Improved coatings, coated separators, batteries, and related methods

Abstract

To provide coating compositions and separators for obtaining secondary lithium ion batteries exhibiting at least improved safety and performance.SOLUTION: A coating composition comprises: a polymeric binder comprising water as a solvent, an aqueous solvent, or a non-aqueous solvent; heat-resistant particles; and at least one component selected from the group consisting of a crosslinker, a low-temperature shutdown agent, an adhesive agent, a thickener, a friction reducing agent, and a high-temperature shutdown agent. Preferably, the polymeric binder comprises at least one selected from the group consisting of a polylactam polymer, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl acetate (PVAc), carboxymethyl cellulose (CMC), an isobutylene polymer, an acrylic resin, and latex.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and benefit of U.S. Provisional Patent Application Serial No. 62 / 365,780, filed July 22, 2016, which is hereby incorporated by reference in its entirety.

[0002] This application relates to porous substrates including battery separators or separator membranes, and / or coated porous substrates including coated battery separators, and / or new and / or improved coatings for batteries or cells including such coatings or coated separators, and / or related methods, including methods of making and / or using same. According to at least certain embodiments, this application relates to new or improved coatings for porous substrates including battery separators, including at least a polymeric binder and heat-resistant particles, with or without additional additives, materials or components, and / or new or improved coated porous substrates including battery separators, wherein the coating includes at least a polymeric binder and heat-resistant particles, with or without additional additives, materials or components. According to at least certain aspects, the present application relates to new or improved coatings for porous substrates, including battery separators, and to new and / or improved coated porous substrates, including battery separators, and more particularly to new or improved coatings for porous substrates, including battery separators, comprising at least (i) a polymeric binder, (ii) heat-resistant particles, and (iii) at least one component selected from the group consisting of a crosslinker, a low-temperature shutdown agent, an adhesive, and a thickener, and / or to new and / or improved coated porous substrates, including battery separators, wherein the coating comprises at least (i) a polymeric binder, (ii) heat-resistant particles, and (iii) at least one component selected from the group consisting of a crosslinker, a low-temperature shutdown agent, an adhesive, a thickener, a friction reducer, and a high-temperature shutdown agent. [Background technology]

[0003] As technological demands increase, so do the demands on separator performance, quality, and manufacturing. Various techniques have been developed to improve the performance characteristics of membranes or porous substrates used as separators in lithium batteries.

[0004] The application of polymer coatings and ceramic-containing polymer coatings is a known method for improving the thermal safety performance of microporous battery separator membranes in lithium batteries. Such coatings can be applied as coatings or layers to one or both sides of a microporous battery separator membrane to promote high-temperature stability, control oxidation at the separator-cathode interface, and improve the safety performance of the microporous battery separator membrane in various battery systems, such as lithium-ion rechargeable (or secondary) battery systems. U.S. Patent No. 6,432,586, incorporated herein by reference in its entirety, discloses various ceramic-coated separators. Furthermore, U.S. Patent Application Publication No. 2014 / 0045033, incorporated herein by reference in its entirety, discloses various ceramic particle-containing polymer coatings for microporous battery separator membranes that can provide improved safety, battery cycle life, and high-temperature performance. Such coatings can include one or more polymer binders, one or more types of inorganic ceramic particles, and an aqueous solvent, a nonaqueous solvent, or water. Such coatings can be applied using a variety of techniques, including, but not limited to, dip coating, knife, gravure, curtain, spray, etc. Additionally, various known ceramic particle-containing polymer coatings can be applied to one or both sides of the microporous battery separator membrane in a variety of thicknesses, for example, 2-6 microns thick.

[0005] As performance standards, safety standards, manufacturing demands, and / or environmental concerns increase, the development of new and / or improved coating compositions for battery separators is desirable.

[0006] One major safety issue with lithium-ion batteries is thermal runaway. For example, abuse conditions such as overcharging, overdischarging, and internal short circuits can lead to battery temperatures much higher than those the battery manufacturers intended their batteries to be used at. In the event of thermal runaway, shutting down the battery, such as by ceasing ion flow across the separator, for example between the anode and cathode, is a safety mechanism used to prevent thermal runaway.

[0007] Another safety issue with lithium-ion batteries is short circuits (hard or soft) that occur when electrodes come into contact with each other. A hard short can occur when the electrodes come into direct contact with each other, or when numerous (perhaps 100) or very large lithium dendrites growing from the anode come into contact with the cathode. The result can be thermal runaway. A soft short can occur when a small or single (or a few, such as 5) lithium dendrite growing from the anode comes into contact with the cathode. A soft short can reduce the cycling efficiency of the battery. Summary of the Invention [Problem to be solved by the invention]

[0008] Separators in lithium-ion batteries need to provide the ability to shut down at least slightly below the temperature at which thermal runaway occurs, while maintaining mechanical properties. A faster shutdown at a lower temperature and for a longer period is highly desirable, for example, so that a user or device has more time to turn off the system. While past ceramic coated separators have been excellent at preventing hard and soft shorts, there is a constant desire to improve this separator's performance. For example, it is desirable to maintain this performance with increasingly thinner coatings. Thus, there is a need for improvements in at least the performance, safety, manufacturing, etc. of past coating compositions and coated battery separators. [Means for solving the problem]

[0009] According to at least selected aspects, the present specification or the present application, disclosure, or invention covered by this specification addresses and / or provides a previous problem, need, or issue, or relates to porous substrates, including battery separators or separator membranes, and / or coated porous substrates, including coated battery separators, and / or new and / or improved coatings for batteries or cells including such coatings or coated separators, and / or related methods, including methods of making and / or using same. According to at least certain aspects, the present specification or the present application, disclosure, or invention covered by this specification relates to new or improved coatings for porous substrates, including battery separators, including at least a polymeric binder and heat-resistant particles, with or without additional additives, materials, or components, and / or new or improved coated porous substrates, including battery separators, wherein the coating includes at least a polymeric binder and heat-resistant particles, with or without additional additives, materials, or components. According to at least certain embodiments, the present application relates to novel or improved coatings for porous substrates, including battery separators, and novel and / or improved coated porous substrates, including battery separators, and more particularly to novel or improved coatings for porous substrates, including battery separators, comprising at least (i) a polymeric binder, (ii) heat-resistant particles, and (iii) at least one selected from the group consisting of a crosslinker, a low-temperature shutdown agent, an adhesive, and a thickener. The present invention relates to a new and / or improved coated porous substrate comprising three components and / or including a battery separator, wherein the coating comprises at least (i) a polymeric binder, (ii) heat-resistant particles, and (iii) at least one component selected from the group consisting of a crosslinker, a low-temperature shutdown agent, an adhesive, a thickener, a friction reducer, and a high-temperature shutdown agent.

[0010] In one aspect, a coating composition is described herein for use on at least one surface of a porous substrate, such as a battery separator. The coating may also be suitable for other purposes, the properties of which, discussed in more detail below with respect to its application to battery separators, make it a suitable coating option. The coating composition includes (i) a polymeric binder, (ii) heat-resistant particles, and (iii) at least one additional component selected from the group consisting of (a) a crosslinking agent, (b) a low-temperature shutdown agent, (c) an adhesive, (d) a thickener, (e) a friction reducer, and (f) a high-temperature shutdown agent. In some embodiments, the binder further includes water as the sole solvent, an aqueous solvent, or a non-aqueous solvent. In some embodiments, the coating composition may also include at least one selected from the group consisting of a surfactant, an antioxidant, a filler, a colorant, a stabilizer, an antifoaming agent, a defoaming agent, a thickener, an emulsifier, a pH buffer, an emulsifier, a surfactant, an anti-settling agent, a leveling agent, a rheology modifier, and a wetting agent.

[0011] In another aspect, a separator for a battery, e.g., a lithium battery, a secondary lithium battery, a lithium-ion battery, a secondary lithium-ion battery, etc., is described, comprising a porous substrate and a coating layer formed on at least one surface thereof. The coating composition comprises a coating composition described herein. In some embodiments, the coating layer is an outermost coating layer, while in other embodiments, a different coating layer is formed over or on the coating layer, in which case the different coating layer may be the outermost layer or another different coating layer formed over or on it. In some embodiments, the coating layer comprising a coating composition described herein is coated on two surfaces of the porous substrate, e.g., two opposing surfaces.

