Method for manufacturing battery cell assembly, battery cell assembly, and battery cell

Abstract

To provide a manufacturing method of a battery cell assembly, and the battery cell assembly.SOLUTION: A method contains steps of: preparing a dispersion element containing a particle of a metal oxide, a metalhydroxide, or a metal oxyhydroxide, and a solvent composition; coating directly a role of a first electrode with the dispersion element; forming a first layer of a separator onto the first electrode; providing a second electrode; and assembling the first and second electrodes so as to interpose a separator between the first electrode and the second electrode. A thickness of the separator is within a range of 0.5 μm to 10 μm, and the particle of the metal oxide, the metalhydroxide, or the metal oxyhydroxide contains first and second sets having first and second aspect ratio distributions respectively. The particle of the first set has a fiber shape, and is featured by a diameter in a range of 3nm to 2 μm, and an aspect ratio in a range of 4 to 1,000,000, and the particle of the second set is a flake.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Claim of Priority under 35 U.S.C. § 119 This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 609,796, filed on Dec. 22, 2017, entitled "Reliable Energy Storage Devices with Flexible Ceramic Layer Separating Electrodes", the entire disclosure of which is hereby expressly incorporated by reference in its entirety.

[0002] Embodiments of the present disclosure generally relate to the design and secondary processing of separators comprising a separator layer including ceramic and their use in electrochemical energy storage devices and other applications, and to the design and secondary processing of improved energy storage devices including separators comprising a separator layer including ceramic.

Background Art

[0003] Highly rechargeable batteries and electrochemical capacitors are suitable for a wide range of household appliances, electric vehicles, grid storage, and other important applications, partly due to their relatively high energy density, relatively high specific energy, lightweight, and potential for long life. However, despite the increasing commercial popularity of these electrochemical energy storage devices, further development is needed, particularly for potential applications in low-emission or zero-emission hybrid or fully electric vehicles, household appliances, energy-efficient cargo ships and locomotives, aerospace applications, and power transmission grids. In particular, further improvements in safety, energy density, specific energy, power density, specific power, cycle stability, and calendar life are required for various electrochemical capacitors and rechargeable batteries, such as rechargeable metal and metal-ion batteries (rechargeable Li and Li-ion batteries, rechargeable Na and Na-ion batteries, rechargeable Mg and Mg-ion batteries, rechargeable K and K-ion batteries, etc.), rechargeable alkaline batteries, rechargeable metal hydride batteries, rechargeable lead batteries, other rechargeable aqueous batteries, double-layer capacitors, hybrid supercapacitors, and other devices. Furthermore, improvements in energy density, specific energy, power density, specific power, and calendar life are required not only for various primary batteries but also for primary and rechargeable batteries that operate at low temperatures (e.g., below -20 °C) or high temperatures (e.g., above 60 °C), such as batteries used in mining applications or special applications, such as thermal batteries, etc.).

[0004] Many separator membranes for these primary and rechargeable electrochemical energy storage devices, such as lithium-ion (Li-ion) batteries, various aqueous batteries, and electrochemical capacitors, are generally made from porous polymeric materials. These membranes need to electrically insulate the anode and cathode within the cell to prevent self-discharge while allowing the transport of electrolyte ions between these electrodes. Known examples of polymeric materials used in the secondary processing of such membranes include olefins (such as polypropylene or polyethylene), cellulose, aramid, nylon, polytetrafluoroethylene, etc. The selection of the polymer for a given membrane application may depend on the electrochemical and chemical stability in contact with both electrodes (anode and cathode), the wettability by the electrolyte, price viability, porosity and pore tortuosity, mechanical properties, thermal characteristics, and other factors during the secondary processing and operation of the device. The typical thickness of such separator membranes within an energy storage device ranges from just 6 microns to about 50 microns. Substantially thinner polymeric membranes are less safe to use, while substantially thicker membranes generally reduce the energy density, specific energy, and power density, specific power of the energy storage device to undesirable levels. The typical porosity of such polymeric membranes ranges from about 30% to about 50%, and for separator membranes used in certain conventional Li-ion batteries, the most typical value is about 40%. Polymer-based separator membranes can be mass-produced and are thin and flexible, but they suffer from a number of limitations, such as, among others, limitations in thermal stability, limitations in strength and toughness (especially when manufactured sufficiently thin), insufficient resistance to dendrite penetration, reduced wettability by some electrolytes, limitations in electrolyte permeability, etc. Such limitations become particularly problematic when the energy storage device reaches its limits, for example, when such a device requires, among other things, faster charging, better stability under high temperature and high stress, longer cycle stability, and longer calendar life.

[0005] Accordingly, there is still a need for improved separator membranes and improved electrochemical energy storage devices in which the electrodes are electrically separated and ionically bonded. Further, improved materials and improved manufacturing processes are still needed. SUMMARY OF THE INVENTION

[0006] The embodiments disclosed herein address the above needs by providing improved batteries, components, and other related materials and manufacturing processes.

[0007] As an example, a separator is disposed with a separator layer that includes a ceramic. The separator layer that includes a ceramic includes porous metal oxide fibers having a diameter in the range of about 3 nm to about 2 microns, an aspect ratio in the range of about 20 to about 100,000, and a total open pore volume between the porous metal oxide fibers in the range of about 0.01 cm 3 / g to about 1 cm 3 / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

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DETAILED DESCRIPTION OF THE INVENTION

[0009] The accompanying drawings are presented to assist in the description of embodiments of the present disclosure and are provided for illustrative purposes only of the embodiments and are not limiting thereof. Unless otherwise specified or implied by the context, different hatchings, shadings, and / or filling patterns in the drawings are intended only to depict the contrast of different components, elements, features, etc., and are not intended to convey the use of specific materials, colors, or other properties that may be defined outside the present disclosure for the particular patterns used.

[0010] Aspects of the present invention are disclosed in the following description and related drawings directed to specific embodiments of the present invention. The term "embodiment of the present invention" does not require that all embodiments of the present invention include the features, advantages, processes, or modes of operation being considered, and alternative embodiments may be devised without departing from the gist of the present invention. Further, well-known elements of the present invention may not be described in detail or may be omitted so as not to obscure other more relevant details. Further, the terminology "at least in part" is intended to be construed as "in part, substantially, or completely".

[0011] For any numerical range described herein with respect to any embodiment of the present invention, it is also intended to implicitly disclose each discrete value within that range in units or increments that match the level of precision characterizing the upper and lower limits of the relevant numerical range. For example, a numerical range of distances from 7 nm to 20 nm (i.e., a precision level where the unit or increment is 1) includes the set of [7, 8, 9, 10, …, 19, 20] (in units of nm) as if the intervening numbers from 8 to 19 were explicitly disclosed in units or increments of 1. In another example, a numerical range of percentages from 30.92% to 47.44% (i.e., a precision level of units or increments of 1 / 100) includes the set of [30.92, 30.93, 30.94, …, 47.43, 47.44] (in %) as if the intervening numbers between 30.92 and 47.44 were explicitly disclosed in units or increments of 1 / 100. Accordingly, any number included in the disclosed numerical range is intended to be interpreted as if those intervening numbers were explicitly disclosed, and such intervening numbers may thereby constitute their own upper and / or lower limits of sub-ranges that fall within the broader range. Thereby, each sub-range (e.g., each range that includes at least one intervening number from the broader range as an upper and / or lower limit) is intended to be interpreted as implicitly disclosed by the explicit disclosure of the broader range.

[0012] The description of one or more of the following embodiments may illustrate specific examples in the context of aluminum-(Al-) or oxygen-(O-) situations involving small (nano) wires, whiskers, (nano) fibers, (nano) ribbons, other elongated particles as well as flakes (sometimes also called "platelets"), (nano) sheets, and other planar-shaped particles including various porous elongated particles or porous planar particles. However, it will be understood that various aspects may be applicable to other compositions (such as other metal oxides as well as metal oxyfluorides, metal fluorides, metal oxynitrides, metal oxyhydroxides (e.g., clays and other oxyhydroxides), metal nitrides, metal oxynitrides, metal carbides, metal oxycarbides, and other various ceramic elongated particles including metal compositions, etc.). Examples of metal (or metalloid) atoms suitable for such compositions include, but are not limited to, at least one of the following or combinations thereof (depending on the specific application): Al, Si, Ti, Li, Cu, Fe, Mg, Na, K, Cs, Ba, Be, C, Zn, Cr, Zr, Y, La, Ce, Sm, Mo, Nb, Ta, W, Ag, Pt.

[0013] The description of one or more of the following embodiments may illustrate specific examples in the context of small (nano) wires, whiskers, (nano) fibers, (nano) ribbons, other elongated particles as well as flakes, (nano) sheets, and other planar-shaped particles including various porous elongated particles or porous planar particles containing a single metal (e.g., aluminum) in the composition. However, it will be understood that various aspects may be applicable to compositions containing two, three or more metals.

[0014] The description of one or more of the following embodiments may illustrate specific examples in the context of a particular type of particle (e.g., (nano) fibers or flakes). However, it will be understood that various aspects may be applicable to compositions containing particles of different shapes (e.g., a combination of fibrous particles and flaky particles), and may exhibit different compositions, microstructures or sizes.

[0015] The description of one or more of the following embodiments may describe specific examples in the context of pure metal oxides, but it will be understood that various aspects may be applicable to compositions that include both an oxide and a portion of an adjacent species of the oxide, such as, among many others, a hydroxide (where a hydrogen atom is bonded to an oxygen atom), a suboxide (where an oxygen atom is bonded to an oxygen atom), a carboxylate (where a metal atom is bonded to a carbonate group), a hydride (where a metal atom is bonded to hydrogen), a nitride (where a metal atom is bonded to nitrogen), a fluoride (where a metal atom is bonded to fluorine), etc. Thus, the coordination number of the metal atoms in such compositions may be different from that of pure oxides.

[0016] The description of one or more of the following embodiments may describe specific examples in the context of pure alkoxides, but it will be understood that various aspects may be applicable to compositions that include both an alkoxide and a portion of an adjacent species of the alkoxide, such as, among many others, a hydroxide (including hydrogen bonded to an oxo group), a suboxide (including oxygen bonded to an oxo group), a carboxylate (an oxo group bonded to a carbonate group), a nitride (an oxo group bonded to nitrogen), etc. Thus, the coordination number of the metal atoms in such compositions may be different from that of pure alkoxides, and the ratio of the alcohol group (-ROH) to the metal atoms may be different from that of pure alkoxides. For example, in the case of an aluminum ethoxide composition, the aluminum (Al) atoms may not be 6 - coordinated (as expected in pure Al(EtOH) 3 ), but may include, for example, 6 - coordinated, 5 - coordinated, and 4 - coordinated Al. Similarly, the molar ratio of the ethoxy group (-EtOH) to the Al atoms may not be 3 (as expected in pure Al(EtOH) 3 ) and may vary, for example, from as high as about 10 to as low as about 0.1.

[0017] In the context of one or more embodiments of the present description, the term "bulk" (such as "small fibers of bulk", "small particles of bulk", "small flakes of bulk", etc.) refers to a sample in which particles (such as small fibers, small flakes, and other small particles, etc.) adhere to each other by chemical, electrostatic, and / or physical mechanisms to form large agglomerates (the average dimension of such agglomerates ranges from about 1 pm to about 10 cm).

[0018] In the context of one or more embodiments of the present description, the term "aspect ratio" refers to the ratio of the longest dimension to the shortest dimension of a material or particle.

[0019] In the context of one or more embodiments of the present description, the term "dispersion" refers to a mixture of one or more solids and one or more liquids, but refers to a mixture in which one or more solids interact with one or more liquids in a way that changes the fluid properties of both the one or more solids and the one or more liquids. For example, when solid (nano) particles of various shapes and sizes are dispersed in a liquid, the viscosity of the liquid increases and the Brownian motion of the particles increases. The term "dispersion" may also refer to the state when solid (nano) particles of various shapes and sizes are suspended in a liquid (solvent). The term "stable dispersion" refers to a state in which particles (such as fibers, flakes, nanoparticles, or particles of various other shapes and sizes) remain suspended for a sufficient time scale during a given processing step (such as casting a dispersion into a film on a substrate, etc.).

[0020] The description of the following one or more embodiments may also describe specific examples in the context of the formation and application of certain oxides of one or more metals, but it will be understood that various aspects of the present disclosure may be applicable to the formation of other ceramic materials (not necessarily oxides) as well as various ceramic-ceramic, ceramic-glass, ceramic-metal, ceramic-carbon, ceramic-polymer, glass-polymer, glass-ceramic-polymer, polymer-polymer, and other composite materials.

[0021] The description of one or more of the following embodiments may also describe specific examples in the context of the formation and application of porous membranes for electrochemical energy storage or energy conversion devices, although various aspects of the present disclosure (particularly, membrane formation, etc.) are applicable to a wide range of other uses, such as, in particular, various composite materials, biomedical and medical uses, sensors (including but not limited to humidity sensors), purification of air membranes and liquid membranes (including but not limited to filtration or purification of various gases or liquids (such as HEPA filtration, etc.) from small particles, bacteria, bacterial spores, viruses, harmful organics, etc.), structural materials and devices, optical devices, electrical or thermal insulation, etc.

[0022] For purposes of simplification and illustration, all elongated particles having suitable size, shape, aspect ratio, density, porosity, crystal structure, and morphology (such as high-density and porous nanofibers and fibers, nanowires, whiskers, nanotubes, nanoribbons, etc.) may generally be referred to herein as "small fibers". In one or more embodiments of the present disclosure, the suitable diameter (or width) of individual small fibers (of various compositions) can range from about 2 nm to about 1 micron, and the suitable length of individual small fibers (of various compositions) can range from about 50.0 nm to about 500.0 mm. In one or more embodiments of the present disclosure, the suitable aspect ratio (width to length) of individual small fibers (of various compositions) can range from about 1:4 to about 1:1,000,000.

[0023] For purposes of simplification and illustration, all planar particles having suitable size, shape, aspect ratio, density, porosity, crystal structure, and morphology are generally referred to herein as "small flakes". In one or more embodiments of the present disclosure, the suitable thickness of individual small flakes (of various compositions) can range from about 0.3 nm to about 0.6 micron, and the suitable average width of individual small flakes can range from about 50 nm to about 5 mm. In one or more embodiments of the present disclosure, the suitable aspect ratio (width to length) of individual small flakes (of various compositions) can range from about 1:4 to about 1:1,000,000.

[0024] For simplicity and illustrative purposes, all particles with a volume of less than about 0.2 microns 3 can generally be referred to herein as "nanoparticles".

[0025] Depending on the application, in one example, the suitable true density (taking into account the closed porosity) of small fibers, small flakes, and nanoparticles is from about 0.3 to about 4 g / cm 3 up to (e.g., in the case of particles containing only Al metal in their composition) and up to about 6 g / cm 3 up to (e.g., in the case of particles containing metals other than Al in their composition). Depending on the application and processing conditions, in one example, the suitable pore volume (e.g., total open pore volume) between individual small fibers, small flakes, and nanoparticles (e.g., including the pore space within the fiber / flake / nanoparticle itself, such as surface pores, etc., and the intervening open pore space between the fiber / flake / nanoparticle when placed in a separator layer containing ceramic) can range from about 0 to about 5 cm 3 / g (e.g., in some designs, from about 0.01 cm 3 / g to about 1 cm 3 / g). Depending on the application and processing conditions, in one example, the microstructure can range from amorphous to nanocrystalline, from nanocrystalline to polycrystalline, from polycrystalline to single crystal, from single crystal to mixtures thereof, and from mixtures thereof to other types. Depending on the application and processing conditions, in one example, the suitable surface roughness of small fibers and small flakes can range from about 0 to about 100 nm.

[0026] Certain conventional polymeric separator membranes used in Li-ion, Na-ion and other rechargeable and primary batteries, as well as electrochemical capacitors (e.g., double-layer capacitors, pseudocapacitors or hybrid devices), and selected types of fuel cells have limited mechanical strength and low thermal stability, such that failure of such polymeric separator membranes can cause thermal runaway and cell explosion. Reducing the thickness of the polymeric separator membrane is advantageous for increasing the energy and power density of these energy storage devices in some applications, but reducing the thickness of the polymeric separator membrane can increase the likelihood of separator failure during cell operation to an unacceptable level, such that it may reduce the mechanical properties to a level where the cell operation is no longer safe, and is thus conventionally not achievable. Certain conventional polymeric separator membranes may further be subject to limitations in wettability by electrolytes and permeability by electrolyte ions, thereby potentially limiting the charge rate and output characteristics of the electrochemical energy storage devices.

[0027] Ceramic materials are known to exhibit good strength, good wettability, and good thermal properties compared to polymers, but are generally too brittle to be used as separator membranes. However, when ceramic materials are processed into various fibers (especially small fibers), the fibrous ceramic materials can become flexible enough to be used as separator membranes according to one or more embodiments. Moreover, in some designs, reducing the diameter of ceramic fibers may increase the specific strength and toughness of the fibers, and other mechanical properties (when normalized by the mass or cross-sectional area of the fibers). Thus, by forming flexible, strong, and thermally stable ceramic separators from small ceramic fibers (and other materials), one or more limitations of conventional polymer separators can be overcome. However, the economical formation of high-performance ceramic separators is difficult. One or more embodiments of the present disclosure are directed to suitable secondary processing methods, suitable forms, and suitable compositions of separator layers (e.g., stand-alone separator membranes independent of the electrodes, or separator coatings directly coated on the electrodes and / or separator membranes) containing ceramic (or pure ceramic) for metal ion batteries based on Li ions, Na ions, K ions, Ca ions, Zn ions, Cu ions, Mg ions, and other rechargeable and primary batteries (including thermal batteries) and electrochemical capacitors (including double-layer capacitors).

[0028] Due to the widespread adoption and popularity of metal ion batteries (such as Li-ion batteries), for the sake of brevity and convenience, the following description may illustrate specific examples in the context of Li and Li-ion batteries. However, it will be readily understood that the various embodiments described below may be applicable to other metal ion battery types.

[0029] In some designs, a separator membrane (or separator membrane layer) containing ceramic fibers (including small ceramic fibers) is about 0.02 cm 3 / g to about 6.00 cm 3 / g (most commonly about 0.2 to about 1.5 cm3 It may be advantageous to indicate the pore volume in the range of / g). For example, if the pore volume is too small, sufficient permeability may not be obtained, but if the pore volume is too large, the mechanical strength of the membrane may be reduced below a desirable level for some applications (e.g., Li ions and other rechargeable batteries).

[0030] Figure 1 shows an example of a metal ion (e.g., Li ion) battery to which the components, materials, methods, and other technologies described herein, or combinations thereof, can be applied according to various embodiments. Here, a cylindrical battery is shown for illustrative purposes, but other types of arrangements may be used as needed, including prismatic batteries or pouch (laminate) batteries, or flexible batteries or coin-type batteries. Examples of battery 100 include a negative anode 102, a positive cathode 103, a separator 104 interposed between anode 102 and cathode 103, an electrolyte (not shown) impregnating separator 104, a battery case 105, and a sealing member 106 that seals battery case 105.

