Improved coatings, coated separators, batteries, and related methods

Abstract

To provide a separator in a lithium ion battery that has the ability to shut down more quickly at lower temperatures for longer periods while maintaining mechanical properties. The present invention provides a coating composition comprising a polymeric binder containing water, an aqueous solvent, or a non-aqueous solvent as a solvent, heat-resistant particles, and 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. Also provided are a battery separator coated with the composition, and a secondary lithium-ion battery comprising the separator.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the 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] The present 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, the present 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 ingredients, and / or new or improved coated porous substrates including battery separators, where the coating includes at least a polymeric binder and heat resistant particles, with or without additional additives, materials or ingredients. According to at least certain embodiments, 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, 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 on one or both sides of a microporous battery separator membrane to promote high temperature stability, control oxidation at the separator-cathode interface of the microporous battery separator membrane, 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. Additionally, 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 polymeric binders, one or more types of inorganic ceramic particles, and an aqueous solvent, a non-aqueous 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, a variety of 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, between 2 and 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, over-discharging, and internal short circuits can lead to battery temperatures much higher than the battery manufacturers intended for their batteries to be used at. In the event of thermal runaway, shutting down the battery, such as cessation of ion flow across a 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 quicker shutdown at lower temperatures and for a longer period of time 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 continuing desire to improve this function of the separator. For example, it is desirable to maintain this function with thinner and thinner coatings. Thus, there is a need for improvements in at least the performance, safety, manufacture, etc. of past coating compositions and coated battery separators. [Means for solving the problem]

[0009] According to at least selected aspects, the present application, disclosure or invention covered herein or hereby 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 application, disclosure or invention covered herein or hereby 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 ingredients, and / or new or improved coated porous substrates including battery separators, where the coating includes at least a polymeric binder and heat resistant particles, with or without additional additives, materials or ingredients. 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 new and / or improved coated porous substrates comprising at least one component, 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 crosslinkers, low temperature shutdown agents, adhesives, thickeners, friction reducers, and high temperature shutdown agents.

[0010] In one aspect, a coating composition is described herein for use on at least one side of a porous substrate, such as a battery separator. The coating may also be suitable for other purposes, the properties of which are discussed in more detail below with respect to its application to a battery separator, making 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 only 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, such as 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, and 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 the coating composition described herein is coated on two surfaces, such as two opposing surfaces, of a porous substrate.

[0012] In further aspects, described are 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, The secondary lithium ion batteries exhibit at least improved safety and performance. Effect 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 lactam-derived copolymers or block copolymers can enhance the thermal stability, enhance electrolyte stability, and enhance 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, e.g., helps prevent the substrate from curling. The addition of a crosslinker to the coating composition according to the present invention results in coatings with lower MD and TD shrinkage and higher thermal stability. The improved safety of the coating compositions described herein is provided by extending the shutdown window, as discussed further herein, so that shutdown begins at a lower temperature. The addition of an adhesive to the coating composition described herein can be used to coat battery electrodes, e.g., lithium This results in a coating that is more adherent to the battery electrodes. The addition of a friction modifier to the coating compositions described herein can result in a reduction in the pin removal force and / or a reduction in the coefficient of friction. From a safety standpoint, coating a battery separator with a coating composition that includes the high temperature shutdown agent described herein results in a better 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 description 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. [Diagram 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 a lactam of FIG. 1, where the polymer chains are PVP chains where R1, R2, R3, R4, and R5 of FIG. 1 are hydrogen and Y is 2. [Diagram 3] Fig. 3 is a schematic diagram of selected coverage of heat-resistant particles by polymer binder. For example, when the ratio of heat-resistant particles to polymer binder is low (e.g., as shown in the right side of Fig. 3), the coverage of heat-resistant particles by binder is high, and when the ratio of heat-resistant particles to polymer binder is high (e.g., as shown in the left side of Fig. 3), the coverage of 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. [Diagram 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 is a schematic diagram of the shutdown window for an uncoated and one-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, 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 the addition of 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 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. [Figure 13] FIG. 13 is a schematic cross-sectional view of an exemplary ceramic coated separator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 comprises 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 comprises 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 comprises one of each of these additional components, e.g., (a), (b), (c), (d), (e), and (f). In some embodiments, the coating composition can comprise two components (a), e.g., two crosslinkers, and one of component (b). Alternatively, the coating composition can comprise three components (c), e.g., three adhesives, and one of component (d). In some coating compositions, a single additive component can act, e.g., 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 may include any possible combination of the additional components (a), (b), (c), (d), (e), and (f).