[0012] In further aspects, composites comprising the separators described herein in direct contact with a lithium-ion battery electrode, secondary lithium-ion batteries comprising the separators described herein, and / or devices or vehicles comprising the separators described herein, or secondary lithium-ion batteries comprising the separators described herein are described. The secondary lithium-ion batteries exhibit at least improved safety and performance. [Effects of the Invention]

[0013] In some preferred embodiments, the polymeric binder comprises, consists of, or consists essentially of a polylactam polymer that is a homopolymer, copolymer, block polymer, or block copolymer derived from a lactam. The use of a lactam-derived copolymer or block copolymer can enhance the thermal stability, electrolyte stability, and wettability and CV performance of the resulting coating layer. In another preferred embodiment, the polymeric binder comprises, consists of, or consists essentially of polyvinyl alcohol (PVA). The use of PVA can result in a low-curl coating layer that helps the substrate to which it is applied remain stable and flat, for example, helping to prevent the substrate from curling. The addition of a crosslinker to the coating composition described in this invention results in a coating with lower MD and TD shrinkage and higher thermal stability. The improved safety of the coating compositions described herein is provided by an extended shutdown window, as discussed further herein, so that shutdown begins at a lower temperature. The addition of adhesives to the coating compositions described herein can be used to coat battery electrodes, e.g., lithium This results in a coating that has better adhesion to the battery electrodes. The addition of a friction reducer to the coating compositions described herein can result in a reduced pin removal force and / or a reduced coefficient of friction. From a safety standpoint, coating a battery separator with a coating composition containing the high temperature shutdown agent described herein results in a superior separator. New and / or improved coated porous substrates (or separators) may also improve safety by exhibiting extended shutdown windows. A wider thermal shutdown window can improve battery safety by reducing the possibility of thermal runaway and the potential for fire or explosion. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a structural illustration of a copolymer or block copolymer, where X is a group capable of creating crosslinks between at least two copolymer or block copolymer chains, such as an epoxide or alkylamine-containing group, and one embodiment of the copolymer block copolymer is derived from a lactam. [Figure 2] FIG. 2 is a schematic diagram of an example of a crosslink between at least two copolymer or block copolymer chains produced by a copolymer block copolymer derived from the lactam of FIG. 1, where the polymer chains are PVP chains in which R1, R2, R3, R4, and R5 are hydrogen and Y is 2. [Figure 3] Figure 3 is a schematic diagram of selected coverage rates of heat-resistant particles with polymer binder. For example, when the ratio of heat-resistant particles to polymer binder is low (e.g., as shown on the right side of Figure 3), the coverage rate of the heat-resistant particles with binder is high, and when the ratio of heat-resistant particles to polymer binder is high (e.g., as shown on the left side of Figure 3), the coverage rate of the heat-resistant particles is low. [Figure 4] FIG. 4 is a schematic cross-sectional view of a single-sided coated (OSC) and a double-sided coated (TSC) embodiment of a coated substrate or coated separator of the present invention, respectively. [Figure 5] FIG. 5 is a graph of an example of shutdown performance with resistance on one axis and temperature on the other axis. [Figure 6]Figure 6 shows a schematic diagram of the shutdown window for an uncoated substrate and a single-sided coated substrate, respectively. The coated substrate has an enlarged shutdown window. [Figure 7] FIG. 7 is a schematic diagram of a lithium battery. [Figure 8] FIG. 8 is a graph showing the shutdown performance of the comparative example and the inventive example. [Figure 9] FIG. 9 is a graphical representation of the extended shutdown performance of an inventive example compared to a comparative example. [Figure 10] Figure 10A is a graph of the shutdown performance of an uncoated substrate, Figure 10B is a graph of the shutdown performance of an uncoated substrate, and Figure 10C is a graph of the shutdown performance of a coated PP / PE / PP substrate and a coated PE / PP / PE substrate. [Figure 11] FIG. 11 is a photographic image showing the increased adhesion of a coating layer to an electrode, such as an anode, by adding an adhesive to the coating composition. [Figure 12] Figure 12 is a photographic image showing the results of a hot tip hole propagation study. The hot tip test measures the dimensional stability of the separator under point-heat conditions. The test involves contacting the separator with the tip of a hot soldering iron and measuring the resulting hole. Smaller holes are more desirable. [Figure 13] FIG. 13 is a schematic cross-sectional view of an exemplary ceramic coated separator. DETAILED DESCRIPTION OF THE INVENTION

[0015] Detailed Description composition In one aspect, the coating compositions described herein comprise, consist of, or consist essentially of: (1) a polymeric binder, optionally with water as the only solvent, an aqueous solvent, or a non-aqueous solvent; (2) heat-resistant particles; and (3) at least one additional component selected from the group consisting of: (a) a crosslinker, (b) a low-temperature shutdown agent, (c) an adhesive, (d) a thickener, (e) a friction reducer, and (f) a high-temperature shutdown agent.

[0016] In some embodiments, the coating composition includes at least two of these additional components, e.g., (a) and (d), (b) and (c), (c) and (e), or (d) and (f). In some embodiments, the coating composition includes at least three of these additional components, e.g., (a), (b), and (d), (a), (c), and (d), or (c), (e), and (f). In other embodiments, the coating composition includes one of each of these additional components, e.g., (a), (b), (c), (d), (e), and (f). In some embodiments, the coating composition can include two components (a), e.g., two crosslinkers, and one of component (b). Alternatively, the coating composition can include three components (c), e.g., three adhesives, and one of component (d). In some coating compositions, a single additive component can act, for example, as an adhesive and a low-temperature shutdown agent, and in other embodiments, the adhesive and the low-temperature shutdown agent are different compounds. The coating composition can include any possible combination of additional components (a), (b), (c), (d), (e), and (f).

[0017] (1) Polymer binder The polymeric binder may comprise, consist of, or consist essentially of at least one of a polymeric material, an oligomeric material, or an elastomeric material, but is not limited to such. Any polymeric, oligomeric, or elastomeric material consistent with the present disclosure may be used. The binder may be ionically conductive, semiconductive, or nonconductive. Any gel-forming polymer suggested for use in lithium polymer batteries or solid electrolyte batteries may be used. For example, the polymeric binder may include at least one, two, three, or the like selected from polylactam polymer, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl acetate (PVAc), carboxymethyl cellulose (CMC), isobutylene polymer, acrylic resin, latex, aramid, or any combination of these materials.

[0018] In some preferred embodiments, the polymeric binder comprises, consists of, or consists essentially of a polylactam polymer that is a homopolymer, copolymer, block polymer, or block copolymer derived from a lactam. In some embodiments, the polymeric material comprises a homopolymer, copolymer, block polymer, or block copolymer according to:

[0019] [ka]

[0020] wherein R1, R2, R3, and R4 are alkyl, aromatic substituents, and R5 is alkyl. wherein the preferred polylactam can be a homopolymer or a copolymer, and the copolymer group X can be derived from vinyl, substituted or unsubstituted alkyl vinyl, vinyl alcohol, vinyl acetate, acrylic acid, alkyl acrylate, acrylonitrile, maleic anhydride, maleimide, styrene, polyvinylpyrrolidone (PVP), polyvinyl valerolactam, polyvinyl caprolactam (PVCap), polyamide, or polyimide, wherein m can be an integer from 1 to 10, preferably 2 to 4, and the ratio of l to n is 0≦l:n≦10 or 0≦l:n≦1. In some preferred embodiments, the lactam-derived homopolymer, copolymer, block polymer, or block copolymer is at least one, at least two, or at least three selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinyl caprolactam (PVCap), and polyvinyl valerolactam.

[0021] In a preferred embodiment, the lactam-derived copolymer block copolymer contains a group in its backbone capable of crosslinking at least two copolymer or block copolymer chains. For example, this group can be an epoxide group or an alkylamine. When the group capable of crosslinking at least two copolymer or block copolymer chains is an epoxide, the epoxide undergoes an epoxidation reaction to form the crosslink. In some embodiments, the addition of a catalyst is required. For example, when the group capable of crosslinking at least two copolymer or block copolymer chains is an epoxide, a catalyst containing an alkylamine group can be added, and when the group is an alkylamine, a catalyst containing an epoxide group can be added. The copolymer or block copolymer described in this paragraph can have a structure as shown in Figure (1), where X is a group capable of creating crosslinks between at least two copolymer or block copolymer chains, such as an epoxide- or alkylamine-containing group. One embodiment of the lactam-derived copolymer block copolymer described in this paragraph is shown in Figure 1 below.

[0022] An example of a crosslink between at least two copolymer or block copolymer chains created by the lactam-derived copolymer block copolymer of FIG. 1 is shown in FIG. In Figure 2, the polymer chains are PVP chains, so R1, R2, R3, R4, and R5 in Figure 1 are hydrogen and Y is 2. The use of lactam-derived copolymers or block copolymers containing groups in their backbones that can create crosslinks between at least two copolymer or block copolymer chains can enhance the thermal stability, electrolyte stability, wettability, and CV performance of the resulting coating layer.

[0023] In another preferred embodiment, the polymeric binder comprises, consists of, or essentially consists of polyvinyl alcohol (PVA). The use of PVA can result in a low-curl coating layer that helps the substrate to which it is applied remain stable and flat, for example, helping to prevent the substrate from curling. When particularly low curl is desired, PVA can be added in combination with any other polymer, oligomer, or elastomeric material described herein. In another preferred embodiment, the polymeric binder can comprise, consist of, or consist essentially of an acrylic resin. The type of acrylic resin is not particularly limited, provided that it is not contrary to the objectives described herein, e.g., to provide a battery separator with improved safety. For example, the acrylic resin may be at least one, two, three, or four selected from the group consisting of polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polymethyl acrylate (PMA), which provides new and improved coating compositions that can be used to manufacture the acrylic resin.

[0024] In other preferred embodiments, the polymeric binder can comprise, consist of, or consist essentially of carboxymethyl cellulose (CMC), isobutylene polymer, latex, or any combination thereof, which can be added alone or together with any other suitable oligomeric, polymeric, or elastomeric materials.

[0025] In some embodiments, the polymeric binder may contain only water, an aqueous or water-based solvent, and / or a non-aqueous solvent. When the solvent is water, in some embodiments, no other solvents are present. An aqueous or water-based solvent may contain a majority (more than 50%) of water, more than 60% water, more than 70% water, more than 80% water, more than 90% water, more than 95% water, or more than 99% water, but less than 100% water. In addition to water, the aqueous or water-based solvent may contain a polar or non-polar organic solvent. The non-aqueous solvent is not limited and can be any polar or non-polar organic solvent suitable for the purposes described herein. In some embodiments, the polymeric binder contains only trace amounts of solvent, while in other embodiments, it contains 50% or more, sometimes 60% or more, sometimes 70% or more, sometimes 80% or more, etc. of solvent.

[0026] The ratio of heat-resistant particles to polymeric binder in the coating composition is 50:50 to 99:1 in some embodiments, 70:30 to 99:1 or 90:1 to 98:2 in other embodiments, and 90:10 to 99:1. This ratio affects the coverage of the heat-resistant particles with the polymeric binder. For example, a low ratio of heat-resistant particles to polymeric binder (e.g., as shown on the right side of Figure 3) results in a high coverage of the heat-resistant particles with the binder. A higher ratio of heat-resistant particles to polymeric binder results in a lower coverage of the heat-resistant particles, as shown on the left side of Figure 3.

