Improved coated separator for lithium battery and related method

Abstract

To provide an improved coated separator.SOLUTION: There is provided a separator for a lithium battery which includes a porous substrate and a coating layer formed on at least one surface of the porous substrate. The coating layer contains ceramic particles 10 providing a porous internal structure to the coating layer and dispersed in a polymer binder 12, and the polymer binder includes one or more water insoluble polymers having a spherical particle shape. The one or more water insoluble polymers are selected from the group comprising a polyvinylidene fluoride (PVDF) homopolymer and copolymers of PVDF and / or vinylidene fluoride (VF2) with one or more of hexafluoropropylene (HFP or [-CF(CF3)-CF2-]), chlorotrifluoroethylene (CTFE), and tetrafluoroethylene (TFE).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority and the benefit of co - pending U.S. Provisional Patent Application No. 62 / 087,953, filed on December 5, 2014, which is hereby incorporated by reference in its entirety.

[0002] This specification discloses various novel, optimized, or improved coated separators, membranes, films, or the like for use in lithium batteries such as lithium-ion batteries or lithium-ion polymer batteries, novel or improved batteries comprising such coated separators, membranes, films, or the like, and methods of making or using such coated separators, membranes, films, or the like. According to at least selected embodiments, aspects, or objectives, this specification discloses novel, optimized, and / or improved ceramic-coated separators, membranes, films, or the like for use in lithium batteries such as lithium-ion batteries or lithium-ion polymer batteries, novel or improved batteries comprising such ceramic-coated separators, membranes, films, or the like, and methods of making or using such ceramic-coated separators, membranes, films, or the like. According to at least certain embodiments, aspects, or objectives, this specification discloses novel or improved water-soluble or aqueous polymer-coated separators, membranes, films, or the like for use in lithium batteries such as lithium-ion batteries or lithium-ion polymer batteries, novel or improved batteries comprising such water-soluble or aqueous polymer-coated separators, membranes, films, or the like, and methods of making or using such water-soluble or aqueous polymer-coated separators, membranes, films, or the like.According to at least certain embodiments, aspects or purposes, herein disclosed are novel or improved water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like for use in lithium batteries such as lithium-ion batteries or lithium-ion polymer batteries, novel or improved batteries comprising such water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like, and methods of making or using such water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like, novel or improved polyvinylidene fluoride or polyvinylidene difluoride (PVDF) homopolymers or copolymers of PVDF with hexafluoropropylene (HFP or [-CF(CF3)-CF2-]), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE), and / or the like, blends and / or mixtures thereof, coated separators, membranes, films or the like, novel or improved porous separators for use in lithium batteries, novel or improved coating or application methods for applying a coating or ceramic coating to a separator for use in a lithium battery, novel or improved PVDF or PVDF:HFP films or membranes, and / or the like. BACKGROUND OF THE INVENTION

[0003] There are various methods for changing the performance characteristics of a porous or microporous membrane used as a separator within a lithium battery (e.g., a lithium-ion battery, etc.). One such method is to apply a porous coating to the surface of the porous or microporous membrane in order to change or enhance the chemical and physical properties of the coated porous separator within a lithium-ion secondary battery. A porous coating layer containing ceramic particles within a polymer matrix or binder can have thermal stability due to the presence of the ceramic particles. At a temperature above the melting temperature of the polymer matrix, the ceramic particles retain their physical integrity and serve to maintain a physical separation wall between the electrodes within the lithium-ion battery, preventing the cathode and anode from coming into contact, which contact could potentially result in a large internal short circuit.

[0004] In a ceramic particle / polymer matrix or binder coating composition, the polymer matrix or binder can serve to provide adhesion between the ceramic particles, adhesion of the coating to the porous base membrane, and / or adhesion of the ceramic-coated separator to the electrode or electrodes (adjacent to or in contact with the ceramic coating) within the lithium-ion battery. Good contact between the separator and the electrode can be important for optimal cycle life in a lithium battery because the presence of a void or space between the separator and the electrode can have an adverse effect on long-term cycle life or battery performance.

[0005] Known ceramic / polyvinylidene fluoride (PVDF) coatings are generally non-aqueous solvent-based and use solvents such as acetone, dimethylacetamide, N-methylpyrrolidone, combinations thereof, or the like. For example, PVDF is used in such coatings because it is inert and stable within a lithium-ion battery system. However, the non-aqueous solvents used to dissolve PVDF are often volatile, can be environmentally destructive, and can produce undesirable emissions if not handled properly, so they may need to be used, disposed of, and / or recycled carefully. Non-aqueous-based coating processes can be costly, can have an unfavorable environmental footprint, and can be difficult to handle due to safety concerns related to their flammability.

[0006] Accordingly, there is a need for a new optimized and / or improved coated separator for at least some applications that has a water-soluble or aqueous coating system or is manufactured using a water-soluble or aqueous coating system, which may be preferred in at least selected situations compared to certain non-aqueous or solvent-based coating systems, due to, for example, performance, cost, environmental, safety, and / or economic factors. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] At least selected embodiments, aspects or objectives of the present invention address the above-described need for a novel optimized and / or improved coated separator for at least certain applications, having or manufactured using a water-soluble or aqueous coating system, which may be preferred under at least selected circumstances compared to certain non-aqueous or solvent-based coating systems, for example, due to performance, cost, environmental, safety, and / or economic factors. According to at least one conceivable preferred specific embodiment, a separator coated with a ceramic coating on at least one side is manufactured using a water-soluble or aqueous coating mixture, coating slurry or coating system.

Means for Solving the Problems

[0008] According to at least selected embodiments, aspects or purposes, the present application or invention relates to various novel, optimized and / or improved coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such coated separators, membranes, films, or the like, and methods of making or using such coated separators, membranes, films, or the like. According to at least certain selected embodiments, aspects or purposes, the present application or invention relates to novel or improved ceramic-coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such ceramic-coated separators, membranes, films, or the like, and / or methods of making or using such ceramic-coated separators, membranes, films, or the like. According to at least certain embodiments, aspects or purposes, the present application or invention relates to novel or improved water-soluble or aqueous polymer-coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such water-soluble or aqueous polymer-coated separators, membranes, films, or the like, and / or methods of making or using such water-soluble or aqueous polymer-coated separators, membranes, films, or the like.According to at least certain embodiments, aspects or purposes, the present application or invention relates to a novel or improved water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separator, membrane, film, or the like for use in a lithium battery such as a lithium-ion battery or a lithium-ion polymer battery, a novel or improved battery comprising such a water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separator, membrane, film, or the like, and / or a method of making or using such a water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separator, membrane, film, or the like, a novel or improved polyvinylidene fluoride or polyvinylidene difluoride (PVDF) homopolymer or a copolymer of PVDF with hexafluoropropylene (HFP or [-CF(CF3)-CF2-]), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE), and / or the like, blends and / or mixtures thereof, a coated separator, membrane, film or the like, a novel or improved porous (or otherwise ion-conductive) separator for use in a lithium battery, a novel or improved coating or coating method for applying a coating or ceramic coating to a separator for use in a lithium battery, a novel or improved PVDF or PVDF:HFP film or membrane, and / or the like.

[0009] In at least certain embodiments or examples, the present invention provides a separator for a lithium battery (e.g., a lithium-ion battery, etc.), the separator comprising: (a) a porous or microporous substrate (single-layer or multi-layer or layers of the same or different materials), and (b) a composite having a coating layer formed on at least one surface of the substrate, the coating layer comprising at least one water-soluble or aqueous polymer binder or matrix, or being formed from at least one water-soluble or aqueous polymer binder or matrix. The water-soluble or aqueous polymer binder or matrix may include one or more typical non-water-soluble polymers (such as PVDF, etc.), and in some embodiments, the water-soluble or aqueous polymer binder or matrix may further include one or more typical water-soluble polymers (by way of example, polyvinyl alcohol (PVA) or polyacrylic acid (PAA), etc.). At least certain selected embodiments or examples of the present invention further provide at least one process for manufacturing a separator for a lithium-ion battery, the process comprising providing a porous or microporous substrate (a preferred substrate may have a safety shut-off function), and forming a composite by coating a coating layer on at least one surface of the substrate, the coating layer comprising at least one water-soluble or aqueous polymer binder or matrix. The water-soluble or aqueous polymer binder or matrix may include one or more typical non-water-soluble polymers (such as PVDF, etc.), and in some embodiments, the water-soluble or aqueous polymer binder or matrix may further include one or more typical water-soluble polymers (by way of example, polyvinyl alcohol or polyacrylic acid, etc.). At least certain selected embodiments or examples of the present invention further provide for the use of the separator of the present invention as described herein within a lithium battery such as a lithium-ion battery.