[0017] (1) Polymer binder The polymeric binder comprises, consists of, or consists essentially of at least one of a polymeric material, an oligomeric material, or an elastomeric material, and is not limited to such. Any polymeric, oligomeric, or elastomeric material not inconsistent with the present disclosure can be used. The binder can be ionically conductive, semiconductive, or nonconductive. Any gel-forming polymer suggested for use in lithium polymer batteries or solid electrolyte batteries can be used. For example, the polymeric binder can include at least one, two, three, etc. selected from polylactam polymers, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl acetate (PVAc), carboxymethyl cellulose (CMC), isobutylene polymers, acrylic resins, latex, aramids, 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. 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, and wherein m can be an integer from 1 to 10, preferably from 2 to 4, with the ratio of l to n being 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), polyvinylcaprolactam (PVCap), and polyvinyl-valerolactam.

[0021] In a preferred embodiment, the lactam-derived copolymer block copolymer comprises a group in its backbone that can create crosslinks between at least two copolymer or block copolymer chains. For example, this group can be an epoxide group or an alkylamine. When the group that can create crosslinks between at least two copolymer or block copolymer chains is an epoxide, the epoxide undergoes an epoxidation reaction to create crosslinks. In some embodiments, the addition of a catalyst is required. For example, when the group that can create crosslinks between 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 that can create 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 capable of creating crosslinks between at least two copolymer or block copolymer chains can enhance the thermal stability, enhance electrolyte stability, and enhance wettability and CV performance of the resulting coating layer.

[0023] 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 to remain stable and flat, for example, helps prevent the substrate from curling.In particular, when 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, and can be any type that is not contrary to the objectives described herein, e.g., to provide a battery separator with improved safety. The acrylic resin may be an acrylic resin that provides a new and improved coating composition that can be used to manufacture. 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), polymethyl acrylate (PMA).

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

[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 in further embodiments, it is 90:10 to 99:1. This ratio affects the coverage of the heat-resistant particles with the polymeric binder. For example, if the ratio of heat-resistant particles to polymeric binder is low (e.g., as shown on the right side of FIG. 3), the coverage of the heat-resistant particles with the binder will be high. The higher the ratio of heat-resistant particles to polymeric binder, the less the coverage of the heat-resistant particles will be, for example, as shown on the left side of FIG. 3.

[0027] In a preferred embodiment, at least one of the heat-resistant particles is coated or partially coated with a polymeric binder. For example, in some embodiments, 0.01-99.99% 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, 0.01-99.99% 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 composition 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 material 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 (SiO2), aluminum oxide (Al2O3), boehmite (Al(O)OH), zirconium dioxide (ZrO2), titanium dioxide (TiO2), and tantalum oxide (TaO2). 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 resins, melamine resins, phenolic resins, polymethyl methacrylate (PMMA) resins, polystyrene resins, polydivinylbenzene (PDVB) resins, 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 (in addition to or instead of being coated or partially coated with a polymeric binder) with a compatibilizer, 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 a lithium ion battery, and these reactions may result in 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 do not undergo oxidation by the electrolyte. Improved oxidation stability can be obtained by placing 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 so limited and includes any compound that can form a bond between two or more polymer chains in the coating composition, so long as the compound is not otherwise inconsistent with 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, multiple epoxy group-containing crosslinking agents are preferred.

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

[0038] The crosslinking agent can be added in any amount consistent with the objectives described herein. In some preferred embodiments, the amount of crosslinking agent 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-limker can be sensitive to the addition of In response to heat, light irradiation, or a change in pH, the coating composition may initiate or catalyze the crosslinking of one or more polymer chains.

[0040] By adding a crosslinking agent to the coating compositions described herein, the inventors of the present application have found that the resulting coatings and battery separators containing said coatings (on one or both sides) exhibit many beneficial properties. These properties include lower shrinkage in the MD and TD directions even at higher temperatures, such as at temperatures of 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, e.g., a coated porous substrate, between two pieces of paper, then sandwiching them together to hold the sample between the papers, and hanging in an oven. For the "150°C for 1 hour" test, the samples are 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 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 for 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 for 1 hour" test. For the "180°C for 20 minutes" test, the sample is placed in an oven at 180°C for 20 minutes and then tested as described above for the "150°C for 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 so limited as long as it is not inconsistent with 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 is meant 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 agents can be particles comprising wax, oligomers, polyethylene (PE), e.g., low density PE, etc. These particles can be coated, uncoated, or partially coated. For example, they can be coated with latex and / or a polymeric binder as disclosed herein. In some embodiments, these coated low temperature shutdown agents can be coated with a high temperature shutdown agent, which is described in more detail below.