[0031] Both liquid electrolytes and solid electrolytes can be used in part or all of the designs described herein. In one example, certain electrolytes for this type of Li-based or Na-based battery are single Li or Na salts (e.g., LiPF for Li ion batteries 6 , NaPF for Na ion batteries 6 or NaClO 4It may be contained in a mixture of organic solvents (e.g., a mixture of carbonates). Other common organic solvents include nitriles, esters, sulfones, sulfoxides, phosphorus-based solvents, silicon-based solvents, ethers, etc. Such solvents may be modified (e.g., sulfonated or fluorinated). The electrolyte may also include ionic liquids (in some designs, neutral ionic liquids; in other designs, acidic and basic ionic liquids). In some designs, suitable electrolytes may include or be based on molten salts (in some designs, such electrolytes can be melt-impregnated into electrodes and / or ceramic-based separator membranes or coatings). In some designs, suitable electrolytes may include solid glasses or ceramic electrolytes that exhibit a melting point lower than that of the ceramic membrane (or layer) and have low solubility in the membrane material at the melt-impregnation temperature (e.g., a solubility of about 0 to 5 vol% in one or more membrane materials). In some designs, the solid-state electrolyte can be dissolved in a solvent, impregnated into a ceramic separator, and formed by firing (e.g., by using common sol-gel processing techniques).

[0032] The electrolyte can also include mixtures of various salts (e.g., a mixture of several Li salts or a mixture of Li salts and non-Li salts for rechargeable Li and Li-ion batteries).

[0033] For example, common salts used in the electrolyte of Li-ion batteries are LiPF 6 However, less common salts include lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium bis(oxalato)borate (LiB(C 2 O 4 )) 2 , lithium difluoro(oxalato)borate (LiBF 2 (C 2 O 4 ))), various lithium imides (e.g., SO 2 FN - (Li + )SO 2 F, CF 3SO 2 N - (Li + )SO 2 CF 3 、CF 3 CF 2 SO 2 N - (Li + )SO 2 CF 3 、CF 3 CF 2 SO 2 N - (Li + )SO 2 CF 2 CF 3 、CF 3 SO 2 N - (Li + )SO 2 CF 2 OCF 3 、CF 3 OCF 2 SO 2 N - (Li + )SO 2 CF 2 OCF 3 、C 6 F 5 SO 2 N - (Li + )SO 2 CF 3 、C 6 F 5 SO 2 N - (Li + )SO 2 C 6 F 5 Or CF 3 SO 2 N - (Li + )SO 2 PhCF 3Such as) etc. are included. Electrolytes for sodium, magnesium, potassium, calcium, copper, zinc and other metal ion batteries are often rarer because these batteries are in the initial stage of development. For example, such rare electrolytes may contain different salts and solvents (in some cases, ionic liquids or molten salts may replace organic solvents for specific applications).

[0034] Conventional electrodes used in lithium-ion batteries can be manufactured by: (i) forming a slurry containing an active material, a conductive additive, a binder solution, and optionally a surfactant or other functional additive; (ii) casting the slurry onto a metal foil (e.g., Cu foil for most anodes and Al foil for most cathodes); and (iii) drying the cast electrode to completely evaporate the solvent.

[0035] Conventional cathode materials used in lithium-ion batteries can be of the intercalation type, in which metal ions are inserted into and occupy positions in the gaps of such materials during charging or discharging of the battery. Such cathodes experience very small volume changes when used in electrodes. Such conventional cathode materials also generally exhibit a high density (e.g., 3.8 - 6 g / cm 3 ) and are relatively easy to mix in a slurry. However, such cathodes exhibit relatively low weight and volume capacities (e.g., less than about 220 mAh / g and less than about 800 mAh / cm 3 respectively).

[0036] Conversion-type cathode materials for rechargeable lithium-ion or lithium batteries can provide higher energy density, higher specific energy, or higher specific or volume capacity compared to intercalation-type cathode materials. For example, fluoride-based cathodes can offer excellent technical potential due to their very high loadings, which can exceed 300 mAh / g in some cases (exceeding 1200 mAh / cm 3 at the electrode level). For example, in the Li-free state, FeF3 provides a theoretical specific capacity of 712 mAh / g; FeF 2 provides a theoretical specific capacity of 571 mAh / g; MnF 3 provides a theoretical specific capacity of 719 mAh / g; CuF 2 provides a theoretical specific capacity of 528 mAh / g; NiF 2 provides a theoretical specific capacity of 554 mAh / g; PbF 2 provides a theoretical specific capacity of 219 mAh / g; BiF 3 provides a theoretical specific capacity of 302 mAh / g; BiF 5 provides a theoretical specific capacity of 441 mAh / g; SnF 2 provides a theoretical specific capacity of 342 mAh / g; SnF 4 provides a theoretical specific capacity of 551 mAh / g; SbF 3 provides a theoretical specific capacity of 450 mAh / g; SbF 5 provides a theoretical specific capacity of 618 mAh / g; CdF 2 provides a theoretical specific capacity of 356 mAh / g; ZnF 2 provides a theoretical specific capacity of 519 mAh / g. A mixture of fluorides (e.g., in the form of an alloy) can provide a theoretically calculated capacity according to the law of mixtures. The use of mixed metal fluorides can sometimes be advantageous (e.g., it may provide a higher rate, lower resistance, higher practical capacity, or longer stability). In the fully lithiated state, the metal fluoride turns into a composite material containing a mixture of metal and LiF clusters (or nanoparticles). Examples of the overall reversible reaction of a conversion-type metal fluoride cathode include, for the CuF 2 system cathode, 2Li + CuF 2 ⇔ 2LiF + Cu, or for the FeF 3 system cathode, 3Li + FeF 3 ⇔ 3LiF + Fe may be included). It will be understood that metal fluoride-based cathodes can be prepared in both a Li-free state, a partially lithiated state, or a fully lithiated state. Another example of a promising conversion-type cathode (or, in some cases, anode) material is sulfur (S) (in a Li-free state) or lithium sulfide (Li2 S, in a fully lithiated state). To reduce the dissolution of the active material during cycling, improve the conductivity, or S / Li 2 To improve the mechanical stability of the S electrode, porous S, Li 2 S, porous S-C composite material, Li 2 S-C composite material, porous S-polymer composite material, or S or Li 2 S, or the formation of other composite materials containing both of them can be utilized.

[0037] Unfortunately, many conversion-type cathodes used in Li-ion batteries suffer from various performance limitations in conventional cell designs. For example, such electrodes can change volume during cycling, generating stress within the separator, which can ultimately fail, especially if the separator is made of a polymer (this is even more problematic when the cell operates at high temperatures). Thus, the use of a more robust ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating) can be particularly advantageous in cells containing conversion-type cathodes. In another example, such cathodes can begin to elute ions, which can pass through the separator and move to the anode, where they can cause damage to the solid electrolyte interphase (SEI) layer. This can lead to a decrease in capacity and an increase in resistance. Polymer separators generally cannot capture such ions, thereby causing the cell to fail. The use of ceramic separators can be advantageous because the polar nature of the ceramic separator can cause adsorption of such ions, thereby improving cell stability. In yet another example, when a portion of a conversion-type cathode dissolves, reprecipitation of dissolution products (such as polysulfides in the case of S-containing cathodes) at the electrode-polymer separator interface can be induced, which can block ion transport. In contrast, ceramic separators can reduce the formation of some of the most soluble species (e.g., longer-chain polysulfides in the case of S-containing cathodes), or adsorb them onto the internal surface, or decompose them into less soluble species. In this regard, the use of ceramic separators with a high specific surface area and high porosity (e.g., in the range of about 20.0 volume % to about 95.0 volume %, and in some designs in the range of about 30.0 volume % to about 85.0 volume %) can be particularly advantageous. In yet another example, a conversion-type active material may require operation of the cell at high temperatures (e.g., between about 30 °C and about 300 °C; e.g., to improve charge / discharge rates) at which the polymer separator can fail. In contrast, ceramic separators can operate effectively at such high temperatures.

[0038] Conventional anode materials used in lithium-ion batteries can also be of the intercalation type, where metal ions are inserted into and occupy the interstitial positions of such materials during battery charging or discharging. Such anodes experience very small volume changes when used as electrodes. However, such anodes exhibit relatively low weight and volume capacities (e.g., less than 370 mAh / g of rechargeable specific capacity and less than 600 mAh / cm 3 of rechargeable volume capacity in the case of graphite-based or carbon-based anodes). Alloying-type anode materials used in lithium-ion batteries provide higher weight and volume capacities compared to intercalation-type anodes. For example, silicon (Si) provides a weight capacity approximately 10 times higher and a volume capacity approximately 3 times higher compared to an intercalation-type graphite (or graphite-like) anode. Thus, in some designs, it may be advantageous to utilize anodes containing from about 2 wt% to about 80 wt% of Si in their composition (e.g., in some designs, anodes containing Si in the range of about 3 wt% to about 70 wt% may be used). In addition to anodes containing Si (including various Si-containing composite and nanocomposite materials), other common examples of anodes containing alloying-type active materials include, but are not limited to, those containing germanium, antimony, aluminum, magnesium, zinc, gallium, arsenic, phosphorus, silver, cadmium, indium, tin, lead, bismuth, and their alloys. In addition to anodes containing alloying-type active materials, other interesting types of high-capacity anodes can include conversion-type anode materials such as metal oxides (including silicon oxide, lithium oxide, etc.), metal nitrides, metal phosphides (including lithium phosphide), and metal hydrides.

[0039] Unfortunately, many alloying or conversion anodes used in Li-ion batteries suffer from various performance limitations in conventional cell designs. For example, such anodes can change volume during cycling, generating stress within the separator, which can ultimately fail, especially if the separator is made of a polymer (this is even more problematic if the cell operates at high temperatures). The use of the more robust ceramic (or ceramic-containing) separator layers described herein (e.g., stand-alone separator membranes or separator coatings) can be particularly advantageous in cells containing alloying or conversion anodes. In some designs, alloying or conversion anodes are thin (compared to graphite), allowing the cell to withstand higher charging currents without failure, and are thus used in Li-ion batteries designed for fast charging. Unfortunately, conventional polymer membranes are substantially resistant to fast charging, inducing an undesirably high voltage drop across the cell, and the potential for the anode or cathode potential to exceed safety limits. In some designs, using the ceramic (or ceramic-containing) separator layers described herein (e.g., stand-alone separator membranes or separator coatings) instead of polymer membranes can enable faster ion transport (e.g., a smaller voltage drop), and is thus particularly advantageous for use in such cells (especially cells designed to charge from a discharged state (or about 0-10% of their full capacity) to about 80-90% of their full capacity in less than about 30-40 minutes, including cells containing high-capacity alloying or conversion anode materials). In some designs, the use of thin (e.g., about 0.5 microns to about 10 microns) ceramic separator layers (e.g., stand-alone separator membranes or separator coatings) with a high (e.g., about 40-90%) internal porosity is advantageous for fast-charging cells (cells designed or capable of charging from a discharged state (or about 0% of their full capacity) to about 80% of their full capacity in less than about 30-40 minutes (or even less than 20 minutes)).

[0040] In some designs, alloying or conversion anodes (and / or conversion cathodes) are used in Li-ion batteries designed to achieve the highest possible specific energy or high energy density. Unfortunately, conventional polymer films are generally somewhat thick (e.g., thinner polymer films may become unsafe), which can limit the achievable energy storage characteristics. In some designs, using a thin (e.g., about 0.5 microns to about 10 microns) and safe ceramic separator layer (e.g., a stand-alone separator membrane or separator coating described herein) instead of a polymer film may result in higher energy storage characteristics, and thus may be particularly advantageous for use in such high specific energy or high energy density cells. In some designs, the use of a separator layer (e.g., a stand-alone separator membrane or separator coating) is particularly advantageous for cells with a specific energy exceeding about 270 Wh / kg (even more so for cells with a specific energy exceeding about 350 - 400 Wh / kg), or for cells with an energy density exceeding about 650 Wh / L (even more so for cells with an energy density exceeding about 750 - 850 Wh / L). Cells with high energy density may release more energy internally during self-discharge events in some designs, so the use of a more thermally and mechanically stable ceramic separator layer (e.g., a stand-alone separator membrane or separator coating) may also be advantageous from the perspective of improved safety.

[0041] Overall, high-power, fast-charging, or high-energy cells (including cells with conversion or alloying anodes or conversion cathodes) have advantages in some designs when a ceramic separator membrane (or ceramic separator layer) is used in the structure.

[0042] Furthermore, in some designs, one or more special cells that operate at elevated temperatures (e.g., operate at a temperature of about 70°C to about 500°C for at least a portion (e.g., from about 0.1% to about 100%) of their operating (charging or discharging) time) can benefit from including a thin (and in some cases flexible), more thermally stable porous ceramic (or ceramic-containing) separator layer (e.g., a stand-alone separator membrane or a separator coating), particularly one that includes small ceramic fibers or small ceramic flakes, as described herein.

[0043] In some designs, an electrically separated ceramic separator membrane suitable for energy storage devices (e.g., among others, Li-ion and Na-ion batteries, high-temperature batteries, primary batteries, electrochemical capacitors, etc.) can be manufactured from fibers of a suitable size and small aspect ratio. In some designs, small ceramic flakes may be used instead of, or in addition to, small ceramic fibers (e.g., the flakes may exhibit a contact area with fibers that is greater than the contact between fibers and other fibers in the case of randomly arranged fibers, thereby potentially enabling a stronger bond, so as to provide a more robust electrical separation between electrodes or to improve the mechanical properties of the separator). In some designs, nanoparticles may be used in addition to small ceramic flakes and / or small ceramic fibers. It should be noted that in some designs, when the flakes are oriented parallel to the plane of the separator layer, the presence of the flakes increases the tortuosity of the pores of the separator, and as a result, the ion transport rate of the separator of a given thickness is reduced. This is one of the reasons why it is advantageous that the flake-shaped particles do not exceed about 90.0 wt% of the final layer composition (in some designs, preferably 50.0 wt% or less) and do not exceed about 40.0% of the total volume of the separator layer (in some designs, preferably less than about 20.0 vol%). In some designs, it may similarly be advantageous to use smaller-sized flakes (e.g., those having a lateral dimension in the range of about 10 nm to about 10 microns). Overall, the use of flake-shaped particles can be highly advantageous in terms of the ability of the separator layer subjected to strain and stress to prevent cracking and / or the formation of internal short circuits during cell operation, although it may be somewhat counterintuitive to those skilled in the art. In some designs, it may be advantageous for small ceramic flakes to include pores (or grooves) for improving ion transport. In some designs, such pores may be oriented substantially perpendicular to the flat regions of the flakes. In some designs, the characteristic dimension of the pores (e.g., the width in the case of slit-shaped pores or the diameter in the case of cylindrical pores) can be in the range of about 0.5 nm to about 500 nm.In some designs, small pores (e.g., less than a threshold of a first characteristic dimension) may not provide sufficiently fast ion transport, while large pores (e.g., exceeding a threshold of a first characteristic dimension or a second characteristic dimension threshold higher than the threshold of the first characteristic dimension) may not provide sufficient electrical separation between the anode and cathode within the cell. In some designs, it may be advantageous for small ceramic fibers to include pores (e.g., open pores or surface pores).

[0044] In some designs, in order to achieve a combination of excellent mechanical properties, excellent transport properties, and highly reliable separation, it may be advantageous to combine small fibers of different sizes within the membrane (e.g., having various subsets where the average diameter of the small fibers differs by about 10 to 100 times, or the length of the small fibers differs by about 10 to 1,000,000 times). In some designs, small fibers can be combined with larger fibers (e.g., fibers having a diameter greater than about 1 micron or a length greater than about 100 microns) to achieve a good combination of the mechanical properties and transport properties of the membrane. In some designs, it may be advantageous to utilize ceramic fibers in the range of about 10 wt% to about 100 wt% with a diameter in the range of about 10 nm to about 200 nm. In some designs, it may be advantageous to utilize ceramic fibers in the range of about 20 wt% to about 100 wt% with a diameter in the range of about 20 nm to about 200 nm. In some designs, it may be advantageous to utilize ceramic fibers in the range of about 10 wt% to about 100 wt% with a length in the range of about 1 micron to about 500 microns. In some designs, it may be advantageous to utilize ceramic fibers in the range of about 20 wt% to about 100 wt% with a length in the range of about 2 microns to about 200 microns. In some designs, the desired variation in the fiber size can also be calculated when comparing the average diameter of the thinnest 10% of the fibers to the average diameter of the thickest 2% of the fibers, or when comparing the average length of the shortest 10% of the fibers to the average length of the longest 2% of the fibers.

[0045] In some designs, it may be advantageous to combine small flakes of different sizes within the membrane (e.g., having small flakes with thicknesses differing by about 3 to 30 times or lateral dimensions of small flakes differing by about 3 to 300 times) to achieve a combination of excellent mechanical properties, excellent transport characteristics, and highly reliable separation. In some designs, small flakes may be combined with large flakes to achieve a good combination of the mechanical properties and transport characteristics of the membrane. In some designs, porous flakes can be combined with non-porous flakes (e.g., for similar reasons). In some designs, to achieve the most preferred performance characteristics (mechanical properties and ion transport rate), it may be advantageous to combine one or two or more types of flakes of different sizes (or different compositions, porosities or surface chemistries) with one or two or more types of fibers of different sizes (or different compositions, porosities or surface chemistries) in the separator layer.

[0046] In some designs, the use of oxides (such as, among other compositions, aluminum oxide or lithium aluminum oxide, magnesium oxide, magnesium aluminum oxide, lithium magnesium aluminum oxide, zirconium oxide) in the form of small fibers or small flakes for the formation of a ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating) can be particularly advantageous in the case of Na-ion or Li-ion batteries (as well as other types of batteries and electrochemical capacitors) containing organic, polymeric, ionic liquid or molten salt (or molten-impregnated solid) electrolytes. In some designs, in the ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating), the advantages of using oxide fibers (especially small fibers) with an aspect ratio in the range of about 4 - 10 to about 1,000,000 rather than "regular" oxide particles with an aspect ratio in the range of about 1 to about 2 - 4) include high fiber flexibility, high fiber strength, high fiber toughness, the ability to achieve a very high porosity upon random packing of the fibers (e.g., about 70% or more, which can be important for high permeability), stronger interactions possible between the fibers (e.g., via larger area of bonding or entanglement compared to the interactions between particles with low aspect ratio), enhanced robustness (or resistance to crack formation or propagation) when the thickness of the electrode changes, enhanced robustness (or resistance to crack formation or propagation) when the area of the electrode is somewhat enlarged (e.g., within about 0.1 - 20%), the ability to achieve smaller pore sizes (e.g., which can be important for preventing potential Li dendrite penetration or internal short circuit during electrical contact between the anode and the cathode) as well as the ability to prepare a thin, porous separator layer (e.g., a stand-alone separator membrane or a separator coating) with low surface roughness and a low proportion of defects. In some designs, the advantage of using porous small ceramic fibers (e.g., with a porosity of about 0.05 volume% to a maximum of about 90 volume%, preferably about 5 volume% - about 40 volume%) rather than high-density small ceramic fibers (and porous small flakes rather than high-density small flakes) is that, for the same particle packing density, the porosity is higher (and thus the permeability is higher).Moreover, the small porous fibers (and optionally small flakes) may not pack as densely as normal wires due to their high surface roughness and low density, which further increases the penetration of the separator layer (e.g., a stand-alone separator membrane or a separator coating). Further, the porous ceramic fibers or flakes are lighter than high-density (e.g., substantially non-porous) ceramic fibers or flakes (even when filled with electrolyte), which is advantageous in terms of increasing the cell weight energy density. Moreover, the porous ceramic fibers or flakes may provide a larger surface area (e.g., when it is necessary to neutralize side reaction products) and may be filled with functional (nano) particles or coatings. The advantages of using smaller ceramic fibers (and smaller ceramic flakes) (e.g., fibers having a diameter of about 2 nm to about 1 micron and a length of about 50 nm to about 5 mm, or flakes having an average thickness of about 0.3 nm to about 0.6 micron and an average width of about 50 nm to about 5 mm) over larger ceramic fibers (and larger ceramic flakes) (e.g., fibers having a diameter of about 1 micron to about 20 microns or flakes having an average thickness of about 0.6 micron to about 3 microns) are, in particular, that the smaller ceramic fibers are stronger, more ductile, and more flexible (e.g., each of which is important for improving the mechanical stability during battery cycling), the level of surface smoothness achievable in the separator layer (e.g., a stand-alone separator membrane or a separator coating) is high (e.g., important for reducing stress concentration and thereby improving the mechanical stability during battery cycling), the pore size is small (thus providing more robust protection against accidental internal short circuits or penetration by small particles), and the membrane thickness is small (thus enabling faster ion transport and higher cell-level energy density).