[0027] In preferred embodiments, at least one of the heat-resistant particles is coated or partially coated with a polymeric binder. For example, in some embodiments, 0.01 to 99.99% of the surface area of at least one heat-resistant particle (or the surface area of all heat-resistant particles) is coated with the binder. In some embodiments, 0.01 to 99.99% of the total surface area of the heat-resistant particles in the composition is coated with the polymeric binder.

[0028] (2) Heat-resistant particles In another aspect, heat-resistant particles are added to the coating compositions described herein. The size, shape, chemical composition, etc. of these heat-resistant particles are not particularly limited. The heat-resistant particles can include organic materials, inorganic materials, such as ceramic materials, or composite materials containing both inorganic and organic materials, two or more organic materials, and / or two or more inorganic materials.

[0029] In some embodiments, heat resistance means that the material comprising the particle, which may include a composite of two or more different materials, does not undergo a substantial physical change, e.g., deformation, at a temperature of 200° C. Exemplary materials include aluminum oxide (Al2O3), silicon dioxide (SiO2), graphite, and the like.

[0030] Non-limiting examples of inorganic materials that can be used to form the refractory particles disclosed herein are: iron oxide, silicon dioxide (SiO), aluminum oxide (AlO), boehmite (Al(O)OH), zirconium dioxide (ZrO), titanium dioxide (TiO), and tantalum oxide (TeO). Tin (TiO2), barium sulfate (BaSO4), barium titanate (BaTiO3), aluminum nitride, silicon nitride, calcium fluoride, barium fluoride, zeolite, apatite, kaolin, mullite, spinel, olivine, mica, tin dioxide (SnO2), indium tin oxide, oxides of transition metals, graphite, carbon, metals, and any combination thereof.

[0031] Non-limiting examples of organic materials that can be used to form the heat-resistant particles disclosed herein are: polyimide resin, melamine resin, phenolic resin, polymethyl methacrylate (PMMA) resin, polystyrene resin, polydivinylbenzene (PDVB) resin, carbon black, graphite, and any combination thereof.

[0032] The refractory particles can be round, irregularly shaped, flakes, etc. The average particle size of the refractory material ranges from 0.01 to 5 microns, 0.03 to 3 microns, 0.01 to 2 microns, etc.

[0033] As mentioned above, in a preferred embodiment, at least one of the heat-resistant particles added to the coating composition described herein is coated or partially coated with a polymeric binder. In other embodiments, the heat-resistant particles may be coated or partially coated with a compatibilizer (in addition to or instead of being coated or partially coated with a polymeric binder), such as a material that makes the particles more compatible with the polymeric binder. In general, the heat-resistant particles may be coated or uncoated in any manner that would not be inconsistent with the objectives described herein.

[0034] Without wishing to be bound by theory, oxidation or reduction reactions may occur during the formation stage of a lithium-ion battery or during charging or discharging of the battery, and these reactions may produce by-products that may be harmful to the battery system. The coating compositions described herein can slow down or prevent oxidation reactions that may occur on uncoated polypropylene (PP) or polyethylene (PE) porous substrates, such as battery separators. Heat-resistant particles, such as particles containing aluminum oxide (Al2O3), are chemically inert and are not susceptible to oxidation by the electrolyte. Improved oxidation stability can be achieved by positioning the coated surface of the separator described herein facing or opposite the cathode or positive electrode.

[0035] (3)Additional ingredients The coating composition includes at least one, or two, or three, etc., of (a) a crosslinking agent, (b) a low-temperature shutdown agent, (c) an adhesive, (d) a thickener, (e) a friction reducer, and (f) a high-temperature shutdown agent.

[0036] (a) Crosslinking agent In another aspect, at least one crosslinking agent can be added to the coating composition.The crosslinking agent is not particularly limited and includes any compound that can form a bond between two or more polymer chains in the coating composition, as long as the compound does not otherwise contradict the purpose described herein.For example, the crosslinking agent can be a compound with multiple reactive groups, such as epoxy groups, acrylate groups, etc.For example, the crosslinking agent can include 2, 3, 4, 5, etc. reactive groups.In some embodiments, a crosslinking agent containing multiple epoxy groups is preferred.

[0037] In a preferred embodiment, the crosslinker can be part of the backbone of a polymeric, oligomeric, or elastomeric material, such as in a polymeric binder. For example, the crosslinker can be an epoxide group of a lactam-derived copolymer or block copolymer, as shown in Figure 1.

[0038] The crosslinker can be added in any amount consistent with the objectives described herein, hi some preferred embodiments, the amount of crosslinker can be added at ppm levels, for example, up to 50,000 ppm, up to 10,000 ppm, up to 5,000 ppm, etc., relative to the total coating composition.

[0039] When adding a cross-linking agent, in some embodiments, a cross-linking agent or catalyst can be added, which can initiate or catalyze, for example, the cross-linking of two polymer chains via the added cross-linking agent. The cross-linking agent can be sensitive to heat, light, or the chemical environment (e.g., pH), for example, the cross-linking agent or cross-linker can be sensitive to the added cross-linking agent or catalyst. They may initiate or catalyze the cross-linking of one or more polymer chains in the coating composition in response to heat, light irradiation, or a change in pH.

[0040] By adding a crosslinking agent to the coating compositions described herein, the inventors have discovered that the resulting coatings and battery separators containing the coatings (on one or both sides thereof) exhibit many beneficial properties. These properties include lower shrinkage in the MD and TD directions, even at higher temperatures, such as 180° C. Adding a crosslinking agent to the coating compositions described herein results in coatings with higher thermal stability.

[0041] Shrinkage is measured by placing a test sample, such as a coated porous substrate, between two sheets of paper, then sandwiching them together to hold the sample between the sheets and hanging it in an oven. For the "150°C, 1 hour" test, the sample is placed in a 150°C oven for 1 hour. After the specified oven heating time, each sample is removed and taped to a flat, opposing surface using double-sided adhesive tape to flatten and smooth it for accurate length and width measurements. Shrinkage is measured in both the machine direction (MD) and the transverse direction (TD) (perpendicular to the MD direction) and is expressed as %MD shrinkage and %TD shrinkage. For the "180°C, 10 minutes" test, the sample is placed in a 180°C oven for 10 minutes and then tested as described above for the "150°C, 1 hour" test. For the "180°C, 20 minutes" test, the sample is placed in a 180°C oven for 20 minutes and then tested as described above for the "150°C, 1 hour" test. Shrinkage can be measured on single-sided coated porous substrates or double-sided coated porous substrates.

[0042] (b) Low-temperature shutdown agent In another aspect, a low-temperature shutdown agent is added to the coating composition described herein.The type of low-temperature agent used is not particularly limited as long as it does not contradict the purpose described herein, such as providing a coating composition that can be used to manufacture safer lithium-ion batteries.In some embodiments, the low-temperature shutdown agent has a melting temperature lower than the melting temperature of the porous film to which the coating composition is applied (or intended to be applied).For example, if the porous film melts at about 135°C, the low-temperature shutdown agent has a melting temperature lower than 135°C.

[0043] In some embodiments, the low temperature shutdown agent has a melting point in the range of 80°C to 130°C, sometimes in the range of 90°C to 120°C, sometimes in the range of 100°C to 120°C, etc. The low temperature shutdown agent can be a particulate having an average particle size ranging from 0.1 to 5.0 microns, 0.2 to 3.0 microns, 0.3 to 1.0 microns, etc. These particles can be coated, uncoated, or partially coated.

[0044] In some preferred embodiments, the low-temperature shutdown agent may be a particle comprising a wax, an oligomer, polyethylene (PE), e.g., low-density PE, or the like. These particles may be coated, uncoated, or partially coated. For example, they may be coated with latex and / or a polymeric binder as disclosed herein. In some embodiments, these coated low-temperature shutdown agents may be coated with a high-temperature shutdown agent, which is described in more detail below.

[0045] The inventors of the present application have found that the low-temperature shutdown agent described herein is particularly It has been discovered that coating a battery separator with a coating composition comprising a low-temperature shutdown agent results in a superior separator. Without wishing to be bound by any particular theory, this improved safety is provided by an extended shutdown window, as discussed further herein, such that shutdown begins at a lower temperature compared to the shutdown window of an uncoated separator or a coated separator in which the coating layer does not include a low-temperature shutdown agent.

[0046] (c) Adhesive In another aspect, an adhesive can be added to the coating composition herein. The compound used as the adhesive is not particularly limited as long as it does not conflict with the objectives described herein. In some embodiments, adding an adhesive to the coating composition described herein results in a coating that has higher adhesion to battery electrodes, such as lithium battery electrodes, compared to a coating formed from a similar coating composition without the adhesive added. The adhesive increases the "stickiness" and / or tack of the coating formed from the coating composition described herein. The adhesion between heat-resistant particles in the coating and the adhesion of the coating layer formed from the coating composition described herein to the porous substrate described herein can also be improved.

[0047] For example, the adhesive strength of the coating to the porous substrate may be greater than 10 N / m, greater than 12 N / m, greater than 14 N / m, greater than 16 N / m, greater than 18 N / m, or greater than 20 N / m. This also applies to embodiments in which the porous substrate has not been pretreated to improve adhesion of the coating layer. Such pretreatments may include corona treatment, plasma treatment, stretching, surfactant treatment / coating, and any other surface treatment and / or coating intended to improve adhesion of the substrate to the coating layer. However, the use of such pretreatments is not required to achieve excellent adhesive strength between the porous substrate and the coating layer, but is not precluded. In some embodiments, the adhesive may be a thermoplastic fluoropolymer such as polyvinylpyrrolidone (PVP) or polyvinylidene difluoride (PVdF).

