 500 mAh / g or more, 600 mAh / g or more, 700 mAh / g or more, 800 mAh / g or more, 900 mAh / g or more, 1000 mAh / g or more, 1100 mAh / g or more, and 1200 mAh / g. It can be h / g or higher, 1300mAh / g or higher, 1400mAh / g or higher, 1500mAh / g or higher, 1600mAh / g or higher, 1700mAh / g or higher, 1800mAh / g or higher, 1900mAh / g or higher, 2000mAh / g or higher, 2500mAh / g or higher, 3000mAh / g or higher, or a range between any two of these values, or any intervening value (e.g., 520mAh / g).

[0082] It is assumed herein that pore size can be adjusted as needed. There are five main methods for adjusting pore size as taught herein. Firstly, the amount of solids, specifically the amount of polyimide precursor monomers (e.g., aromatic or aliphatic diamines and aromatic or aliphatic dianhydrides), can adjust pore size. Smaller pore sizes result from a larger amount of solids per unit volume of fluid, as there is less available space for tighter interconnections to occur. It should be noted that strut width does not change to a measurable extent regardless of the amount of solids used. The amount of solids is more related to how dense the network becomes.

[0083] Pore ​​size adjustment can be achieved by using radiation (e.g., radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays, gamma rays) on composite materials that are either in a polyimide state or a carbon state. Radiation has an oxidizing effect, which results in an increase in surface area, an increase in pore size, and a broadening of the pore size distribution. Thirdly, pore size is affected by macroscopic compression of the polyimide composite material. In some cases, pore size decreases with compression.

[0084] Pore ​​size adjustment can be achieved by ionic bombardment of composite materials in either a polyimide or carbon state. The effect of ionic bombardment depends on the specified method. For example, there is addition ionic bombardment (e.g., CVD), which involves the addition of something and results in a decrease in pore size. There is also destructive ionic bombardment, which increases pore size. Finally, pore size can be adjusted (increased or decreased) by heat treatment under different gas environments, such as the presence of carbon dioxide or carbon monoxide, a chemically active environment, or a hydrogen reduction environment. For example, a carbon dioxide environment is known to produce activated carbon, which, in the case of activation, removes mass, increasing pore size and surface area.

[0085] Lithium can be used with carbon aerogels in various ways, such as pre-depositing by ex situ lithium plating or melt injection before cell assembly. For pre-deposited lithium within carbon aerogels, examples include carbon aerogels pre-treated to promote Li penetration, and carbon aerogels pre-doped with Si (a known additive to promote Li penetration). For carbon aerogels lithified (or plated) in situ during formation, examples include providing sufficient Li available in the electrolyte and cathode, and plating the carbon aerogel such that, during initial charging, less than 50% of the Li is lost due to SEI formation.

[0086] Lithium in carbon aerogel can take several forms. For example, self-supporting carbon aerogel monoliths, carbon aerogel on copper current collectors, carbon aerogel on lithium metal, and carbon aerogel beads. Carbon aerogel has high conductivity and can function as a current collector. Beads can be used in standard battery manufacturing slurry / casting methods. Beads of specific dimensions and particle size distributions can be manufactured, and large amounts of Li metal can be impregnated onto individual beads and post-cast beads as electrodes.

[0087] In the case of carbon aerogels, lithium penetration can be achieved via melt injection and electrodeposition. A narrow and controllable particle size distribution helps to result in uniform lithium deposition during charging, which can help reduce or prevent the formation of dendritic crystals. In one embodiment, when a carbon aerogel is present between the lithium metal and the separator, during battery operation, the carbon aerogel is reduced during charging, and Li ions (from the Li metal underlayer and electrolyte) are deposited on the surface of the carbon aerogel. Then, during discharge, the accumulated Li ions in the carbon aerogel are released, and the Li metal underlayer can continue to replenish Li ions as needed, but dendritic crystals cannot propagate. Carbon aerogel moderator / barrier layers are prepared with desired surface area, pore size, and pore size distribution to achieve high capacity, long cycle life, excellent power characteristics, and improved safety.

[0088] Within the context of this disclosure, the terms “char content” and “char yield” refer to the amount of carbonized organic material present in an organic aerogel after exposure to high-temperature pyrolysis. The char content of an aerogel can be expressed as the ratio of the amount of organic material present in the aerogel framework after high-temperature pyrolysis to the total amount of material in the original aerogel framework before high-temperature pyrolysis. This ratio can be measured using thermogravimetric analysis, such as TG-DSC analysis. Specifically, the char yield in an organic aerogel can be correlated with the percentage of weight retained by the organic aerogel material when subjected to high carbonization temperatures during TG-DSC analysis (with weight losses resulting from water evaporation, organic gas release, and other material lost from the aerogel framework during high-temperature pyrolysis). For the purposes of this disclosure, the char yield correlates with carbonization exposure temperatures up to 1000°C. Preferably, the aerogel material of the present disclosure, which can function as a precursor of a carbon-based aerogel, can have a char yield of about 50% or more, about 55% or more, about 60% or more, about 65% or more, or about 70% or more.

[0089] Coating materials The coating materials disclosed herein are used to coat the porous outer surface of the carbon-based cores disclosed herein.

[0090] While not limited to theory, the coatings disclosed herein may act as a barrier preventing the electrolyte of a battery cell (e.g., a lithium-ion battery cell) from penetrating a carbon-based core that can be used as an electrode component, thereby suppressing or mitigating swelling of the carbon-based core during the charge-discharge process. Such coatings may also help improve the abrasion resistance, chemical resistance, and morphogenesis of the carbon-based core (e.g., porous carbon-based materials such as aerogel, ambigel, xerogel, cryogel, etc.).

[0091] The coating may be conductive or non-conductive.

[0092] In some examples, the coating may filter the passage of other atoms and / or molecules based on their size. In some examples, the coating is tailored to support size selectivity in ionic and molecular diffusion. For example, the coating may allow lithium ions to diffuse freely, while larger cations such as cathode metals and molecules such as electrolyte species are blocked. In some examples, the coatings disclosed herein can function as a diffusion barrier for metal ions, e.g., Li ions. Lithium ions have a migration barrier of about 0.7 eV or less through the coating. As used herein, the term “diffusion barrier” refers to the potential that Li ions must overcome when moving under the action of a concentration gradient.