[0047] In some designs, it can be advantageous for individual small ceramic (e.g., oxide) fibers (or flakes) within the separator membrane layer to exhibit an average tensile strength in the range of about 50 MPa to about 50 GPa (e.g., in the range of about 100 MPa to about 50 GPa) (e.g., among other advantages, for improving cell stability or improving cell assembly yield). In some designs, about 0.5 GPa to about 50 GPa.

[0048] In some designs, a separator layer (e.g., a stand-alone separator membrane or a separator coating) containing such a ceramic may further contain about 0.1 to 50 wt% of a polymer, or about 0.01 to 50 wt% of another type of ceramic particles of various shapes and sizes (hereinafter referred to as "secondary" ceramic particles), or both (e.g., for improving mechanical properties, or for shutting down the cell during overheating, or for improving the adhesion of the anode or the electrochemical stability, etc.) may be advantageous. In some designs, the polymer composition or the secondary ceramic particle composition may be disposed in a separate, discrete layer within such a separator layer (e.g., a stand-alone separator membrane or a separator coating). In some designs, the ceramic-based separator layer may be prepared as a stand-alone membrane, while in other designs, the ceramic-based separator layer can be realized as a coating of at least one electrode (e.g., the anode or the cathode or both), or can be used as both a membrane and a coating for optimal performance (e.g., the best reliability). In some designs, the ceramic-based separator layer can be realized as a coating on one or both sides of a polymer separator membrane (e.g., an aramid separator membrane). In some designs, to achieve desired performance characteristics, one electrode is coated with one type of separator layer (e.g., a polymer separator layer, or a separator layer containing one type / composition of ceramic material or one size distribution or aspect ratio distribution of ceramic material or one shape of ceramic material, or a separator layer containing a mixture of one type of polymer and one type of ceramic material or a mixture of ceramic materials including bonded or porous particles, etc.), and the other electrode may be coated with another type of separator layer (e.g., a separator layer containing another type / composition of ceramic material or a mixture of ceramic materials or another size distribution or aspect ratio distribution of ceramic material or another shape of ceramic material, or a separator layer containing a different polymer / ceramic mixture, etc.).For example, in some designs, performance improvements can be achieved based on the suppression of different side reactions on the electrodes, and / or based on different sizes of particles within the electrodes, or based on different requirements for the electrochemical stability of the anode and cathode, or based on matching or controlling the mechanical properties of different layers to reduce or prevent the formation of cracks or defects that could cause cell failure, and / or based on other reasons.

[0049] In some designs, the electrodes can be further flattened and made planar by coating them with a polymer, ceramic, or hybrid polymer / ceramic nanoparticles (of various shapes and sizes). In some designs, such a coating may be deposited prior to further coating with a layer containing small ceramic (e.g., oxide) fibers or small ceramic flakes. As an exemplary example, a self-leveling dispersion (e.g., with a target average thickness of about 3 pm) can be coated onto an electrode with a known thickness of about 80 pm (one-sided) and a maximum particle (or agglomerate) size of about 10 pm to achieve an electrode with a thickness variation of less than + / - about 1 pm. In some designs, the wet thickness can be adjusted so that surface defects are necessarily substantially covered (buffered out) by the separator layer coating.

[0050] Depending on the specific application and the composition of the membrane, in some designs, a suitable porosity in the separator layer (e.g., a stand-alone separator membrane or a separator coating) can range from about 5 volume % to a maximum of about 99.9 volume % (more preferably, from about 20.0 volume % to about 85.0 volume %), and a higher porosity may be desired for thicker separator membranes or for applications that require faster ion transport.

[0051] In some designs, a porous and flexible ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating), at least a portion of which is bonded to each other (e.g., locally sintered, or by chemical (primary) bonding, or by a ceramic or polymer or hybrid ceramic / polymer bonding layer), can include small fibers that are locally bonded to each other and / or bonded to other types of particles (e.g., flakes or particles with a low aspect ratio). In some designs, such bonding can include, in addition to or instead of chemical bonding, secondary bonding (e.g., hydrogen bonding or van der Waals bonding). Individual hydrogen bonds or van der Waals bonds are significantly weaker (exhibit lower bond energies) than individual chemical bonds, but they offer the great advantage that they can repair and improve new secondary bonds (after being broken). In contrast, broken chemical bonds are often irreparable or difficult to repair. Due to the large contact area between fibers (or flakes or particles of different shapes) involving hydrogen bonding and high-density secondary bonding, in some designs, the low strength of individual secondary bonds may be compensated for, resulting in the possibility of forming a very strong overall bond between adjacent particles (e.g., fibers, flakes, etc.). In some designs, a porous and flexible ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating), at least a portion of which is bonded to each other (e.g., locally sintered, or by chemical bonding, or by a ceramic or polymer or hybrid ceramic / polymer bonding layer), can include small flakes that are locally bonded to each other and / or bonded to other types of particles (e.g., fibers or particles with a low aspect ratio). In some designs, such bonding can include, in addition to or instead of chemical bonding, hydrogen bonding or van der Waals bonding.In some designs, a porous and flexible ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating) can include both small flakes or small fibers, at least some of which are bonded to each other (e.g., locally sintered, or bonded to each other locally by chemical bonding, or by using a ceramic or polymer or hybrid ceramic / polymer bonding layer). In some designs, such bonding can include hydrogen bonding or van der Waals bonding in addition to, or instead of, chemical bonding. In some designs, a porous and flexible ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating) can include fibers or flakes of different sizes. In some designs, it can be advantageous for the average bond strength (e.g., average tensile strength) in the bonding regions (between individual fibers or flakes or between particles of different shapes) to be in the range of about 0.01% to greater than about 100.0% (e.g., about 1% to greater than about 100%) of the average strength (e.g., average tensile strength) of the individual small fibers (or small flakes). Higher bond strength is generally advantageous for achieving high strength of the membrane. In some designs, some of the small fibers (or small flakes) can be used in combination with other (e.g., even smaller) fibers (or flakes), but in order to achieve desirable mechanical properties, they have a substantially greater diameter or thickness (e.g., 3 to 50 times), or a substantially greater length (e.g., 3 to 1,000 times), or a substantially greater aspect ratio (e.g., 3 to 1,000 times), or substantially different (e.g., 3 to 1,000 times) elasticity (maximum strain) or stiffness (modulus of elasticity), or a substantially different (e.g., about 2 to about 1,000 times) bending radius than the fibers with which they are combined. In some designs, it can be advantageous for the separator membrane layer strength to be in the range of about 1.0 MPa to about 2,000.0 MPa (in some designs, about 10.0 MPa to about 500.0 MPa) (e.g., in both tensile and compression tests). The higher the strength, the more it can help reduce the layer thickness and defects in cell manufacturing during assembly. Furthermore, the higher the strength, the more the robustness of the cell during operation can be improved.Good bonding between individual fibers (e.g., small fibers) can help achieve such strength values.

[0052] In some designs, small fibers (or small flakes) can be used in combination with large fibers (e.g., fibers having a diameter greater than about 1 micron and less than about 10 microns) or large flakes (e.g., flakes having an average thickness greater than about 0.6 micron and less than about 3 microns) to improve the properties or manufacturability of the membrane. In some designs, at least some of the small fibers (or small flakes) are bonded to the large fibers (or large flakes). Such an arrangement can allow for an improvement in mechanical stability in some designs. In some designs, the fibers may be intertwined. In some designs, the aspect ratio of at least a portion of the fibers (e.g., about 0.1 - 100%) may exceed 100. In some designs, the length of at least some of the fibers (e.g., about 0.1 - 100%) may exceed one or more average linear dimensions (e.g., average diameter) of the active electrode particles. In some designs, the length of at least some of the fibers (e.g., about 0.1 - 100%) may exceed one or more average linear dimensions (e.g., average diameter) of the active electrode particles by about 2 to about 20,000 times.

[0053] In some designs, it may be advantageous to manufacture and utilize a porous and flexible ceramic separator layer (e.g., a stand-alone separator membrane or separator coating containing small fibers) having a sufficiently low bending radius. Such parameters may depend on the mechanical properties of the membrane (e.g., the bonding area and strength between fibers, average fiber length, etc.), porosity, level of fiber entanglement, membrane thickness, and specific requirements may depend on whether the separator is stand-alone, in the form of a coating on an electrode or another membrane, the cell assembly method, cell size and shape (e.g., cylindrical cell and pouch-type cell) and / or other parameters. In some designs, it is preferred to achieve and utilize a separator layer with a minimum bending radius in the range of about 0.005 cm to about 20 cm (in some designs, about 0.1 mm to about 3 cm, in other designs, about 0.2 cm to about 2 cm).

[0054] Typical calculation units of battery cells generally include half of the anode current collector foil, one side of the anode coating, a separator layer, one side of the cathode coating, and half of the cathode current collector foil per unit area. In some designs, a porous and flexible ceramic separator layer deposited (as a coating) on either one (or both) of the surfaces of one electrode (or both electrodes) or one (or both) of the separator membranes may include small fibers or small flakes that are not strongly bonded to each other or are not strongly bonded to larger fibers or flakes using strong chemical bonds. Instead, in some designs, the small fibers or small flakes may be bonded to each other or to larger fibers or flakes using electrostatic forces or van der Waals forces or hydrogen bonds, or by using a small amount (e.g., about 0.01 to 30 wt%) of a polymer binder. In some designs, when the electrodes increase in lateral dimension during cycling, the small fibers or flakes within such one or more layers can advantageously move relative to each other without forming cracks or other undesirable defects that could cause cell failure. In some designs, using two or more separator coatings in the calculation unit of a battery cell (e.g., one on the cathode and one on the anode, or one on the separator and one on the cathode, or one on the cathode, one on the anode, and a third on the separator, etc.) can be advantageous in terms of reducing the probability of forming an internal short circuit, improving the yield of high-quality cells, and improving the robustness of the cells.

[0055] In some designs, it may be advantageous for a stand-alone separation coating layer containing small ceramic (e.g., oxide) fibers or small flakes to exhibit a thickness in the range of about 3.0 microns to about 60.0 microns (in some designs, about 5.0 microns to about 15.0 microns). For example, if the membrane thickness is too large, the energy and power density of the battery may decrease to an undesirably low level, while if the membrane thickness is too small, handling becomes difficult, achieving a high cell production yield, and preventing defects (e.g., formation of internal short circuits, etc.) during cell operation can be achieved.

[0056] As described above, in some designs, at least one (or both) of the electrodes may be coated with a separator layer. In some designs, there may be no additional stand-alone separator membranes used in the cell. In some designs, the secondary processing process for such a separator layer may require the formation of a stable dispersion of small ceramic (e.g., oxide) fibers (or flakes or other suitable particles). In conventional cell construction, stand-alone sheets of polymeric separators are secondary processed and sold to cell manufacturing facilities in large rolls. These sheets are either divided into the form factors of the desired cell structure or held as sheets wound into multi-layer cells. In some designs, a coatable dispersion of small ceramic (e.g., oxide) fibers (or flakes or other suitable particles) may be directly coated onto the surface of the electrodes while the electrodes are still on the roll (e.g., by using a roll-to-roll process). In some designs, the formation of a suitable separator coating layer can make it possible to reduce the volume fraction of the inactive material in the cell (e.g., such a layer can be configured thinner than a stand-alone separator; e.g., advantageously, the thickness is about 0.5 microns to about 5.0 microns), further simplify cell construction, and reduce the secondary processing cost of the cell. In some designs, various polar solvents can be effectively utilized for the formation of a suitable dispersion of small ceramic (e.g., oxide) fibers (or flakes or other suitable particles). Suitable examples of such solvents include, but are not limited to, water, various alcohols (ethanol, methanol, acetone, propanol, and many others), various glycols, various glycol ethers, various ethers, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), methyl ethyl ketone (MEK), hexamethylphosphoramide, cyclopentanone, acetonitrile, tetramethylene sulfoxide, ε-caprolactone, and many others (depending on polymer applications, available equipment, costs, and other factors).In some designs, the suitable viscosity of a dispersion (colloid) of small ceramic (e.g., oxide) fibers (or flakes or other suitable particles) can range from about 1 to about 10,000 cp (e.g., depending on the coating method used) and can be adjusted by adjusting the weight percentage of the solids and / or additives. In some designs, the high tensile strength requirements established for conventional stand-alone separators (established to enable processing of wound rolls of separator membranes) are significantly reduced or even completely eliminated. In some designs, suitable dispersions can include a polymer binder or a surfactant or both. For example, such polymers can help produce a more uniform dispersion of small fibers (or small flakes or small particles) and achieve better mechanical properties. In some designs, a plasticizer can be used in combination with the polymer to improve the coating characteristics of the separator. In some designs, the suitable proportion of the polymer binder in the final coating layer can range from about 0 to about 50 wt% (e.g., from about 0.5 wt% to about 50 wt%). In some designs, the suitable porosity of the final coated separator layer can range from about 10 vol% to about 90 vol% (e.g., more preferably from about 25 vol% to about 80 vol%). In some designs, such a coated separator layer can be deposited using pre-metered coating means (e.g., spray coating or slot die (or gravure) coating methods, etc.) or self-metered coating means (e.g., in particular, dip coating, roller coating, knife edge coating). In some designs, the coating layer can advantageously be deposited using a solvent-free (solvent-less) process. Examples of such suitable coatings can include, but are not limited to, magnetic assisted impaction coating, supercritical fluid spray coating, electrostatic coating, dry powder coating, photocurable coating. In some designs, it can be advantageous to heat treat the coating layer prior to final cell assembly.The suitable heat treatment temperature can be in the range of about 40 to about 200 °C, depending on the composition of the coating and the chemical properties of the battery. Such treatment can improve the adhesion and mechanical properties of the coating, help remove unwanted contaminants, or advantageously redistribute the polymeric components (if present) in the coating. In some designs, it may be advantageous not to calendar the electrodes after depositing the separator coating (e.g., to prevent the formation of unwanted defects or for other performance, stability, or cost-benefit reasons).

[0057] It should be noted that suspension compositions containing small fibers (or small flakes) as disclosed herein for the preparation of coated separator layers can also be effectively used for the preparation of stand-alone membranes. Similarly, the same or similar methods can be used for the preparation of stand-alone membranes as described herein for the preparation of coated separator layers.

[0058] In some applications (e.g., in some air filtration or some liquid filtration, or in some membranes used in energy storage (e.g., Li-ion batteries) or energy conversion (e.g., fuel cells)), the separation layers described herein can be deposited on another stand-alone or supported membrane (e.g., a membrane having larger pores or a membrane that can exhibit better mechanical properties). As described above, in some designs, at least one surface of the stand-alone battery separator membrane can also be coated with small ceramic (e.g., oxide) fibers (or flakes or other suitable particles). Such separator coatings may contain polymers and may be used in combination with the coating of at least one electrode to enhance the safety of the cell. In some designs, a roll-to-roll coating system may be utilized for the separator membrane coating.

[0059] In some designs, slot die coating can be particularly advantageously used to form a separator layer coating from a suitable dispersion of small ceramic (e.g., oxide) fibers and other suitable particles or mixtures thereof (e.g., on the surface of one or both electrodes). In some designs, this dispensing process can be particularly beneficial in situations where there are defects on the electrode surface. For example, if it is known that there is a significant thickness variation on the surface of the electrode (e.g., + / - about 1 pm or + / - about 3 pm), that uncertainty may be added to the target thickness of the separator. In this way, the valleys of the electrode can be filled and the peaks of the electrode may have an additional buffer of the separator layer. Further, since the small fibers may have a length dimension comparable to the uncertainty of the electrode coating, in some designs, it may generally be sufficient to dispense a coating of such fibers at a thickness that is twice the uncertainty of the coating layer plus the desired thickness of the separator to cover any peaks.

[0060] As described above, in some designs, a ceramic-based separator layer for energy storage applications (e.g., a stand-alone separator membrane or separator coating) can, when used in a device, be impregnated with a liquid or (at the operating temperature) solid electrolyte to obtain excellent strength, fracture resistance, outstanding thermal stability, low coefficient of thermal expansion, relatively high dielectric constant, low cost, scalable manufacturability in thin form (e.g., in some designs up to about 0.1 - 0.5 microns), good wettability with a wide range of materials, stability against reduction at low fixed potential (e.g., about 0 V with respect to Li / Li+ in the case of aluminum oxide) and oxidation at high potential (e.g., about 10 V with respect to Li / Li+), resistance to dendrite growth and / or other beneficial properties of the disclosed membranes, and these beneficial properties make the ceramic-based separator layer (e.g., a stand-alone separator membrane or separator coating) particularly attractive in a wide range of energy storage applications including, but not limited to, energy storage devices based on various metal ions (e.g., Li ions, Na ions, Mg ions, etc.) such as batteries (e.g., Li and Li-ion batteries, Na and Na-ion batteries, Mg and Mg-ion batteries), electrochemical capacitors, hybrid devices, etc.

[0061] In some designs, it may be advantageous to deposit a layer of another material on the surface of small ceramic (e.g., oxide) fibers (or flakes). This can be for reasons such as a desirable change in mechanical properties, a change in dielectric properties, a change in interfacial properties (e.g., interfacial energy, strength, wetting angle, tribology properties, etc.), a change in optical properties, protection from unwanted side reactions, and / or other reasons. In some designs, the thickness of a suitable surface layer for other materials can vary from as thin as a sub-monolayer (e.g., a discontinuous single layer with an average thickness in the range of about 0.01 - 0.2 nm) to as thick as about 1.00 pm (1 micron). In one example, an average layer thickness in the range of about 0.3 nm to about 30 nm may be preferred for many applications.

[0062] Depending on the application, the surface layer of the small ceramic fibers (or flakes) can be a polymer, carbon, dielectric, or ceramic material. Examples of suitable ceramic surface layers include, but are not limited to, various oxides, various chalcogenides (e.g., sulfides) and oxychalcogenides, various halides (e.g., fluorides) and oxyhalides, various nitrides and oxynitrides, various carbides and oxycarbides, various borides, mixtures thereof, and the like. In some applications, the surface layer of the small ceramic fibers (or flakes) can also be advantageous for forming a composite surface layer coating. In some applications, the surface layer of the small ceramic fibers (or flakes) can also be advantageous for forming a porous coating layer. In some designs, the pores of the coating layer can be filled with another functional material. In some applications, the coating layer may leave closed pores within the porous oxide fibers. In some applications, these closed pores can be filled (pre-filled) with another functional material. In some applications, the pores can be open. In some applications, the coating layer can include one or more closed and filled (pre-filled) pores together with one or more open pores (or surface pores).

[0063] In some applications, it may be advantageous to dispose two or more layers of material as a surface coating on the small ceramic fibers (or flakes). These layers can differ in terms of composition, density, porosity, surface chemistry, mechanical or optical properties, and / or other substantial differences. For example, the inner layer of the coating can have smaller pores, while the outer layer of the coating may have no pores, and thus can form closed pores within the small fibers or flakes. Such pores can advantageously be filled with another useful material that can diffuse from the membrane during the operation of the device (e.g., an electrolyte additive).