[0048] The single-time adhesion of the coating layer to the battery electrodes is measured as follows: a coated battery separator as described herein is placed between the electrodes, electrolyte is injected into the space between the electrodes, and the electrode-coated separator composite is heat-pressed at 90°C for 12 hours. Following this, the composite is disassembled, e.g., the separator is separated from the electrodes, and the separator is observed. If a lot of black material, which is the electrode material, is observed on the separator, this indicates higher adhesion between the separator and the electrode. A smaller amount of black material, or electrode material, indicates lower adhesion.

[0049] (d) thickener In another aspect, a thickener can be added to the coating composition described herein.The thickener used is not particularly limited and can be any thickener that does not contradict the purpose described herein.In some embodiments, the thickener is added to adjust the viscosity of the coating composition described herein.An exemplary thickener is, for example, carboxymethylcellulose (CMC).

[0050] (e) Friction reducers In another aspect, a friction reducer can be added to the coating compositions described herein. The friction reducer is not so limited and can be any friction reducer that is not inconsistent with the objectives described herein. For example, in some embodiments, when a film formed from a coating composition containing a friction reducer is compared to a film formed from a coating composition that does not contain a friction reducer, the addition of a friction reducer can result in a decrease in pin removal force and / or wear. This can result in a reduced coefficient of friction. In some embodiments, coatings formed from the coating compositions described herein are "tacky," or adhere well to electrodes when wet, e.g., when wet with electrolyte, and have good pin removal when dry. For example, in some embodiments, films formed from coating compositions containing friction reducers have a pin removal force of 7100 g or less, in some embodiments less than 6500 g, and in some embodiments less than 6000 g. In some embodiments, the coefficient (static) is in the range of 0.2 to 0.8, sometimes 0.3 to 0.7, sometimes 0.4 to 0.6, and sometimes 0.3 to 0.5.

[0051] Pin removal properties are quantified using the following procedure to measure pin removal force (g).

[0052] A battery winding machine is used to wind the separator (comprising, consisting of, or consisting essentially of a porous substrate having a coating layer applied to at least one surface thereof) around a pin (or core or mandrel). The pin is a two-piece cylindrical mandrel with a 0.16 inch diameter and a smooth outer surface. Each piece has a semicircular cross section. The separator, described below, is wound onto the pin. An initial force (tangential) on the separator is 0.5 kgf, after which the separator is wound at a rate of 10 inches per minute in 24 seconds. During winding, a tension roller engages the separator wound on the mandrel. The tension roller comprises a 5 / 8 inch diameter roller located opposite the separator feed, a 3 / 4 inch pneumatic cylinder to which 1 bar of air pressure is applied (when engaged), and a 1 / 4 inch rod interconnecting the roller and cylinder.

[0053] The separator consists of two 30 mm (width) x 10" pieces of membrane to be tested. Five of these separators are tested, the results averaged, and the average value reported. Each piece is spliced to the separator feed roll of the winder with a 1" overlap. Ink marks are made on the free end of the separator, 1 / 2" and 7" from the distal end of the splice. The 1 / 2" mark is aligned with the far side of the pin (i.e., the side adjacent to the tension roller), the separator is engaged between the pieces of the pin, and winding begins with the tension roller engaged. When the 7" mark is approximately 1 / 2" from the jelly roll (separator wrapped around the pin), the separator is cut at that mark, and the free end of the separator is secured to the jelly roll with a piece of adhesive tape (1" wide, 1 / 2" overlap). The jelly roll (i.e., the pin with the separator wrapped around it) is removed from the winder. An acceptable jelly roll is free of wrinkles and stretch. The jelly roll is tested with a load cell (50 lbs x 0.02 lbs; Chatillon DFGS 50) on a tensile strength tester (i.e., Chatillon Model TCD from Chatillon Inc., Greensboro, NC). The strain rate is 2.5 inches per minute, and data from the load cell is recorded at a rate of 100 points per second. The peak force is reported as the pin removal force.

[0054] The static COF (coefficient of friction) is measured according to the method entitled "Method for determining the coefficient of friction of paper and board" in JIS P 8147. In some preferred embodiments, the friction reducer is a fatty acid salt. For example, the friction reducer may be a metal stearate such as Li stearate or Ca stearate. Other possible friction reducers include siloxane, silicone resin, fluororesin, wax (e.g., paraffin wax, microcrystalline wax, low molecular weight polyethylene, other hydrocarbon wax), fatty acid ester (e.g., methyl stearate, stearyl stearate, stearic acid monoglyceride), fatty amide (e.g., stearamide, palmitamide, methylene bisstearamide), and any combination of the aforementioned friction reducers.

[0055] (f) High-temperature shutdown agent According to another aspect, a high-temperature shutdown agent is added to the coating composition described herein.The type of high-temperature agent used is not particularly limited, as long as it is consistent with the objectives described herein, such as providing a coating composition that can be used to manufacture safer lithium-ion batteries.In some embodiments, the high-temperature shutdown agent has a melting temperature higher than the melting temperature of the porous film to which the coating composition is applied (or intended to be applied).For example, if the porous film melts at about 135°C, the high-temperature shutdown agent has a melting temperature higher than 135°C.

[0056] In some embodiments, the high temperature shutdown agent has a melting point in the range of 140°C to 220°C, sometimes in the range of 150°C to 200°C, sometimes in the range of 160°C to 190°C, sometimes in the range of 170°C to 180°C, etc.

[0057] The high temperature shutdown agent can be a particulate having an average particle size ranging from 0.1 to 5.0 microns, 0.2 to 3.0 microns, 0.3 to 1.0 microns, etc. These particles can be coated, uncoated, or partially coated.

[0058] In some preferred embodiments, the high-temperature shutdown agent may be particles comprising polyvinylpyrrolidone (PVP) or polyvinylidene difluoride (PVdF). These particles may be coated, uncoated, or partially coated. For example, they may be coated with latex and / or polymeric binders as disclosed herein. In some embodiments, these coated particles are coated with a low-temperature shutdown agent as described above.

[0059] The present inventors have discovered that coating a battery separator with a coating composition containing the high-temperature shutdown agent described herein results in a superior separator, particularly from a safety standpoint. While not wishing to be bound by any particular theory, it is believed that this improved safety results from extending the shutdown window, discussed further herein, to higher temperatures compared to an uncoated separator or a coated separator in which the coating layer does not contain the high-temperature shutdown agent.

[0060] (4) Optional additives In another aspect, one or more of the following additional components are optionally added: surfactants, antioxidants, fillers, colorants, stabilizers, antifoaming agents, defoamers, thickeners, emulsifiers, pH buffers, emulsifiers, surfactants, anti-settling agents, leveling agents, rheology modifiers, and wetting agents. Two or more, three or more, four or more, etc. of these optional additional components can also be added to the coating compositions described herein.

[0061] Separator In another aspect, described herein is a separator comprising, consisting of, or consisting essentially of a porous substrate and a coating layer formed on at least one side of the porous substrate. Single-sided and double-sided coated separators according to some embodiments herein are shown in FIG.

[0062] The coating layer may comprise, consist of, consist essentially of, and / or be formed from any one of the above coating compositions. The coating layer may be wet, dry, crosslinked, non-crosslinked, etc. The coating may be applied over a PVD layer, or the PVD layer may be applied over the coating. The coating may be applied over an adhesive layer, or the adhesive layer may be applied over the coating.

[0063] The new and / or improved separators described herein have the following features or improvements: The coated separator may have or exhibit one or more of the following characteristics: (1) a desired level of porosity as observed and measured by SEM; (2) a desired Gurley number to indicate permeability; (3) a desired thickness; (4) a desired level of incorporation of the polymeric binder such that the coating is improved compared to known coatings; (5) desired properties resulting from the processing of the coated separator, including, but not limited to, how the coating is mixed, how the coating is applied to the substrate, and how the coating dries on the substrate; (6) improved thermal stability, as indicated, for example, by desirable behavior in hot tip hole propagation studies; (7) reduced shrinkage when used in lithium batteries, such as lithium ion batteries; (8) improved adhesion between the refractory particles in the coating; (9) improved adhesion between the coating and the substrate; (10) improved adhesion between the coated separator and one or both electrodes of the battery, and / or (11) improved pin removal force and / or coefficient of friction. These and other related attributes of the improved coated separator are described in more detail elsewhere in this application.

[0064] The new and / or improved coated separators can have superior quality and uniformity, thus providing good manufacturing yields. The new and / or improved coated separators can provide batteries with improved capacity and improved cycling performance. They can have fewer defects, such as fewer gel defects and / or fewer crater defects, than other known coated separators. The improved and / or coated separators can have improved coating adhesion to porous substrates. The adhesion strength can be greater than 10 N / m, greater than 12 N / m, greater than 14 N / m, greater than 16 N / m, greater than 18 N / m, or greater than 20 N / m.

[0065] The new and / or improved coated porous substrates (or separators) may also provide improved safety by exhibiting an extended shutdown window, particularly compared to the shutdown window of the porous substrate itself (e.g., an uncoated porous substrate or separator). The extended shutdown window of the new and / or improved separators disclosed herein extends to between about 80°C and about 200°C, compared to a window of about 130°C to 175°C for the substrate itself. The extended shutdown window of the new and / or improved substrates is also stable, e.g., a constant or relatively constant resistance is measured across the separator throughout the window. For example, in some embodiments, the resistance measured across the separator is greater than 10,000 ohms / cm across the window. 2 It remains super.