[0045] The inventors of the present application have determined that the low temperature shutdown agent described herein is particularly suitable for use in a device that is ... 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 increased 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 an adhesive is not so limited as long as it is not inconsistent with the purpose described herein. In some embodiments, adding an adhesive to the coating composition described herein results in a coating that has higher adhesion to a battery electrode, such as a lithium battery electrode, 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 is also true in embodiments where the porous substrate is not 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 good 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 one-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. The less black material, or electrode material, the lower the adhesion.

[0049] (d) Thickener In another aspect, thickener can be added to the coating composition described herein.The thickener used is not so limited and can be any thickener that is not inconsistent with the purpose described herein.In some embodiments, 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 modifier can be added to the coating compositions described herein. The friction modifier is not so limited and can be any friction modifier that is not inconsistent with the objectives described herein. For example, in some embodiments, when a film formed from a coating composition that includes a friction modifier is compared to a film formed from a coating composition that does not include a friction modifier, the addition of a friction modifier can result in a reduction in pin removal force and / or wear. In some embodiments, the coatings formed from the coating compositions described herein are "tacky" or adhere well to the electrodes when wet, e.g., when wet with electrolyte, and have good pin removal when dry. For example, in some embodiments, the pin removal force of films formed from coating compositions containing friction reducers is 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] The pin removal properties are quantified using the following procedure to measure the 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 on at least one surface thereof) around a pin (or core or mandrel). The pin is a two-piece cylindrical mandrel with a diameter of 0.16 inches and a smooth outer surface. Each piece has a semicircular cross section. The separator, described below, is wound onto the pin. The 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 at 1 / 2" and 7" from the free end of the separator, i.e., distal to the spliced ​​end. 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 stretches. The jelly roll is tested on a tensile strength tester (i.e., Chatillon Model TCD from Chatillon Inc., Greensboro, NC) along with a load cell (50 lbs x 0.02 lbs; Chatillon DFGS 50). 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 can be a metal stearate such as Li stearate, Ca stearate, etc.Other possible friction reducers can be 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, monoglyceride stearate), fatty amide (e.g., stearamide, palmitamide, methylene bisstearamide), and any combination of the above 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 so limited, as long as it is not inconsistent with the purpose described herein, for example, providing a coating composition that can be used to manufacture a safer lithium-ion battery.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 is meant 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 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 a particle 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 inventors of the present application have found that coating a battery separator with a coating composition that includes the high temperature shutdown agent described herein results in a superior separator, particularly from a safety standpoint. Without 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 include the high temperature shutdown agent.

[0060] (4) Optional Added Ingredients 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 coated 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 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 is dried on the substrate; (6) improved thermal stability, for example, as indicated 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 coated separator and one or both electrodes of the battery; and / or (10) improved pin removal force and / or coefficient of friction. These objectives and other related attributes of the improved coated separator are described in more detail in other portions of this application.

[0064] The new and / or improved coated separator may have superior quality and uniformity, thus providing good manufacturing yields. The new and / or improved coated separator may provide batteries with improved capacity and improved cycling performance. It may have fewer defects, such as fewer gel defects and / or fewer crater defects, than other known coated separators. The improved and / or coated separator may have improved coating for adhesion to the porous substrate. The adhesion strength 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.

[0065] The new and / or improved coated porous substrates (or separators) may also provide improved safety by exhibiting an extended shutdown window, particularly as 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., as 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 or equal to 10,000 ohms / cm throughout the window. 2 It remains super.

[0066] This is considered stable. At times, the measured resistance across the separator may be as low as 100,000 ohms / cm over the extended shutdown window of the new and / or improved separators disclosed herein. 2Incipient shutdown of the new and / or improved separators disclosed herein is also rapid. Sometimes, during incipient shutdown, the resistance measured across the separator drops below 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 are a lower onset or initiation temperature, a faster or more rapid shutdown speed, and a sustained, consistent, longer, or extended thermal shutdown window. In a preferred embodiment, the shutdown speed 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 upon shutdown. An example of shutdown performance is shown in FIG. 5.