[0064] In some designs, different methods may be suitable for forming the surface layer. These include, but are not limited to, conversion reactions and deposition reactions carried out in a gaseous or liquid environment and combinations thereof. Examples of suitable deposition methods in the gas phase include, but are not limited to, various types of chemical vapor deposition (CVD) (including plasma-enhanced deposition), atomic layer deposition (ALD), physical vapor deposition (PVD, such as sputtering, pulsed laser deposition, thermal evaporation, etc.), and various combinations thereof. CVD and ALD may be preferred in some applications that require more conformal and more uniform (and relatively more economical) deposition. Examples of suitable liquid phase deposition include, but are not limited to, electroplating, plating, electrophoretic deposition, layer-by-layer deposition, sol-gel, chemical solution deposition or chemical bath deposition (CSD or CBD), etc.

[0065] In some designs, some synthesis techniques are particularly advantageous for forming small-diameter ceramic fibers (or small flakes) suitable for the separator layer (e.g., a stand-alone separator membrane or a separator coating) composition.

[0066] In some designs, techniques for the synthesis of small-diameter ceramic fibers and flakes include catalytic-assisted chemical vapor deposition (CVD), synthesis based on cylindrical templates, hydrothermal synthesis, electrospinning, formation of small rolls from platelets, etc. In some applications, such techniques may be plagued by high cost and low yield (especially in the case of CVD, electrospinning, and hydrothermal synthesis at high pressure). Moreover, the small fibers and small flakes produced by such techniques may be difficult or expensive (or not safe) to incorporate into the separator layer (e.g., a stand-alone separator membrane or a separator coating) composition.

[0067] In contrast, according to at least one embodiment of the present disclosure, small ceramic fibers (and / or small ceramic flakes) produced by certain techniques can be particularly advantageous for use in forming a suitable ceramic separator layer (e.g., a stand-alone separator membrane or a separator coating) composition. Further, in some designs, it can be advantageous to incorporate small ceramic fibers (or flakes) produced via different techniques.

[0068] One exemplary technique for forming small ceramic fibers (or flakes) is by the controlled oxidation of one or more molten metals or one or more metal alloys. In one example, small metal oxide fibers can be produced by the controlled oxidation of liquid aluminum or aluminum alloys, or liquid magnesium or magnesium alloys (in some designs, by using certain additives in these aluminum or magnesium alloys, such as, in particular, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, selenium, sulfur, silicon, germanium, tellurium, cerium, praseodymium, neodymium, cerium, promethium, samarium, europium, gadolinium, gallium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, etc.). The small ceramic fibers produced by this technique can exhibit a diameter in the range of about 3 nm to about 20 nm and a very high aspect ratio (e.g., within the range of about 50 to about 500,000), and about 0.01 cm 3 / g to about 1 cm 3The total open pore volume between ceramic fibers with a small / g range (for example, when disposed in a separator layer containing ceramic, includes the open pore volume of individual fibers such as surface pores, as well as any intervening pore spaces trapped within the fibers) may further be included. In some composite designs, the length of ceramic (e.g., oxide) fibers produced by such techniques may exceed about 1 cm, and in some cases even exceed about 10 cm (in some special cases, the length may even exceed about 100 cm). Further, in some designs, such small ceramic fibers (e.g., aluminum oxide fibers) have a total volume of 1 cm 3 or about 1000 cm 3 or (in some cases) about 1000,000 cm 3It can be manufactured in bulk (as large blocks or aggregates) that may exceed. Thus, in some designs, these bulk pieces of weakly bonded small fibers may be separated and processed to produce a suitable separator layer (e.g., a stand-alone separator membrane or a separator coating). In some designs, small ceramic (e.g., oxide) fibers may be produced by the controlled oxidation of one or more solid metal alloys of one or more suitable compositions at a suitable temperature (e.g., when no passivation oxide layer is formed and it is energetically favorable for the material to convert to a fibrous shape during the oxidation process). Another exemplary technique for the formation of small ceramic fibers (or flakes) can involve the formation of small organometallic fibers (e.g., metal alkoxide fibers, such as, in particular, aluminum ethoxide or lithium-aluminum-ethoxide or aluminum-magnesium ethoxide or aluminum-magnesium-lithium ethoxide, etc.) and subsequent conversion of them to those small ceramic (e.g., oxide) fibers. The formation of such small organometallic fiber intermediates can be effectively used for the secondary processing of porous small ceramic (e.g., oxide) fibers with controlled porosity and crystallinity (such fibers can be made, for example, X-ray amorphous or produced as polycrystals with grains of controlled size). In some designs, the formation and (membrane) use of small fibers that are amorphous (or polycrystalline with an average grain size in the range of less than about 20.0 nm, e.g., between about 0.5 nm and about 20.0 nm) can be particularly attractive (e.g., these amorphous or nanocrystalline fibers may be less brittle and exhibit higher strength or other beneficial properties).In an exemplary example, such techniques include (i) forming one or more suitable bimetallic alloys of one or more suitable compositions (e.g., Al-Li, Mg-Li, Al-Mg-Li, etc.) (e.g., a lithium-containing metal alloy with a Li content in the range of about 4 atomic % to about 50 atomic %), (ii) preferentially dissolving the more reactive metal (e.g., Li from an Al-Li or Mg-Li or Al-Mg-Li alloy), and at the same time forming small organometallic fibers of one or more less reactive metals (e.g., Al or Mg or composite metal alkoxides such as ethoxides, isopropoxides, methoxides and other related compounds), and exposing such one or more bimetallic alloys to one or more suitable solvents (e.g., suitable alcohols such as ethanol, isopropanol) to prevent passivation of the less reactive metal, (iii) exposing the small organometallic fibers to an oxygen-containing environment (e.g., dry air) to convert the small organometallic into small oxide fibers that may be porous (e.g., aluminum oxide (e.g., Al. 2 O 3)or magnesium oxide (e.g., MgO) or composite aluminum-magnesium oxide or composite aluminum-lithium oxide or aluminum-magnesium-lithium oxide or other oxides, etc.). In some techniques, small alkoxide (e.g., ethoxide) fibers may be formed from alkoxide (e.g., ethoxide) powders via solution growth in alcohol (e.g., ethanol) at high temperature (e.g., 50 to 200 °C). In some designs and applications (e.g., when used as a separator in a Li-ion battery), small oxide (or oxyhydroxide or oxyfluoride or oxynitride or, more generally, oxygen-containing) fibers or small oxide (or oxyhydroxide or oxyfluoride or oxynitride or, more generally, oxygen-containing) flakes may advantageously contain from about 2.0 atomic % to about 50.0 atomic % aluminum (Al) atoms (e.g., in some designs, from about 2.0 atomic % to about 40.0 atomic % aluminum (Al) atoms). In some designs and applications (e.g., in some filters and certain battery types), small oxide (or, more generally, oxygen-containing) fibers or small oxide (or, more generally, oxygen-containing) flakes may advantageously contain from about 0.1 atomic % to about 35.0 atomic % silicon (Si) atoms.

[0069] In some synthesis methods, the small manufactured organometallic fibers may form agglomerates (clusters), which can be at least partially separated (peeled off) into individual fibers or smaller clusters by heat treatment in a solvent (e.g., alcohol, such as ethanol, methanol, propanol, isopropanol, etc.) at a temperature in the range of about room temperature to about 200 °C (depending on specific chemical properties and solvent characteristics, including boiling points and vapor pressures at different temperatures). In some designs, the small manufactured oxide fibers may contain a significant amount of residual lithium (e.g., about 0.01 - 20 atomic %), thereby forming lithium-aluminum oxide or lithium-magnesium oxide or lithium-aluminum-magnesium oxide among other suitable compositions. In some designs of Li-ion batteries, the presence of such Li can be advantageous for the stability of the cell. In some synthesis designs, water or an aqueous solution of a desired pH (e.g., basic) can be used instead of one or more solvents to form metal hydroxide, metal, or metal oxide fibers. In some synthesis designs, the organometallic fibers may be at least partially converted to hydroxide fibers before conversion to oxide (or other ceramic) fibers. In some designs, the small ceramic fibers manufactured via the above synthesis process may exhibit an average diameter in the range of about 20 nm to about 2,000 nm (depending on synthesis conditions) and a high aspect ratio (e.g., in one example, about 20 to about 100,000, and in another example, about 50 to about 100,000). In some synthesis designs, the length of the ceramic (e.g., oxide) fibers manufactured via the above synthesis process may exceed about 10 microns. In some synthesis designs, the length of the small ceramic (e.g., oxide) fibers manufactured via the above synthesis process may exceed about 1 mm. In some designs, the small ceramic (e.g., oxide) fibers can form large aggregates or blocks (bulk pieces) when separated from the solvent and dried.

[0070] Another preferred exemplary technique for the formation of small ceramic fibers (or flakes), which similarly involves the intermediate formation of small organometallic (precursor) fibers (e.g., alkoxide precursor fibers), is based on the blow spinning (e.g., melt spinning or solution spinning) of organometallic (precursor) fibers and their subsequent conversion to their oxide (or other ceramic) fibers (including porous fibers) by heat treatment in a controlled gaseous environment (e.g., dry air or an oxygen-containing environment). In some designs, the conversion from the (precursor) fibers to oxide (or other ceramic) fibers occurs during blow spinning when the process is carried out in a suitable (e.g., oxygen-containing) gaseous environment at elevated temperatures. In some designs, flame pyrolysis can be effectively utilized. In some designs, polymers and / or other materials can be added to the blow spinning precursor solution to control its viscosity, (nano) fiber morphology, and the porosity of the final product (small fibers). In some designs, the polymer can be combusted or oxidized in the final product (small fibers) or otherwise (at least partially) removed.

[0071] In some designs, a dispersion of small ceramic (e.g., oxide) fibers (or small or large flakes) produced via the above synthesis process (or by other suitable synthesis processes) can be formed by taking one or more blocks (or one or more bundles or one or more aggregates) of small ceramic fibers (or small or large flakes), adding a solvent (e.g., alcohol or water), and then using physical agitation (e.g., milling, sonication, ultrasonic treatment, various other mixing techniques, etc.) to break up the bundles and freely suspend the individual small ceramic fibers or flakes (or small bundles of fibers or flakes less than about 10 - 20) in the solvent. In some designs, the bundles can be broken to extract the individual small ceramic fibers or flakes by heating to a high temperature (e.g., about 50 - 200 °C) and exposing to high pressure (e.g., about 1 - 1000 atm.). In some designs, a surfactant can be added to achieve a better (e.g., more stable, or containing a larger portion of the individual fibers or flakes) suspension.

[0072] In some designs, blocks (bulk pieces) of as-manufactured small ceramic (e.g., oxides such as aluminum oxide or magnesium oxide or other suitable oxides) fibers (or flakes) can be physically or chemically bonded to each other in a way that is substantially weaker than the chemical bonds that form the atomic structure of the material in the fibers (or flakes). Such weak bonds between individual fibers or flakes can be cut using appropriate forms of machining without breaking the individual fibers or flakes too much (or at least not excessively). Examples of suitable machining include, but are not limited to: ball milling (including high impact or high energy ball milling), shaker milling, planetary milling, roller milling, agitator bead milling, sonication, and ultrasonication. In some examples, the length of the as-manufactured individual ceramic fibers (or flakes) may be too long to form a stable suspension and / or be used in a separator membrane or separator coating layer. The optimal length of the individual ceramic fibers (or flakes) depends on the specific application, the specific solvent, and the specific characteristics or other elements of the designed separator layer (e.g., a stand-alone separator membrane or separator coating), but when manufactured according to the above synthesis process, it is rare for the maximum small fiber length (or the diameter of the maximum small flake) to exceed 500 microns. In some designs, the conditions suitable for the formation of a stable dispersion of small ceramic (e.g., oxides such as aluminum oxide or magnesium oxide or other suitable oxides) fibers (especially those with particles produced by the oxidation of a metal or alloy melt) or flakes (especially flakes with a thickness of less than about 50 nm) are described below.

[0073] Figure 2 shows an example image of a stand-alone Al 2 O 3 nano-fiber separator membrane 201. The membrane in this example is Al 2 O 3Prepared by coating a nanofiber dispersion and drying the coating to remove it from a substrate. Al 2 O 3 The nanofiber dispersion was prepared from as-manufactured Al 2 O 3 Nanofiber blocks (bulk pieces).

[0074] Figure 3 shows an example of a cross-sectional micrograph of a separator membrane 301 made of Al 2 O 3 Nanofibers taken by scanning electron microscopy (SEM). The membrane in this example was prepared from an Al 2 O 3 Nanofiber dispersion, and the Al 2 O 3 Nanofiber dispersion was prepared from as-manufactured Al 2 O 3 Nanofiber blocks (bulk pieces).

[0075] In some designs, milling conditions (e.g., speed, size or diameter of the medium, mass of the medium, shape of the container, type of milling, etc.) may affect the dispersion characteristics (e.g., final aspect ratio and final size distribution of small fibers or small bundles thereof, etc.).

[0076] In some process designs, a roller mill can be used to disperse the bulk of small fibers (or flakes) and achieve a final fiber (or flake) aspect ratio exceeding 10,000. In some examples, a roller mill can be used to disperse the bulk of small fibers (or flakes) and achieve a final aspect ratio exceeding about 5,000. In some examples, a roller mill can be used to disperse the bulk of small fibers (or flakes) and achieve a final aspect ratio exceeding about 1,000.

[0077] In some process designs, the bulk of small fibers (or flakes) can be placed in a (e.g., cylindrical) container along with a milling medium and a solvent. Various examples of the quality of the milling medium, the solvent, and the milling conditions are described below. In some examples (especially with respect to particles produced by oxidation of a metal or alloy melt), the diameter of the milling medium can be selected between about 0.01 cm and about 0.1 cm. In some examples, the diameter of the milling medium can be selected between about 0.1 cm and about 1 cm. In some examples, the diameter of the milling medium can be selected between about 1 cm and about 5 cm. In some designs, milling media of different sizes (e.g., diameters) and / or compositions can be combined to achieve the most desirable dispersion. In some designs, the optimal size (e.g., diameter) of the milling medium can depend on the dimensions and properties of the fibers (or flakes), the speed of mechanical agitation, the size of the container, the density of the milling medium, and / or other conditions. For example, if the diameter of the milling medium is too small (e.g., less than about 0.01 cm), there may be a non-uniform mixture of small fibers (or flakes) with a wide aspect ratio distribution and / or bundles of fibers (or flakes) that are not fully separated and dispersed. Such dispersions can have low coating quality, particularly non-wettability to the substrate, non-uniform coating thickness, and macro-porosity (the empty space of the cut film within the coating). A separator film or membrane made from a dispersion with low coating quality may have weak breaking and tensile strength, be prone to short-circuiting during secondary processing or cycling of the cell, and exhibit low ion transport properties. On the other hand, if the milling medium is too large, a medium with a diameter much larger than the width of the nanowire may not be able to interact efficiently, so the resulting dispersion can be composed of numerous bundles of wires with a large aspect ratio. Such dispersions can produce a coating film or separator membrane with insufficient surface uniformity and micro-porosity (the empty space between large fiber bundles of an undesirably large size).Films made from dispersions with low coating quality will have weakened fracture and tensile strength and will be prone to short - circuiting.

[0078] In some process designs, it may be advantageous to combine multiple media sizes for milling small ceramic fibers (or flakes), and / or use multiple milling stages with media of different sizes, and more generally, use various milling conditions (which may include using various solvents, various media, various milling energies and speeds, etc.). In some designs, it may be advantageous to mill small ceramic fibers (or flakes) through multiple stages that include different types of agitation (e.g., combining different types of milling, or combining milling and sonication (or ultrasonication) in one or more stages).

[0079] In some process designs, the solvent used in the milling process can be water. In some designs, the solvent used in the milling process can be an alcohol with a carbon chain size in the range of 1 to 5 carbons, or in the range of 6 to 10 carbons. In some designs, the optimally sized alcohol molecules (e.g., to achieve the most stable dispersion containing the highest proportion of individual small fibers or flakes or flakes / fibers of the desired size) may be affected by multiple parameters due to their influence on the dipole moment. In some designs, the solvent can be a glycol or a glycol ether. In some designs, surfactants or other additional solvents or additional salts (which may include organic or inorganic salts) can be added in small or moderate amounts (e.g., from about 0.00001 volume% to about 20 volume%) to improve the quality of the dispersion or to induce doping of the small fibers at a later stage after the preparation of the membrane (or coating) (e.g., to induce local sintering or bonding between the fibers or flakes). In some designs, different sized (or batches) of fibers can contain different additives. In some designs, these batches are mixed together prior to coating the electrode / separator or forming the membrane. In some designs, special doping of individual batches or fibers (or flakes) of different compositions can induce bonding between binders from different batches without inducing equivalent bonding between fibers (or flakes) of the same batch (e.g., by heat treatment). In some designs, the additives can be added after the dispersion or milling process. When the additives are used in the dispersion / milling process, the choice of solvent can be affected by the compatibility of the solvent and the additives. In one example, the influence of the dipole moment of the solvent can affect the flocculation (aggregation) time of particles of a given size (e.g., fibers or flakes).

[0080] In some designs, suitable materials for the milling media include, by way of example only, yttria (Y 2 O 3 ) stabilized zirconia oxide (YZT), cordierite (Al 2 O 3) can be steel, tungsten carbide, etc. In some designs, the material of the milling medium can have a great influence on the properties of the dispersion. For example, if the medium is not dense enough, the medium may not have enough inertia to break up and disperse large bundles of nanowires at a given milling speed. Conversely, if the density of the milling medium is greater than the desired density, it can cause fiber (or flake) breakage perpendicular to its "long axis", resulting in particles with an undesirable small aspect ratio.

[0081] In some designs, one or more polymers (including plasticizers in some designs) and / or one or more surfactants can be added to the slurry during milling to assist in the formation of a stable colloid containing individual small fibers (or flakes) or aggregates of only a relatively small number of small fibers or flakes (e.g., from about 2 to about 2,000).

[0082] In some examples, a suitable amount of addition of small ceramic (e.g., oxide) fibers (or flakes) in the milling container can be from about 0.01 to about 1 wt% of the total mass of the dispersion (e.g., flakes / fibers + medium + solvent + additives). In some examples, a suitable amount of addition of small ceramic (e.g., oxide) fibers (or flakes) in the milling container can be from about 1 to about 10 wt% of the total mass of the dispersion. In some designs, if the weight percentage is too high, milling may take a very long time or the medium may not affect the small fibers (or flakes) in the desired way necessary to create a substantially uniform and stable dispersion. Further, in some designs, the amount of addition of small fibers (or flakes) can directly affect the final viscosity of the dispersion, which can be an important parameter for the quality of the final separator coating (or separator membrane). For example, if the weight percentage is too low, due to medium-medium impacts / interactions during milling, the milling medium may wear out unnecessarily excessively and the dispersion viscosity may be lower than desired. In some examples, the amount of addition of the milling medium in the milling container can be from about 1 to about 50 wt% of the total mass / weight of the mixture (flakes / fibers, solvent, and additives). In some examples, the amount of addition of the milling medium in the milling container can be from about 50 to about 100 wt% of the total mass / weight of the mixture (flakes / fibers, solvent, and additives). In some examples, the amount of addition of the milling medium in the milling container can be from about 100 to about 200 wt% of the total mass / weight of the mixture (flakes / fibers, solvent, and additives). In some examples, the amount of addition of the milling medium in the milling container can be from about 200 to about 300 wt% of the total mass / weight of the mixture (flakes / fibers, solvent, and additives). In one example, if the weight percentage of the milling medium is too low, milling may take a very long time or the medium may not affect the nanowires in the desired way necessary to create a substantially uniform and stable dispersion. Further, in one example, the amount of addition of the milling medium can directly affect the final viscosity of the dispersion, which can be an important parameter for the quality of the final separator film / membrane.On the other hand, for example, when the weight percentage of the medium is too low, the milling medium may be excessively worn due to the impact of medium on medium, and the viscosity of the dispersion may be lower than desired.