[0093] The coating may contain materials selected from organic molecules, polymers, metals, transition metals, nonmetals, metal-organic frameworks (MOFs), or combinations thereof. Alternatively, the coating may be formed from precursors(s) of organic molecules, polymers, metals, transition metals, nonmetals, metal-organic frameworks (MOFs), or combinations thereof. In some examples, the polymer is selected from the group consisting of polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyimide, polyamide, or derivatives thereof. In some examples, the organic molecules, polymers, or combinations thereof are carbonized at temperatures >1000°C, 800°C, 700°C, or 650°C. In some examples, the organic molecules, polymers, or combinations thereof are cyclized at temperatures >400°C, 300°C, or 250°C.

[0094] In general, suitable polymers for coating the outer surface of carbon-based cores include most hydrocarbon-based organic polymers, including thermoplastics and thermosetting materials. Such polymers include, without limitation, polyimide, polyamide, polyarylamide, polybenzimidazole, polybutylene, polyurethane, cellulose acetate, cellulose nitrate, ethylcellulose, ethylene vinyl alcohol, polyperfluoroalkoxyethylene, fluorocarbon, polyketone, polyetherketone, liquid crystal polymer, nylon, polyether, polyetherimide, polyethersulfone, natural rubber, synthetic rubber, acrylic (emulsion or solution), nitrile, ethylene propylene, ethylene propylene diene methylene, polyethylene, chlorosulfonated polyethylene, neoprene, Hypalon, ethylene acrylic, Viton, acrylonitrile-butadiene acrylate, acrylonitrile-butadiene styrene terpolymer, acrylonitrile-chlorinated polyethylene styrene terpolymer, acrylate maleic anhydride terpolymer, acrylonitrile-methyl methacrylate, acrylonitrile styrene copolymer, acrylonitrile styrene acrylate, bismaleimide, cellulose acetate Cellulose acetate butyrate, cellulose acetate propionate, cellulose nitrate, cycloolefin copolymer, chlorinated polyethylene, chlorinated polyvinyl chloride, cellulose triacetate, chlorotrifluoroethylene, diallyl phthalate, ethylene acrylic acid copolymer, ethylcellulose, ethylene chlorotrifluoroethylene, ethylene-methyl acrylate copolymer, ethylene n-butyl acetate, epoxy, ethylene propylene diene monomer rubber, ethylene propylene copolymer rubber, ethylene propylene rubber, foamed polystyrene, ethylene tetrafluoroethylene, ethylene vinyl acetate, ethylene / vinyl acetate copolymer, ethylene vinyl alcohol, fluorinated ethylene propylene, high-density polyethylene, high-impact polystyrene, high molecular weight high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear polyethylene, maleic anhydride, methyl methacrylate / ABS copolymer, methyl methacrylate butadiene styrene terpolymer, medium-density polyethylene, melamine formaldehyde,Melamine phenols, nitrile butadiene rubber, olefin-modified styrene acrylonitrile, phenolic polymers, polyacetic acid, polyamide-imide, polyaryl ether ketone, polyester alkyd, polyaniline, polyacrylonitrile, polyarylamide, polyaryl sulfone, polybutylene, polybutadiene acrylonitrile, polybutazine, polybenzimidazole, polybutylene naphthalate, polybutadiene styrene, polybutylene terephthalate, polycarbonate, polycarbonate / acrylonitrile butadiene styrene blend, polycaprolactone, polycyclohexylene terephthalate, glycol-modified polycyclohexyl terephthalate, polymonochlorotrifluoroethylene, polyethylene, polyether block amide or polyester block amide, polyether ether ketone, polyetherimide, polyether ketone, polyether ketone, polyethylene naphthalene, polyethylene oxide, polyethersulfone, polyethylene terephthalate, glycol-modified polyethylene terephthalate Perfluoroalkoxy, polyimide, polyisoprene, polyisobutylene, polyisocyanurate, polymethacronitrile, polymethyl methacrylate, polymethylpentene, paramethylstyrene, polyoxymethylene, polypropylene, polyphthalamide, chlorinated polypropylene, polyphthalate carbonate, polyphenylene ether, polymer polyisocyanate, polyphenylene oxide, polypropylene oxide, polyphenylene sulfide, polyphenylene sulfone, polypropylene terephthalate, polystyrene, polystyrene / Polyisoprene block copolymer, polysulfone, polytetrafluoroethylene, polytetramethylene terephthalate, polyurethane, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyryl, polyvinyl chloride, polyvinyl chloride acetate, polyvinylidene acetate, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl fluoride, polyvinylcarbazole, polyvinyl alcohol, polyvinylpyrrolidone, styrene acrylonitrile, styrene butadiene, styrene butadiene rubber, styrene butadiene styrene block copolymer,The following materials may be selected: styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-maleic anhydride copolymer, styrene-methyl methacrylate, styrene / α-methylstyrene, styrene-vinyl acrylonitrile, urea-formaldehyde, ultra-high molecular weight polyethylene, ultra-low density polyethylene, unsaturated polyester, vinyl acetate, vinyl acetate ethylene, ultra-low density polyethylene, foamed polystyrene, their derivatives, and their copolymers.

[0095] In preferred examples, the coating may include one or more of the following: polyethylene, Kapton, polyurethane, polyester, natural rubber, synthetic rubber, Hypalon, plastic alloy, PTFE, polyvinyl halide, polyester, neoprene, acrylic, nightlight, EPDM, EP, Viton, vinyl, vinyl acetate, ethylene vinyl acetate, styrene, styrene acrylate, styrene-butadiene, polyvinyl alcohol, polyvinyl chloride, acrylamide, phenol, or a combination thereof.

[0096] In some examples, the coating contains soft carbon. In one example, the coating is a pitch-derived carbon coating. In another example, the pitch-derived carbon coating contains soft carbon.

[0097] According to some examples of this disclosure, the coatings include pitch-derived carbon. In some examples, the pitch-derived carbon includes soft carbon. As used herein, the term “soft carbon” refers to amorphous carbon formed by the carbidization of pitch. Soft carbon represents graphitizable non-graphitic carbon with higher electronic conductivity, the degree of graphitization and interlayer distance of which can be adjusted by heat treatment.

[0098] In some examples, the coating is selected from soft carbon derived from pitch, carbon black, and spherical carbon derived from mesitylene.

[0099] While not theoretically bound, the pitch-derived carbon coatings of this disclosure significantly inhibit the formation of defects and oxygen-containing groups. The pitch-derived carbon coatings of this disclosure (e.g., soft carbon) can withstand the severe volume expansion that occurs during Si lithiation due to their high mechanical strength resulting from long-range graphite ordering (e.g., crystallinity). A typical pitch-derived carbon coating of this disclosure includes ordered graphite regions with controllable crystallinity. While not theoretically bound, the controllable crystallinity of the pitch-derived carbon coating improves electrochemical performance by providing excellent electron transfer properties and structural elasticity. Graphite ordering of the pitch-derived carbon coating can be controlled by increasing the heat treatment temperature in the range of 500–1400°C. Stepwise carbonization can be performed to gradually adjust the crystallinity.