[0010] In at least certain embodiments or examples, the present invention provides a separator for a lithium battery (e.g., a lithium-ion battery, etc.), the separator comprising: (a) a porous or microporous substrate (single-layer or multi-layer or layers of the same or different materials), and (b) a porous or microporous coating layer formed on at least one surface of the substrate, the coating layer being formed from a mixture of particles (such as ceramic particles, fibers, powders, beads, or the like) and a water-soluble or aqueous polymer binder or matrix. The water-soluble or aqueous polymer binder or matrix may include one or more typical non-water-soluble polymers (such as PVDF), and in some embodiments, the water-soluble or aqueous polymer binder or matrix may further include one or more typical water-soluble polymers (by way of example, polyvinyl alcohol or polyacrylic acid, etc.). At least selected embodiments or examples of the present invention further provide at least one process for manufacturing a separator for a lithium-ion battery, the process including providing a porous or microporous substrate and providing a porous or microporous composite by coating a coating layer on at least one surface of the substrate, the coating layer including a mixture of particles and a water-soluble or aqueous polymer matrix or binder. At least selected embodiments or examples of the present invention further provide for the use of the separator of the present invention as described herein within a lithium battery such as a lithium-ion battery.

Advantages of the Invention

[0011] The separators described herein can be advantageous, for example, when used within a lithium-ion battery, for their high-temperature integrity and improved safety performance. Exemplary improved separators for lithium-ion batteries are coated with a mixture of one or more types of particles (e.g., organic or inorganic particles, such organic particles can include, but are not limited to, high-temperature polymer particles, and such inorganic particles can include, but are not limited to, ceramic particles) and one or more water-soluble or aqueous polymer binders or materials, the water-soluble or aqueous polymer binder or material can include one or more typical non-water-soluble polymers (such as PVDF or its various copolymers), and further can include one or more typical water-soluble polymers (by way of example, polyvinyl alcohol or polyacrylic acid, etc.). Among other features, by the composition of the coating layer and the method of applying it to the substrate, the ceramic coating layer can be better adhered to one or more of the substrate and / or the electrodes, and better adhesion can also occur between the ceramic particles and the water-soluble or aqueous polymer binder or matrix. In addition, the coating layer can prevent an oxidation reaction from occurring at the interface between the coated separator and at least one of the battery electrodes, can prevent short circuits, can reduce shrinkage, can provide thermal stability, can extend the blocking performance, and / or can improve the safety and / or overall performance of the separator, separator manufacturing, cell, battery, lithium-ion battery, product, device, or vehicle including the cell or battery, etc.

[0012] While not desiring to be bound by theory, oxidation and / or reduction reactions can occur during the formation stage of a lithium-ion battery and / or during charging or discharging of a lithium-ion battery, and these reactions can produce by-products that can harm the battery system. The coating can reduce the rate of oxidation reactions that can occur with uncoated polypropylene (PP) or polyethylene (PE) separators or can prevent oxidation reactions. Ceramics such as aluminum oxide (Al2O3) are chemically inert and do not oxidize in electrolytes. An improvement in oxidation stability can be obtained by orienting or placing the coated side of the separator described herein towards or in contact with one or more electrodes within the battery, for example, the cathode or positive electrode.

[0013] Furthermore, the ceramic coating of the exemplary invention can enable a lithium-ion secondary battery to reach higher voltage levels and / or can result in an increase in energy density in a lithium-ion secondary battery.

[0014] In various embodiments herein, as a result, the present invention is directed to an improved, novel, optimized, and / or modified separator for use in a cell or battery, the separator including a particular substrate and a particular coating, the coating being optimized based on the contents and type of particles (e.g., inorganic particles such as ceramic particles, or organic particles such as high-temperature polymer particles, or a combination thereof), the particles being optimized based on their particle size, shape, and type, and the content and type of an aqueous or water-soluble polymer binder or matrix, the water-soluble or aqueous polymer binder or matrix possibly including a combination of one or more typical water-insoluble polymers (such as PVDF) and, in some embodiments, together with one or more typical water-soluble polymers (e.g., polyvinyl alcohol or polyacrylic acid, for example), the binder and / or matrix material(s) being optimized based on the water content, polymer content, monomer content, comonomer content, copolymer content, solubility in water, and / or insolubility in water.

[0015] Additionally, such improved separators may have or exhibit one or more of the following characteristics or improvements: (a) a desirable level of porosity observed and measured by SEM; (b) a desirable Gurley number (ASTM Gurley and / or JIS Gurley) indicating permeability; (c) a desirable thickness such that desirable Gurley and other properties are obtained; (d) one or more desirable levels of fusion of the polymer binder such that the coating is improved compared to known coatings; (e) including, but not limited to, how the coating is mixed, how the coating is applied to the substrate, and how the coating is dried on the substrate, desirable properties resulting from the processing of the coated separator; (f) improved thermal stability as indicated by desirable behavior, for example, in hot tip hole propagation investigations; (g) reduced shrinkage when used in a lithium battery such as a lithium-ion battery; (h) improved adhesion between ceramic particles within the coating; (i) improved adhesion between the coating and the substrate; and / or (j) improved adhesion between the coated separator and one or both electrodes of the battery. These objectives and other related characteristics of the improved coated separator are described in more detail below.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0017] According to at least selected embodiments or purposes, the present invention provides a separator for a lithium battery such as a lithium-ion battery (although the use of the separator is also contemplated for other batteries), the separator comprising a composite having a microporous substrate and a coating layer formed on at least one surface of the porous substrate, the coating layer being formed from a mixture of particles and / or particles (inorganic and / or organic particles) and a water-soluble or aqueous polymer binder. The present invention further provides a process for manufacturing a separator for a lithium-ion battery, the process involving providing a porous substrate such as a polyolefin substrate and forming a porous composite by applying a coating layer on at least one surface of the porous substrate, the coating layer comprising a mixture of particles and / or particles (inorganic and / or organic particles) and a water-soluble or aqueous polymer binder, the water-soluble or aqueous polymer binder may include one or more typical non-water-soluble polymers (such as PVDF), and further may include one or more typical water-soluble polymers (by way of example, polyvinyl alcohol or polyacrylic acid, etc.). The present invention further provides for the use of the separator within a lithium-ion battery.

[0018] The separators described herein may be advantageous for use in lithium-ion batteries due to their high-temperature integrity and improved safety performance. This improved, optimized, novel, or modified separator for lithium-ion batteries is coated with a mixture of one or more types of particles (e.g., inorganic particles such as ceramic particles and / or organic particles such as high-temperature polymer particles) and one or more water-soluble or aqueous polymer binders, and the water-soluble or aqueous polymer binder may include one or more typical water-insoluble polymers (such as PVDF and / or its various copolymers), and in certain embodiments, may further include one or more typical water-soluble polymers (by way of example, polyvinyl alcohol or polyacrylic acid, etc.). The coating layer may prevent an oxidation reaction from occurring at the interface between the coated separator and the electrodes in the battery and / or may improve the safety and / or overall performance of the lithium-ion battery. In embodiments where one surface of the separator substrate is coated with the coating mixture described above, the coated surface may be arranged to contact any of the electrodes in the lithium-ion battery and, in certain embodiments, to contact the cathode. Further, in other embodiments, two or more surfaces of the separator substrate may be coated with the coating mixture described above.

[0019] Preferred particles suitable for the coatings described herein have an average diameter size of from about 50 nm to about 1,000 nm, preferably an average diameter of from about 50 nm to about 800 nm, and most preferably an average diameter of from about 50 nm to about 600 nm. The particles can be rectangular, spherical, elliptical, cylindrical, oval, dog-bone shaped, or amorphous, etc., but are not limited thereto and can be of various shapes. "Particles" can also be in fibrous form or fibers. In some embodiments, the particles are extremely small and thus may have a large surface area per gram, which can enhance the absorption performance of the coating material and the interaction with the polymer matrix of the particles. Further, in some embodiments, particles as purchased from particle manufacturers may be pre-coated with some material, for example, to enhance the compatibility with the polymer matrix of the particles, perhaps to make it more uniform, to improve the solubility of the particles within a portion of the polymer matrix, the dispersibility of the particles within the polymer matrix, to avoid agglomeration of the particles, and / or to stabilize the particles within the coating slurry.