[0083] In some designs, the rotational speed of the milling vessel can have a significant impact on the quality of the dispersion and may depend on the size and density of the milling media, the density and mechanical properties of the small fibers (or flakes), the density difference between the fibers and the solvent, the size of the milling vessel, and / or other parameters. In some examples, a suitable rotational speed for the milling vessel can be between about 50 and about 100 rpm. In some examples, a suitable rotational speed for the milling vessel can be between about 100 and about 200 rpm. In some examples, a suitable rotational speed for the milling vessel can be between about 200 and about 300 rpm. In some examples, a suitable rotational speed for the milling vessel can be between about 300 and about 400 rpm. In some examples, a suitable rotational speed for the milling vessel can be between about 400 and about 600 rpm. In some examples, a suitable rotational speed for the milling vessel can be between about 600 and about 2000 rpm. In some examples, a suitable speed for the milling vessel can be between about 0.3 and about 1 m / sec. In some examples, a suitable speed for the milling vessel can be between about 1 and about 2 m / sec. In some examples, a suitable speed for the milling vessel can be between about 2 and about 3 m / sec. In some examples, a suitable speed for the milling vessel can be between about 3 and about 6 m / sec. In some examples, a suitable speed for the milling vessel can be between about 6 and about 14 m / sec. In some designs, if the rotational speed of the milling vessel is too high, the resulting dispersion can contain small fibers with an undesirably low aspect ratio (e.g., down to nearly spherical nanoparticles). In some designs, a separator layer (e.g., a stand-alone separator membrane or a separator coating film) made from such an undesirable dispersion can be prone to embrittlement and cracking, with reduced mechanical properties such as weakened fracture and tensile strength, and may be prone to short-circuiting (e.g., during secondary processing and / or cycling). In one example, if the rotational speed of the milling vessel is too low, the rotational speed of the mill may not provide the media with sufficient energy to break up large bundles of fibers (flakes), and the resulting dispersion can consist of a non-uniform mixture of small fibers (or flakes) with an undesirably wide distribution of aspect ratios.Such dispersions can create films having insufficient surface uniformity and micro-porosity (e.g., void spaces between large fiber bundles of undesirably large size). Separator layers (e.g., stand-alone separator membranes or separator coating films) made from such undesirable dispersions may exhibit low quality (e.g., weakened break and tensile strength, and be prone to short circuits during cell construction or operation). In some examples, suitable milling times can range from about 10 to about 30 minutes. In some examples, suitable milling times can range from about 30 to about 60 minutes. In some examples, suitable milling times can range from about 60 to about 120 minutes. In some examples, suitable milling times can range from about 120 to about 240 minutes. In some examples, suitable milling times can range from about 240 to about 480 minutes. In some examples, suitable milling times can range from about 480 minutes to 5 days.

[0084] At the end of the milling procedure, the resulting milled product (e.g., a milled mixture of small ceramic fibers or flakes with a solvent and / or additives, etc.) can be characterized as a slurry. In some examples, a suitable final slurry viscosity can be in the range of about 50 to about 500 centipoise. In some examples, a suitable final slurry viscosity can be in the range of about 500 to about 1000 centipoise. In some examples, a suitable final slurry viscosity can be in the range of about 1000 to about 2000 centipoise. In some examples, a suitable final slurry viscosity can be in the range of about 2000 to about 10,000 centipoise. In some designs, when creating a stable functional dispersion of small ceramic fibers (or flakes), the final slurry viscosity can be an important parameter that can be controlled by the amount of milling medium added, the amount of small ceramic fibers (or flakes) added, the solvent composition, the additive composition, and / or the processing conditions. In some designs, the above conditions that can be used to control the final slurry viscosity containing small ceramic fibers (or flakes) may be quite different from the conditions that can be used to create a dispersion of nanoparticles with a similar viscosity. In other words, a desired dispersion can have a specific viscosity, but not all dispersions with a specific viscosity are desired.

[0085] There are many possible combinations for the material of the milling medium, the solvent, the additives, the milling medium size, the amount of small fibers (e.g., Al 2 O 3 or MgO or ZrO 2 fibers, etc.) added, the milling speed, and the milling time, but some such combinations can produce a much better quality of the final separator layer (e.g., a stand-alone separator membrane or a separator coating) than other combinations.

[0086] In one exemplary example of a suitable slurry formulation, 8 g of bulk small Al produced by the oxidation of an Al alloy melt 2 O 3The fibers were crushed into small pieces of about 0.05 g and placed in an 8-ounce jar. Next, 16 steel media with a diameter of 1 / 2 inch were added to the jar together with 200 ml of ethanol, and no additives were added (no salts or solvent additives). The sample was mixed on a roller and milled at 160 rpm for 12 hours to achieve a high-quality dispersion with the desired uniformity and small-sized fibers with the desired aspect ratio.

[0087] As described above, in some designs, the milling conditions optimal for achieving a good dispersion of small fibers (or flakes) from the bulk can be clearly different from those optimal for nanoparticles or large particles. For example, in some designs, media with a size of about 0.1 mm or less should preferably be used to obtain a dispersion of nanoparticles with an average size of about 100 nm. Further, in some designs, the ratio of the milling speed to the addition amount needs to be further optimized according to the type of particles being milled, the solvent, and the milling time. In contrast, in some designs, it may be preferable to use a media size of 1 mm or more to achieve a good dispersion of small fibers with a diameter of about 100 nm (e.g., suitable for secondary processing of the separator layer, such as as a stand-alone separator membrane or separator coating).

[0088] In the above example, it may be useful to consider the dimensions of the material before milling. As an example, in a milling process, the size of particles with a dimension of about 100 pm can be reduced by milling using media with a size of about 10 mm so that the average longest dimension (e.g., the length of a fiber or the width of a flake) becomes about 10 pm. In the case of fibers, in some designs, the media size can be selected to target the maximum dimension (length) of the fiber for size reduction. For example, if the fiber has a length of about 100 pm and a diameter of about 100 nm, selecting a large media diameter such as about 10 mm can preferentially reduce the length of the fiber to about 10 pm. Further, in some designs, when nanofibers of 100 pm × 100 nm are bundled into a bundle with a width of about 100 pm, the nanofibers are divided into a maximum size of about 10 pm by the milling media, but the bundle is preferentially broken and may become single fibers with a diameter of about 100 nm and an average length of less than about 10 pm, so most will be even smaller.

[0089] In some designs, the aspect ratio of the small fibers (or flakes) in the final dispersion (e.g., before forming a separator layer, such as a stand-alone separator membrane or a separator coating) can preferably be in the range of about 1:4 to about 1:1,000,000. In some examples, the aspect ratio can be in the range of about 1:50 to about 1:500. In other examples, the aspect ratio can be in the range of about 1:500 to about 1:5,000. In still other examples, the aspect ratio can be in the range of about 1:5,000 to about 1:50,000. In some designs, the aspect ratio can affect the mechanical properties (including flexibility, strength, and toughness) as well as the pore size distribution and density of the separator layer (e.g., a stand-alone separator membrane or a separator coating). In some designs, it may be desirable to combine fibers of different sizes and different aspect ratios. In some designs, the larger fibers can preferably exhibit a smaller average aspect ratio (e.g., about 2 times or about 4 times or more) compared to the smaller fibers or smaller flakes (when flakes are used instead of or in addition to fibers). Similarly, in some designs, it can be advantageous to combine small fibers and small flakes (each having its own aspect ratio distribution), or to combine larger fibers and small flakes (each having its own aspect ratio distribution), or to combine small fibers, larger fibers, and additional flakes (each having its own aspect ratio distribution).

[0090] In one exemplary example, a dispersion of small fibers with an average aspect ratio of about 1,000 (e.g., an average diameter of about 5 - 8 nm) can be mixed with another dispersion of larger fibers with an average aspect ratio of about 250 (e.g., an average diameter of about 40 - 60 nm) at a weight ratio of about 2:1. This dispersion mixture can be characterized as having a bimodal aspect ratio distribution characteristic of the two parent dispersions. Next, this mixed suspension can be utilized in the preparation of an effective separator layer (e.g., a stand-alone separator membrane or a separator coating).

[0091] In another exemplary example, a dispersion of fibers with a small average aspect ratio of about 1,000 (e.g., an average diameter between about 5 and 8 nm) can be mixed with another dispersion of fibers with a larger average aspect ratio of about 150 (e.g., an average diameter between about 40 and 60 nm) at a weight ratio of about 1:1. This dispersion mixture can be characterized by having a bimodal aspect ratio distribution characteristic of the two parent dispersions. Next, this mixed suspension can be utilized in the preparation of another effective separator layer (e.g., a stand-alone separator membrane or a separator coating).

[0092] In yet another exemplary example, a dispersion of fibers with a small average aspect ratio of about 1,000 (e.g., an average diameter between about 5 and 8 nm) can be mixed with another dispersion of porous flakes with a small average aspect ratio of about 200 (e.g., an average thickness between 3 and 6 nm) at a weight ratio of about 4:1. This dispersion mixture can be characterized by having a bimodal aspect ratio distribution characteristic of the two parent dispersions. Next, this mixed suspension can be utilized in the preparation of another effective separator layer (e.g., a stand-alone separator membrane or a separator coating).

[0093] In addition to flakes and fibers of various sizes, other types and shapes of particles or nanoparticles can be utilized in the preparation of separator layers (e.g., stand-alone separator membranes or separator coatings) in other embodiments of the present disclosure (e.g., in particular, nanostars, nanorings, planar and three-dimensional dendritic nanostructures).

[0094] Returning to the use of additives for suitable dispersions, in addition to co-solvents and salts (both organic and inorganic salts), other types of additives include, but are not limited to, (polymeric) binders, sintering agents, anti-aggregation agents, thickeners, emulsifiers, electrostatic stabilizers, surfactants, anti-aggregation agents, and / or other types of additives that can be added to the solvent (e.g., before making the dispersion) or to the dispersion itself to achieve the desired dispersion. Such materials are referred to as "additives" in the present disclosure.

[0095] In one exemplary example, an additive (e.g., a surfactant) may be added in an amount of about 2 wt% (relative to the weight of both the solvent and the small fibers or flakes) prior to the stirring process (e.g., milling). In another exemplary example, if a dispersion is pre-formed, two types of additives (e.g., a sintering aid in an amount of about 3 wt% (relative to the weight of both the solvent and the small fibers or flakes), and a surfactant in an amount of about 2 wt% (relative to the weight of both the solvent and the small fibers or flakes)) may be added. In yet another exemplary example, an additive (e.g., a surfactant in an amount of about 4 wt% relative to the weight of both the solvent and the small fibers or flakes) may be added during the application of the dispersion. In yet another exemplary example, an additive (e.g., a sintering aid) may be added to a separator layer (e.g., a stand-alone separator membrane or a separator coating) made from a dispersion of small fibers (or flakes) after applying the dispersion as a fine mist. In one example, one or more additives may also be sprayed onto a separator layer (e.g., a stand-alone separator membrane or a separator coating) (or dried fibers or flakes), deposited on top of a separator coating (or separator membrane), or introduced as a gaseous medium (vapor) among other addition methods.

[0096] In some designs, when a stand-alone separator membrane is prepared from ceramic (e.g., oxides such as aluminum oxide, lithium aluminum oxide, magnesium oxide, aluminum-magnesium oxide, lithium magnesium oxide, lithium-aluminum-magnesium oxide, zirconium oxide, etc.) particles (small flakes, small fibers, etc.), it may be important to use one or a combination of various processing techniques to achieve good mechanical properties. An example of a suitable processing technique is to bond together individual (e.g., randomly packed, mostly in-plane) small fibers or flakes (e.g., by pressure-assisted sintering or sintering including other means) in a final form to form a ceramic separator membrane. In some designs, when the dispersion contains a mixture of particles of various shapes and sizes (e.g., small fibers and large fibers or small fibers and flakes, etc.), the bonding can occur between different types of particles (e.g., in addition to inter-particle bonding of the same type). In some designs, the bonded (e.g., by local sintering) fibers (or flakes) can ideally retain the desired bending and rigidity properties while increasing the fracture and tensile strength, among other desirable properties. In some designs, one issue when using oxide fibers or flakes (e.g., small Al 2 O 3 fibers or flakes) is that such fibers (or flakes) may require high temperatures (e.g., exceeding about 800 °C) to induce bonding to each other (e.g., via sintering) without using additives, and may become undesirably coarse during the heat treatment process. Grain coarsening can sometimes cause an undesirable decrease in porosity and flexibility, and can increase brittleness and fracture toughness. Therefore, in some designs, it may be desirable to use grain growth inhibitors to achieve bonding (e.g., sintering) at low temperatures where substantial grain coarsening does not occur, or to reduce (minimize) grain coarsening at high temperatures.

[0097] In some designs, suitable additives may take the form of alkali hydroxides (e.g., LiOH, NaOH, KOH, etc.). Such hydroxides can be converted to oxides upon heating and can form eutectics with small oxide (e.g., Al 2 O 3 , MgO, ZrO 2 , etc.) fibers (or flakes), thereby enabling a lower sintering temperature. In some designs, such additives are introduced into a dispersion (suspension) of fibers (or flakes) or a pre-formed separator layer (e.g., a stand-alone separator membrane or separator coating) and are heat-treated at a temperature high enough to provide adequate mobility but low enough to induce conversion to oxides that are mainly located in areas where adjacent fibers (or flakes) contact each other.

[0098] In some designs, the separator membrane can be formed from small, elongated particles of an organometallic compound (e.g., a metal alkoxide such as aluminum alkoxide, such as aluminum ethoxide among many others) rather than from small, elongated ceramic (e.g., oxide) particles (e.g., small fibers or small flakes, etc.) of a suitable shape and size.

[0099] In one exemplary example, a small concentrated solution of LiOH in one solvent (“solvent A”) (anhydrous butanol in this example) can be added to a suspension of small aluminum (or magnesium or other suitable metal) alkoxide (e.g., aluminum ethoxide or magnesium isopropoxide, etc.) fibers (e.g., about 50 - 100 nm in diameter) dispersed in another solvent (“solvent B”) (anhydrous ethanol in this example). The mixture is then coated onto a substrate to form a thin (e.g., about 20 microns thick) film. If a dried film remains, the hydroxide and alkoxide phases can be converted to the oxide phase by heating the sample in an oxidizing environment (e.g., dry air) at a high temperature (e.g., about 300 - 1100 °C).

[0100] In some designs, it may be advantageous to form a separator layer (e.g., a separator coating or a stand-alone separator membrane) using a mixture of ceramic (e.g., oxide) particles of a suitable shape and size (e.g., small fibers or small flakes) and particles of a suitable shape and size of an organometallic compound (e.g., among others, a metal alkoxide such as aluminum alkoxide such as aluminum ethoxide). In the case of a membrane, heat treatment of the deposited membrane in a controlled environment softens the organometallic particles (e.g., small alkoxide fibers), while the ceramic particles (e.g., small oxide fibers) help the mixture retain the desired shape. Next, the heat treatment can bond the small oxide fibers to the small alkoxide fibers, whereby the oxide fibers cause the alkoxide fibers to bond (link) to each other. Further heat treatment of the membrane in an oxidizing environment can convert the alkoxide to an oxide that forms an oxide film with the desired properties (e.g., sufficient strength, flexibility, porosity, etc.). Similar additives can also be used in mixtures of alkoxides and oxides as in the case of pure oxide particles (e.g., fibers, flakes, etc.).

[0101] In some designs, suitable additives are alkali nitrates (in particular, LiNO 3 , NaNO 3 , KNO 3 , CsNO 3It may take the form of (such as), and may also decompose and react with ceramic (such as oxide) or organometallic (such as alkoxide) fibers or flakes or other particles in the original dispersion. In one exemplary example, a small concentrated solution of lithium nitrate in solvent A may be added to a solution of aluminum alkoxide (in this example, ethoxide) nanowires dispersed in solvent B. Next, the mixture is coated on a substrate to form a thin film (for example, about 5 to 100 microns), dried, and heat-treated (for example, at about 300 to 800 °C). In this example, solvent A is an anhydrous alcohol such as butanol, although not limited thereto, and solvent B is an anhydrous alcohol such as methanol, although not limited thereto. If a dried film remains, by heating the sample in an oxidizing environment, the nitrate and alkoxide phases can be converted to an oxide phase.

[0102] In some designs, suitable additives can also take the form of alkali alkoxides including LiOR, NaOR, KOR, CsOR, where R is an alkane having 1 to 10 carbon atoms.

[0103] In some designs, it may be advantageous to add lithium alkoxide to small alkoxide fibers (or flakes) in various organic solvents (for example, to aluminum or magnesium alkoxide) to control the relative solubility of the alkoxide (for example, to enable precipitation of lithium alkoxide within small metal alkoxide fibers that are later used as a sintering agent). In one exemplary example, a small concentrated solution of lithium alkoxide in solvent A may be added to a solution of small aluminum alkoxide fibers dispersed in solvent B. Next, the mixture is coated as a thin film (for example, about 3 to 50 microns) on a substrate. When the vapor pressure of solvent B is higher than that of solvent A, as solvent B evaporates, lithium alkoxide begins to precipitate and nucleate at the junctions of aluminum alkoxide nanowires where most of the surface area is available. In this example, solvent A can be an anhydrous alcohol such as butanol or another suitable solvent, and solvent B can be an anhydrous alcohol such as methanol or another suitable solvent.

[0104] In some designs, after adding suitable additives, small ceramic (e.g., oxide) or organometallic (e.g., alkoxide) fibers (or flakes or other suitable particles) are heat-treated (and bonded, e.g., sintered, where most fibers will be bonded to at least one adjacent particle such as an adjacent fiber of a flake) to form a mechanically robust porous membrane. In some synthetic designs, at least a portion of the organometallic (e.g., alkoxide) fibers (or flakes or other suitable particles) (e.g., in the membrane) can be at least partially converted to hydroxide or oxyhydroxide fibers (or flakes or other suitable particles) prior to conversion to ceramic (e.g., oxide) fibers (or flakes or other suitable particles). In some designs, such an intermediate phase can serve to bond these fibers (or flakes or other suitable particles) to form a mechanically robust porous membrane with desirable flexibility and porosity. In some designs, box furnaces, tube furnaces, belt furnaces, induction heaters or other devices can be utilized for the heat treatment. Depending on the application, suitable processing temperatures can range from about 100°C to about 1100°C for the formation of an Al 2 O 3 separator membrane and from about 100°C to about 2000°C for the formation of an MgO separator membrane. For other types of ceramic separator membranes, suitable processing temperatures can range from about 100°C to about 2000°C. In some exemplary examples, the maximum heat treatment temperature can be about 200°C to about 300°C, about 300°C to about 400°C, about 400°C to about 500°C, about 500°C to about 600°C, about 600°C to about 700°C, about 700°C to about 800°C, about 800°C to about 900°C, about 900°C to about 1000°C, or about 1000°C to about 1100°C. In some designs, it is preferred that the sintering temperature be optimized to be in harmony with the chemical nature of the additive such that the melting point or chemical reaction (i.e., phase transformation or eutectic melt) enabling sintering of the small (e.g., oxide) fibers occurs at a lower temperature than would be required without the additive.