[0066] This is considered stable. At times, the measured resistance across the separator is less than 100,000 ohms / cm over the extended shutdown window of the new and / or improved separators disclosed herein. 2The new and / or improved separators disclosed herein also exhibit rapid incipient shutdown. Sometimes, during incipient shutdown, the resistance measured across the separator reaches 10 Ω / cm as the temperature increases by 1-5°C. 2 Less than 10,000 Ω / cm 2 For example, the resistance increases to over 5 ohms / cm at 120°C. 2 to 10,000 ohms / cm at 125°C 2 A temperature increase of only 4, 3, 2, or 1 degree may be required for this increase in resistance to occur.

[0067] Preferred thermal shutdown characteristics include a lower onset or initiation temperature, a faster or more rapid shutdown rate, and a sustained, consistent, longer, or extended thermal shutdown window. In a preferred embodiment, the shutdown rate is at least 2000 ohms (Ω)·cm² / sec or 2000 ohms (Ω)·cm² / degree, and the resistance across the separator increases by at least two orders of magnitude during shutdown. An example of shutdown performance is shown in Figure 5.

[0068] A shutdown window, as described herein, generally refers to a time / temperature window extending from the initiation or onset of shutdown, e.g., at which the separator begins to melt sufficiently to close its pores, e.g., resulting in a cessation or slowing of ionic flow between the anode and cathode, and / or an increase in resistance across the separator, to the time / temperature at which the separator begins to decompose, e.g., decomposes, resuming ionic flow and / or decreasing resistance across the separator. An example of an extended shutdown window as described herein is shown in Figure 6.

[0069] Figure 6 shows that the shutdown window of a coated porous substrate according to embodiments described herein is broadened compared to the shutdown window of the porous substrate itself, for example, before coating with one of the coating compositions described herein. Shutdown initiation or onset occurs at about 135°C for the uncoated porous substrate and occurs sooner after coating. Without wishing to be bound by any particular theory, this may result from the addition of a low-temperature shutdown agent described herein to the coating compositions and / or coatings described herein. The low-temperature shutdown agent may melt before the porous substrate, filling or partially filling its pores and causing premature (low-temperature) shutdown initiation.

[0070] Figure 6 also shows that the shutdown period is extended from 170°C in the uncoated porous substrate to approximately 190°C after coating. Without wishing to be bound by any particular theory, this may result from the addition of the high-temperature shutdown agent described herein to the coatings and coating compositions described herein. The high-temperature shutdown agent may degrade at a higher temperature than the porous substrate itself. In some embodiments described herein, only the shutdown onset temperature is lowered (widening the window), in other embodiments, only the high-temperature endpoint of the shutdown window is raised (widening the window), and in some embodiments, the upper and lower shutdown windows are extended, for example, as shown in Figure 6.

[0071] Shutdown can be measured using an electrical resistance test, which measures the electrical resistance of the separator membrane as a function of temperature. Electrical resistance (ER) is defined as the resistance (Ω·cm2) of the separator filled with electrolyte. The temperature during the electrical resistance (ER) test is increased at a rate of 1 to 10°C per minute. When thermal shutdown occurs in a battery separator membrane, the ER is approximately 1,000 to 10,000 ohm·cm. 2Higher levels of resistance are reached, on the order of 1000 Ω. The combination of a lower thermal shutdown onset temperature and a longer shutdown temperature duration increases the sustained shutdown window. A wider thermal shutdown window can improve battery safety by reducing the possibility of thermal runaway and the potential for fire or explosion.

[0072] One exemplary method for measuring separator shutdown performance is as follows: 1) Place a few drops of electrolyte on the separator to saturate it, and then place the separator into the test cell. 2) Ensure the heating press is below 50°C. If so, place the test cell between the platens and compress the platens slightly so that only light pressure is applied to the test cell (<50 lbs for Carver "C" compression). 3) Connect the test cell to the RLC bridge and begin recording the temperature and resistance. Once a stable baseline is achieved, begin increasing the temperature of the heating press at 10°C / min using the temperature controller. 4) Turn off the heating platens when the maximum temperature is reached or when the separator impedance drops to a low value. 5) Open the platens and remove the test cell. Allow the test cell to cool. Remove and discard the separator.

[0073] (1) Porous base material The porous substrate used in the separators described herein is not particularly limited and can be any porous substrate consistent with the objectives described herein. For example, the porous substrate can be any porous substrate that can be used as a battery separator. The porous substrate can be a macroporous substrate, a mesoporous substrate, a microporous (microporous) substrate, or a nanoporous substrate. In some preferred embodiments, the porosity of the porous substrate is 20 to 90%, 40 to 80%, 50 to 70%, etc. Porosity is measured using ASTM D-2873 and is defined as the percentage of voids, e.g., pores, within the area of the porous substrate, measured in the machine direction (MD) and transverse direction (TD) of the substrate. In some embodiments, the porous substrate has a JIS Gurley of 0.5 to 1000 seconds, in some embodiments a JIS Gurley of 100 to 800 seconds, in other embodiments a JIS Gurley of 200 to 700 seconds, and in other embodiments a JIS Gurley of 300 to 600 seconds. Gurley, as used herein, is defined as the Japanese Industrial Standard (JIS) Gurley. and is measured using an OHKEN permeability tester in this specification. Gurley is defined as the time (in seconds) required for 100 cc of air to pass through 1 square inch of film at a constant pressure of 4.9 inches of water. In some embodiments, the pores are circular, e.g., with a sphericity coefficient of 0.25 to 8.0, oval, or elliptical.

[0074] The material of the porous substrate is not particularly limited. The polymer used in the porous substrate can be characterized as a thermoplastic polymer. These polymers can be further characterized as semi-crystalline polymers. In one embodiment, the semi-crystalline polymer can be a polymer having a crystallinity ranging from 20 to 80%. Such polymers can be selected from the following group: polyolefins, fluorocarbons, polyamides, polyesters, polyacetals (or polyoxymethylenes), polysulfides, polyvinyl alcohols, copolymers thereof, and combinations thereof.

[0075] Polyolefins may include polyethylene (LDPE, LLDPE, HDPE, UHMWPE), polypropylene, polybutene, polymethylpentene, copolymers thereof, and blends thereof. Fluorocarbons may include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), ethylene chlorotrifluoroethylene (ECTFE), ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy (PFA) resins, copolymers thereof, and blends thereof. Polyamides may include, but are not limited to, polyamide 6, polyamide 6 / 6, nylon 10 / 10, polyphthalamide (PPA), copolymers thereof, and blends thereof. Polyesters include polyester terephthalate (PET), polybutylene terephthalate (PBT), poly-1-4-cyclohexylene dimethylene terephthalate (PCT), polyethylene naphthalate (PEN), and liquid crystal polymers (LCP). Polysulfides include, but are not limited to, polyphenyl sulfide, polyethylene sulfide, copolymers thereof, and blends thereof. Polyvinyl alcohols include, but are not limited to, ethylene vinyl alcohol, copolymers thereof, and blends thereof. In some embodiments, the porous substrate comprises at least one selected from the group consisting of polyolefins (PO), such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyethylene terephthalate (PET), aramid, polyvinylidene fluoride, polymer blends, polymers, copolymers, and polymer composites (with inorganic fillers such as Al2O3, SiO2, etc.) including block polymers thereof, and blends, mixtures, or combinations thereof.

[0076] The porous substrate may contain other components. For example, these components may be fillers (used to reduce the cost of the porous substrate but which otherwise may affect the manufacturing of the porous substrate or its physical properties). The composition may contain additives such as inert particles that do not significantly affect the mechanical properties, antistatic agents, antiblocking agents, antioxidants, lubricants (to facilitate manufacturing), and the like.

[0077] Various materials can be added to polymers to modify or enhance the properties of porous substrates. Such materials include, but are not limited to: (1) polyolefins or polyolefin oligomers with a melting temperature below 130°C; (2) mineral fillers, including, but not limited to, calcium carbonate, zinc oxide, diatomaceous earth, talc, kaolin, synthetic silica, mica, clay, boron nitride, silicon dioxide, titanium dioxide, barium sulfate, aluminum hydroxide, magnesium hydroxide, and mixtures thereof; (3) elastomers, including, but not limited to, ethylene-propylene copolymers (EPR), ethylene-propylene-diene copolymers (EPDM), styrene-butadiene copolymers (SBR), styrene-isoprene copolymers (SIR), ethylidene norbornene copolymers (ENB), epoxies, and polyurethanes and blends thereof; and (4) wetting agents, including, but not limited to, ethoxylated alcohols, primary polymeric carboxylic acids, glycols (e.g., polypropylene glycol and polyethylene glycol), functionalized polyolefins, and the like. (5) Lubricants, such as silicones, fluoropolymers, oleamide, stearamide, erucamide, calcium stearate, or other metal stearates. (6) Flame retardants, such as brominated flame retardants, ammonium phosphate, ammonium hydroxide, alumina trihydrate, and phosphate esters. (7) Crosslinking or coupling agents. (8) Polymer processing aids. (9) Nucleating agents of any kind, including beta-nucleating agents for polypropylene. Beta-nucleating polypropylene is disclosed in U.S. Patent No. 6,602,593. A beta-nucleating agent for polypropylene is a substance that produces beta crystals in polypropylene.

[0078] In some embodiments, the porous substrate is a single layer containing one or more plies, a two-layer structure in which each layer can contain one or more plies, or a multilayer structure in which each layer can contain one or more plies. When the porous substrate is a multilayer porous substrate, it can contain 3 to 10 layers, 4 to 9 layers, 5 to 8 layers, or 6 to 7 layers. In some multilayer embodiments, the porous substrate contains, in that order, a polypropylene (PP) layer containing a majority (greater than 50% of the polymer component) of PP, a polyethylene (PE) layer containing a majority of PE, and another PP layer containing a majority of PP. In other embodiments, the multilayer porous substrate contains, in that order, a PE layer containing a majority of PE, a PP layer containing a majority of PP, and another PE layer containing a majority of PE. The layer containing a majority of PP or PE can contain PP or PE, respectively, in an amount greater than 50% and up to 100% of the polymer component.