[0020] In some embodiments, for example, organic particles such as high-temperature polymer particles can be used. In various other embodiments, inorganic particles can be used to prepare the coatings described herein. Examples of inorganic particles suitable for the coatings described herein include various inorganic particles such as ceramics, metal oxides, and the like, and can include aluminum oxide (Al2O3), titanium oxide (TiO2), silicon oxide (SiO2), zinc oxide (ZnO2), metal hydroxides, metal carbonates, silicic acid, kaolin, talc, minerals, glass, and the like, as well as mixtures thereof. The type of ceramic can be selected based on its electrochemical stability, wettability with the electrolyte, oxidation resistance, and chemical inertness within a lithium-ion battery.

[0021] In one or more embodiments, the Al2O3 particles can be used as ceramic particles within a coating for a battery separator. Without wishing to be bound by theory, Al2O3 can function as a scavenger for "junk" species, perhaps species that can cause capacity fade within a lithium-ion battery. Additionally, the Al2O3 particles can have excellent electrolyte wettability and good affinity for the electrolyte, which can result in good electrolyte absorption rates and provide better cycle performance for the lithium-ion battery. With regard to ion mobility, the coating layer described herein has a finely porous internal structure. The irregular shape and stacking of the ceramic particles within this coating layer results in a less dense coating layer that does not restrict the transport of ions through the battery system, as is evident from the measurable Gurley, which is a measure of breathability, of the coating layer. The finely porous internal structure of the ceramic / polymer coating can provide a tortuous, meandering path for electrolyte ions to travel through the coating layer. The high surface area of the nanoscale-sized ceramic particles can increase the amount of electrolyte wetted, enhance electrolyte absorption, and result in improved overall battery performance. The tortuous paths present within the stacked arrangement of the ceramic particles provide a longer path for ions to travel not only within the coating layer but also at the ceramic / electrode interface, which can together prevent the growth of lithium dendrites.

[0022] In certain embodiments of the coatings described herein, preferred, exemplary non - water - soluble polymers can be selected, for example, from poly(vinylidene fluoride) (PVDF) homopolymers or hexafluoropropylene (HFP or [-CF(CF3)-CF2-]), or chlorotrifluoroethylene (CTFE), or tetrafluoroethylene (TFE), and / or copolymers of PVDF and / or vinylidene fluoride (VF2) with the like, and mixtures thereof. Preferred polymers can provide a matrix for the ceramic particles and function as a binder, promoting and providing adhesion 1) between particles within the ceramic / polymer coating layer, 2) between the coating layer and the base substrate or porous membrane, and / or 3) between the coated separator membrane and the battery electrodes. Good adhesion between particles can be important so that the resulting coating layer has physical integrity and does not peel off. Good adhesion between the ceramic / polymer coating layer and the base substrate and between the coated separator membrane and the battery electrodes is important to ensure sufficient and optimal ionic conductivity of the electrolyte during charge and discharge cycles in the battery and to reduce impedance to ion mobility in such interfacial layers.

[0023] In addition, a polymer binder, such as a non - water - soluble polymer component like a PVDF polymer or copolymer, and the ceramic particles should be chemically stable with the electrolyte and should not react or dissolve in the electrolyte in certain preferred embodiments, as that would result in undesirable by - products that could negatively affect battery performance. Thus, the PVDF polymer or copolymer functions as a filler within the coating.

[0024] In one particular embodiment, the coatings described herein are formed from a solution (or suspension or slurry) containing one or more PVDF homopolymers or copolymers in water. PVDF homopolymers and copolymers are typically insoluble in water. In the prior art, PVDF homopolymers and copolymers are traditionally dissolved in a solvent such as acetone or the like. The coatings described herein result from the application of a slurry comprising ceramic particles and an aqueous PVDF solution or suspension, and the PVDF solution or suspension is preferably stabilized using one or more performance enhancing additives. Such performance enhancing additives can include, but are not limited to, defoamers, antifoaming agents, fillers, anti-settling agents, levelers, rheology modifiers, wetting agents, pH buffers, surfactants including fluorinated and non-fluorinated surfactants, thickeners, emulsifiers including fluorinated and non-fluorinated emulsifiers, and fugitive adhesion promoters. Some of these performance enhancing additives are described in U.S. Patent Publication Nos. 2012 / 0015246 and 2013 / 0079461, and current U.S. Patent No. 9,068,071, which are incorporated herein by reference. The coating formulations described herein combine a water-insoluble PVDF polymer or copolymer in an aqueous solution or suspension with preferred ceramic particles in a stable, homogeneously dispersed slurry.

[0025] In some embodiments, it is a typical water-insoluble polymer (such as a PVDF polymer or copolymer) that helps to adhere the ceramic particles together at various contact points.

[0026] In other specific embodiments, the coatings described herein include just the typical non - water - soluble polymers described above, but further include one or more typical water - soluble binders or components or polymers. Thus, in the various embodiments described herein, the coatings applied to the microporous base membrane or substrate include at least two components, including particles such as organic and / or inorganic particles, and one or more typical non - water - soluble components such as typical non - water - soluble polymers like PVDF homopolymers or copolymers. In various other embodiments, the coatings applied to the microporous base membrane or substrate include at least three components, including particles such as organic and / or inorganic particles, one or more typical non - water - soluble components (such as PVDF copolymers or homopolymers), and one or more typical water - soluble binders or components or polymers.

[0027] In some cases, one or more typical water - soluble polymers or binders can enhance the mutual adhesion at various contact points of the ceramic particles and / or can achieve excellent adhesion to the base microporous substrate and / or one or more electrodes of the polymer - ceramic coating. Examples of water - soluble polymers or binders useful herein can include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, poly lactam, polyacrylic acid, polyacrylate, and polyvinyl acetate. In some cases, the preferred water - soluble polymer or component can provide a matrix for the ceramic particles and function as a binder to provide and facilitate adhesion 1) between the particles within the ceramic / polymer coating layer and / or 2) between the coating layer and the base substrate or porous membrane and / or between the coating layer and one or more electrodes.

[0028] A slurry containing an aqueous solution of a water-insoluble polymer such as PVDF, optionally one or more water-soluble binders or polymers or components, and ceramic particles should be properly mixed to minimize or avoid unwanted aggregation of the ceramic particles, to avoid an unwanted increase in viscosity, to ensure uniform mixing of the ceramic particles in the matrix, to obtain a smooth and uniform coating, and / or to obtain a stable coating slurry. The method of mixing the ceramic particles with an aqueous solution of a water-insoluble polymer such as PVDF and, in some embodiments described herein, one or more water-soluble binders or polymers to form a coating slurry is important in the overall success of producing a stable and uniformly mixed coating slurry that results in a separator with improved properties when applied to a porous or microporous substrate, with no or minimal particle aggregation and sedimentation.

[0029] The coating slurries described herein may exhibit Newtonian rheology, but are made using only high shear mixing, for example at 5,000 - 6,000 rpm and / or in combination with a ball mill (or ball mill mixing) to yield a well-mixed and stable ceramic / PVDF slurry, and in some embodiments, a well-mixed and stable ceramic / water-insoluble PVDF / water-soluble binder(s) slurry. Such well-mixed and stable ceramic / PVDF slurries and, in some embodiments, well-mixed and stable ceramic / water-insoluble PVDF / water-soluble binder(s) slurries can exhibit excellent dispersion, meaning the slurry can be stable, can be homogeneously mixed during mixing, and can remain stable and uniformly mixed, thus avoiding significant sedimentation between the time of mixing and the time of applying the slurry to a porous membrane substrate. The viscosity can be independent of the shear rate, but an unfavorable mixing method can result in particle aggregation and produce a non-uniform coating layer that can be non-uniform in thickness and density.

[0030] To obtain sufficient adhesion from the PVDF binder between ceramic particles, between the ceramic / PVDF coating and the separator substrate / membrane, and / or between the ceramic / PVDF-coated separator and the electrodes of a lithium-ion battery, the range of ceramic to the polymer binder content of the coatings described herein can vary, preferably from about 50 to 95% ceramic by weight and about 5 to 50% PVDF by weight. Preferably, the optimal balance of ceramic particles to PVDF (or polymer) provides good to excellent adhesion 1) between ceramic particles, 2) between the ceramic / PVDF coating and the base separator or substrate (porous membrane or film), and / or 3) between the ceramic / PVDF-coated separator and one or both electrodes of a lithium-ion battery. Achieving a good to excellent adhesion balance for the three aforementioned "types" of adhesion can enable a desired level of ionic conductivity through the separator during the life of the lithium-ion battery (and thus better overall battery performance). To achieve the desired adhesion performance and high-temperature stability within the lithium-ion battery and to provide an antioxidant barrier at the coating-electrode interface, more preferred ranges of ceramic and PVDF (or polymer) can include from about 50 to 95% ceramic and about 5 to 50% PVDF (or polymer) by weight, or in some embodiments, from about 60 to 90% ceramic and about 10 to 40% PVDF (or polymer) by weight, or in some embodiments, from about 70 to 90% ceramic and about 10 to 30% PVDF (or polymer) by weight, or in still some embodiments, from about 80 to 90% ceramic and about 10 to 20% PVDF (or polymer) by weight.