[0100] In the examples of the present disclosure, substantially any method for coating according to the conventions of the art may be used. Examples of preferred coating techniques include, but are not limited to, sol-gel coating, e.g., solidification processes, knife-over-roll coating, immersion or saturated coating, reverse-roll (all forms) coating, direct-roll coating, gravure coating, printed rotary screen coating, curtain coating, die coating or extrusion, spray coating, transfer coating, electrostatic coating, brush coating, vapor deposition, flocking, hot knife or hot-melt extrusion, and combinations thereof.

[0101] In the examples of this disclosure, the coating can be applied to the surface of a carbon material (e.g., carbon aerogel beads) or to the surface of a carbon precursor material (e.g., aerogel, xerogel, cryogel, or ambigel material, e.g., polyimide beads).

[0102] In certain examples, typical coatings of the present technology (e.g., polymer coatings, pitch coatings, soft carbon coatings, pitch-derived carbon coatings) can be applied to the surface of an aerogel material (e.g., a precursor of a carbon aerogel material before a heat treatment step, e.g., a carbonization step). In one example, the application of such a coating can be achieved by spraying a molten coating material, a coating material in solution, a coating material in suspension, or a combination thereof through a nozzle or similar apparatus. U.S. Patents 5,180,104, 5,102,484, 5,683,037, 5,478,014, 5,687,906, 6,488,773, and 6,440,218 teach spray nozzles, spray guns, and other apparatus that can be used in this embodiment, all of which are incorporated herein by reference. In yet another example, the coating is applied via a dip coating method.

[0103] In another example, a typical coating is applied via the sol-gel method. The coating material, dissolved or dispersed in a solution, solidifies on the surface of the aerogel material (e.g., aerogel beads) by a solidifying solvent or solidifying agent. In some examples, the solidifying solvent includes DMF, DMAC, DMSO, methanol, ethanol, isopropyl alcohol, water, or mixtures thereof. In another example, the solidifying solvent includes an aqueous electrolyte solution. A typical bead coating process suitable for application to the surface of the aerogel material (e.g., aerogel beads) of this disclosure is shown in Figure 1.

[0104] In one example, a typical coating material and a typical aerogel material (e.g., aerogel beads) of the present disclosure are dispersed in a dispersion medium (e.g., silicone oil) to prepare an emulsion (e.g., a slurry), and then the emulsion is brought into contact with a solidifying solvent. Although not bound by theory, when the emulsion is brought into contact with the solidifying solvent, the coating material solidifies or hardens almost instantaneously around the aerogel material, thereby forming a solid coating layer on the surface of the aerogel material. That is, the addition of the solidifying solvent leads to the formation of a coated aerogel material. In one example, the time required to add the solidifying solvent to the emulsion (e.g., a slurry of the coating material and aerogel material in a dispersion medium) is at least 150 seconds, at least 600 seconds, at least 20 minutes, at least 30 minutes, at least 60 minutes, at least 2 hours, at least 3 hours, at least 6 hours, at least 12 hours, at least 24 hours, or at least 48 hours.

[0105] In several examples, the coagulation solvent is miscible with the solvent (e.g., dispersion medium) used to prepare the coating aerogel material solution or slurry.

[0106] In certain cases, typical coated aerogel materials of this technology (e.g., polymer coatings, pitch coatings, carbon-coated aerogel beads) undergo at least one further heat treatment step (e.g., a softening process, a carbonization step).

[0107] As described above, the surface of a typical aerogel material of this technology can be coated using any method for coating that is conventionally known in the art (e.g., spray coating, solidification process). The coating of this technology can also be directly bonded to the surface of a carbon-based core (e.g., carbon aerogel material). That is, no intermediate layer is deposited or formed between the core and the coating. In several examples, the carbon aerogel material is obtained by treating the aerogel material (e.g., carbonizing) before applying or supplying the coating material. As a result, the carbonization step is not required after the application of the coating material.

[0108] In certain examples, exemplary coatings (e.g., polymer coatings, pitch coatings, soft carbon coatings, pitch-derived carbon coatings) can be applied to the surface of a carbon aerogel material. That is, any carbonization step for the aerogel was performed before applying the exemplary coating. In one example, the application of such a coating can be achieved by spraying molten coating material, coating material in solution, coating material in suspension, or a combination thereof through a nozzle or similar apparatus. Spray nozzles, spray guns, and other apparatus that can be used in this embodiment are taught in U.S. Patents 5,180,104, 5,102,484, 5,683,037, 5,478,014, 5,687,906, 6,488,773, and 6,440,218, all of which are incorporated herein by reference. In yet another example, the coating is applied via a dip coating method.

[0109] In another example, the coating is applied via the sol-gel method. The coating material, dissolved or dispersed in a solution, solidifies on the surface of the carbon aerogel material with a solidifying solvent. In some examples, the solidifying solvent includes DMF, DMAC, DMSO, water, or mixtures thereof. An exemplary bead coating process suitable for application to the carbon-based cores of this disclosure is shown in Figure 1.

[0110] The coating thickness can be varied depending on the end application and the properties of the selected polymer. For example, the coating thickness may be approximately 2,500 nm or less, or approximately 100 nm to 2,000 nm, or approximately 200 nm to 500 nm.

[0111] For specific applications, it is desirable to use a flexible coating so that, once coated, the bending modes of the carbon aerogel or aerogel material (or aerogel composite material) are not significantly hindered. Thus, polymer coatings with elastic behavior or low rigidity are preferred.

[0112] In another example, the surface of a porous carbon-based material (e.g., an aerogel material) is modified before coating. Surface treatment methods include plasma treatment, corona treatment, or other chemical modifications. This procedure may help in the deposition of the desired coating to achieve, for example, better deposition of the coating, a more uniform thickness, or better adhesion to the core.

[0113] Once applied, the coating, along with the composite material, may be subjected to other processing steps such as drying, curing, carbonization, and sintering for reasons such as solvent removal, better adhesion to the core, improved mechanical properties, and many others. One non-limiting mode of carrying out embodiments of the present disclosure includes an electric conveyor together with one or more spray systems and one or more temperature treatment units, preferably ovens, and other mechanical equipment that automates the process in an industrial environment. The carbon core is supplied into the system through a moving conveyor element that carries the core to the spray system. The spray system may consist of one or more spray heads from which the spray characteristics can be individually controlled. Curing / drying is brought to the coating by a heat treatment unit such as an infrared or UV oven. The spray and heat treatment units can be arranged sequentially or in any combination to bring the desired thickness and finish on the coated core. If a solvent is used in the spray process, appropriate equipment such as a hood and VOC reduction device may be used.