[0079] The porous substrate can be manufactured by any one of wet-formation, dry-formation, particle-stretching, and beta-nucleated biaxially oriented (BN-BOPP) manufacturing methods. The porous substrate can be manufactured, for example, by the dry-stretching process (known as the Celgard® dry-stretching process) of Celgard LLC, Charlotte, North Carolina. The porous substrate can be any polyolefin microporous separator membrane available from Celgard LLC, Charlotte, North Carolina. Alternatively, in other embodiments, the porous substrate can be manufactured by a wet-formation process, sometimes known as a phase separation or extraction process, which may involve the use of solvents and / or oils from Celgard Korea Co., Ltd., Korea, Asahi Kasei Co., Ltd., Japan, and / or Tonen Co., Ltd., Japan. Alternatively, in other embodiments, the porous substrate can be a nonwoven membrane.

[0080] A preferred porous substrate can be fabricated by dry stretching and has pores less than 2 μm in size. Microporous substrates are, for example, thin, flexible polymer sheets, foils, or films with multiple pores extending therethrough. Such porous substrates are useful for, but not limited to, mass transfer membranes, pressure regulators, filtration membranes, medical devices, and electrochemical storage devices. The porous substrates herein may be used in a wide variety of applications, including separators for semiconductors, membranes for use in fuel cells, and the like. The porous substrates herein are perhaps preferably manufactured by the dry stretching method (also known as the CELGARD method). The dry stretching method refers to a method in which pore formation results from the stretching of a non-porous precursor. Kesting, R., Synthetic Polymeric See Membranes, A structural perspective, Second Edition, John Wiley & Sons, New York, NY, (1985), pages 290-297. Dry stretching is distinguished from wet and particle stretching, as discussed above.

[0081] In one embodiment, the porous substrate can be a dry-stretched porous substrate that 1) has substantially slit, trapezoidal, or circular pores, and 2) has a ratio of longitudinal tensile strength to transverse tensile strength in the range of 0.1 to 20, preferably 0.5 to 10. See Figures 1 to 5 for pore shapes. The round pores in Figures 1 to 3 are different from the slit-shaped pores in Figures 4 to 5 and Kesting, ibid. The pore shapes of the porous substrate can be further characterized by the aspect ratio, i.e., the ratio of the length to the width of the pores. In one embodiment of the porous substrate of the present invention, the aspect ratio of the circular pores ranges from 0.75 to 1.25. This is in contrast to the aspect ratio of the dry-stretched membrane with slit-like pores, which is greater than 5.0. Regarding the ratio of the longitudinal tensile strength to the transverse tensile strength, in one embodiment of the circular pores, this ratio is 0.5 to 5.0. This ratio differs from the corresponding ratio of the slit-pore membrane, which is greater than 10.0.

[0082] Machine direction (MD) and transverse direction (TD) tensile strength was measured according to ASTM-882 procedure. and measured using an Instron Model 4201. The porous substrate may be further characterized as follows: an average pore size in the range of 0.03 to 0.30 microns (μm); a porosity in the range of 20 to 80%; and / or a transverse tensile strength greater than 50, preferably 100, and more preferably 250 Kg / cm. 2 The foregoing values are exemplary and are not intended to be limiting, and therefore should be considered merely representative of the present porous substrate. Pore size is measured using an Aquapore available from Porous Materials, Inc. (PMI). Pore size is expressed in μm.

[0083] The porous substrates of the present invention are preferably produced by a dry stretching process in which the precursor is stretched in the MD, TD, or biaxially (i.e., stretched in both the MD and TD directions), a process which is described in more detail below.

[0084] Generally, the method for producing the porous substrate described above includes extruding a non-porous precursor and then stretching the non-porous precursor in the MD, TD, or biaxial direction. Optionally, the non-porous precursor may be annealed before stretching. In one embodiment, the biaxial stretching includes longitudinal stretching and transverse stretching, with simultaneous controlled longitudinal relaxation. The longitudinal stretching and transverse stretching can be simultaneous or sequential. In one embodiment, longitudinal stretching is followed by transverse stretching, with simultaneous longitudinal relaxation. This sequential process will be described in more detail below.

[0085] Extrusion is generally conventional (conventional means conventional with respect to the dry stretching method). The extruder can have a slot die (for flat precursors) or an annular die (for parison precursors). In the latter case, inflation parison technology (e.g., blow-up ratio (BUR)) can be used. However, the birefringence of the non-porous precursor does not need to be as high as in the case of conventional dry stretching methods. For example, in a conventional dry stretching method for producing a porous substrate having a porosity of >35% from a polypropylene resin, the birefringence of the precursor is >0.0130, but in the method of the present invention, the birefringence of the PP precursor can be as low as about 0.0100. In another example, for a porous substrate having a porosity of >35% from a polyethylene resin, the birefringence of the precursor can be >0.0280, but in the method of the present invention, the birefringence of the PE precursor can be as low as about 0.0240.

[0086] In one aspect, annealing (optional) can be carried out at a temperature between Tm - 80°C and Tm - 10°C (Tm is the melting temperature of the polymer). In other aspects, it is a temperature between Tm - 50°C and Tm - 15°C. Some materials such as polybutene, for example materials having a high crystallinity after extrusion, may not require annealing.

[0087] The longitudinal stretching can be carried out as low-temperature stretching or high-temperature stretching or both, and as a single step or multiple steps. In one aspect, the cold stretching can be carried out at <Tm - 50°C, and in another aspect, at <Tm - 80°C. In one aspect, the hot stretching can be carried out at <Tm - 10°C. In one aspect, the total machine direction stretching can be in the range of 50 - 500%, and in another aspect, in the range of 100 - 300%. During the longitudinal stretching, the precursor may contract laterally (conventionally). The transverse stretching following the MD stretching preferably includes simultaneous controlled longitudinal relaxation. This means that the precursor contracts (i.e., relaxes) in a controlled manner longitudinally while being stretched laterally.

[0088] Transverse stretching can be performed as a low-temperature step, a high-temperature step, or a combination of both. In one embodiment, the total transverse stretching can be in the range of 100 to 1200%, and in another embodiment, in the range of 200 to 900%. In one embodiment, the controlled longitudinal relaxation can be in the range of 5 to 80%, and in another embodiment, in the range of 15 to 65%. In one embodiment, transverse stretching can be performed in multiple stages. During transverse stretching, the precursor may or may not shrink in the longitudinal direction. In one embodiment of multi-stage transverse stretching, the first transverse step can include transverse stretching with controlled longitudinal relaxation, followed by simultaneous transverse and longitudinal stretching, followed by transverse relaxation and no longitudinal stretching or relaxation. Optionally, the precursor after longitudinal and transverse stretching can be subjected to heat setting, additional MD or TD stretching, etc.

[0089] In some embodiments, the ratio of machine direction (MD) tensile strength to transverse direction (TD) tensile strength is 0.5 to 10.0, in some embodiments 0.5 to 7.5, and in some embodiments 0.5 to 5.0. MD and TD tensile strengths are measured using an Instron Model 4201 according to ASTM-882 procedures.

[0090] In some embodiments, the porous film has a puncture strength of 400 g / mil or greater. Puncture strength is measured using an Instron Model 4442 based on ASTM D3763. Measurements are taken across the width of the microporous membrane (e.g., porous substrate or film), and puncture strength is defined as the force required to puncture the test sample.

[0091] (2) Coating layer In one aspect, the coating layer may be the outermost coating layer of the separator, e.g., it may have no other different coating layers formed thereon, or it may have at least one other different coating layer formed thereon. For example, in some embodiments, a different polymer coating layer may be coated over or on top of the coating layer formed on at least one surface of the porous substrate. In some embodiments, the different polymer coating layer may comprise, consist of, or consist essentially of at least one of polyvinylidene fluoride (PVdF) or polycarbonate (PC).

[0092] In some embodiments, the coating layer is applied over one or more other coating layers already applied to at least one surface of the porous substrate. For example, in some embodiments, the layers already applied to the porous substrate are thin, very thin, or ultrathin layers of at least one of an inorganic material, an organic material, a conductive material, a semiconductive material, a nonconductive material, a reactive material, or a mixture thereof. In some embodiments, the layers are It is a metal or metal oxide-containing layer. In some preferred embodiments, the metal-containing layer and metal oxide-containing layer, for example, the metal oxide of the metal used in the metal-containing layer, are formed on the porous substrate before the coating layer containing the coating composition described herein is formed. Sometimes, the total thickness of the one or more layers already applied is less than 5 microns, sometimes less than 4 microns, sometimes less than 3 microns, sometimes less than 2 microns, sometimes less than 1 micron, sometimes less than 0.5 microns, sometimes less than 0.1 microns, and sometimes less than 0.05 microns.

[0093] In some embodiments, the thickness of the coating layer formed from the above coating composition is less than about 12 μm, sometimes less than 10 μm, sometimes less than 9 μm, sometimes less than 8 μm, sometimes less than 7 μm, and sometimes less than 5 μm. In at least certain selected embodiments, the coating layer is less than 4 μm, less than 2 μm, or less than 1 μm.

[0094] The coating method is not particularly limited, and the coating layer described herein can be coated onto the porous substrate by at least one of the following, for example, as described herein: extrusion coating, roll coating, gravure coating, printing, knife coating, air knife coating, spray coating, dip coating, or curtain coating. The coating process can be carried out at room temperature or at an elevated temperature.