[0031] Non-limiting examples of base substrate porous and / or microporous membranes can include any commercially available single-layer, two-layer, three-layer, and / or multi-layer (co-extruded or laminated) porous membranes manufactured by dry or wet methods (both generally known to those skilled in the art). By way of example, the substrate can be a polymeric porous or microporous layer that can be adapted to block or interrupt ion conductivity or flow between the anode and cathode of a lithium-ion battery in the event of thermal runaway. Porous membranes useful as substrates in conjunction with the coatings described herein can include, for example, membrane products commercially available from manufacturers such as Celgard, LLC located in Charlotte, North Carolina, USA, Asahi Kasei located in Tokyo, Japan, and Tonen located in Tokyo, Japan, but are not limited thereto. The substrate can have a porosity in the range of about 20% to 80%, preferably in the range of about 28% to 60%, and can have an average pore size in the range of about 0.02 to about 2 microns, preferably in the range of about 0.03 to about 0.5 microns, and in some embodiments, in the range of about 0.08 to about 0.5 microns. The substrate can also have a Gurley number in the range of about 5 to 300 seconds, preferably in the range of about 15 to about 150 seconds, more preferably in the range of about 20 to about 80 seconds, and in some embodiments, in the range of about 30 to about 80 seconds. This Gurley number is the ASTM Gurley and refers to the time required for 10 cc of air to pass through a 1 square inch membrane under 12.2 inches of water. The substrate can be a polyolefin and can include, for example, polyethylene, polypropylene, or a combination thereof including homopolymers and / or copolymers of such polyolefin(s).

[0032] The preferred thickness of the ceramic / PVDF coating layer can range from about 2 to about 10 μm, more preferably from about 2 to about 8 μm, and most preferably from about 3 to about 5 μm. In certain embodiments, the coating layer is even thinner, having a thickness of less than 2 microns. Possible methods for applying the ceramic / PVDF coating include, but are not limited to, Meyer rod, dip, gravure, slot die, printing, doctor blade coating, and spray methods. The coating process can be carried out at room temperature or at elevated temperature. The ASTM Gurley value of the improved coated separator described herein can, in some embodiments, be about 5 to 300 seconds, preferably about 15 to 150 seconds, in some embodiments less than about 75 seconds, in some embodiments less than about 50 seconds, in some embodiments less than about 40 seconds, in some embodiments less than about 30 seconds, and in some embodiments less than about 20 seconds. Additionally, in some embodiments, the Gurley test on the coated separator can be performed using the JIS Gurley method described herein. In such embodiments, the JIS Gurley value for the coated separator according to the present invention can be within the ranges according to the various examples described herein, and in some particular preferred embodiments, less than about 300 seconds, in others less than about 250 seconds, in still others less than about 200 seconds, in others less than about 150 seconds, and in yet others less than about 125 seconds.

[0033] The coated substrate can be dried at a temperature of about 40 - 100 °C in a furnace, or at a temperature below the melting temperature of the base film, at room temperature in air and / or depending on the film speed through a drying oven. In certain embodiments, drying in a furnace may be preferred as the adhesion of the coating to the substrate can be improved during drying in the furnace compared to drying at room temperature in air. The drying step in the coating application process can serve to evaporate most or substantially all of the moisture originally present in the coating slurry that contains ceramic particles, one or more non - water - soluble polymers (such as PVDF homopolymers or copolymers), and optionally, one or more water - soluble binders or polymers.

[0034] Without wishing to be bound by theory, in certain embodiments of the present invention, drying the coating at room temperature can result in what appears to be polymer particles (such as PVDF particles) simply existing on the surface of the porous substrate without providing excellent adhesion of the coating layer to the substrate. As just one example, FIG. 7 is a 40,000x magnification SEM side view of a coating layer containing only PVDF particles (no ceramic particles) that has been coated on a substrate and dried at room temperature in air. In FIG. 7, the spherical PVDF particles appear to simply be present on the surface of the substrate without necessarily providing the desired adhesion of the coating layer to the substrate. In various embodiments, the spherical or substantially spherical PVDF particles function as a kind of filler.

[0035] In some embodiments, when the coated separator is dried in an oven at a temperature of, for example, about 50 - 60 °C, the water-insoluble polymer particles (e.g., PVDF nanoparticles or nanospheres with a lower melting temperature (< 100 °C)) appear to "fuse" or soften or melt somewhat, presumably improving the resulting adhesion between the ceramic particles and the polymer material, and / or the resulting adhesion to the microporous base membrane of the ceramic / PVDF coating, and / or the resulting adhesion to any battery electrodes of the coated separator. This can simulate what happens to PVDF spherical type particles when such a coated separator is laminated to an electrode.

[0036] In some embodiments, the water-insoluble PVDF particles can remain spherical in shape after drying (see, for example, FIGS. 5, 13, 17, 18, 25, 27, and 28) and when laminated to the electrodes of the coated separator, and the processes involving heat and pressure can contribute to the excellent adhesion of the coated separator of the present invention to the electrodes. In some embodiments, the water-insoluble PVDF particles can swell in the electrolyte and can strengthen the adhesion of the coated separator membrane to the electrodes. FIG. 33 is a photograph of a coated separator of the present invention on which a dry adhesion peel test has been performed, where the coated separator is laminated to an electrode and the coated separator is manually pulled away from the electrode. The black regions on the surface of the coated separator can indicate the layer of the electrode adhered to the coated separator, indicating excellent adhesion of the coating layer to the electrode.

[0037] The various embodiments of the present invention have been described in the context of achieving various objects of the present invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention.

[0038] According to at least selected embodiments, aspects or purposes, various novel or improved coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such coated separators, membranes, films, or the like, and methods of making or using such coated separators, membranes, films, or the like, novel or improved ceramic-coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such ceramic-coated separators, membranes, films, or the like, and methods of making or using such ceramic-coated separators, membranes, films, or the like, novel or improved water-soluble or aqueous polymer-coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such water-soluble or aqueous polymer-coated separators, membranes, films, or the like, and methods of making or using such water-soluble or aqueous polymer-coated separators, membranes, films, or the like, novel or improved water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like, and methods of making or using such water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like, novel or improved polyvinylidene fluoride or polyvinylidene difluoride (PVDF) homopolymers or hexafluoropropylene (HFP or [-CF(CF3)-CF2-]),Chlorotrifluoroethylene (CTFE), vinylidene fluoride (VF, 2- HFP), tetrafluoroethylene (TFE), and / or copolymers of PVDF with the like, blends and / or mixtures thereof, coated separators, membranes, films or the like, novel or improved porous separators for use in lithium batteries, novel or improved coating or application methods for applying a coating or ceramic coating to a separator for use in a lithium battery, novel or improved PVDF or PVDF:HFP films or membranes, and / or the like are provided.

[0039] Examples In the following examples, various coated separators for use in lithium ion batteries were formed and tested.

[0040] Example 1 An aqueous PVDF / ceramic coating slurry has a D50 average particle size of 0.65 μm, a bulk tap density of 0.8 g / cm 3 and a volume of 4.6 m 225 grams of high-purity alumina particles having a BET surface area of / g were prepared by uniformly dispersing them using two aqueous solutions or suspensions of PVDF:HFP (available from Arkema Inc., located in King of Prussia, Pennsylvania, USA, under the product line Kynar® Latex, which varies depending on the content of HFP and is described in more detail below), 18.7 grams of a 50:50 blend of formulation #1, formulation #2, and formulation #3. Improved mixing was first achieved by pre-wetting the alumina particles with the solution or suspension of formulation #1. Dispersion was achieved using a Silverson High Shear L4M-5 mixer at 5000 rpm for 12 minutes at room temperature. The slurry was hand-coated onto the surface of a Celgard® 2400 PP microporous membrane (a membrane made by the dry process, also known as the Celgard® process, having a thickness of about 25 μm, a porosity of about 41%, a pore diameter of about 0.04 μm, and a JIS Gurley value of about 620 seconds, corresponding to an ASTM Gurley value of about 25 seconds) using a doctor blade. The coated sample was dried in air at room temperature.