[0114] In some examples, the coating includes an electrically insulating material (e.g., a non-conductive material).

[0115] In some examples, the coating includes a conductive material. The conductive material (e.g., carbon) can be formed from a precursor of a non-conductive material (e.g., a polymer). In other examples, the conductive material is formed from a precursor of a first conductive material (e.g., a metal or transition metal).

[0116] The coating of this technology is permeable to metal ions and / or metal atoms. The coating is also impermeable to fluids.

[0117] In some cases, the permeability of a coating depends on its porosity (e.g., pore size, pore volume, or a combination thereof).

[0118] In some designs, the coating may be generally uniform, while in others, it may have a non-uniform composition that gradually changes with radial distance (for example, from the inner surface to the outer surface).

[0119] In some examples, the coating may comprise multiple layers. For example, the multiple layers may include an outer layer formed from an electrically insulating material to prevent electrochemical reduction of the aqueous metal-ion electrolyte on the anode or to prevent electrochemical oxidation of the aqueous metal-ion electrolyte on the cathode. This may be achieved by an insulating outer layer corresponding to a portion of the voltage drop between the anode and cathode, thereby reducing the voltage drop across the aqueous metal-ion electrolyte. In other examples, the multiple layers may include a conductive layer for electrically connecting active material particles, an interfacial layer to improve the uniformity or adhesion of another layer, a mechanically stable layer to improve the mechanical stability of the conformal, metal ion / and / metal atom permeable coating, or an auxiliary protective layer to prevent electrochemical reduction of the aqueous metal-ion electrolyte on the anode or to prevent electrochemical oxidation of the aqueous metal-ion electrolyte on the cathode.

[0120] Lithium-ion battery A basic example of a lithium-ion battery includes a cathode, an anode electrically connected to the cathode, an electrolyte placed between the anode and the cathode, and a separator similarly placed between the anode and the cathode.

[0121] The electrolyte is an ion-conducting material and may contain solvents, ionic liquids, metal salts, ions, such as metal ions or inorganic ions, polymers, ceramics, and other components. The electrolyte may be an organic solid or an inorganic solid or liquid, such as a solvent containing a dissolved salt (for example, a non-aqueous solvent). Examples of non-aqueous electrolytes include organic solvents such as cyclic carbonates, linear carbonates, fluorinated carbonates, benzonitriles, acetonitriles, tetrahydrofurans, 2-methyltetrahydrofurans, γ-butyrolactones, dioxolanes, 4-methyldioxolanes, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyl sulfoxides, dioxanes, 1,2-dimethoxyethanes, sulfolanes, dichloroethanes, chlorobenzenes, nitrobenzenes, diethylene glycols, dimethyl ethers, and mixtures thereof. Examples of salts that can be contained in electrolytes include lithium salts, such as LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, and LiN(C) x F 2x+1 SO2)(C y F 2y-1 Examples include SO2), (χ and y are natural numbers), LiC, LiI, and mixtures thereof. In some examples, the liquid molecule contains an electrolyte solvent (electrolyte). The electrolyte solvent of this disclosure can be selected from any of the preferred electrolytes described above. In particular, the electrolyte can be selected from ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), fluorinated ether (F-EPE), 1,3-dioxolane (DOL), dimethoxyethane (DME), or combinations thereof.

[0122] A separator is typically a thin, porous, or semipermeable insulating film with high ion permeability. Separators can be made of polymers such as olefin polymers (e.g., polyethylene, polypropylene, and / or polyvinylidene fluoride). When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte can also act as a separator.

[0123] The anode consists of an active anode material that participates in the electrochemical reaction during battery operation. Examples of anode active materials include elemental materials such as lithium, alloys of Si and Sn or other lithium compounds, and intercalation host materials such as graphite. For example, anode active materials may include metals and / or metalloids that can alloy with lithium, its alloys, or its oxides. Metals and metalloids that can alloy with lithium include Si, Sn, Al, Ge, Pb, Bi, and Sb. For example, oxides of metals / metalloids that can alloy with lithium include lithium titanate, vanadium oxide, lithium vanadium oxide, SnO2, or SiO2. x (0 <x<2)であってもよい。

[0124] The cathode consists of an active cathode material that participates in the electrochemical reaction during battery operation. The active cathode material may be a lithium composite oxide and may include layered materials such as LiCoO2, olivine-type materials such as LiFePO4, spinel-type materials such as LiMn2O4, and similar materials. Spinel-type materials include those having a structure similar to natural spinel LiMn2O4. These contain small amounts of nickel cations in addition to lithium cations, and optionally include anions other than manganese salts. As an example, such a material is one with the formula LiNi (0.5-x) Mn 1.5 M x Includes O4 (0 ≤ x ≤ 0.2, where M is Mg, Zn, Co, Cu, Fe, Ti, Zr, Ru, or Cr).

[0125] Within the context of this disclosure, the term “cycle life” refers to the number of complete charge / discharge cycles that an anode or battery (e.g., a LIB) can support before its capacity drops to less than approximately 80% of its original rated capacity. Cycle life can be affected by various factors, such as the mechanical strength of the underlying substrate (e.g., carbon aerogel) and the maintenance of the aerogel’s interconnectivity. It should be noted that these factors, which actually remain relatively constant over time, are remarkable aspects of the particular examples of this disclosure. Cycle life may also be determined by methods known in the art, including, for example, cycle testing, without limitation. A battery cell undergoes repeated charge / discharge cycles at a given current rate and operating voltage. Within the context of this disclosure, measurements of cycle life are obtained according to this method unless otherwise specified. Energy storage devices such as batteries or their electrodes may have a cycle life of approximately 25 cycles or more, 50 cycles or more, 75 cycles or more, 100 cycles or more, 200 cycles or more, 300 cycles or more, 500 cycles or more, 1000 cycles or more, or any two of these values.

[0126] This disclosure includes an electrical energy storage device having at least one anode containing a composite material of the technology as described herein, at least one cathode, and an electrolyte having lithium ions. The electrical energy storage device can have a first cycle efficiency (i.e., the Coulomb efficiency of the cell from a first charge-discharge) of at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, any intercalation value (e.g., 65%), or a range between any two of these values ​​(e.g., a range of about 30% to about 50%). As previously stated herein, the reversible capacity can be at least 150 mAh / g. At least one cathode can be selected from the group consisting of conversion cathodes such as lithium sulfide and lithium air, and intercalation cathodes such as phosphates and transition metal oxides.