[0095] The coating layer may be non-porous, nanoporous, microporous, mesoporous, or macroporous. The coating layer may have a JIS Gurley of 10,000 or less, 1,000 or less, 700 or less, sometimes 600 or less, 500 or less, 400 or less, 300 or less, 200 or less, or 100 or less. For non-porous coating layers, the JIS Gurley is The rley can be 800 or more, 1,000 or more, 5,000 or more, or 10,000 or more (i.e., "infinite Gurley"). In the case of nonporous coating layers, the coating is nonporous when dry, but is an excellent ionic conductor, especially when wetted with electrolyte.

[0096] Complex, vehicle or device The composite includes any of the separators described above and one or more electrodes, such as an anode, a cathode, or an anode and a cathode, disposed in direct contact therewith. The type of electrode is not particularly limited. For example, the electrode may be one suitable for use in a lithium-ion secondary battery. A lithium-ion battery according to some embodiments herein is shown in FIG.

[0097] Suitable anodes can have an energy capacity of 372 mAh / g or greater, preferably 700 mAh / g or greater, and most preferably 1000 mAh / g or greater. The anodes are composed of lithium metal foil or lithium alloy foil (e.g., lithium aluminum alloy), or mixtures of lithium metal and / or lithium alloy with materials such as carbon (e.g., coke, graphite), nickel, copper, and the like. The anodes are not made exclusively from lithium-containing intercalation compounds or lithium-containing insertion compounds.

[0098] A suitable cathode may be any cathode compatible with the anode and may include an intercalation compound, an insertion compound, or an electrochemically active polymer. Suitable interlayer materials are, for example, MoS2, FeS2, MnO2, TiS2, NbSe3, LiCoO2, LiNiO2, LiMn2O4, VO 13 , V2O5, and CuCl2. Suitable polymers include, for example, polyacetylene, polypyrrole, polyaniline, and polythiophene.

[0099] Any of the above separators may be used in any vehicle that is fully or partially battery powered, e.g. It can be incorporated into electric vehicles or devices, such as cell phones or laptops. Various aspects of the present invention have been described to accomplish various objectives of the present invention. It should be recognized that these aspects 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. [Example]

[0100] (1) At least the following coating compositions are envisioned:

[0101] Table 1 [Table 1]

[0102] [Table 2]

[0103] [Table 3]

[0104] CJ: Heat-resistant particles, polymers comprising a polymer derived from lactam, optionally together with water, aqueous solvent, or non-aqueous solvent as solvent. CM: heat-resistant particles and PVA binder, optionally water, aqueous solvent, or non-aqueous solvent as a solvent. CS: Heat-resistant particles containing an acrylic binder, optionally containing water, an aqueous solvent, or a non-aqueous solvent as a solvent. a: any crosslinker described herein b: any cold shutdown agent described herein c: any adhesive described herein d: any thickening agent described herein e: any friction reducer described herein f: any high temperature shutdown agent described herein

[0105] (1) Exemplary Improved Shutdown Mode As discussed above, the addition of a low-temperature shutdown agent and / or a high-temperature shutdown agent can extend the shutdown window of a coated separator compared to its uncoated counterpart or a coated counterpart whose coating does not include a low-temperature shutdown agent and / or a high-temperature shutdown agent.

[0106] (a) In one exemplary embodiment, a coated battery separator (invention example) according to some embodiments described herein was prepared. The coating composition contained polyethylene beads as a CJ and a low-temperature shutdown agent (b) and was coated onto a three-layer porous substrate comprising a polypropylene (PP) layer, a polyethylene (PE) layer, and a polypropylene (PP) layer. The shutdown characteristics of this coated battery separator were evaluated according to the electrical resistance test described herein and compared with those of the three-layer porous substrate itself (i.e., an uncoated comparative example). The results are shown in Figure 8. Figure 8 shows that the shutdown window of the comparative example is approximately 125°C to approximately 175°C. When the coating is applied, the lower end of the shutdown window shifts from approximately 125°C to approximately 95°C, i.e., a shift of approximately 30°C. The upper shutdown window limits of the inventive example and the comparative example are approximately the same. Therefore, overall, the shutdown window of the inventive example is extended by approximately 30°C, resulting in a safer battery separator.

[0107] (b) In another exemplary embodiment, a coated separator (embodiment of the present invention) is prepared, the coating of which comprises CJ and PVDF as a high-temperature shutdown agent (f). The porous substrate in this example is the same as that described in Example 2(a) above. The shutdown window of this coated separator (an example of the present invention) was evaluated according to the electrical resistance test described herein and compared to an uncoated three-layer porous substrate or separator (comparative example). The results are shown in Figure 9. In this embodiment, the shutdown window of the example of the present invention is reduced by approximately 5°C, and the upper limit of the shutdown window is extended to >180°C, e.g., a resistance of >10,000 Ω·cm2 is obtained at temperatures >180°C, resulting in a very safe battery.

[0108] (c) In another exemplary embodiment, two coated separators were prepared by coating one side of a multi-layer (three-layer) porous substrate containing PP-PE-PP and PE-PP-PE with a coating containing CJ and polyvinylpyrrolidone (PVP), e.g., a high-temperature shutdown agent. The coating was 3 microns thick. These are examples of the present invention. The shutdown windows of these coated separators (examples of the present invention shown in Figure 10B) were evaluated according to the electrical resistance test described herein and compared with uncoated multi-layer (three-layer) porous substrates containing PP-PE-PP and PE-PP-PE, respectively (comparison examples shown in Figures 10A and 10C). Extended shutdown characteristics above 190°C were observed for both the single-side-coated PP-PE-PP porous substrate and the single-side-coated PE-PP-PE substrate.

[0109] (3) Illustrative improved shrinkage behavior (a) The addition of at least a thickener and / or a crosslinker to the coating compositions described herein reduces the shrinkage of separators containing coating layers made from these coating compositions, including at high temperatures. In Table 2 below, coating compositions containing only CS, CS and d (thickener), and CS, d, and a (crosslinker) were prepared. In these compositions, the CS and thickener are the same. CS and thickener

[0110] Shrinkage is measured in both the machine direction (MD) and the transverse direction (TD) and is expressed as %MD shrinkage and %TD shrinkage. For the "180°C, 10 minutes" test, the sample is placed in an oven at 180°C for 10 minutes, then tested as described above for the "150°C, 1 hour" test. For the "180°C, 20 minutes" test, the sample is placed in an oven at 180°C for 20 minutes, then tested as described above for the "150°C, 1 hour" test. Shrinkage can be measured for single-side coated porous substrates or double-side coated porous substrates.

[0111] Thickness is measured in micrometers (μm) using an Emveco Microgage 210-A micrometer thickness tester and test procedure ASTM D374.

[0112] Table 2 [Table 4]

[0113] (4) Adhesion of the exemplary improved coating layer to the electrode As mentioned above, the addition of an adhesive to the coating compositions described herein increases the adhesion of the coating layer to an electrode, eg, an anode. (a) An example of the present invention was prepared identical to that prepared in Section 2(b) above. The adhesion of the coating layer of this example to the anode was evaluated as described herein. The results are shown in Figure 11. Figure 11 shows that much of the electrode material, i.e., from the anode, was transferred to the separator, indicating good adhesion between the coating layer and the anode.

[0114] (5) Exemplary Embodiments of Improved Coating Layer Adhesion to Porous Substrates As mentioned above, the addition of an adhesive to the coating compositions described herein increases the adhesion of the coating layer to the porous substrate without pre-treating the porous substrate.

[0115] (6) Improved Pin Removal Force Example Embodiments As noted above, for example, the addition of a friction reducer to the coating compositions described herein can improve the pin removal force of the coating layer (and separators including such coating layers). The invention examples from Section 2(c) above (invention examples, i.e., one-side coated PP-PE-PP porous substrate and one-side coated PE-PP-PE porous substrate) were compared to an uncoated PP-PE-PP porous substrate (control). The pin removal test described herein was performed three times, collecting three data points, and the data are reported in Table 3 below.

[0116] Table 3 [Table 5]

[0117] (7) Exemplary Embodiments of the Improved Hot Tip Test As noted above, the separators disclosed herein have improved thermal stability, as demonstrated by desirable behavior in, for example, hot tip hole propagation studies. The hot tip test measures the dimensional stability of the separator under point-heating conditions. The test involves contacting the separator with the tip of a hot soldering iron and measuring the resulting hole. Smaller holes are more desirable.

[0118] (a) Hot tip testing was performed on the embodiments from Section 2(c) above. The results are reported in Table 4 below and Figure 12. The single-sided coated PE-PP-PE and PP-PE-PP substrates (Invention Examples) were found to perform better (smaller pores) than the uncoated control (Control), which was an uncoated PP-PE-PP porous substrate.

[0119] Table 4 [Table 6]

[0120] The selected aluminum oxide coating on the separator can be produced by the physical vapor deposition (PVD) process. The main advantages of the PVD process over other conventional coating techniques are: Roll-to-roll manufacturing; capable of producing hundreds of meters per minute Homogeneous, uniform coating with complete coverage · Low defect or binderless coating Thickness can be adjusted from a few nanometers to microns

[0121] Referring to Figure 13, an example of a separator 20 of the present invention is shown. Separator 20 includes a ceramic composite layer or coating 22 and a polymer microporous layer 24. The ceramic composite layer is adapted to at least prevent shrinkage, oxidation, electronic shorting (e.g., direct or physical contact between the anode and cathode), and / or inhibit dendritic growth. The polymer microporous layer may be, and preferably is, adapted to at least prevent direct or physical contact between the anode and cathode under normal conditions, and / or support desired battery performance, and / or block ionic conductivity (or flow) between the anode and cathode at elevated temperatures, preventing or terminating thermal runaway.