[0041] A scanning electron microscope photograph (SEM) of the surface of this coated separator membrane taken at a magnification of 10,000x is shown in Figure 1. Irregularly shaped ceramic particles 10 and a PVDF binder 12 are seen in the SEM of Figure 1, and the PVDF binder 12 is either fused or somewhat melted or bonded to form a coating layer together with the ceramic particles 10. Additionally, voids 14 are seen in the SEM of Figure 1.

[0042] The components of the coating prepared in this example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

[0043] Example 2 The aqueous PVDF / ceramic coating slurry has a D50 average particle size of 0.65 μm, a bulk tap density of 0.8 g / cm 3 and a volume of 4.6 m 239 grams of high-purity alumina particles having a BET surface area of / g were prepared by dispersing them using 16.8 grams of PVDF formulation #1 blend described in Example 1 above. The improved mixing was achieved by first wetting the alumina particles with the solution or suspension of formulation #1. The dispersion was achieved by using a Silverson High Shear L4M-5 mixer at 5000 rpm for 12 minutes at room temperature and then using a ball mill mixer (MTI Shimmy Ball Mixer) for 20 minutes. The ceramic / PVDF slurry was manually coated on the surface of a Celgard® 2400 PP microporous membrane (the characteristics of the membrane are described in Example 1 above) using a doctor blade, and the moisture was removed by drying in an oven at 79 °C. The SEM of the surface of this coated separator membrane taken at 10,000x magnification is shown in Figure 2. The components of the coating formed in this example are shown in Table 1 below, and the characteristics of the coated separator membrane are reported in Table 2 below.

[0044] Example 3 The aqueous PVDF / ceramic coating slurry has a D50 average particle size of 0.65 μm, a bulk tap density of 0.8 g / cm 3 and a 4.6 m 266 grams of high-purity alumina particles having a BET surface area of / g were prepared by mixing and uniformly dispersing them with 23.5 grams of Formulation #2, an aqueous suspension of Kynar® Latex product available from Arkema and generally described as water (55 - 65%) and PVDF:HFP (PVDF:HFP having a melting temperature in the range of about 114 - 120 °C). The improved mixing was achieved by first wetting the alumina particles with the solution or suspension of Formulation #2. The dispersion was achieved by using a Silverson High Shear L4M-5 mixer at 3000 rpm for 5 minutes at room temperature and then mixing with a ball mill mixer (MTI Shimmy Ball Mixer) for 20 minutes. The slurry was hand-coated onto the surface of a Celgard® EK0940 polyethylene microporous membrane (a membrane made by the wet method, having a thickness of about 9 μm, a porosity of about 40%, and a JIS Gurley value of about 130 seconds corresponding to an ASTM Gurley value of about 5 seconds) using a doctor blade, and the coated sample was oven-dried at 65 °C. The SEM of the surface of this coated separator membrane taken at 10,000x magnification is shown in Figure 3. The components of the coating prepared in this example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

[0045] Example 4 The aqueous PVDF / ceramic coating slurry has a D50 average particle size of 0.65 μm, a volumetric tap density of 0.8 g / cm 3 and 4.6 m 266 grams of high-purity alumina particles having a BET surface area of / g were prepared by mixing with 16.4 grams of formulation #2 (described above) and uniformly dispersing. The improved mixing was achieved by first wetting the alumina particles with the solution or suspension of formulation #2. The dispersion was achieved by using a Silverson High Shear L4M-5 mixer at 5000 rpm for 10 minutes at room temperature and then mixing with a ball mill mixer (MTI Shimmy Ball Mixer) for 15 minutes. The slurry was hand-coated and applied onto the surface of a Celgard® EK0940 polyethylene microporous membrane (as described in Example 3 above) using a Meyer rod size 3, and the coated sample was oven-dried at 60°C. The components of the coating formed in this example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

[0046] Example 5 Using the aqueous PVDF / ceramic coating slurry used in Example 4, a Celgard® EK0940 polyethylene microporous membrane was coated using a Meyer rod size 24, and the coated sample was oven-dried at 60°C. The components of the coating formed for this example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

[0047] Example 6 Using the aqueous PVDF / ceramic coating slurry used in Example 4, a Celgard® 2400 polypropylene microporous membrane was coated using a doctor blade, and the coated sample was oven-dried at 60°C. The SEM of the surface of this coated separator membrane taken at a magnification of 20,000x is shown in Figure 4. The components of the coating formed for this example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

[0048] Example 7 The aqueous PVDF / ceramic coating slurry has a D50 average particle size of 0.65 μm, 0.8 g / cm3 with a volume tap density of and 4.6 m 2 138 grams of high purity alumina particles having a BET surface area of / g were uniformly dispersed and prepared using 30 grams of formulation #3, a Kynar® Latex product available from Arkema and generally described as an aqueous suspension of water (55 - 65%) and PVDF:HFP (PVDF:HFP has a melting temperature in the range of about 152 - 155 °C). The improved mixing was first achieved by pre-wetting the alumina particles with the solution or suspension of formulation #3. The low content of the HFP copolymer in PVDF:HFP in formulation #3 may be the reason for the higher melting temperature of PVDF:HFP in formulation #3 compared to PVDF:HFP in formulation #2. Without wishing to be bound by theory, changing the content of the copolymer (e.g., HFP in the PVDF:HFP copolymer) can affect the adhesion of the polymer solution or suspension to the ceramic particles and the overall adhesion to the coating film, and ultimately the adhesion between the coated separator and one or both electrodes of the lithium-ion battery. If there is too much or too little of the copolymer (such as HFP) used, it can affect the crystallinity of the coating, can affect the thickness of the coating, and thereby can affect the adhesion of the coating.

[0049] The dispersion was achieved using a Silverson High Shear L4M-5 mixer at room temperature for 5 minutes at 5000 rpm and for 10 minutes at 6700 rpm. The slurry was hand-coated onto the surface of a Celgard® EK0940 polyethylene microporous membrane using a Meyer rod size 24. The coated samples were oven-dried at 60 °C for 10 minutes and further dried at room temperature in air. The SEM of the surface of this coated separator membrane taken at 35,000x magnification is shown in Figure 5. The components of the coating of this example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

[0050] Example 8 The aqueous PVDF / ceramic coating slurry was prepared by mixing 112 grams of high-purity alumina particles having a D50 average particle size of 0.65 μm, a bulk tap density of 0.8 g / cm 3 and a BET surface area of 4.6 m 2 / g with 18.7 grams of Formulation #1 blend described in Example 1 above, and uniformly dispersing them. The improved mixing was achieved by first wetting the alumina particles with the Formulation #1 solution or suspension. The dispersion was achieved by using a Silverson High Shear L4M-5 mixer at room temperature for 10 minutes at 2500 rpm and then for 10 minutes at 5000 rpm, followed by mixing for 10 minutes with a ball mill mixer (MTI Shimmy Ball Mixer). The slurry was hand-coated onto the surface of a Celgard® 2400 polypropylene microporous membrane using a doctor blade, and the coated sample was oven-dried at 60 °C. Two SEMs of the surface of this coated separator membrane are shown in FIGS. 6(a) (10,000x magnification) and 6(b) (20,000x magnification), and an SEM of the cross-section of this coated separator membrane taken at 1,000x magnification is shown in FIG. 6(c). The components of the coating for this example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

[0051] Comparative Example 1 The non-aqueous PVDF ceramic coating solution was prepared by mixing 30 grams of high-purity fumed alumina particles having an average diameter of 100 nm with 30 grams of Solef 21216 PVDF:HFP (commercially available from Solvay) in acetone. The coating was hand-coated onto a Celgard® EK0940 polyethylene microporous membrane using a doctor blade and dried at room temperature in air. An SEM of the surface of this coated separator membrane taken at 10,000x magnification is shown in FIG. 8. The components of the coating for this comparative example are shown in Table 1 below, and the properties of the coated separator membrane are reported in Table 2 below.

Table 1

Table 2

[0052] The coated separator membranes of Examples 1 to 8 are useful in lithium ion secondary batteries and are coated with ceramic particles and a water-soluble or aqueous polymer binder. The above Table 1 lists the formulation information related to the compositions of Examples 1 to 8 over a range of ceramic / PVDF:HFP ratios from about 1:1 to about 6:1. Examples 1 to 8 were coated using an aqueous or water-soluble coating that does not contain any non-aqueous solvents such as acetone, N-methylpyrrolidone, dimethylacetamide, or the like. Comparative Example 1 (CE1) having a ceramic / PVDF:HFP ratio of 1:1 was coated using acetone as the primary solvent.