[0127] In different examples, the composite materials of the present disclosure may be applied to both the positive and negative electrodes of an electrochemical energy storage device, or to the electrodes (either positive or negative) individually. In various examples, the cathode, anode, or solid electrolyte material is coated with the composite materials of the present technology. [Examples]

[0128] The following examples are included to demonstrate preferred embodiments of the Technology. However, as those skilled in the art will understand from the outset, many modifications can be made to the specific examples disclosed, but similar or comparable results can still be obtained without departing from the spirit and scope of the Technology.

[0129] Example 1: Production of polyacrylonitrile (PAN) fibers by a coagulation process Dry spinning or wet spinning methods are typically used to produce PAN fibers. In this example, a wet spinning route was followed, which involved extruding a PAN solution into a bath containing a coagulant (e.g., DMSO or DMAC) and a non-solvent (e.g., water).

[0130] In the coagulation bath, the fibers slowly began to coagulate and continued until they formed a dense structure. The coagulation process relies on two diffusion mechanisms: the diffusion of the solvent from the fibers into the bath and the diffusion of the non-solvent from the bath into the fibers. Both mechanisms occur simultaneously. The balance between these two processes leads to the precipitation of PAN into fibrous form. Coagulation can be influenced by various reaction parameters such as polymer composition, coagulation bath composition, and coagulation bath temperature.

[0131] Example 2: Preparation of PAN-coated carbon / silicon beads by solidification. A slurry of PAN solution and C / Si beads was prepared in a clean beaker (Figure 2). Depending on the PAN content in the solution (e.g., viscosity), the slurry was mixed under a mechanical mixer for 5 minutes to 16 hours. The slurry was then poured into a homogenized dispersant medium (e.g., silicone oil, mineral oil, hydrocarbon) to ensure better dispersion / scattering of the beads in the dispersant medium. In Figure 2, silicone oil was used as the dispersant medium. The homogenizer mixer was set to a speed of 3,000 to 9,000 rpm, depending on the viscosity of the dispersant medium. Once good dispersion of the C / Si beads was achieved, with the C / Si beads covered by a layer of PAN solution, a coagulating solvent (aqueous solution, e.g., H2O or EtOH / H2O mixture) was added to the homogenized bath while mixing the solution. When the coagulant solvent comes into contact with the PAN solution layer covering each C / Si bead, the PAN instantly solidifies or hardens around the bead, thereby forming a solid PAN coating layer on the C / Si bead.

[0132] Bead coating (e.g., aerogel beads) by PAN solidification was performed using two different routes. As shown in Figure 3, Process 1 describes the route for coating wet polyimide / silicone beads (wet beads meaning those newly prepared by the sol-gel process), while Process 2 describes the same route for coating carbonized beads (C / Si beads). Both processes use solidification in a homogenized oil medium to ensure better bead dispersion and avoid bead aggregation. Finally, the beads are filtered, washed, dried (supercritical, subcritical, or dried under ambient conditions), and carbonized. The beads in Process 2 underwent two carbonization cycles.

[0133] There are at least two different routes for the carbonization of PAN-coated C / Si (or polyimide / Si) beads. Route 1 involves heat treatment at 300°C in air for 1–6 hours to obtain complete cyclization of PAN, followed by carbonization at a temperature above 650°C under an inert gas for 2–5 hours. Route 2 utilizes direct carbonization at a temperature above 650°C under an inert gas for 2–5 hours.

[0134] Example 2.1 Preparation of PAN-coated carbon / silicon beads by solidification via Process 1 Polyimide / silicone beads (silicone available from Evonik Industries AG, North Rhine-West Phalia, Germany) were prepared via a sol-gel route using DMAC as the solvent and 100 cSt (Centistoke) silicone oil as the dispersant medium for bead production. After multiple washes with ethanol, the cake or bead gel was divided into two equal portions (~75 g each). One portion of the sample was supercritically dried with CO2 (i.e., uncoated beads, uncoated #1), and the other portion (wet bead gel) was coated with PAN using Process 1, as described in Figure 3.

[0135] A 5% PAN solution was prepared by dissolving 5 g of PAN in 95 g of DMAC. The solution was then mixed for 6 hours. Next, 75 g of wet bead gel was mixed in the PAN solution for 20-30 minutes until a homogeneous slurry was obtained. The slurry was poured into a silicone oil bath mixed at 7500 rpm using a homogenizer and mixed for 2 minutes. Ethanol solution (50 / 50:EtOH / H2O) was slowly added to the system while mixing. The appearance of the mixture changed from black to gray, indicating solidification of PAN. After coating the beads, they were separated from the oil, washed with ethanol (and heptane to remove residual oil), and filtered. The coated beads were also supercritically dried, similar to the uncoated bead gel.

[0136] The obtained PAN-coated aerogel beads were divided into two samples. One sample (Sample A) was heat-treated in air at 300°C and then carbonized at 650°C under N2. The other sample (Sample B) was directly carbonized at 1050°C under N2. Table 1 summarizes the carbonization conditions and structural properties of the three different beads. [Table 1]

[0137] The coated beads show a reduction in surface area. Referring to Table 1, the surface area of ​​uncoated #1 is larger than that of the two coated samples. That is, samples A and B appear to have coatings covering at least a portion of the available surface area. For example, sample B, which underwent route 2, shows a surface area that is approximately 43% smaller than that of the uncoated sample (uncoated #1). The data suggest that the coating covers at least a portion of the surface area of ​​the uncoated sample.

[0138] The decrease in the surface area of ​​the beads after coating suggests that the PAN coating may have the desired porosity characteristics with respect to its permeability. For example, when phenolic resin was used as the coating material, the surface area of ​​the system increased, suggesting that phenolic resin may be undesirable as a coating material for fluid impermeability.

[0139] The SEM images shown in Figures 4A and 4B and 5A-5C demonstrate the presence of a carbon coating layer on the C / Si beads. Therefore, the PAN coating process by solidification appears promising for further improvement and optimization. However, this pathway (process 1) exhibits some imperfections and some uncoated areas on the beads. The carbonization temperature (pathway 1: 300°C / air, then 650°C / N2; in contrast, path 2: 1050°C / N2) does not appear to affect the quality of the coating. However, temperature may directly affect porosity (surface area) and possibly battery performance.