[0105] In some designs, it may be advantageous to change the sintering atmosphere during heat treatment (e.g., to enable chemical reactions at desirable temperatures between additives and small ceramic (such as oxide) fibers, or surface reactions between small ceramic fibers). Examples of such atmospheres include, but are not limited to, in particular, nitrogen, argon, helium, hydrogen, water vapor (H 2 O), and oxygen gas or various mixtures thereof (e.g., those with a volume fraction of about 0 to about 100%). In some designs, the gas environment (e.g., in particular, H 2 O) can significantly improve the surface diffusion of species on the surface of small fibers (compared to bulk diffusion), and as a result, bonding can occur at a sufficiently low temperature such that undesirable grain coarsening does not proceed at an unduly rapid rate.

[0106] In some techniques, a reactive gas can be applied to heat small ceramic (e.g., oxide) or organometallic (e.g., alkoxide) fibers (or flakes or other suitable particles). In some designs, the heating rate and the ratio of the reactive gas flow to the non-reactive gas flow (when using a gas mixture) can be optimized for the most favorable film formation. In some designs, the ratio of the reactive gas to the non-reactive gas can range from about 0.1 to 0.990, and the temperature ramp rate can generally range from about 0.1 °C / min to about 1000 °C / min, depending on the composition and chemistry of the mixture, pressure, and environment (e.g., atmosphere). Examples of reactive gases include, but are not limited to, CO 2 、H 2 O、NH 4 OH、NH 3 、O 2 、H 2 、and NF 3 . Examples of non-reactive gases include Ar, N 2 , and other noble metals.

[0107] In some designs, laser treatment or plasma treatment can be used to induce bonding between small ceramic (e.g., oxide) or organometallic (e.g., alkoxide) fibers.

[0108] In some designs, mechanical pressure (or hydrostatic pressure) (e.g., within the range of about 1 to about 50,000 atm.) can be advantageously applied during sintering (bonding) to increase the interfiber contact surface area during the sintering (bonding) process. In some examples, such pressure can be applied by hot pressing, pressure due to gravity, or negative pressure due to dynamic vacuum.

[0109] In some designs, the heat applied to small ceramic (e.g., oxide) or organometallic (e.g., alkoxide) fibers (or flakes or other suitable particles) can use a specific ramp rate during one or more heating stages for optimal film formation. For example, a suitable ramp rate can generally range from about 0.1 °C / min to about 1000 °C / min, depending on the composition and chemistry of the mixture, pressure, and environment (e.g., atmosphere).

[0110] In some designs, the polymer separator can include oxide particles incorporated within one of the pores or on its surface. In these examples, the main function of the polymer separator is to electrically separate the anode and cathode, while the oxide particles are added to provide a special level of safety at high temperatures where the polymer membrane can shrink and break. Unfortunately, the overall thermal stability of such composite membranes can be quite poor, the adhesion of the particles to the membrane may not be very good (e.g., ceramic particles may fall out of the membrane during handling), and the overall thickness of such composite membranes is generally quite large (e.g., in some designs about 1 to 30 microns, in other designs within about 15 to 30 microns).

[0111] One or more embodiments of the present disclosure provide for the addition of one or more polymeric additives that serve primarily as an improved mechanical support or as a binder that binds (or aids in binding) small ceramic (e.g., oxide) fibers (or other suitable particles such as flakes or mixtures thereof) together (or, in some designs, with an electrode or another membrane). In such designs, the addition of the polymer improves the mechanical properties (e.g., strength, flexibility, adhesion, fracture toughness, etc.) of the separator membrane or separator membrane layer containing the small fibers. In some designs, by adding the polymer to the membrane, when the separator membrane is in direct contact with the anode at a potential where electrochemical reduction can generally occur, the electrochemical reduction of small ceramic (e.g., oxide) fibers (or other suitable particles such as flakes or mixtures thereof) can be reduced or prevented. For example, an anode containing lithium or graphite or Sn or Si in a Li-ion battery may be exposed to a sufficiently low potential that can induce unwanted electrochemical reduction of the oxide (or ceramic) fibers in direct contact with it, which can lead to irreversible Li loss. In some designs, a thin layer of the polymeric binder between the anode and the membrane or the addition of a small amount of the polymeric binder to the membrane can prevent such unwanted results.

[0112] In some designs, at least a portion of the polymeric component of the membrane (including other suitable particles such as small ceramic (e.g., oxide) fibers or flakes or mixtures thereof) can be in the form of polymeric fibers (including porous fibers and small fibers) or polymeric flakes (including small flakes and porous flakes) or composite material fibers containing polymers or composite material flakes containing polymers. Such polymeric fibers (or flakes) can combine with and / or entangle with small ceramic fibers (flakes) to improve the mechanical properties or processability of the separator membrane. Due to the high elasticity (and deformability) of the polymeric component, the polymeric component helps to form bonds with ceramic particles over a wider contact area, thus enhancing the overall strength of the membrane. Moreover, in some designs, the polymeric component can enhance the overall elasticity and overall toughness of the membrane. In some designs, the polymeric component (e.g., fibers or flakes) can help to form a more stable suspension of ceramic particles to form a more uniform separation layer. In some designs, the polymeric fibers or flakes can have dimensions or aspect ratios smaller than those of the ceramic fibers or flakes (e.g., the polymeric fibers or flakes can have a diameter or thickness in the range of about 1 nm to about 200 nm). In some designs, when the diameter of the polymeric fibers is small, the proportion of chemical groups is high (compared to the total mass of the polymer), and furthermore, the polymeric fibers or flakes are more easily deformable (e.g., bending around ceramic particles), thus potentially forming more bonds with ceramic particles. Moreover, small polymeric fibers (or flakes) can exhibit higher (normalized cross-sectional area) strength (compared to large polymeric fibers or flakes). At the same time, large fiber dimensions result in an absolutely high fiber strength and can thus be advantageous in some designs. Thus, in other designs, the polymeric fibers or flakes can have dimensions or aspect ratios larger than those of the ceramic fibers or flakes (e.g., within a diameter or thickness range of about 200 nm to about 10 microns).In still other designs, it may be advantageous to utilize combinations of polymer fibers (or flakes) of different sizes, or to utilize both fibrous (flaky) and non-fibrous polymers (e.g., as particles having a lower aspect ratio or random shape, or as a coating). In some designs, the polymer fibers or flakes may form primary (chemical) bonds with the ceramic particles within the membrane. In other designs, the polymer fibers or flakes may form secondary bonds with the ceramic particles (the advantages of which have already been described). Depending on the use and dimensions of the ceramic particles, the aspect ratio of the polymer fibers or polymer flakes can range from about 10 to about 10,000,000.

[0113] In some designs, it may be advantageous for individual polymer flakes or fibers to exhibit a tensile strength in the range of about 10 MPa to about 10 GPa. In some designs, it may be advantageous for polymer flakes or fibers to exhibit a thermal stability in the range of about 120 °C to about 400 °C. Examples of polymer fibers (or nanofibers) having such thermal and mechanical properties include, but are not limited to, various cellulose fibers (or nanofibers), various chitin fibers (or nanofibers), and various aramid fibers (or nanofibers).

[0114] In some designs, it may be advantageous for individual polymer flakes or fibers to include functional groups for primary or secondary bonding with ceramic fibers (including small fibers) or flakes (including small flakes).

[0115] In some designs, it may be advantageous for a separator layer containing ceramic to exhibit a tensile strength (measured in air at room temperature) in the range of about 1 MPa to about 1,000 MPa. In some designs, it may be advantageous for a separator layer containing ceramic to exhibit a tensile strength in the range of about 1 MPa to about 1,000 MPa within the operating temperature range (the specific temperature range varies depending on the application; in some designs, it can range, for example, from as low as -70 °C to as high as +200 °C).

[0116] In some designs, it may be advantageous for a separator layer containing ceramic to exhibit a room temperature tensile strength in the range of about 1 MPa to about 1,000 MPa when immersed in an electrolyte or electrolyte solvent mixture.

[0117] In some designs, it may be advantageous for a separator layer containing ceramic to exhibit a compressive strength (measured in air at room temperature) in the range of about 1 MPa to about 2,000 MPa. In some designs, it may be advantageous for a separator layer containing ceramic to exhibit a compressive strength (measured in air at room temperature) in the range of about 1 MPa to about 2,000 MPa in the operating temperature range (the specific temperature range varies depending on the application; in some designs, it can range, for example, as low as -70°C to as high as +200°C).

[0118] In some designs, it may be advantageous for a separator layer containing ceramic to exhibit a room temperature tensile strength in the range of about 1 MPa to about 1,000 MPa when immersed in an electrolyte or electrolyte solvent mixture.

[0119] In some designs, it may be advantageous for a separator layer containing ceramic to exhibit a room temperature compressive strength in the range of about 1 MPa to about 2,000 MPa when immersed in an electrolyte or electrolyte solvent mixture.

[0120] In some designs, a separator layer containing ceramic may exhibit an air permeability (pressure difference applied across the entire membrane) of about 1 L / m 2 second to about 50,000 L / m 2 second, depending on the application and the permeability of the support electrode or membrane (if present). The higher the air permeability, the more advantageous it may be for high-speed applications of batteries and supercapacitors.

[0121] In some designs, it can be advantageous for the separator layer containing ceramic to exhibit a pore exclusion size of about 1 micron or less (e.g., about 10 nm to about 1,000 nm). That is, even if large pores are present in the separator layer, they are connected only by sub-micron pores, so particles larger than, for example, 1 micron (or a specific pore exclusion size) cannot penetrate the membrane.

[0122] As described above, the polymer ceramic membrane can be advantageously heat-treated (including heat-treatment under pressure) at a temperature in the range of about 40 to about 300 °C (depending on the polymer composition and properties such as glass transition temperature, decomposition temperature, thermal expansion, etc.). In some designs, a polymer-containing composite membrane containing small ceramic (e.g., oxide) fibers (or other suitable particles such as flakes or mixtures thereof) can include composite fibers containing both smaller ceramic (e.g., oxide) fibers and one or more polymers. In some designs, the proportion of such composite fibers in the separation membrane can be in the range of about 1 to about 100 wt%. Such composite fibers (including small composite fibers) can be manufactured by various spinning techniques such as blow spinning, electrospinning (e.g., melt spinning or solution spinning), and more traditional spinning techniques (e.g., wet spinning, dry jet spinning, dry spinning, etc.). Such methodologies can depend on the formation of a polymer-small fiber-solvent colloid or, for example, in the case of melt spinning, the formation of a polymer-small fiber melt. In one example, blow spinning and electrospinning can produce composite fibers with a much smaller diameter (down to 10 nm if the small ceramic fibers are 10 nm or less). During spinning, in some designs, most of the small ceramic fibers can be oriented parallel to the length of the fiber.

[0123] The relative weight, distribution, and volume fraction of the polymer in various (e.g., the above-mentioned) polymer-small ceramic fiber (or polymer-small ceramic flake or, more generally, polymer-ceramic particle) composite membranes determine their thermal, physical, and chemical properties and can be optimized for specific applications. For example, an increase in the proportion of the polymer component may result in a decrease in polarity, a decrease in thermal stability, an increase in thermal expansion, a decrease in strength, an improvement in flexibility, an increase in maximum elongation, an improvement in processability, and a decrease in oxidation stability. In another example, an increase in the proportion of small ceramic (e.g., oxide) fibers (or flakes or other suitable particles) may result in good electrolyte wetting, a high average dielectric constant, surface dipoles and electrostatic interactions with the particles, high mechanical strength (especially when compressed), high wear resistance, a low coefficient of thermal expansion, and / or good thermal stability. In a further example, the highest fracture toughness or toughness coefficient of such a membrane can be achieved for some optimal weight fractions of the components (depending on processing conditions, size, properties and shape of the small ceramic fibers, properties and shape of the polymer component, bond between the polymer and ceramic particles, contact area between the polymer and ceramic particles, etc.). Overall, in some designs, the appropriate amount (relative to the total weight of the ceramic polymer) of the polymer component (or binder) of the separator membrane is generally in the range of about 0.0 wt% to about 80.0 wt% (depending on the application, but also on the preparation conditions and the desired separator membrane properties). Depending on the processing conditions, an excessive proportion of the polymer component may cause, among other undesirable membrane properties, a decrease in the permeability and porosity of the membrane, a decrease in wetting by the electrolyte, and a decrease in thermal stability.

[0124] In some designs of the polymer-ceramic composite membrane, small ceramic (e.g., oxide) fibers (or other suitable particles such as flakes or mixtures thereof) can provide most of the electrical separation between the anode and the cathode, while one or more polymer additives can still provide some increased electrical separation between the anode and the cathode. In one example, a relatively small weight percentage of the added polymer (e.g., about 0.1 to 20 wt% based on the total weight of the dry composite membrane) can be used to bond small ceramic (e.g., oxide) fibers (or other suitable particles such as flakes or mixtures thereof) at their joints or to the electrode layer itself, with the aim of adapting well to changes in the size of one or more electrodes during cycling. In some examples (e.g., when the membrane is prepared from a dispersion), the polymer binder can be added to the dispersion of small ceramic (e.g., oxide) fibers (or flakes or other particle types) in an amount of about 0.001 to 0.01 wt% (based on the total mass of the oxide fibers or other oxide particles and the solvent). In other examples, the binder is added to the small fiber dispersion in an amount of about 0.01 to 0.1 wt% (based on the total mass of the oxide fibers or other oxide particles and the solvent), and in still other examples, the binder can be added to the dispersion in an amount of about 0.1 to 50 wt% (based on the total mass of the oxide fibers or other oxide particles and the solvent). The relative proportion of small ceramic (e.g., oxide) fibers in the polymer-ceramic composite membrane can be quite broad and can range from about 5 wt% to about 99.9 wt%. In some designs, the polymer component can also help achieve a uniform distribution of ceramic particles within the membrane layer. In some designs, the polymer component may form a primary (chemical) bond with the ceramic particles. In other designs, the polymer component may form a secondary (e.g., hydrogen or van der Waals) bond with the ceramic particles. In some designs, both primary and secondary bonds can exist between the polymer component and the ceramic particles.

[0125] In some examples (depending on the particular application, synthesis method, and desired properties), the polymeric component of a composite polymer - small ceramic fiber (or polymer - small ceramic flake, or more generally, polymer - ceramic) membrane may include a thermosetting or thermoplastic polymer (stand - alone, as a mixture, or as a copolymer component), including, but not limited to, various polysaccharides and, without limitation, mixtures of polysaccharides with other polymers such as proteins (e.g., in particular, arabinoxylan, gum arabic, xanthan gum, pectin, chitin and chitin derivatives, various modified natural polymers such as cellulose and cellulose derivatives including cellulose acetate (CA), cellulose acetate butyrate (CBA), carboxymethyl cellulose (CMC), cellulose nitrate (CN), ethyl cellulose (EC), especially cellulose derivatives, alginates including alginic acid and its salts); acrylonitrile - butadiene - styrene (ABS); allyl resin; casein (CS); cresol - formaldehyde (CF); chlorinated polyethylene (CPE); chlorinated polyvinyl chloride (CPVC); various epoxies (polyepoxides) (including fluorinated epoxies); epichlorohydrin copolymer (ECO); ethylene - propylene - diene terpolymer (EPDM); ethylene - propylene copolymer (EPM); ethylene - vinyl acetate copolymer (EVA); ethylene - vinyl alcohol (E / VAL);Various fluoropolymers (e.g., polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy polymer (PFA / MFA), fluorinated ethylene-propylene (FEP), tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride and their copolymers (e.g., THV), polyethylene tetrafluoroethylene (ETFE), polyethylene chlorotrifluoroethylene (ECTFE), various perfluoroelastomers (FFPM / FFKM), chlorotrifluoroethylene vinylidene fluoride (FPM / FKM), tetrafluoroethylene propylene (FEPM), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoropolyoxetane, polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), etc., various fluorocarbons, various fluorosilicone rubbers (vinyl, methyl, etc.)); various ionomers - thermoplastic polymers; isobutene-isoprene copolymer (IIR); various liquid crystal polymers (LCP); melamine formaldehyde (MF); natural rubber (NR); phenol-formaldehyde plastic (PF); polyoxymethylene (POM); polyacrylate (ACM); polyacrylic acid (PAA); polyacrylamide, polyacrylonitrile (PAN); various polyamides (PA) (including various aromatic polyamides often called aramid or polyaramid); polyaryl ether ketone (PAEK); polybutadiene (PBD); polybutylene (PB); polybutylene terephthalate (PBTP); polycarbonate (PC); polychloromethyloxirane (epichlorohydrin polymer) (CO); polychloroprene (CR); polydicyclopentadiene (PDCP); polyester (in the form of thermoplastic or thermosetting polycondensates); polyether ether ketone (PEEK); polyether imide (PEI); polyether sulfone (PES); polyethylene (PE); polyethylene chlorinates (PEC); polyethylene terephthalate (PET);Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS); phenol-formaldehyde (PF); polyimide (PI) (as a thermoplastic or thermosetting polycondensate); polyisobutylene (PIB); polymethyl methacrylate (PMMA); polymethylpentene (PMP); polyoxymethylene (POM); polyketone (PK); polymethylpentene (PMP); polyethylene oxide (PEO); polyphenylene oxide (PPO); polyphenylene sulfide (PPS); polyphthalamide (PTA); polypropylene (PP); propylene oxide copolymer (GPO); polystyrene (PS); polysulfone (PSU); polyester urethane (AU); polyether urethane (PUR); polyvinyl alcohol (PVA); polyvinyl acetate (PVAc); polyvinyl butyral (PVB); polyvinyl chloride (PVC); polyvinyl formal (PVF); polyvinylidene chloride (PVDC); styrene-acrylonitrile copolymer (SAN); styrene-butadiene copolymer (SBR and YSBR); various silicones (SI) (e.g., polydimethylsiloxane, polymethylhydrosiloxane, hexamethyldisiloxane, Sylgard® , various silicone elastomers ((phenyl, methyl)(PMQ), (phenyl, vinyl, methyl)(PMVQ), (vinyl, methyl)(VMQ), etc.); polyisoprene; urea-formaldehyde (UF) is included. In some designs, some such polymers may be at least partially fluorinated.;

[0126] In some designs, the polymers and copolymers of the composite polymer-small ceramic fiber membranes can include at least one of the following monomer components: In particular, acrylates and modified acrylates (such as methyl acrylate, methyl methacrylate, etc.), diallyl phthalate, dianhydrides, amines, alcohols, anhydrides, epoxies, dipodals, imides (polyimides), furans, melamines, parylenes, phenol-formaldehyde, polyesters, urea-formaldehyde, urethanes, acetals, amides, butylene terephthalate, carbonates, ether ketones, ethylene, phenylene sulfide, propylene, styrene, sulfones, vinyls, vinyl butyral, vinyl chloride, butylene, chlorobutyl, fluorobutyl, bromobutyl, epichlorohydrin, fluorocarbon, isoprene, neoprene, nitriles, sulfides, silicones, etc.