[0053] The above Table 2 lists the coating layer thickness, Gurley, and adhesion performance data for the coated samples of Examples 1 to 8 and Comparative Example CE1. The various coatings in the examples are porous, as indicated by samples having Gurley values and by the presence of voids on the surface of the coated samples shown in the SEMs of FIGS. 1 to 6. The internal structure of the ceramic / PVDF coating layer is shown in FIG. 6(c), which shows a cross-sectional view of the coated separator.

[0054] It has been observed that the various coatings in the examples have good to excellent adhesion between the ceramic particles and between the coating layer and the base film or substrate, indicating that the water-soluble coating system provided the required adhesion performance even in the absence of a non-aqueous solvent in the coating formulation.

[0055] Various ceramic / PVDF:HFP-coated samples from the examples also showed improved thermal stability, as indicated by the improvements in the hot chip hole propagation test results listed in Table 3 below. Improvements in the size of hole propagation were observed regardless of whether the base film was PE or PP. Figures 9, 10, and 11 are photographs of the shape and size of the holes after removal of the hot chip probe, taken using an optical microscope. These photographs provided evidence of an improved reaction to contact with ultra-high heat due to the ceramic / PVDF:HFP coating.

[0056] In Figure 9(b), a "control" sample of uncoated Celgard® EK0940 polyethylene film was tested for hot chip hole propagation, and in Figure 9(a), the coated sample of Example 3 (the coating had a ceramic to PVDF:HFP ratio of approximately 2.8:1) was tested for hot chip hole propagation. As shown in Table 3 below, for the sample of Example 3, a reduction of more than 40% in hole propagation was observed.

[0057] In Figure 10(b), a "control" sample of uncoated Celgard® 2400 polypropylene film was tested for hot chip hole propagation, and in Figure 10(a), the coated sample of Example 6 (the coating had a ceramic to PVDF:HFP ratio of approximately 4:1) was tested for hot chip hole propagation. As shown in Table 3 below, for the sample of Example 6, a reduction of more than 50% in hole propagation was observed.

[0058] In Figure 11, the coated sample of Example 8 (the coating had a ceramic to PVDF:HFP ratio of approximately 6:1) was tested for hot chip hole propagation. As shown in Table 3 below, for the sample of Example 8, a reduction of more than 40% in hole propagation was observed compared to the hole propagation of the control sample tested in Figure 10(b).

Table 3

[0059] Examples 9 to 18 below were prepared by: 1) mixing aluminum oxide (Al2O3) ceramic particles with neutralized polyacrylic acid (PAA) in a ball mill mixer; and 2) adding a water-soluble PVDF solution or suspension to the Al2O3-dispersant mixture mixed with one or more water-soluble binders (such as polyacrylate) to form a homogeneous and well-mixed slurry.

[0060] Example 9 Example 9 is a three-layer microporous base film of PP / PE / PP with an uncoated thickness of 12.3 μm, which is single-sided coated with a water-soluble coating formulation having a weight percentage ratio of 50:50 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The coating formulation contains PVDF with a molecular weight exceeding 300,000. The thickness of the coating layer is 3.4 μm.

[0061] Example 10 Example 10 is a three-layer microporous base film of PP / PE / PP with an uncoated thickness of 12.3 μm, which is single-sided coated with a water-soluble coating formulation having a weight percentage ratio of 50:50 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The coating formulation contains PVDF with a molecular weight exceeding 1,000,000. The thickness of the coating layer is 4.0 μm.

[0062] Example 11 Example 11 is a three-layer microporous base film of PP / PE / PP with an uncoated thickness of 17.8 μm, which is single-sided coated with a water-soluble coating formulation having a weight percentage ratio of 50:50 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The coating formulation contains PVDF with a molecular weight exceeding 1,000,000. The thickness of the coating layer is 2.8 μm.

[0063] Example 12 Example 12 is a three-layer microporous base film of PP / PE / PP with an uncoated thickness of 17.8 μm, which is single-sided coated with a water-soluble coating formulation having a weight percentage ratio of 50:50 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The coating formulation contains PVDF with a molecular weight exceeding 300,000. The thickness of the coating layer is 2.1 μm.

[0064] Example 13 Example 13 is a three-layer microporous base film of PP / PE / PP with an uncoated thickness of 17.8 μm, which is single-sided coated with a water-soluble coating formulation having a weight percentage ratio of 50:50 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The coating formulation contains PVDF with a molecular weight exceeding 300,000. The thickness of the coating layer is 1.0 μm.

[0065] Table 4 below lists separator characteristic data for Examples 9 to 13, all coated with a binder:ceramic ratio of 50:50. The Al2O3 ceramic particles in the PVDF-Al2O3 aqueous slurry are 0.5 μm in diameter and have a D50 particle size distribution. The PVDF particle size is 100 nm to 1,000 nm.

Table 4

[0066] Example 14 Example 14 is a PE microporous base film with an uncoated thickness of 9 μm, which is coated on one side with a water-soluble coating formulation having a weight percent ratio of 20:80 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The coating formulation contains PVDF with a molecular weight exceeding 300,000. The thickness of the coating layer is 4.2 μm.

[0067] Example 15 Example 15 is a PE microporous base film with an uncoated thickness of 9 μm, which is coated on one side with a water-soluble coating formulation having a weight percent ratio of 20:80 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The thickness of the coating layer is 3.5 μm.

[0068] Example 16 Example 16 is a PE microporous base film with an uncoated thickness of 9 μm, which is coated on one side with a water-soluble coating formulation having a weight percent ratio of 20:80 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The thickness of the coating layer is 5.0 μm.

[0069] Example 17 Example 17 is a PE microporous base film with an uncoated thickness of 9 μm, which is coated on one side with a water-soluble coating formulation having a weight percent ratio of 20:80 of polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The coating formulation contains PVDF with a molecular weight exceeding 300,000. The thickness of the coating layer is 5.6 μm.

[0070] The following Table 5 lists separator characteristic data for Examples 14 to 17, all coated with a binder:ceramic ratio of 20:80. The Al2O3 ceramic particles in the PVDF-Al2O3 aqueous slurry are 0.5 μm in diameter and have a D50 particle size distribution. The PVDF particle size is from 100 nm to 1,000 nm.

Table 5

[0071] Example 18 Example 18 is a PE microporous base film with an uncoated thickness of 9 μm, which is single-sided coated with a water-soluble coating formulation having a weight percent ratio of 10:90 polyvinylidene fluoride (PVDF) polymer to aluminum oxide (Al2O3) ceramic particles. The thickness of the coating layer is 6.9 μm.

[0072] The following Table 6 lists separator characteristic data for the separators of Examples 13 and 14 (repeated data from Tables 4 and 5 above) and Example 18, each coated with PVDF binder:ceramic ratios of 50:50, 20:80, and 10:90. The Al2O3 ceramic particles in the PVDF-Al2O3 aqueous slurry are 0.5 μm in diameter and have a D50 particle size distribution. The PVDF particle size is from 100 nm to 1,000 nm.

Table 6

[0073] The ratio of polymer to ceramic content can be selected to balance the excellent adhesion of the polymer-ceramic coating to the electrode, in which case the adhesion can be due to the swelling of the water-soluble binder in the electrolyte and / or can be due to the melting of PVDF if PVDF has a low melting temperature of less than 100 °C, more preferably less than 80 °C, and most preferably less than 60 °C. Additionally, the ratio of polymer to ceramic content can be selected to optimize and / or reduce the thermal shrinkage of the polymer-ceramic coated separator. The 20:80 water-insoluble polymer binder:ceramic ratio in Examples 14, 15, 16 and 17 can exhibit a low longitudinal (MD) thermal shrinkage of 11.4% or less and a low transverse (TD) thermal shrinkage of 7% or less. Further, the 10:90 water-insoluble polymer binder:ceramic ratio in Example 18 can exhibit a low longitudinal (MD) thermal shrinkage of 1.3% or less and a low transverse (TD) thermal shrinkage of 2.4% or less.

[0074] The ratio of water-soluble to water-insoluble binder content can be selected to optimize the adhesion of the polymer-ceramic coating to the base separator. The ratio of 1:20 water-soluble binder(s) to water-insoluble binder(s), more preferably a ratio of 1:15, and most preferably a ratio of 1:10, is for promoting excellent adhesion of the polymer-ceramic coating to the base separator substrate and for excellent adhesion of the ceramic particles within the polymer-ceramic coating layer to eliminate the dropout or loss of ceramic particles during handling of the separator during manufacture or cell winding.