[0140] Example 2.2 Preparation of PAN-coated carbon / silicon beads by solidification via Process 2 In this example, carbon aerogel beads (uncoated #2) were used. These beads were 440m 2 A high surface area of ​​1 / g was obtained. To coat the beads, 3.53 grams of carbon aerogel (uncoated #2) was mixed with 26 g of PAN solution (5% wt PAN in DMAC) for 20-30 minutes until a homogeneous slurry was obtained. The slurry was poured into a silicon oil bath mixed at 7500 rpm using a homogenizer and mixed for 2 minutes. Ethanol solution (50 / 50:EtOH / H2O) was slowly added to the system while mixing. The appearance of the mixture changed from black to gray, indicating solidification of PAN. After coating the beads, they were separated from the oil and filtered after being washed with ethanol (and heptane to remove residual oil). The carbon PAN coated beads were supercritically dried. Note that other drying methods can be used in other examples. For example, the beads could also be subcritically dried or dried under ambient conditions to obtain xerogel or ambigel.

[0141] The obtained PAN-coated aerogel beads were divided into two samples. One sample was heat-treated in air at 300°C and then carbonized at 650°C under N2 (Sample C), while the other portion was directly carbonized at 1050°C under N2 (Sample D). Table 2 summarizes the carbonization conditions and structural properties of the three different beads.

[0142] Since the starting material (carbon aerogel beads) is silicon-free, the surface area of ​​the PAN-coated carbon beads is larger than that of the PAN-coated carbon / silicon beads previously characterized in Process 1. The presence of silicon in the carbon structure contributes significantly to the reduction in the system's surface area; that is, the higher the silicon content, the smaller the surface area. The coated beads show a reduction in surface area. Referring to Table 2, the surface area of ​​uncoated #2 is larger than that of the two coated samples. That is, samples C and D appear to have a coating that covers at least a portion of the available surface area. For example, sample C, which underwent Route 2, shows a surface area that is approximately 25% smaller than that of the uncoated sample (uncoated #2). The data suggest that the coating covers at least a portion of the surface area of ​​the uncoated sample. [Table 2]

[0143] By increasing the carbonization temperature of the PAN-coated carbon aerogel to 1600-2200°C, the surface area of ​​the system could be further reduced by graphitization of the PAN layer.

[0144] SEM images (Figures 6–10B) show fully coated beads (i.e., the entire bead is coated with PAN). Regardless of the carbonization temperature profile, both samples C and D show PAN coating on the entire surface of the beads. The presence of PAN coating is well demonstrated in high-magnification SEM images (Figures 7A, 7B, 9A, 9B, 10A, and 10B). In particular, Figures 10A and 10B show the PAN layer covering the fibrous structure of the carbon aerogel. This coating appears to be free of imperfections.

[0145] Example 3: Direct solution-based pitch coating onto PI (polyimide) beads Solution-based pitch coating was applied to the surface of polyimide (PI) gel beads prepared by an emulsion process. After obtaining the PI beads, the PI beads were further polymerized by thermal imidization in a furnace (250–400°C, 2 hours). Without thermal imidization, dimethylacetamide (DMAC), used in the next step, could dissolve the polyamic acid (PAA) present in the PI gel beads. First, the pitch was dissolved in the DMAC solvent, and the DMAC / pitch slurry was stirred for several minutes, then the PI gel beads were added while stirring, and the mixture was stirred at over 100 RPM for 30 minutes. The temperature of the mixture was then raised to 50°C–120°C, and the mixture was stirred overnight at 100 RPM to evaporate the DMAC. After the solvent (e.g., DMAC) was dried, the pitch-coated PI beads were gently ground using a mortar and pestle.

[0146] Next, the pitch-coated PI beads were heated to 250-300°C and maintained at that temperature for 2 hours to induce a softening process. This softening process allows the solid pitch to be converted into a viscous liquid, enabling uniform pitch coating. The pitch-coated PI beads were then subjected to a carbonization process at 1050°C for 2 hours. In the carbonization process, the PI beads were transformed into a carbon-based core, and the pitch coating was transformed into a soft carbon coating layer. The degree of graphitization and interlayer distance of the pitch coating were adjusted during the carbonization process.

[0147] Example 4: Direct solution-based pitch coating onto carbon beads A solution-based pitch coating was applied to the surface of carbon beads. After obtaining PI beads, the PI gel beads were subjected to a carbonization process at 1050°C for 2 hours to obtain carbon-based cores, e.g., carbon beads. First, pitch was dissolved in DMAC solvent to obtain a DMAC / pitch slurry. The DMAC / pitch slurry was then stirred for several minutes, then the carbon beads were added while stirring, and the mixture was stirred at over 100 RPM for 30 minutes. The temperature of the mixture was then raised to 50°C to 120°C, and the mixture was stirred overnight at 100 RPM to evaporate the DMAC. After the solvent (e.g., DMAC) was dried, the pitch-coated carbon beads were gently ground using a mortar and pestle.

[0148] Next, the pitch-coated carbon beads were heated to 250-300°C and maintained at that temperature for 2 hours to induce a softening process. This softening process allows the solid pitch to be converted into a viscous liquid, thus enabling uniform pitch coating. The pitch-coated carbon beads were then subjected to a carbonization process (at 1050°C for 2 hours) to adjust the degree of graphitization and interlayer distance of the pitch coating.

[0149] Table 3 summarizes the structural properties of solution-based pitch-coated carbon beads, as well as the first cycle efficiency (FCE) of energy storage devices (e.g., Li-ion batteries) to which pitch-coated PI and carbon beads are applied. [Table 3]

[0150] Solution-based pitch coating was also applied to Si / C composite beads. Pitch-coated Si / C composite beads were obtained using the same protocol as in Examples 3 and 4. The effects of the softening and carbonate steps were investigated.

[0151] Table 4 summarizes the structural properties of solution-based pitch-coated Si / C composite beads, as well as the first cycle efficiency (FCE) of energy storage devices (e.g., Li-ion batteries) to which pitch-coated Si / C beads are applied.

[0152] The results shown in Table 4 demonstrate that pitch-coated Si / C beads provide higher FCE and cycle efficiency compared to pitch-coated carbon beads shown in Table 3. Pitch-coated Si / C composite particles that underwent softening and carbonization steps were found to be more efficient than pitch-coated Si / C composite particles that were not carbonized. The softening process appears to contribute to the improvement of the electrochemical performance of the electrodes. While not theoretically bound, this may be because the softening process allows for a uniform coating of the pitch-containing beads. [Table 4]

[0153] Example 5: Direct spray-drying base pitch coating on PI (polyimide) beads A spray-drying-based pitch coating was applied to the surface of polyimide (PI) gel beads prepared by an emulsion process. After obtaining the PI beads, the PI beads were further polymerized by thermal imidization in a furnace (250-400°C, 2 hours). Without thermal imidization, the dimethylacetamide (DMAC) used in the next step could dissolve the polyamic acid (PAA) present in the PI gel beads. First, the pitch was dissolved in the DMAC solvent, then the DMAC / pitch slurry was stirred for several minutes, followed by the addition of the PI gel beads while stirring, and then stirred at over 100 RPM for 30 minutes.