[0127] In some designs, silane coupling agents can be used to create strong bonds between polymers and ceramic (e.g., oxide) interfaces. These molecules generally can link non-reactive surfaces because they have functional organic groups and functional silane groups (R-Si-X3, where R is an organic ligand and X is generally alkoxy, acyloxy, halogen, or amine). These groups can covalently bond or physically interact with polymer and inorganic (ceramic such as oxide) surfaces. Examples of the three main structures of silane coupling agents include trialkoxysilane, monoalkoxysilane, and dipodal silane. The bonding proceeds by hydrolysis of the silane groups, and hydroxy-functional groups can be generated. The individual silane monomers can then polymerize through a condensation reaction. Next, the hydroxy groups bonded to silicon can hydrogen bond to the hydroxy bonds of the inorganic substrate and subsequently be used as oxygen for cross-linking to the siloxane polymer to form a covalent bond. The organic functional groups are also connected to the siloxane polymer and can function as sites for organic molecules to bond either chemically (e.g., covalently) or by secondary bonding / physical interactions (e.g., van der Waals, ionic interactions, hydrogen bonding, etc.). Anhydrous bonding may also be possible, where the monomer silane groups covalently bond to the inorganic substrate through oxane bonds. Adding monomers to the substrate may be able to produce a monolayer thin film of the silane coupling agent. Silane coupling agents can be used with polymers by treating the finished polymer or by including the silane coupling agent as a copolymer. Silane coupling agents can be used for modifying resins by compounding or coating, or for surface treatment of fillers or ceramic particles.

[0128] In some designs, a silane coupling agent can be used to obtain a stronger connection to the inorganic (e.g., ceramic) and organic (e.g., polymer) components in the composite separator layer material. The composite separator layer containing the silane coupling agent can have improved mechanical stability, good thermal stability, higher ionic conductivity, and other property improvements. With the help of the silane coupling agent, a wider range of polymer materials that can normally be used with incompatible (or non-bonding) ceramics may also be available. In one example, the ceramic material (e.g., ceramic fiber or flake) is functionally modified using a silane coupling agent. Both hydrolytic (usually trialkoxysilane, dialkoxysilane) or anhydrous (monoalkoxysilane) covalent bonds can be used depending on the ceramic, precursor, and / or water sensitivity of the surrounding material. This can be anhydrous liquid phase deposition (in one example, using a reflux substrate containing about 5% silane coupling agent in toluene, tetrahydrofuran, and / or hydrocarbon solution), aqueous alcohol deposition (in one example, about 95% EtOH / about 5% H adjusted to a mixture of about pH 5) 2In O, about 2% silane is used), aqueous deposition (in one example, about 0.5 - 2.0% silane adjusted to a pH of about 5.5 and about 0.1% non-ionic surfactant are used), dip coating (in one example, by immersing the ceramic sample in a 2% silane solution for about 1 - 2 minutes), spray deposition (in one example, by spraying a 25% silane solution onto the ceramic powder or film), or vapor deposition (in one example, at about 5 - 50 Torr and about 50 °C to about 200 °C) can be carried out. The hydrolysis stability of the ceramic-polymer matrix may be increased using dipodal silanes. Alternatively, a silane coupling agent can be introduced as a monomer component of the copolymer to improve mechanical strength, thermal stability, and bonding ability. Some examples of silane coupling agents that can be used to crosslink ceramic composites include, but are not limited to: among other functional silanes, acrylate, methacrylate, aldehyde, amino, anhydride, azide, carboxylate, phosphonate, sulfonate, epoxy, ester, halogen, hydroxyl, isocyanate, masked isocyanate, phosphine, phosphate, sulfur, vinyl, olefin, polymer, UV active, fluorescent, chiral, trihydro, dipodal, etc.

[0129] In some designs, it may be advantageous for the composite film to utilize a thermally stable polymer that maintains at least 50% of the room temperature tensile strength at high temperatures in the range of about 120.0 °C to about 450.0 °C in an inert environment or in air (in some designs, it may be desirable for such thermally stable temperatures to exceed 150 °C or even 200 °C). In some designs, such polymers may advantageously contain nitrogen (N) and / or fluorine (F) in their atomic composition. In some designs, the atomic fraction of N or F or both (N + F) can range from about 5 atomic % to about 70 atomic %. Examples of such polymers include, but are not limited to, Viton (chemical structure (C 3 F 6 ) n (C 2 H 2 F2 ) m ) and various polyimides (especially semi - aromatic and aromatic polyimides) (for example, among many, pyromellitic dianhydride and p,p’ - diaminodiphenyl ether, polyimide (III) of poly - oxydiphenylene - pyromellitimide). In some designs, it may be advantageous to utilize polyimides with side chains or functionalized polyimides to bond with small ceramic fibers.

[0130] In some designs, it may be advantageous to expose a membrane of compatible polymer - small particles (e.g., small ceramic fibers, small ceramic flakes, etc.) to ultraviolet (UV) light at a temperature close to room temperature in a compatible atmosphere, which cures / cross - links the polymer without degrading its properties (in some cases simply in air, in an oxygen - containing environment).

[0131] In some designs, a metal salt or salt mixture (e.g., inorganic or organic or mixed) can be added to a suspension (dispersion) of small alkoxide or oxide fibers (e.g., flakes or other suitable particles or particle mixtures) before forming the separator membrane, or before permeating the membrane after its pre - formation and drying. Such salts or salt mixtures can have various anions (e.g., F - , Cl - , Br - , I - , NO 3 - , SO 4 - , CO 3 2- , C 2 O 4 2- , ClO 4 - , BF 4 - , PF 6 -and may include the hydrated forms of these and other compounds). Examples of suitable organic anions of suitable salts include, but are not limited to, acetate and substituted acetates, 2-ethylhexanoate and substituted carboxylic acids, cyclopentadienide, substituted cyclopentadienide, cyclooctadienide and substituted cyclooctadienide, triphenylphosphine and substituted triphenylphosphine, acetylacetonate and substituted acetylacetonate, diketimine and substituted diketimine, bipyridine and substituted bipyridine, bis[1-N,N-dimethylamino)-2-propanolato (DMAP), acetonitrile dihalide, carbonyl and substituted carbonyl, cyclohexane and substituted cyclohexane, stearate and substituted stearate, porphyrin and substituted porphyrin, formate, acetate and alkyl acetate. Examples of cations (or mixtures thereof) of suitable salts include, but are not limited to, in particular, Al 3+ Li + Na + Mg 2+ Ca 2+ Cr 3+ Cr 4+ Cr 5+ Cr 6+ K + Zr 4+ Zn 2+ Sr 2+ Ti 4+ Sc 3+ Fe 2+ Fe 3+ Cu 2+ and the like. In some designs, Rb + Co 2+ Co 3+ Ni 2+ Mn + Mn 2+ Mn 3+ Mn 4+ Mn 5+ Mn 6+ Mn 7+ Ta 3+ Ta 4+ Ta 5+ Si 4+ Ge4+ , La 3+ , V 5+ , V 3+ , Cs + , Ba 2+ , Sr 2+ etc. can also be used.

[0132] Such salts or salt mixtures can be dissolved in a compatible solvent before their addition. Next, these metal salts can be converted to oxides by exposure to UV light, binding adjacent particles (such as small fibers or flakes, etc.) to form a robust and flexible separator layer (such as a stand-alone separator membrane or separator coating). In some examples, Ga(OR) 3 , Ti(OR) 4 , Zr(OR) 4 , V(OR) 5 , Ni(OR) 2 , CuOR, Zn(OR) 2 , LiOR, NaOR, KOR, Mg(OR) 2 , Ca(OR) 2 etc. of metal alkoxides can be added to a dispersion of small fibers of ceramic (such as oxide) and other particles and can be converted to oxides by exposure to UV light and an oxygen-containing atmosphere (such as the ambient atmosphere, etc.). Since this process is at a low temperature, it minimizes thermal stress and is suitable for heat-sensitive substrates, so it is particularly attractive (for example, it is very attractive for forming a separator layer as a coating on the surface of an electrode or separator).

[0133] In some designs, siloxane can be used as a binding additive, which can be converted to SiO 2 . For example, O 2 is converted to O 3- by UV light at 185 nm, and then O 3- can photodissociate to form molecular oxygen and atomic oxygen under exposure to UV light at 254 nm. Next, atomic oxygen can react with siloxane (or metal alkoxide) to form SiO 2 (or metal oxide). In other designs, SiO 2The binder can be formed by gas-phase chemical adsorption of organosilane followed by photo-oxidation using 172 nm vacuum ultraviolet (VUV) light.

[0134] In some designs, small organometallic fibers (e.g., small alkoxide fibers) (or flakes or other suitable particles) or small hydroxide fibers (or flakes or other suitable particles) can be converted to oxide fibers (or flakes or other suitable particles) by exposure to ultraviolet light or ozone. In some designs, such exposure to UV light can induce bonding of the randomly (or oriented) fibers (or flakes) to other adjacent fibers (or flakes), producing a robust and flexible oxide film. In some designs, such small organometallic (or hydroxide) fibers (or flakes) can be mixed with oxide or other ceramic fibers (small or large) or flake-shaped particles (small or large) prior to UV exposure. In some designs, the fiber (or flake) dispersion (with or without additional salts) can be coated onto a substrate prior to UV exposure. In some designs, the fiber (or flake) coating can be dried prior to UV exposure. In some designs, the fiber (or flake) coating can be densified prior to UV exposure (e.g., by applying mechanical pressure, e.g., by calendaring). In some designs, the fiber (or flake) coating can be heated prior to UV exposure (e.g., to a temperature in the range of about +30 °C to about 500 °C or higher).

[0135] In some designs, the UV exposure can be performed at elevated temperatures. In some designs, such elevated temperatures can be in the range of about +30 °C to about 1200 °C.

[0136] In some designs, by using a very thin (e.g., less than about 5 - 10 pm) and very porous (e.g., porosity greater than about 75% of the total porosity) aluminum oxide (or other suitable oxides and suitable ceramics) membrane, it may be possible to improve or maintain the required level of safety while significantly increasing the rate characteristics and energy density not only of Li and Li-ion batteries but also of other batteries. Coupled with mechanical integrity and flexibility, this level of porosity, which is beneficial for high rate characteristics, may be achievable using small fibrous or flaky structures. However, ceramic structures based on "regular" (e.g., approximately spherical) particles, in contrast, require a fairly high density of packing to form a mechanical network and are generally not very flexible. Since they have high stability at high potentials, such membranes can be used in combination with high voltage cathodes (e.g., cathodes with an average lithiation potential of about 3.9 to about 5.6 V versus Li / Li+) in Li and Li-ion battery cells.

[0137] As described above, in addition to using a stand-alone (e.g., porous aluminum oxide) separator membrane, small fibers or flakes (e.g., made of aluminum oxide or porous aluminum oxide) can be deposited directly onto at least one of the electrodes (or onto another membrane) by using casting (e.g., slot die casting or blade casting), or by spray deposition, or by deposition using an electric field, or by dip coating, or by another suitable method. In some designs, such deposited fibers can provide a small resistance to ion transport and occupy a relatively small space while serving as an integrated (thin and flexible) membrane that separates the anode and cathode from direct electrical contact. In examples where the separator is manufactured by casting from a dispersion or by spray drying, the separator can be dried at a temperature in the range of about 40 °C to about 400 °C (after casting / spray drying).

[0138] Figure 4 shows a small Al on the electrode for generating a separator layer as a coating on the anode 402 of a Si-based Li-ion battery coated on a Cu foil 401 2 O 3 An example of the fiber coating 403 is shown.

[0139] Figure 5 shows the performance characteristics comparison of four full cells with Si-based Li-ion battery anodes (thickSSAnode and thinSSAnode) constructed with either of two thicknesses of small Al 2 O 3 fiber separators directly coated on a high-voltage lithium cobalt oxide (LCO) cathode and a Si anode, and conventional commercially available polymer (PP) separators (control 4 and control 5). All cells tested were constructed with the same anode and cathode. The capacity (mAh / g) is normalized by the weight of the anode coating. The mid-cycle hysteresis (V) was recorded when the cell was cycled at C / 2 rate. It can be clearly seen in Figure 5 that the cells with small Al 2 O 3 fiber separator layer coatings have less hysteresis.

[0140] Al 2 O 3 In addition to the separator layer (e.g., coating or stand-alone film), other ceramic separator layers (including layers made of or containing small fibers or small flakes such as porous small fibers and flakes) can be used as separators in Li-ion and other batteries. These include MgO, ZrO 2 , various mixed oxides, etc. Some important parameters in the design are generally the mechanical properties, the stability of the ceramic membrane in the electrolyte, and the absence of electrochemical side reactions (e.g., significant lithiation or dissolution in contact with the electrode) when in direct contact with the positive or negative electrode.

[0141] In some applications, in order to further reduce the small side reactions with the electrodes, it may be advantageous to deposit a porous polymer layer on one or both sides of a stand-alone ceramic (Al 2 O 3 , MgO, ZrO 2 etc.) separator membrane. For example, when using such a membrane in a Li or Li-ion (or Na or Na-ion or other metal or metal-ion) battery, depositing such a porous polymer layer (e.g., porous ethylene, porous propylene, porous aramid, porous cellulose, porous saccharides, etc. - other examples of suitable polymers are described above) on the anode side of the membrane can reduce or prevent undesirable side reactions (e.g., lithiation, electrochemical reduction, etc.) between the anode and the ceramic separator. Similarly, by forming such a porous polymer layer on the cathode side of the membrane, potential undesirable oxidation reactions can be reduced. In some designs, a suitable thickness for such a porous polymer layer can range from about 10 nm to about 10 microns. In some applications of Li and Li-ion (or other metal or metal-ion batteries), in order to prevent direct contact between the ceramic wire and Li (e.g., in the case of Li dendrite formation), it may be advantageous to deposit a thin (e.g., about 1 nm to about 200 nm), mostly non-porous (high density) polymer layer on the inner surface of the membrane (e.g., around individual wires). In some designs, it is further preferred that such a polymer layer is stable in contact with Li and exhibits a high interfacial energy at the polymer / Li interface. In this case, the formation of Li dendrites can result in a significant increase in the energy of the system, and their growth may be significantly reduced or eliminated. In contrast, direct contact between Li and many ceramic materials results in the formation of a low-energy interface, which reduces the surface energy of Li dendrites and thus favors their propagation unnecessarily.

[0142] In some applications, a ceramic (e.g., Al 2 O 3 , MgO, ZrO 2It may be advantageous for the porous polymer layer on one or both sides of the membrane (such as etc.) to be thermoresponsive (or to include a thermoresponsive layer), and to close the pores when a specific temperature is exceeded. Since the membrane blocks the electric current when a specific temperature (for example, selected in the range of about 70°C to about 120°C in some applications) is exceeded, this can provide an additional safety function for the cell. In some designs, the thermoresponsive layer may include a thermoplastic material that melts above the critical temperature (for example, selected in the range of about 70°C to about 120°C in typical applications) to block Li-ion conduction.

[0143] In some applications, it can be particularly advantageous to use a separator layer (e.g., a stand-alone separator membrane or separator coating) of small fibers or flakes of an oxide (e.g., aluminum oxide, magnesium oxide, zirconium oxide, etc.) or other suitable ceramic (including but not limited to porous small fibers or flakes) (especially in combination with the polymer coatings discussed above) in medium (e.g., about 10 mAh to about 200 mAh), large (e.g., about 200 mAh to about 10,000 mAh), or extra-large (e.g., greater than about 10,000 mAh) cell metal anode-based battery cells (e.g., because the safety that is particularly important for medium or large or extra-large cells is enhanced). Examples of suitable metal anode-based battery cells include, but are not limited to, cells having a Li anode (e.g., as in a Li metal battery), a Mg anode (e.g., as in a Mg metal battery), a Na anode (e.g., as in a Li metal battery), a Zn anode (Zn or Zn alloy anode and many battery chemistries including an electrolyte that does not induce dissolution or reduction of a small wire membrane), a K anode (e.g., as in a K metal battery). In some designs, rechargeable metal anode batteries can particularly benefit from this membrane technology. The metal anode of such a rechargeable battery cell can undergo metal stripping (dissolving into the electrolyte as ions) during discharge and may be re-plated during charging. This process can cause the formation of dendrites that can induce internal short circuits, which can lead to battery failure (furthermore, in some cases, various safety risks such as fires, which are particularly known in the chemistry of Li batteries). The use of surface layer protection by a solid electrolyte or solid ceramic protective layer is often expensive and not always suitable and does not necessarily protect the cell from dendrite penetration (especially in situations where the battery can be subjected to shock or various stresses, such as when used for transportation).In some battery research, it is common for the majority of scientists to utilize so-called half-cells (such as Li half-cells) equipped with a metal anode (usually very small coin-type cells with a capacity of less than about 10 mAh) to evaluate the performance of electrode materials or separators. However, not only is the cost of the metal anode high, but also due to concerns about reliability and safety (especially when a flammable organic electrolyte is used, as the size of the cell increases, more energy will be released during thermal runaway and rapid decomposition induced by dendrites), the use of metal anodes in commercially available cells (especially rechargeable cells equipped with aqueous liquids and organic electrolytes) is rare. Using the small fiber or flake separator layer (such as a separator membrane or separator coating) (for example, some examples include porous aluminum oxide or magnesium oxide or zirconium oxide membranes) described herein, where the elastic modulus of the membrane material is relatively high, the porosity is high, and it has (potentially important) small (for example, on average less than about 2 microns, more preferably less than about 0.25 microns) tortuous pores, there is a possibility of significantly suppressing or eliminating the growth of dendrites. Moreover, relatively fast deposition (electroplating) of metals (such as Li, Mg, Zn, etc.) and thus high power density can be obtained. Metal dendrites can penetrate many polymer membranes in some applications (for example, during the growth of metal dendrites in cells equipped with polymer separator membranes), but metal dendrites may not be able to penetrate individual small oxide fibers (such as small aluminum oxide fibers), even if these are coated with a polymer layer. Therefore, in some applications, the formation of metal dendrites requires the dendrites to grow around small fibers, which may significantly increase the specific surface area of the dendrites. The small features of the membrane wall, its roughness, its dielectric properties, or its surface properties may also be involved in suppressing the growth of dendrites.

[0144] In some designs, medium, large, or extra-large cells with other (non-metallic) anodes (e.g., Si-based or graphite-based) can also benefit significantly by using small fibers (including, but not limited to, small porous fibers) or small flakes of porous ceramic (e.g., flexible) or a separator layer (e.g., a separator membrane or a separator coating) in the construction, due to greatly improved safety, higher compressive strength, lower ionic resistance, better thermal stability, or other beneficial properties.