[0068] A shutdown window as described herein generally refers to a window of time / temperature extending from the initiation or onset of shutdown, e.g., at which the separator begins to melt sufficiently to close its pores, e.g., causing a cessation or slowing of ion 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 ion flow, and / or decreasing resistance across the separator. An example of an extended shutdown window as described herein is shown in FIG. 6.

[0069] FIG. 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. The initiation or onset of shutdown occurs at about 135° C. for an uncoated porous substrate, and occurs sooner after coating. Without wishing to be bound by a particular theory, this may result from the addition of a low-temperature shutdown agent, as described herein, to the coating compositions and / or coatings described herein. The low-temperature shutdown agent may melt before the porous substrate and fill or partially fill its pores, causing early (low-temperature) shutdown initiation.

[0070] FIG. 6 also shows that the period of shutdown is extended from 170° C. in the uncoated porous substrate to about 190° C. after coating. Without wishing to be bound by a 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 end point of the shutdown window is raised (widening the window), and in some embodiments the upper and lower parts of the shutdown window are extended, for example as shown in FIG. 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, on the order of 1000 mAh, are reached. The combination of a lower thermal shutdown onset temperature and a longer duration of the shutdown temperature increases the sustained shutdown window. A wider thermal shutdown window can improve battery safety by reducing the chance of thermal runaway and the potential for fire or explosion.

[0072] One exemplary method for measuring the shutdown performance of a separator is as follows: 1) Place a few drops of electrolyte on the separator to saturate it, and place the separator into the test cell; 2) Ensure that the heating press is below 50°C, and 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 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 impedance of the separator drops to a low value; 5) Open the platens and remove the test cell; Allow the test cell to cool; Remove and dispose of the separator.

[0073] (1) Porous base material The porous substrate used in the separator described herein is not so limited and can be any porous substrate not inconsistent 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 an 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 it is 300 to 600 seconds. Gurley is defined herein as the Japanese Industrial Standard (JIS Gurley) and is measured herein using an OHKEN permeability tester. 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 polymers used in the porous substrate can be characterized as thermoplastic polymers. These polymers can be further characterized as semi-crystalline polymers. In one embodiment, the semi-crystalline polymer can be a polymer having a crystallinity in the range of 20-80%. Such polymers can be selected from the following groups: 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 polymer (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 including block polymers thereof (with inorganic fillers Al2O3, SiO2, etc.), 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 may otherwise affect the manufacture of the porous substrate or its physical properties). The composition may contain additives such as inert particles which do not significantly affect the mechanical properties of the composition, antistatic agents, antiblocking agents, antioxidants, lubricants (for ease of manufacture), and the like.

[0077] Various materials can be added to the polymer to modify or enhance the properties of the porous substrate. Such materials include, but are not limited to: (1) polyolefins or polyolefin oligomers having a melting temperature below 130°C; (2) mineral fillers include, but are 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 the like, and mixtures thereof; (3) elastomers include, but are not limited to, ethylene-propylene (EPR), ethylene-propylene-diene (EPDM), styrene-butadiene (SBR), styrene isoprene (SIR), ethylidene norbornene (ENB), epoxies, and polyurethanes and blends thereof; (4) wetting agents include, but are 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, phosphate esters. (7) Crosslinking or coupling agents. (8) Polymer processing aids. (9) Nucleating agents of any kind, including beta nucleating agents for polypropylene. Beta nucleated polypropylene is disclosed in U.S. Pat. No. 6,602,593. Beta nucleating agents for polypropylene are materials that produce beta crystals in polypropylene.

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

[0079] The porous substrate can be manufactured by any one of wet manufacturing, dry manufacturing, particle stretch manufacturing, and beta-nucleated biaxially oriented (BN-BOPP) manufacturing. The porous substrate can be manufactured, for example, by the dry stretch process (known as the Celgard® dry stretch 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 process, which can include the use of solvents and / or oils from Celgard Korea Co., Ltd., Korea, Asahi Kasei Co., Ltd., Japan, and / or Tonen Co., Ltd., Japan, sometimes known as phase separation or extraction methods. Alternatively, in other embodiments, the porous substrate can be a non-woven type membrane.