[0075] Disclosed herein are various novel or improved coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such coated separators, membranes, films, or the like, and methods of making or using such coated separators, membranes, films, or the like. According to at least selected embodiments, aspects, or purposes, disclosed herein are novel or improved ceramic-coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such ceramic-coated separators, membranes, films, or the like, and methods of making or using such ceramic-coated separators, membranes, films, or the like. According to at least certain embodiments, aspects, or purposes, disclosed herein are novel or improved water-soluble or aqueous polymer-coated separators, membranes, films, or the like for use in lithium batteries such as lithium ion batteries or lithium ion polymer batteries, novel or improved batteries comprising such water-soluble or aqueous polymer-coated separators, membranes, films, or the like, and methods of making or using such water-soluble or aqueous polymer-coated separators, membranes, films, or the like.According to at least certain embodiments, aspects or purposes, novel or improved water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like for use in lithium batteries such as lithium-ion batteries or lithium-ion polymer batteries, novel or improved batteries comprising such water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like, and methods of making or using such water-soluble or aqueous polyvinylidene fluoride (PVDF) polymer-coated separators, membranes, films, or the like, novel or improved polyvinylidene fluoride or polyvinylidene difluoride (PVDF) homopolymers or copolymers of PVDF with hexafluoropropylene (HFP or [-CF(CF3)-CF2-]), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE), and / or the like, as well as vinylidene fluoride (VF2), blends and / or mixtures thereof, coated separators, membranes, films or the like, novel or improved porous separators for use in lithium batteries, novel or improved coating or application methods for applying a coating or ceramic coating to a separator for use in a lithium battery, novel or improved PVDF or PVDF:HFP films or membranes, and / or the like are disclosed herein.

[0076] A separator membrane for a lithium-ion battery is also disclosed, the separator membrane having a porous coating layer formed on at least one surface of a porous substrate. The coating layer can be formed from a coating slurry containing water, ceramic particles, one or more non-water-soluble polymers or binders, and in some embodiments, a mixture of one or more water-soluble polymers or binders. The present invention further provides a process for manufacturing a separator membrane for a lithium-ion battery, in which a porous coating layer, which can be formed from the mixture described immediately above, is formed on at least one surface of a porous substrate. This improved, novel or modified separator can be advantageous when used in a lithium-ion battery due to its high-temperature melting integrity and improved safety performance. The ceramic / polymer coating layer can prevent oxidation from occurring at the interface between the coated separator and the electrodes of the lithium-ion battery and can improve the safety and overall performance of the lithium-ion battery.

[0077] Test Method Gurley ASTM-D726(B) Test Gurley is the resistance to the flow of air measured with a Gurley densometer (e.g., Model 4120). ASTM Gurley is the time (in seconds) required to pass 10 cc of air through a 1 square inch product under a pressure of 12.2 inches of water.

[0078] Gurley JIS P8117 Test JIS Gurley is a permeability test defined as Japanese Industrial Standard (JIS Gurley) JIS P8117 and measured using an OHKEN permeability tester. JIS Gurley is the time (in seconds) required to pass 100 cc of air through a 1 square inch film under a constant pressure of 4.8 inches of water.

[0079] Thickness Test The thickness is measured using an Emveco Microgage 210-A precision micrometer thickness gauge in accordance with test procedure ASTM D374. The thickness value is reported in units of micrometers, μm.

[0080] Basis weight Using a graduated metal template, cut a test sample of area 1 ft 2 (and convert to cm 2 ). Weigh the sample and calculate the basis weight in mg / cm 2 .

[0081] Heat shrinkage: Shrinkage is measured by placing the coated test sample between two sheets of paper and then suspending it in an oven by clipping it to hold the sample between the papers. For the "130 °C for 1 hour" test, place the sample in the oven at 130 °C for 1 hour. After heating in the oven for the specified time, remove each sample and, to accurately measure the length and width, use single-sided adhesive tape to attach it to the surface of a flat counter, flattening and stretching it. Shrinkage is measured in both the machine direction (MD) and the transverse direction (TD) and expressed as %MD shrinkage and %TD shrinkage.

[0082] High-temperature electrical resistance (high-temperature ER): High-temperature electrical resistance is the measurement of the resistance of the separator film while the temperature is rising linearly. The increase in resistance measured as impedance corresponds to the collapse of the porous structure due to the melting or "blocking" of the separator film. The sharp decrease in resistance corresponds to the opening of the separator due to the melting of the polymer; this phenomenon is referred to as the loss of "melt integrity". If the separator film maintains a high level of electrical resistance, this indicates that the separator film can prevent short circuits within the battery.

[0083] Adhesion test The adhesion of the coating to the base substrate can be subjectively evaluated by any, or all, of the following methods, listed in order of increasing durability or adhesion strength of the coating layer to the base substrate: 1) Rub the surface of the coating with the tip of the tester's index finger to determine whether the coating peels off the underlying substrate, 2) Apply a 3M Post-it® sticker to the coated side of the coated membrane substrate and pull the 3M Post-it® sticker away from the coated membrane substrate to test whether the coating peels off the substrate, and 3) Apply Scotch® tape to the coated side of the coated membrane substrate and pull the Scotch® tape away to test whether the coating peels off the substrate. The examples described herein tested the adhesion by rubbing the surface of the coated sample with the tip of the tester's index finger (rubbing the surface of the coating) and observing whether the coating peeled off the underlying substrate. If the coating remained attached to the substrate even with the standard frictional pressure using the tip of the tester's index finger, the adhesion was described as "good". If the coating remained attached to the substrate even after very strong frictional pressure using the tip of the tester's index finger, the adhesion was described as "excellent".

[0084] The adhesion of the coated separator membrane to the electrode can be evaluated by a dry adhesion test in which a sample of the coated membrane is laminated to the electrode using heat and pressure. After cooling to room temperature, the electrode / coated membrane sample is pulled apart by hand. Observe whether there is electrode material on the surface of the coated membrane, which will often appear black in appearance. The presence of electrode material on the surface of the pulled-apart coated separator membrane indicates that the coating layer adhered very well to the electrode.

[0085] Hot Chip Hole Propagation Test A hot chip probe with a chip diameter of 0.5 mm at a temperature of 450 °C is moved towards the surface of the separator test sample placed on the aluminum foil disposed on the glass substrate as shown in Fig. 12. The hot chip probe is moved towards the sample at a speed of 10 mm / min and brought into contact with the surface of the test sample for 10 seconds. The results of the test are presented as digital images taken with an optical microscope, showing both the shape and size (in millimeters) of the holes after the hot chip probe is removed. The minimum propagation of the holes in the separator test sample from contact with the hot chip probe simulates the desired reaction of the separator to local hot spots, which can occur during an internal short circuit in a lithium-ion battery.

[0086] It should be recognized that the foregoing embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention. The present invention may be embodied in other forms without departing from its spirit and characteristics, and accordingly, reference may be made to the appended claims and / or the foregoing specification as indicating the scope of the present invention. Additionally, the invention disclosed herein may be appropriately practiced even in the absence of elements not specifically disclosed herein.