[0145] In some applications, using an ion-permeable (e.g., porous) polymer layer between a membrane containing small fibers or flakes of an oxide (e.g., aluminum oxide, magnesium oxide, zirconium oxide, etc., including but not limited to porous small fibers or flakes) and at least one electrode can be beneficial for use as a separator in an electrochemical cell (e.g., a battery cell). In some designs, such a polymer layer may be deposited on the membrane or on the electrode, or simply sandwiched between the ceramic membrane and at least one electrode. In some designs, such a polymer layer can perform various useful functions. In one example, it can reduce stress concentration at the interface between the electrode and the porous oxide separator (e.g., because polymers are generally softer and more deformable than oxides). This can lead to improved reliability during cell assembly when the cell stack is pressurized and more reliable cell operation. In another example, such a polymer layer can make the handling of the oxide separator easier (e.g., during cell assembly or during the manufacture of the oxide film). In yet another example, such a polymer layer can enhance the adhesion between the oxide film and the electrode (e.g., functioning essentially as an adhesive / adhesion layer). In yet another example, such a polymer layer can improve the electrochemical stability of the oxide film. As described above, for example, in the case of a Li or Li-ion battery, using a polymer layer between the oxide film and the anode can reduce or prevent the reduction of the oxide due to Li or other undesirable interactions at low potentials (e.g., about 0.1 to less than 2 V versus Li / Li+, depending on the chemical properties of the oxide and the electrolyte). In this case, not only oxides of aluminum, magnesium, and zirconium, but also many other oxides that are generally unstable or significantly less stable when in contact with Li can be utilized (e.g., silicon oxide, zinc oxide, iron oxide, magnesium oxide, cadmium oxide, copper oxide, chromium oxide, titanium oxide, various combinations of oxides, etc.).When a polymer layer is placed between the oxide film and the cathode, various undesirable interactions between the oxide and the electrolyte or the cathode at higher potentials (e.g., greater than about 3 - 4 V vs. Li / Li+, depending on the chemical nature of the oxide and electrolyte) can be prevented or minimized. In yet another example, such a polymer layer can function as an additional safety mechanism. For example, it can prevent ion transport (e.g., by closing pores, or by making the electrolyte solvent impermeable, or by other mechanisms) when heated above a critical temperature (or cooled below a critical temperature). In some designs, a suitable porosity for such a polymer layer can range from about 0 to about 99 volume % (more preferably, from about 10 to about 90 volume %). In some designs, a suitable thickness for such a polymer layer can range from about 5 nm to about 20 microns (more preferably, from about 10 nm to about 10 microns). In some designs, a thickness less than about 5 nm may reduce the usefulness of such a polymer layer, while a thickness greater than about 20 microns may unnecessarily increase the thickness of the entire separator stack and induce detrimental effects (e.g., shrinkage of the polymer during heating may also damage the oxide film). In some designs, the polymer layer may be part of a multilayer (including oxide fibers or oxide flakes) film, or may be deposited on at least one electrode, or may be prepared as a stand - alone film. The composition of the polymer layer can depend on the desired specific functionality and the specific chemical nature of the electrochemical cell, and can be selected from the list of polymer compositions considered in conjunction with the polymer composites described herein.

[0146] In some applications, it can also be highly advantageous to use small fibers or flakes of oxides (such as aluminum oxide, magnesium oxide, zirconium oxide, etc.) or other suitable ceramics (including, but not limited to, small porous fibers and small porous flakes) as thermally stable, electrically insulated mechanical reinforcement for the electrodes of various batteries (such as Li and Li-ion batteries, Na and Na-ion batteries, etc.) and other electrochemical energy storage devices, electrolytes of solids (such as polymers, ceramics, glass-ceramics, or composite materials), and separators. In some designs, the small fibers, for example, in contrast to carbon nanotubes or carbon fibers and nanofibers, are electrically non-conductive in aluminum oxide and other oxides, so they can improve the mechanical strength, fatigue resistance, and overall durability of the electrodes without providing an electrochemically active surface area that is undesirable for electrolyte decomposition. Moreover, the use of small fibers of oxides (such as aluminum oxide, magnesium oxide, etc.) or other suitable ceramics can be advantageous for providing (and maintaining during cycling) fast ion paths within the electrodes. For example, the pores of small fibers of porous oxides (such as aluminum oxide or magnesium oxide, etc.) can be utilized as paths for ion access from the top surface of the electrode to the bulk. Since these pores can remain filled with electrolyte and be free of electrolyte decomposition products, and furthermore, the mechanical strength of the oxide may be large enough to withstand the volume changes of the operating electrode without inducing pore collapse, in some designs, such pores can be well utilized to maintain a high ionic conductivity within the electrodes during cycling.

[0147] Figure 6 shows an example of a small oxide fiber coating 601 that includes small lithium aluminum oxide fibers produced from small aluminum ethoxide fibers containing lithium impurities. Such small aluminum ethoxide fibers were in turn produced by exposing Li-Al alloy particles to absolute ethanol.

[0148] Figure 7A shows an example of a composite film 701 produced by casting from a colloidal solution containing both small oxide fibers (Al 2 O 3 ) in this example) and a polymer (PVA, average molecular weight (MW) of about 30,000). PVA was dissolved in an ethanol solvent and the oxide fibers were suspended in such a solution. A weight ratio of about 91:9 (oxide:polymer) was used in this example. The image shown in Figure 7A was recorded using a scanning electron microscope (SEM). Figure 7B shows an example of the bending radius of the composite film 701 of Figure 7A where a small bending radius of about 2.5 mm is achieved without breaking. The MW of the polymer can vary widely, but the optimal MW depends on the composition of the polymer, the solvent used, the solubility of the polymer in the solvent, the proportion of the polymer, and / or other parameters. In some designs, a suitable MW can range from about 500 to about 5,000,000.

[0149] Figures 8A - 8J show examples of some schematic diagrams of various composite membranes containing small ceramic particles and manufactured according to different exemplary embodiments. Figure 8A shows the simplest case of a 100% ceramic separator membrane containing small fibers 802A with intervening pores 804A; Figure 8B shows a ceramic membrane containing the small fibers and pores shown in Figure 8A, but also further including a porous polymer coating 806B on one side; Figure 8C shows a ceramic membrane containing small fibers, pores, and polymer coating 806B, but also further including another polymer coating 808C on the opposite side of the ceramic membrane; Figure 8D shows a ceramic - polymer composite membrane having a polymer 810D present in the bulk of the membrane (e.g., as a binder) between small fibers 812D with intervening pores 814D; Figure 8E shows a ceramic - polymer composite membrane containing small ceramic fibers (or flakes) 818E and polymer fibers (or flakes) 818E; Figure 8E shows a ceramic membrane containing fibers of substantially different diameters and lengths (e.g., long and thick fibers 820F and short and thin fibers 822F); Figure 8G shows a ceramic membrane containing fibrous - shaped particles 824G and non - fibrous - shaped particles 826G (e.g., flakes with aspect ratio > 4, irregular - shaped particles with aspect ratio < 2, etc.) having intervening pores 828G; Figure 8H shows a ceramic - ceramic composite membrane containing two or more types (830H and 832H) of fibers of different morphologies and / or compositions or microstructures; Figure 8I shows a ceramic composite membrane containing small fibers 834I having a coating shell 836I on their surfaces (e.g., made of a polymer or another ceramic layer); Figure 8J shows a ceramic - polymer composite separation membrane layer containing small ceramic (e.g., oxide) fibers 838J, low - aspect - ratio ceramic (e.g., oxide) particles 840J filling the gaps between electrode particles 842J (which are then electrically connected to an electrode current collector 844J), low - aspect - ratio ceramic (such as oxide) particles 846J disposed between fibers 838J, and a polymer binder 848J, and the ceramic - polymer composite separation membrane layer is directly coated on an electrode surface (e.g., on a Si - containing anode or other suitable anode or cathode).

[0150] FIG. 9 shows an example of a ceramic platelet 901 that can be used in a separator layer coating according to some embodiments of the present disclosure. The ceramic platelet 901 shown in FIG. 9 represents an example of a flake-shaped configuration of a component containing ceramic of a separator layer containing ceramic (e.g., in this example, Al 2 O 3 formed from small metal oxide flakes (or platelets)). In one example, flake-type (or platelet-type) small ceramic particles as shown in FIG. 9 can be synthesized by various techniques, including, but not limited to, exfoliation (or partial etching) of layered materials, various vapor deposition techniques (e.g., by chemical vapor deposition, etc.), various solution synthesis techniques (e.g., heating of reaction solutions containing sol-gel, hydrothermal, solvothermal, metal salts, metal alkoxides, metal silicates or other suitable metals including precursors). In a further example, a catalyst or capping agent or surfactant can be used in the synthesis of flake-type (or platelet-type) small ceramics (e.g., such as those shown in FIG. 9) in some designs.

[0151] In addition to the energy storage applications of the above-described separation membranes containing small ceramic (e.g., oxides such as aluminum oxide, lithium aluminum oxide, magnesium aluminum oxide, lithium magnesium aluminum oxide, magnesium oxide, lithium magnesium oxide, etc.) fibers (e.g., in Li-ion and other batteries or supercapacitors), their use in air purification applications (e.g., HEPA filtration) is also very attractive and can be very advantageous. For example, the high porosity (e.g., about 40 - 80 volume %) of such membranes can reduce the resistance to air flow, and thus increase the amount of air processed (purified) per unit membrane area. In a further example, the small pore size of the small fibers can enable effective exclusion (filtration) of submicron particles. In some designs, due to the high polarity of the oxide fibers (the presence of a high dipole moment on their surface), such materials can further adsorb particles smaller than (the pore size of the membrane) due to the strong electrostatic interaction between the surface of the small fibers and the small particles, which enables more effective filtration (compared to polymeric HEPA filter membranes). In some designs, the high mechanical strength and abrasion resistance of the ceramic fibers increase the lifespan of the ceramic membrane. Further, in some designs, many of the filtered particles may burn in air (or plasma) at a temperature lower than the stability temperature of the all-ceramic membrane. Thus, the ceramic membrane based on small fibers can be easily cleaned without much damage. In contrast, HEPA filters based on certain fibrous glasses or polymeric fibers are thermally unstable and cannot be purified by such means. The good thermal stability of the ceramic filter compared to the polymeric filter also enables the effective use of the small fiber-based membrane filter of the ceramic and its long-term stability in high-temperature climates or in applications where the temperature is relatively high (e.g., in vehicle filters, various factories, etc.). In contrast, small polymeric HEPA filters often degrade rapidly when exposed to high temperatures for a long time. Similarly, many polymeric membranes lose strength and ductility when exposed to low temperatures. Thus, they may degrade in cold climates.In contrast, small ceramic fiber-based membrane filters do not significantly degrade their mechanical properties even when cooled to below about minus (-) 70 °C.

[0152] In some designs, the use of small ceramic (e.g., oxide) fibers, especially porous fibers, is also very advantageous because their pores (or outer surfaces) can be easily filled with a durable metal or metal oxide-based catalyst (e.g., titanium oxide, copper, copper oxide, iron oxide, iron copper oxide, cupric oxychloride, ferric oxychloride, ferric copper oxychloride, etc.) in the form of, for example, nanoparticles or coatings. Such catalysts can not only decompose organic contaminants but also help effectively kill bacteria, bacterial spores, and viruses. The deposition of such nanoparticles can be carried out via infiltration based on a solution of precursor salts and subsequent oxidation (when forming oxide nanoparticles) or reduction (when forming metal nanoparticles) thereof. A large surface area of small fibers, especially small porous fibers, can make it possible to use one or more catalysts in high loadings without significantly degrading the mechanical properties of the membrane.

[0153] Similarly, it may be advantageous to use the above-described separation membranes containing small ceramic (e.g., oxides such as aluminum oxide, lithium aluminum oxide, magnesium aluminum oxide, lithium magnesium aluminum oxide, magnesium oxide, lithium magnesium oxide, etc.) fibers (including porous ones and those compounded with catalysts and antibacterial agents), particularly when the achieved average pore size is quite small (e.g., about 0.02 to 0.6 microns) for water purification applications. In some designs, such membranes can be very durable and highly effective in removing bacteria and various toxic particles from water (e.g., to form water that is safe enough for drinking water or for washing hands, face, body, or food (e.g., fruits, berries, vegetables, etc.) or tableware). In some designs, such membranes can be incorporated into a straw to enable direct drinking from a water reservoir (e.g., a lake or a river) that may be contaminated with various harmful bacteria or viruses. Similarly, such membranes can be incorporated into various water containers (e.g., for generating drinking water).

[0154] This description is provided to enable a person skilled in the art to make or use embodiments of the invention. However, since various modifications to these embodiments will be readily apparent to those skilled in the art, it is understood that the present disclosure is not limited to the specific compositions, process steps, and materials disclosed herein. That is, the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the present disclosure. For example, the synthesis of the described flexible ceramic membranes may be used in various composite material or separator membrane applications in addition to the described use in energy storage and conversion devices.

Claims

1. 1. A method of manufacturing a battery cell assembly including a first electrode, a second electrode, and a separator, comprising: (A1) providing a dispersion containing metal oxide, metal hydroxide or metal oxyhydroxide particles and a solvent composition; (A2) coating the dispersion directly onto a roll of the first electrode to form a first layer of the separator on the first electrode; (A3) providing the second electrode; (A4) assembling the first electrode and the second electrode by interposing the separator between the first electrode and the second electrode; The thickness of the separator is in the range of 0.5 μm to 10 μm, the metal oxide, metal hydroxide, or metal oxyhydroxide particles comprising (1) a first set of the metal oxide, metal hydroxide, or metal oxyhydroxide particles having a first aspect ratio distribution, and (2) a second set of the metal oxide, metal hydroxide, or metal oxyhydroxide particles having a second aspect ratio distribution; the first set of metal oxide, metal hydroxide or metal oxyhydroxide particles are fibrous in shape and characterized by a diameter in the range of 3 nm to 2 μm and an aspect ratio in the range of 4 to 1,000,000; The method of claim 1, wherein the second set of metal oxide, metal hydroxide, or metal oxyhydroxide particles are flakes.

2. The method of claim 1, wherein the aspect ratio ranges from 20 to 100,000.

3. The method of claim 1, wherein the aspect ratio is in the range of 4-10.

4. The method of claim 1 , wherein an average aspect ratio of the second aspect ratio distribution is less than an average aspect ratio of the first aspect ratio distribution.

5. 2. The method of claim 1, wherein the second set of metal oxide, metal hydroxide, or metal oxyhydroxide particles comprises no more than 50.0% by weight of the first layer.

6. The method of claim 1 further comprising the step of heat treating at least the first layer at a temperature range of 40°C to 200°C.

7. 2. The method of claim 1, wherein (A3) comprises coating the dispersion directly onto a roll of the second electrode to form the second layer of the separator.

8. The method of claim 1 , wherein the separator does not include a stand-alone separator layer.

9. 2. The method of claim 1, wherein the metal oxide, metal hydroxide, or metal oxyhydroxide particles contain between 2 atomic % and 40 atomic % aluminum (Al).

10. The method of claim 1 , wherein the separator further comprises a polymer in the range of 0.1% to 50% by weight.

11. The method of claim 10, wherein the polymer comprises a thermoplastic that melts in the range of 70°C to 120°C.

12. The method of claim 10 , wherein the polymer comprises a polymeric binder.

13. The method of claim 1 , wherein at least a portion of the metal oxide, metal hydroxide, or metal oxyhydroxide particles are bundled together.

14. The method of claim 1, wherein the porosity of the separator is in the range of 25% to 80% by volume.

15. The total pore volume between the particles of said metal oxide, said metal hydroxide, or said metal oxyhydroxide is less than 0.01 cm ３ / g to 1 cm ３ The method of claim 1, wherein the molecular weight is in the range of 1 / g.

16. the first electrode is an anode electrode, 2. The method of claim 1, wherein the anode electrode comprises 3% to 70% by weight of silicon (Si).

17. 2. The method of claim 1, wherein the solvent composition comprises one or more of water, alcohol, glycol, glycol ether, ether, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), methyl ethyl ketone (MEK), hexamethylphosphoramide, cyclopentanone, acetonitrile, tetramethylene sulfoxide, and ε-caprolactone.

18. 10. The method of claim 1, wherein the coating of the dispersion is carried out by spray coating, slot die coating, gravure coating, dip coating, roller coating, and / or knife edge coating.

19. The method of claim 1, wherein the separator exhibits a minimum bend radius in the range of 0.1 mm to 3 cm.

20. The method of claim 1, wherein the separator exhibits a tensile strength in the range of 1 MPa to 1,000 MPa.

21. The method of claim 1, wherein the separator exhibits a pore exclusion size in the range of 10 nm to 1 μm.

22. 2. The method of claim 1, wherein a functional surface coating is deposited on the metal oxide, metal hydroxide, or metal oxyhydroxide particles to a surface layer thickness in the range of 0.3 nm to 30 nm, the functional surface coating comprising polymer, carbon, dielectric, and / or different ceramic materials.

23. 10. The method of claim 1 further comprising the step of producing said metal oxide, said metal hydroxide, or said metal oxyhydroxide particles by conversion of alkoxide precursor particles.

24. A first electrode, A second electrode, and A separator interposed between the first electrode and the second electrode. Equipped with the separator comprises a first layer comprising particles of a metal oxide, metal hydroxide or metal oxyhydroxide, the first layer being deposited directly on the first electrode; The thickness of the separator is in the range of 0.5 μm to 10 μm; the metal oxide, metal hydroxide, or metal oxyhydroxide particles comprising (1) a first set of the metal oxide, metal hydroxide, or metal oxyhydroxide particles having a first aspect ratio distribution, and (2) a second set of the metal oxide, metal hydroxide, or metal oxyhydroxide particles having a second aspect ratio distribution, the first set of the metal oxide, metal hydroxide, or metal oxyhydroxide particles being fibrous in shape and characterized by a diameter in the range of 3 nm to 2 μm and an aspect ratio in the range of 4 to 1,000,000; The battery cell assembly, wherein the second set of metal oxide, metal hydroxide, or metal oxyhydroxide particles are flakes.

25. 25. The battery cell assembly of claim 24, wherein the aspect ratio ranges from 20 to 100,000.

26. 25. The battery cell assembly of claim 24, wherein the aspect ratio ranges from 4 to 10.

27. 25. The battery cell assembly of claim 24, wherein an average aspect ratio of the second aspect ratio distribution is less than an average aspect ratio of the first aspect ratio distribution.

28. 25. The battery cell assembly of claim 24, wherein the second set of metal oxide, metal hydroxide, or metal oxyhydroxide particles comprises less than or equal to 50.0% by weight of the first layer.

29. 25. The battery cell assembly of claim 24, wherein the separator comprises a second layer comprising particles of a metal oxide, metal hydroxide or metal oxyhydroxide, the second layer being deposited on the first layer.

30. 25. The battery cell assembly of claim 24, wherein the separator does not include a stand-alone separator layer.

31. 25. The battery cell assembly of claim 24, wherein the metal oxide, metal hydroxide, or metal oxyhydroxide particles contain between 2 atomic % and 40 atomic % aluminum (Al).

32. 25. The battery cell assembly of claim 24, wherein said separator further comprises a polymer in the range of 0.1% to 50% by weight.

33. 33. The battery cell assembly of claim 32, wherein the polymer comprises a thermoplastic material having a melting point in the range of 70°C to 120°C.

34. 33. The battery cell assembly of claim 32, wherein the polymer comprises a polymeric binder.

35. 25. The battery cell assembly of claim 24, wherein at least a portion of the metal oxide, metal hydroxide, or metal oxyhydroxide particles are bound together.

36. 25. The battery cell assembly of claim 24, wherein the separator has a porosity in the range of 25% to 80% by volume.

37. The total pore volume between the particles of said metal oxide, said metal hydroxide, or said metal oxyhydroxide is less than 0.01 cm ３ / g to 1 cm ３ 25. The battery cell assembly of claim 24, wherein the molecular weight is in the range of 1 / g.

38. the first electrode is an anode electrode, 25. The battery cell assembly of claim 24, wherein the anode electrode comprises between 3% and 70% silicon (Si) by weight.

39. 25. The battery cell assembly of claim 24, wherein said separator exhibits a minimum bend radius in the range of 0.1 mm to 3 cm.

40. 25. The battery cell assembly of claim 24, wherein said separator exhibits a tensile strength in the range of 1 MPa to 1,000 MPa.

41. 25. The battery cell assembly of claim 24, wherein said separator exhibits a pore exclusion size in the range of 10 nm to 1 μm.

42. 25. The battery cell assembly of claim 24, wherein the metal oxide, metal hydroxide, or metal oxyhydroxide particles are provided with a functional surface coating exhibiting a surface layer thickness in the range of 0.3 nm to 30 nm, the functional surface coating comprising a polymer, carbon, dielectric, and / or ceramic material.

43. 25. The battery cell assembly of claim 24; and electrolyte, wherein the electrolyte permeates the separator of the battery cell assembly.

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