[0122] Under typical operating conditions, the ceramic composite layer 22 of the separator 20 must be sufficiently conductive to allow ionic flow between the anode and cathode so that the desired amount of current can be generated by the cell. Layers 22 and 24 should adhere well to one another, i.e., not unintentionally separate. Layers 22 and 24 can be formed by lamination, coextrusion, PVD, or coating processes. The ceramic composite layer 22 may be a coating or a separate layer having a thickness ranging from 0.001 micron to 50 microns, preferably from 0.01 micron to 25 microns, and more preferably from 0.50 microns to 10 microns (if the separator is double-sided coated, perhaps preferably from 0.25 microns to 5 microns on each side). The polymeric microporous layer 24 is preferably a separate membrane having a thickness ranging from 1 micron to 50 microns, preferably from 2 microns to 25 microns, and more preferably from 3 microns to 12 microns. The total thickness of the separator 20 is in the range of 1 micron to 100 microns, preferably in the range of 2 microns to 50 microns, and more preferably in the range of 3 microns to 25 microns.

[0123] The ceramic composite layer 22 includes a matrix material or binder 26 having particles 28, such as inorganic or ceramic particles, dispersed therethrough. The ceramic composite layer 22 may be porous or non-porous (some matrix or binder materials swell and gel in the electrolyte and can transport ions even when the dry separator has a high Gurley (1,000 or even 10,000 Gurley) before wetting, and the ionic conductivity of the layer 22 depends primarily on the selection of porosity, electrolyte, matrix material 26, and particles 28. The matrix material 26 or particles 28 of the layer 22 may function to prevent dendrite growth and to maintain the electrodes spaced apart at high temperatures, respectively. The matrix material 26 can be a component of the separator, providing some protection against electronic short circuits. The matrix material 26 can also function as a gel electrolyte or polymer electrolyte (e.g., carrying an electrolyte salt). The matrix material 26 preferably comprises about 0.5 to 95 wt. % of the ceramic composite layer 22, and the inorganic particles 28 preferably form about 5 to 95.5 wt. % of the layer 22. Preferably, the composite layer 22 contains 10 to 99 wt. % of the inorganic particles. Most preferably, the composite layer 22 contains 20 to 98 wt. % of the inorganic particles.

[0124] The matrix material 26 may be a solvent or PVDF, acrylic, polyamide, and / or any gel-forming polymer proposed for use in lithium polymer batteries or solid electrolyte batteries. The matrix material 26 may be ionically conductive or non-conductive, such as an aqueous-based polymer or binder, such as a polymer, copolymer, or mixture thereof, or a combination, blend, or mixture thereof. The matrix material 26 may be selected from, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyurethane, polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polytetraethylene glycol diacrylate, copolymers, and mixtures thereof. Preferred matrix materials are PVDF and / or PEO and copolymers thereof. PVDF copolymers include PVDF:HFP (polyvinylidene fluoride:hexafluoropropylene) and PVDF:CTFE (polyvinylidene fluoride:chlorotrifluoroethylene). Most preferred matrix materials include PVDF:CTFE with less than 23% by weight CTFE, PVDF:HFP with less than 28% by weight HFP, any type of PEO, and combinations, blends, mixtures, or copolymers thereof.

[0125] Although inorganic particles 28 are typically considered non-conductive, these particles develop a conductive or superconductive surface upon contact with the electrolyte that improves the conductivity (reducing resistance) of separator 20. Inorganic particles may be selected from, for example, silicon dioxide (SiO), aluminum oxide (AlO), boehmite, kaolin, clay, barium sulfate, calcium carbonate (CaCO), titanium dioxide (TiO), SiS, SiPO, etc., or combinations, blends, or mixtures thereof. Preferred inorganic particles may be boehmite, kaolin, SiO, AlO, barium sulfate, and / or CaCO. The particles may have an average particle size ranging from 0.001 microns to 25 microns, preferably ranging from 0.01 microns to 2 microns, and most preferably ranging from 0.05 microns to 0.5 microns.

[0126] The microporous polymer layer 24 can be any of several types of microporous membranes (e.g., monolayer or multilayer), sheets, films, or layers, such as those available from Celgard LLC of Charlotte, North Carolina. The microporous polyolefin product is manufactured by Asahi Kasei, Inc., Tokyo, Japan, among others. Layer 24 can have a porosity ranging from 10 to 90%, preferably from 20 to 80%. Layer 24 can have an average pore size ranging from 0.001 to 2 microns, preferably from 0.05 to 0.5 microns. Layer 24 can have a Gurley number ranging from 5 to 150 seconds, preferably from 10 to 80 seconds. (The Gurley number is the time it takes 10 cc of air to pass through a 1-square-inch membrane in 12.2 inches of water.) Layer 24 is preferably polyolefin-based. Preferred polyolefins include polyethylene and polypropylene, or combinations, blends, copolymers, block copolymers, or mixtures thereof.

[0127] Various embodiments of the present invention have been described to accomplish various objectives 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 invention.

Claims

1. a polymeric binder containing water, an aqueous solvent, or a non-aqueous solvent as a solvent; heat-resistant particles; at least one component selected from the group consisting of a crosslinker, a low temperature shutdown agent, an adhesive, a thickener, a friction reducer, and a high temperature shutdown agent; 1. A coating composition comprising:

2. 10. The coating composition of claim 1, wherein the polymeric binder comprises at least one selected from the group consisting of polylactam polymers, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl acetate (PVAc), carboxymethyl cellulose (CMC), isobutylene polymers, acrylic resins, and latexes.

3. 3. The coating composition of claim 2, wherein the polymeric binder comprises a polylactam polymer that is a homopolymer, copolymer, block polymer, or block copolymer derived from a lactam.

4. The polymeric binder has the formula (1): 【Chemical 1】 In the formula, R １ , R ２ , R ３ , and R ４ is an alkyl or aromatic substituent, and R ５ is alkyl, aryl, or fused ring; and wherein the preferred polylactams can be homopolymers or copolymers, and the copolymer group X can be derived from vinyl, substituted or unsubstituted alkyl vinyl, vinyl alcohol, vinyl acetate, acrylic acid, alkyl acrylate, acrylonitrile, maleic anhydride, maleimide, styrene, polyvinylpyrrolidone (PVP), polyvinylvalerolactam, polyvinylcaprolactam (PVCap), polyamide, or polyimide; wherein m can be an integer from 1 to 10, preferably from 2 to 4, and the ratio of l to n is 0≦l:n≦10 or 0≦l:n≦1; The coating composition of claim 3, comprising a polylactam represented by the formula:

5. 4. The coating composition of claim 3, wherein the lactam-derived homopolymer or copolymer is at least one selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinylcaprolactam (PVCap), and polyvinylvalerolactam.

6. the polymer coating is a polylactam according to formula (2); 【Chemistry 2】 In the formula, R １ , R ２ , R ３ , and R ４ is an alkyl or aromatic substituent; R ５ is alkyl, aryl, or fused ring; m is an integer of 1 to 10, preferably 2 to 4; and wherein the ratio of l to n is 0≦l:n≦10 or 0≦l:n≦1; and X is an epoxide or an alkylamine; The coating composition of claim 3 comprising:

7. 7. The coating composition of claim 6, wherein X is an epoxide and the catalyst comprises an alkylamine or an epoxide.

8. 10. The coating composition of claim 1, wherein the polymeric binder comprises polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl acetate (PVAc), carboxymethyl cellulose (CMC), isobutylene polymer, acrylic resin, and / or latex.

9. 2. The coating composition of claim 1, wherein the heat-resistant particles are an organic material or a mixture of an organic material and an inorganic material, and the organic material comprises at least one selected from the group consisting of a polyimide resin, a melamine resin, a phenolic resin, a polymethyl methacrylate (PMMA) resin, a polystyrene resin, a polydivinylbenzene (PDVB) resin, carbon black, and graphite.

10. 10. The coating composition of claim 9, wherein the ratio of the heat-resistant particles to the binder in the coating composition is from 50:50 to 99:

1.

11. 10. The coating composition of claim 9, wherein 0.01 to 99.99% of the surface area of at least one of the refractory particles is coated with the binder.

12. The coating composition of claim 1 , wherein the crosslinker comprises multiple reactive groups.

13. 13. The coating composition of claim 12, wherein the crosslinker is an epoxy crosslinker containing multiple reactive epoxy groups.

14. 13. The coating composition of claim 12, wherein the crosslinker is an acrylate crosslinker containing multiple reactive acrylate groups.

15. 10. The coating composition of claim 1, wherein the low-temperature shutdown agent comprises at least one of polyethylene (PE) and polyvinylpyrrolidone (PVP).

16. The coating composition of claim 1 , wherein the adhesive comprises a thermoplastic fluoropolymer.

17. The friction reducer is selected from the group consisting of metal stearates, siloxanes, silicone resins, fluororesins, The coating composition according to claim 1, wherein the at least one selected from the group consisting of waxes and fatty amides.

18. 10. The coating composition of claim 1, wherein the high temperature shutdown agent has a melting point of 140 to 220°C.

19. 10. The coating composition of claim 1, wherein the high temperature shutdown agent is selected from polyvinylpyrrolidone (PVP) or polyvinylidene difluoride (PVDF).

20. 10. The separator of claim 1, wherein the coating layer further comprises another, different coating layer formed thereon.

21. A secondary lithium ion battery comprising the separator of any one of claims 1 to 20.

22. A composite comprising the separator of any one of claims 1 to 20 in direct contact with an electrode for a secondary lithium ion battery.

23. A vehicle or device comprising the separator according to any one of claims 1 to 20 or the battery according to claim 21.

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