[0087] The present invention includes the following configurations. (1) A separator for a lithium battery, comprising a porous substrate and a coating layer formed on at least one surface of the porous substrate, wherein the coating layer is formed from a coating slurry containing ceramic particles and a polymer binder, and the polymer binder is dispersed in water or an aqueous solution. (2) The separator according to (1), wherein the separator is for a secondary lithium battery. (3) The separator according to (1), wherein the substrate is microporous. (4) The separator according to (1), wherein the coating is porous. (5) The separator according to (4), wherein the coating is microporous. (6) The polymer binder is a polyvinylidene fluoride (PVDF) homopolymer, a copolymer of PVDF, or a mixture thereof, and the copolymer of PVDF includes PVDF copolymerized with one or more of hexafluoropropylene (HFP or [-CF(CF3)-CF2-]), chlorotrifluoroethylene (CTFE), and tetrafluoroethylene (TFE) and / or vinylidene fluoride (VF2), the separator according to (1). (7) The ceramic particles include one or more of metal oxides, metal hydroxides, metal carbonates, silicic acid, kaolin, talc, minerals, glass, and mixtures thereof, and the metal oxides include one or more of aluminum oxide (Al2O3), titanium oxide (TiO2), silicon oxide (SiO2), zinc oxide (ZnO2), and mixtures thereof, the separator according to (1). (8) The ceramic particles have an average diameter of 50 nm to 1,000 nm, the separator according to (1). (9) The coating layer includes about 50% to about 95% by weight of ceramic particles and about 5% to about 50% by weight of a polymer binder, the separator according to (1). (10) The porous substrate is a single-layer, two-layer, three-layer, or multi-layer porous membrane, the separator according to (1). (11) The thickness of the coating layer is about 2 to about 10 μm, the separator according to (1). (12) The aqueous solution of the polymer binder further includes one or more of a defoaming agent, a dispersant, an antifoaming agent, a filler, an anti-settling agent, a leveling agent, a rheology modifier, a wetting agent, a pH buffer, a fluorinated surfactant, a non-fluorinated surfactant, a thickener, an emulsifier, a fluorinated emulsifier, a non-fluorinated emulsifier, and a fugitive adhesion promoter, the separator according to (1). (13) The porous substrate is a microporous membrane including one or more polyolefins, the separator according to (1). (14) A separator for a lithium battery, comprising a porous substrate and a coating layer formed on at least one surface of the porous substrate, wherein the coating layer is formed from a coating slurry containing ceramic particles, one or more water-soluble polymer binders, and one or more water-insoluble polymer binders, and the solvent is water. (15) The separator according to (14), wherein the substrate is microporous. (16) The separator according to (14), wherein the coating is porous. (17) The separator according to (14), wherein the coating is microporous. (18) The water-insoluble polymer binder is a polyvinylidene fluoride (PVDF) homopolymer, a copolymer of PVDF, or a mixture thereof, and the copolymer of PVDF comprises PVDF and / or vinylidene fluoride (VF2) copolymerized with one or more of hexafluoropropylene (HFP or [-CF(CF3)-CF2-]), chlorotrifluoroethylene (CTFE), and tetrafluoroethylene (TFE). The separator according to (14). (19) The water-soluble polymer binder is carboxymethyl cellulose, polyvinyl alcohol, polyamide, or polyacrylate. The separator according to (14). (20) A process for manufacturing a coated separator for a lithium battery, comprising: (a) providing a porous substrate; (b) applying a coating slurry containing ceramic particles and a polymer binder in water or an aqueous solution or suspension onto at least one surface of the porous substrate; and (c) drying the coating slurry to form a coating layer on the porous substrate. (21) The process according to (20), further comprising mixing the ceramic particles and an aqueous solution of the polymer binder together, and the mixing is achieved by one or more of high-shear mixing and ball-mill mixing. (22) The process according to (20), further comprising the step of mixing together the ceramic particles, a dispersant, and an aqueous solution of a water-soluble and a water-insoluble polymer binder, the mixing being achieved by one or more of high-shear mixing and / or ball-mill mixing. (23) The process according to (20), wherein the coating slurry is dried at a temperature of 40 °C or higher. (24) A lithium-ion battery comprising an electrode, an electrolyte, and the separator of (1), wherein the ceramic particles in the coating layer maintain an amount of physical separation between the electrodes in the lithium battery at a temperature above the melting temperature of the polymer binder, thereby preventing contact between the electrodes. (25) A lithium-ion battery comprising an electrode, an electrolyte, and the separator of (1), wherein the coating layer prevents or reduces the possibility of an oxidation reaction occurring at the interface between the separator and one or more electrodes. (26) A process for manufacturing a coated separator for a lithium-ion battery, comprising: (a) providing a porous substrate; (b) applying a coating slurry containing ceramic particles and a polymer binder in water or an aqueous solution or suspension onto at least one surface of the porous substrate; and (c) drying the coating slurry to form a coating layer on the porous substrate. (27) The process according to (26), further comprising the step of mixing together the ceramic particles and an aqueous solution of a polymer binder, the mixing being achieved by one or more of high-shear mixing and ball-mill mixing. (28) The process according to (26), further comprising the step of mixing together the ceramic particles, a dispersant, and an aqueous solution of a water-soluble and a water-insoluble polymer binder, the mixing being achieved by one or more of high-shear mixing and / or ball-mill mixing. (29) The process according to (26), wherein the coating slurry is dried at a temperature of 40 °C or higher. (30) A lithium battery comprising an electrode, an electrolyte, and the separator of (14).

Claims

1. A porous substrate; a coating layer formed on at least one surface of the porous substrate; A separator for a lithium battery comprising:

1. A separator for a lithium battery, wherein the coating layer comprises ceramic particles dispersed in a polymeric binder that imparts a porous internal structure to the coating layer, the polymeric binder comprising one or more water-insoluble polymers having a spherical particle shape.

2. The one or more water insoluble polymers may be selected from the group consisting of polyvinylidene fluoride (PVDF) homopolymer, hexafluoropropylene (HFP or [-CF(CF ３ )-CF ２ -]), chlorotrifluoroethylene (CTFE), and tetrafluoroethylene (TFE) copolymerized with PVDF and / or vinylidene fluoride (VF ２ 2. The separator for a lithium battery according to claim 1, wherein the separator is selected from the group consisting of:

3. The ceramic particles include one or more of a metal oxide, a metal hydroxide, a metal carbonate, a silicate, a kaolin, a talc, a mineral, a glass, and mixtures thereof, and the metal oxide is aluminum oxide (Al ２ O ３ ), titanium oxide (TiO ２ ), silicon oxide (SiO ２ ), zinc oxide (ZnO ２ 10. The separator for a lithium battery of claim 1, comprising one or more of:

4. 2. The separator for a lithium battery according to claim 1, wherein the ceramic particles have an average diameter of 50 to 1,000 nm.

5. 10. The separator for a lithium battery according to claim 1, wherein the coating layer comprises about 50% to about 95% by weight of ceramic particles and about 5% to about 50% by weight of a polymer binder.

6. 10. The separator for a lithium battery according to claim 1, wherein the porous substrate is a single layer, a bilayer, a trilayer, or a multilayer porous membrane.

7. 2. The separator for a lithium battery according to claim 1, wherein the coating layer has a thickness of about 2 to about 10 μm.

8. 10. The separator for a lithium battery according to claim 1, wherein the polymer binder further comprises one or more water soluble polymers.

9. 9. The separator for a lithium battery according to claim 8, wherein the one or more water soluble polymers are selected from the group consisting of polyvinyl alcohol, polylactam, polyacrylic acid, polyvinyl acetate, and polyacrylate.

10. 9. The separator for a lithium battery according to claim 8, wherein the ratio of said water-soluble polymer to said water-insoluble polymer is 1:

10.

11. 10. The separator for a lithium battery according to claim 1, wherein the coating surface comprises one or more water-insoluble polymers having a spherical particle shape.

12. 10. The separator for a lithium battery of claim 1, wherein said ceramic particles have an irregular shape.

13. 2. The separator for a lithium battery according to claim 1, wherein the coating layer is formed on both sides of the porous substrate.

14. 10. The separator for a lithium battery according to claim 1, wherein said ceramic particles are deposited in said polymer binder.

15. A porous substrate; a coating layer formed on at least one surface of the porous substrate; A separator for a lithium battery comprising:

1. A separator for a lithium battery, wherein the coating layer comprises organic particles adhered to a polymeric binder that imparts a porous internal structure to the coating layer, the polymeric binder comprising one or more water-insoluble polymers having a spherical particle shape.

16. The one or more water insoluble polymers may be selected from the group consisting of polyvinylidene fluoride (PVDF) homopolymer, hexafluoropropylene (HFP or [-CF(CF ３ )-CF ２ -]), chlorotrifluoroethylene (CTFE), and tetrafluoroethylene (TFE) copolymerized with PVDF and / or vinylidene fluoride (VF ２ 16. The separator for a lithium battery according to claim 15, wherein the separator is selected from the group consisting of:

17. 16. The separator for a lithium battery according to claim 15, wherein the porous substrate is a single layer, a bilayer, a trilayer, or a multilayer porous membrane.

18. 16. The separator for a lithium battery according to claim 15, wherein the coating layer has a thickness of about 2 to about 10 μm.

19. 16. The separator for a lithium battery according to claim 15, wherein the polymer binder further comprises one or more water soluble polymers.

20. 20. The separator for a lithium battery according to claim 19, wherein the one or more water soluble polymers are selected from the group consisting of polyvinyl alcohol, polylactam, polyacrylic acid, polyvinyl acetate, and polyacrylate.

21. 16. The separator for a lithium battery according to claim 15, wherein the coating layer further comprises ceramic particles.

22. The ceramic particles include one or more of a metal oxide, a metal hydroxide, a metal carbonate, a silicate, a kaolin, a talc, a mineral, a glass, and mixtures thereof, and the metal oxide is aluminum oxide (Al ２ O ３ ), titanium oxide (TiO ２ ), silicon oxide (SiO ２ ), zinc oxide (ZnO ２ 22. The separator for a lithium battery of claim 21 comprising one or more of:

23. A lithium battery comprising the lithium battery separator of claims 1 to 15.

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