[0080] A possibly preferred porous substrate can be produced by dry stretching and has pores less than 2 μm. A microporous substrate is, for example, a thin, flexible polymer sheet, foil, or film having a plurality of pores therethrough. Such porous substrates are useful for, but are not limited to, mass transfer membranes, pressure regulators, filtration membranes, medical devices, electrochemical storage devices, and the like. 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 stretch process (also known as the CELGARD process). Dry stretch refers to a process in which pore formation results from stretching of a non-porous precursor. See 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 the wet and particle stretching methods, as discussed above.

[0081] In one embodiment, the porous can be a dry stretched porous substrate having 1) substantially slit, trapezoidal, or circular pores, and 2) a ratio of longitudinal tensile strength to transverse tensile strength in the range of 0.1 to 20, preferably 0.5 to 10. For pore shapes, see Figures 1 to 5. The round pores in Figures 1 to 3 are different from the slit shaped pores in Figures 4 to 5 and Kesting ibid. Different. In addition, the pore shape of the porous substrate can be characterized by the aspect ratio, i.e., the ratio of the length to the width of the pore. 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 slit-like pore dry-stretched membrane, which is greater than 5.0. With respect to the ratio of the longitudinal tensile strength to the transverse tensile strength, in one circular pore embodiment, this ratio is 0.5 to 5.0. This ratio is different from the corresponding ratio of the slit-like pore membrane, which is greater than 10.0.

[0082] Machine direction (MD) and transverse direction (TD) tensile strength were measured according to ASTM-882 procedure. 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 aforementioned values ​​are exemplary values, are not intended to be limiting, and therefore should be considered merely representative of the present porous substrate. Pore size is measured using Aquapore available from Porous Materials, Inc. (PMI). Pore size is expressed in μm.

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

[0084] In general, the method for producing the aforementioned porous substrate comprises 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 comprises a longitudinal stretching and a transverse stretching, with simultaneous controlled longitudinal relaxation. The longitudinal stretching and transverse stretching may be simultaneous or sequential. In one embodiment, the longitudinal stretching is followed by a transverse stretching, with simultaneous longitudinal relaxation. This sequential process is 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 need not 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 another aspect, 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 lateral stretching following the MD stretching preferably includes simultaneous controlled longitudinal relaxation. This means that it enables the precursor to contract (i.e., relax) in a controlled manner longitudinally at the same time as it is stretched laterally.

[0088] The 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 100-1200%, and in another embodiment, in the range of 200-900%. In one embodiment, the controlled longitudinal relaxation can be in the range of 5-80%, and in another embodiment, in the range of 15-65%. In one embodiment, the transverse stretching can be performed in multiple stages. During the transverse stretching, the precursor may or may not shrink in the longitudinal direction. In one embodiment of the multi-stage transverse stretching, the first transverse step can include a transverse stretch with controlled longitudinal relaxation, followed by a simultaneous transverse and longitudinal stretch, followed by a transverse relaxation and no longitudinal stretch or relaxation. Optionally, the precursor after the 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, 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 more. Puncture strength is measured using an Instron Model 4442 based on ASTM D3763. Measurements are taken at both ends of 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 the coating layer 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 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 side of the porous substrate. For example, in some embodiments, the layers already applied to the porous substrate are thin, very thin, or ultra-thin 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 the 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 comprising the coating composition described herein is formed. Sometimes, the total thickness of these already applied one or more layers 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, 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, nano-porous, micro-porous, meso-porous or macro-porous. 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 Gu 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 a nonporous coating layer, 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 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 may 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 or lithium alloy foils (e.g., lithium aluminum alloys), or mixtures of lithium metal and / or lithium alloys 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, V6O 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 invention have been described to accomplish various objectives of the invention. It should be recognized that these aspects are merely illustrative of the principles of the 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. EXAMPLES

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

[0101] Table 1 [Table 1]

[0102] [Table 2]

[0103] [Table 3]

[0104] CJ: Heat resistant particles, polymers comprising a lactam derived polymer, optionally together with water, aqueous or non-aqueous solvent as a solvent. CM: heat resistant particles and PVA binder, optionally with water, aqueous 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 modifier described herein f: any high temperature shutdown agent described herein