[0154] Next, the temperature of the mixture was raised to 160°C to dry the beads. This spray-drying step allows for a uniform pitch coating on the PI beads. The pitch-coated PI beads were then heated to 250-300°C and maintained at that temperature for 2 hours to allow for a softening process (e.g., a process to obtain soft carbon from the pitch).

[0155] The softening process allows the solid pitch to be converted into a viscous liquid, enabling uniform pitch coating. The pitch-coated carbon beads then undergo a carbonization process (2 hours at 1050°C), where the underlying PI core beads are converted to carbon and the pitch coating is converted to soft carbon.

[0156] Table 5 summarizes the structural properties of spray-based pitch-coated carbon beads, as well as the first cycle efficiency (FCE) of energy storage devices (e.g., Li-ion batteries) to which pitch-coated Si / C beads are applied. [Table 5]

[0157] As shown in Table 5, the Coulomb efficiency from the first charge-discharge cycle (FCE) of the electrode using pitch-coated carbon beads was relatively higher (improved) compared to the electrode using control beads.

[0158] Example 6: Direct spray-drying base pitch coating onto carbon beads A spray-drying-based pitch coating was applied to the surface of the carbon beads. After obtaining the PI beads, the PI gel beads were subjected to a carbonization process at 1050°C for 2 hours to obtain carbon-based cores, such as carbon beads. First, pitch was dissolved in DMAC solvent to obtain a DMAC / pitch slurry, which was then stirred for several minutes, followed by the addition of carbon beads while stirring, and then stirred at over 100 RPM for 30 minutes.

[0159] Next, the temperature of the mixture was raised to 160°C to dry the beads. This spray-drying step allows for a uniform pitch coating on the carbon beads. The pitch-coated carbon beads were then heated to 250-300°C and maintained at that temperature for 2 hours to allow for a softening process (e.g., a process to obtain soft carbon from the pitch).

[0160] The softening process allows the solid pitch to be converted into a viscous liquid, enabling uniform pitch coating and allowing adjustment of the degree of graphitization and interlayer distance. The pitch-coated carbon beads were further subjected to a carbonization process (2 hours at 1050°C).

[0161] Although this disclosure has been illustrated and described in particular with reference to its embodiments, various modifications of form and detail may be made therein without departing from the scope of the art encompassed in the appended claims, as will be apparent to those skilled in the art. Some embodiments of the present invention are shown below. [Embodiment 1] A composite material used in electrical energy storage systems, a. A carbon-based core having a porous outer surface, b. A coating on at least a portion of the porous outer surface of the carbon-based core, wherein the coating is (i) substantially permeable to at least one metal ion or metal atom, and (ii) substantially impermeable to a liquid, The composite material, including the above. [Embodiment 2] The composite material according to Embodiment 1, wherein the liquid contains an electrolyte solvent. [Embodiment 3] The composite material according to Embodiment 2, wherein the electrolyte solvent is selected from ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), fluorinated ether (F-EPE), 1,3-dioxolane (DOL), dimethoxyethane (DME), or a combination thereof. [Embodiment 4] The composite material according to Embodiment 1, wherein at least one of the metal ions is a lithium ion. [Embodiment 5] The composite material according to Embodiment 1, wherein at least one metal atom is a lithium atom. [Embodiment 6] The composite material according to Embodiment 1, wherein the coating has a thickness of approximately 2,500 nm or less, or a thickness of approximately 100 nm to approximately 2,000 nm, or a thickness of approximately 200 nm to 500 nm. [Embodiment 7] The coating is a composite material according to Embodiment 1 or Embodiment 6, extending into the porous outer surface of the carbon-based core. [Embodiment 8] The composite material according to Embodiment 7, wherein the coating extends within the porous outer surface of the carbon-based core for a length of approximately 2,500 nm or less, or approximately 100 nm to approximately 2,000 nm, or approximately 200 nm to approximately 500 nm. [Embodiment 9] The composite material according to Embodiment 1, wherein the coating is uniform on at least a portion of the porous outer surface of the carbon-based core. [Embodiment 10] The composite material according to Embodiment 1, wherein the coating is continuous on at least a portion of the porous outer surface of the core. [Embodiment 11] The composite material according to Embodiment 1, wherein at least a portion of the porous outer surface of the core is at least 70%, at least 90%, or at least 95% of the porous outer surface. [Embodiment 12] The composite material according to Embodiment 1, wherein the coating includes a conductive material. [Embodiment 13] The conductive material is a composite material according to Embodiment 12, formed from a precursor of a non-conductive material. [Embodiment 14] The composite material according to embodiment 12 or 13, wherein the conductive material is carbon. [Embodiment 15] The composite material according to Embodiment 13, wherein the non-conductive material is a polymer. [Embodiment 16] The conductive material is a composite material according to Embodiment 12, formed from a precursor of the first conductive material. [Embodiment 17] The composite material according to Embodiment 16, wherein the first conductive material is selected from a metal or a transition metal. [Embodiment 18] The composite material according to Embodiment 1, wherein the coating comprises a material selected from organic molecules, polymers, metals, transition metals, nonmetals, metal-organic frameworks (MOFs), or combinations thereof. [Embodiment 19] The composite material according to Embodiment 18, wherein the polymer is selected from the group consisting of polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyimide, polyamide, or derivatives thereof. [Embodiment 20] The composite material according to Embodiment 18, wherein the coating comprises polyacrylonitrile (PAN). [Embodiment 21] The composite material according to Embodiment 18, wherein the organic molecule, the polymer, or a combination thereof is carbonized. [Embodiment 22] The composite material according to Embodiment 18, wherein the coating comprises polyacrylonitrile carbide (PAN). [Embodiment 23] The composite material according to Embodiment 1, wherein the coating is a carbon-based coating. [Embodiment 24] The carbon-based coating is derived from pitch, as described in Embodiment 23. [Embodiment 25] The coating penetrates into the pores of the carbon-based core, as described in Embodiment 1. [Embodiment 26] The composite material according to Embodiment 1, wherein the carbon-based core has a low bulk density, and the low bulk density is in the range of about 0.25 g / cc to about 1.0 g / cc. [Embodiment 27] The composite material according to Embodiment 1, wherein the carbon-based core includes a skeletal framework, and the skeletal framework includes an array of interconnected pores. [Embodiment 28] The composite material according to Embodiment 1, wherein the carbon-based core has a pore volume of at least 0.3 cc / g. [Embodiment 29] The composite material according to Embodiment 1, wherein the carbon-based core has a porosity of about 10% to about 90% of the volume of the core. [Embodiment 30] The composite material according to Embodiment 1, wherein the carbon-based core is a monolith. [Embodiment 31] The composite material according to Embodiment 1, wherein the carbon-based core is in the form of particles. [Embodiment 32] The composite material according to Embodiment 1, wherein the particles are substantially spherical and have a diameter of about 100 nm to about 4 mm, or about 5 μm to about 4 mm. [Embodiment 33] The composite material according to Embodiment 1, wherein the carbon-based core includes a carbon-based aerogel, a carbon-based xerogel, a carbon-based ambigel, a carbon-based aerogel xerogel hybrid material, a carbon-based aerogel ambigel hybrid material, a carbon-based aerogel ambigel xerogel hybrid material, or a combination thereof. [Embodiment 34] The composite material according to Embodiment 1, wherein the carbon-based core includes activated carbon, carbon black, carbon fibers, carbon nanotubes, pyrolysis carbon, graphite, graphene, or a combination thereof. [Embodiment 35] The composite material according to Embodiment 1, wherein the carbon-based core comprises one or more additives, the additives present in the composite material at a level of at least about 5 to 60 weight percent. [Embodiment 36] The composite material according to Embodiment 34, wherein the additive comprises one or more electrochemically active dopants. [Embodiment 37] The composite material according to Embodiment 35, wherein the electrochemically active dopant is selected from the group consisting of silicon, germanium, tin, antimony, gold, silver, zinc, magnesium, platinum, and aluminum. [Embodiment 38] The composite material according to Embodiment 1, wherein the coating includes a conductive additive. [Embodiment 39] The composite material according to Embodiment 37, wherein the conductive additive includes carbon, carbon nanotubes, graphene, graphite, metal, metal oxide, silicon carbide, or a combination thereof. [Embodiment 40] The carbon-based core is a composite material according to Embodiment 1, having a capacity of approximately 200 mAh / g to approximately 3000 mAh / g. [Embodiment 41] The composite material according to Embodiment 1, wherein the carbon-based core has an electrical conductivity of at least about 1 S / cm. [Embodiment 42] The composite material according to Embodiment 1, wherein the coating has an electrical conductivity of at least about 1 S / cm. [Embodiment 43] The composite material according to Embodiment 1, wherein the energy storage system is a battery. [Embodiment 44] The composite material according to embodiment 42, wherein the battery is a rechargeable battery. [Embodiment 45] The composite material according to embodiment 43, wherein the rechargeable battery is a lithium-ion battery. [Embodiment 46] A rechargeable battery comprising the composite material described in any one of Embodiments 1 to 45. [Embodiment 47] A method for improving the performance of a rechargeable battery, comprising incorporating a composite material described in any one of Embodiments 1 to 46 into the rechargeable battery. [Embodiment 48] A method for preparing a composite material according to any one of Embodiments 1 to 45, a. Prepare a carbon-based core with an outer surface. b. Obtaining the composite material by coating at least a portion of the porous outer surface of the carbon-based core, The method, including the method described above. [Embodiment 49] The method according to Embodiment 47, further comprising the step of subcritical or supercritical drying before the step of coating at least a portion of the porous outer surface of the core. [Embodiment 50] The method according to Embodiment 47, further comprising the step of subcritical or supercritical drying after the step of coating at least a portion of the porous outer surface of the core. [Embodiment 51] The method according to Embodiment 48, further comprising a carbonization step between the step of coating at least a portion of the porous outer surface of the core and the step of subcritical or supercritical drying. [Embodiment 52] The method according to Embodiment 50, further comprising a second carbonization step after the step of coating at least a portion of the porous outer surface of the core. [Embodiment 53] The method according to Embodiment 49, further comprising a carbonization step after the step of subcritical or supercritical drying of the composite material. [Embodiment 54] The method according to embodiment 47, wherein the step of coating at least a portion of the porous outer surface of the core includes a solidification process. [Embodiment 55] The method according to embodiment 47, wherein the step of coating at least a portion of the porous outer surface of the core includes a spray coating process. [Embodiment 56] The spray coating process is according to Embodiment 54, which includes a high-speed spray drying method using a spray supply. [Embodiment 57] The method according to embodiment 47, wherein the step of coating at least a portion of the porous outer surface of the core includes an immersion coating process.

Claims

1. A composite material used in electrical energy storage systems, a. A carbon-based core having a porous outer surface, comprising a carbon-based aerogel, a carbon-based xerogel, a carbon-based ambigel, a carbon-based aerogel xerogel hybrid material, a carbon-based aerogel ambigel hybrid material, a carbon-based aerogel ambigel xerogel hybrid material, or a combination thereof, b. A carbon-based coating on at least a portion of the porous outer surface of the carbon-based core, wherein the carbon-based coating (i) is substantially permeable to at least one metal ion or metal atom, (ii) is substantially impermeable to liquids, and (iii) contains carbide polyacrylonitrile (PAN), Includes, The composite material is 166 to 337 m ２ A composite material having a BET surface area within the range of / g.

2. The composite material according to claim 1, wherein the liquid contains an electrolyte solvent.

3. The composite material according to claim 2, wherein the electrolyte solvent is selected from ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), fluorinated ether (F-EPE), 1,3-dioxolane (DOL), dimethoxyethane (DME), or a combination thereof.

4. The composite material according to claim 1, wherein at least one metal ion is a lithium ion and at least one metal atom is a lithium atom.

5. The composite material according to claim 1, wherein the coating has a thickness of 2,500 nm or less, a thickness of 100 nm to 2,000 nm, or a thickness of 200 nm to 500 nm.

6. The composite material according to claim 1, wherein the coating extends into the porous outer surface of the carbon-based core.

7. The composite material according to claim 6, wherein the coating extends within the porous outer surface of the carbon-based core by a length of 2,500 nm or less, 100 nm to 2,000 nm, or 200 nm to 500 nm.

8. The composite material according to claim 1, wherein the coating is continuous on at least a portion of the porous outer surface of the core, and at least a portion of the porous outer surface of the core is at least 70% of the porous outer surface, at least 90% of the porous outer surface, or at least 95% of the porous outer surface.

9. The composite material according to claim 1, wherein the coating penetrates into the pores of the carbon-based core.

10. The composite material according to claim 1, wherein the carbon-based core has a bulk density in the range of 0.25 g / cc to 1.0 g / cc, a pore volume of at least 0.3 cc / g, and a porosity of 10% to 90% of the volume of the core.

11. The composite material according to claim 1, wherein the carbon-based core includes a skeletal framework, and the skeletal framework includes an array of interconnected pores.

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