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

[0106] (a) In one exemplary embodiment, a coated battery separator (inventive example) according to some embodiments described herein was prepared. The coating composition included polyethylene beads as CJ and low temperature shutdown agent (b) and was coated on a three-layer porous substrate including a polypropylene (PP) layer, a polyethylene (PE) layer, and a polypropylene (PP) layer. The shutdown properties of this coated battery separator were evaluated according to the electrical resistance test described herein and compared to the three-layer porous substrate itself (i.e., the uncoated comparative example). The results are shown in FIG. 8. FIG. 8 shows that the shutdown window of the comparative example is from about 125° C. to about 175° C. When the coating is applied, the lower end point of the shutdown window shifts from about 125° C. to about 95° C., i.e., a shift of about 30° C. The upper limit of the shutdown window of the inventive example and the comparative example is almost the same. Thus, overall, the shutdown window of the inventive example is expanded by almost 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 (inventive example) was evaluated according to the electrical resistance test described herein and compared to an uncoated tri-layer porous substrate or separator (comparative example). The results are shown in FIG. 9. In this embodiment, the shutdown window of the inventive example is reduced by about 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 a multi-layer (3-layer) porous substrate comprising PP-PE-PP and PE-PP-PE with a coating, e.g., a high temperature shutdown agent, comprising CJ and polyvinylpyrrolidone (PVP) on one side of the porous substrate. The coating was 3 microns thick. These are examples of the present invention. The shutdown window of these coated separators (examples of the present invention shown in FIG. 10B) was evaluated according to the electrical resistance test described herein and compared to uncoated multi-layer (3-layer) porous substrates comprising PP-PE-PP and PE-PP-PE, respectively (comparative examples shown in FIG. 10A and FIG. 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 including coating layers made from these coating compositions, including at elevated temperatures. In Table 2 below, coating compositions were prepared including CS only, CS and d (thickener), and CS, d and a (crosslinker). In these compositions, the CS and thickener are the same in these compositions. 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 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 an oven at 180°C for 20 minutes and then tested as described above for the "150°C, 1 hour" test. Shrinkage can be measured on single-side coated 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, such as an anode. (a) An example of the 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 adhesion of coating layers to porous substrates As discussed 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) Exemplary embodiments of improved pin removal force As noted above, for example, the addition of a friction modifier 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-sided coated PP-PE-PP porous substrate and one-sided 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 mentioned above, the separators disclosed herein have improved thermal stability, as demonstrated, for example, by desirable behavior in 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 in Figure 12. It was found that the single-sided coated PE-PP-PE and PP-PE-PP substrates (invention examples) performed 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 a 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 / minute - Homogeneous, uniform coating with complete coverage · Low defect or binder-free 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. The separator 20 includes a ceramic composite layer or coating 22 and a polymeric 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 polymeric 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 cell performance, and / or block ionic conductivity (or flow) between the anode and cathode at elevated temperatures and prevent or stop thermal runaway.

[0122] Under typical operating conditions, the ceramic composite layer 22 of the separator 20 must be sufficiently conductive to allow ion flow between the anode and cathode so that a desired amount of electrical current can be generated by the cell. Layers 22 and 24 should adhere well to one another, i.e., unintentional separation should not occur. 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 in the range of 0.001 microns to 50 microns, preferably in the range of 0.01 microns to 25 microns, and more preferably in the range of 0.50 microns to 10 microns (if the separator is double-sided coated, perhaps preferably in the range of 0.25 microns to 5 microns on each side). The polymeric microporous layer 24 is preferably a separate membrane having a thickness in the range of 1 micron to 50 microns, preferably in the range of 2 microns to 25 microns, and more preferably in the range of 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 will 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 provide a high conductivity by preventing dendrite growth and keeping the electrodes apart at high temperatures, respectively. The matrix material 26 may be a component of a separator that provides some degree of protection against electronic shorting. The matrix material 26 may also act as a gel electrolyte or polymer electrolyte (e.g., carrying an electrolyte salt). The matrix material 26 preferably comprises about 0.5-95% by weight of the ceramic composite layer 22, with the inorganic particles 28 preferably forming about 5-95.5% by weight of said layer 22. Preferably, the composite layer 22 contains 10%-99% by weight of the inorganic particles. Most preferably, the composite layer 22 contains 20%-98% by weight of the inorganic particles.

[0124] The matrix material 26 may be a solvent or a 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 aqueous-based polymers or binders, such as 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% CTFE by weight, PVDH:HFP with less than 28% HFP by weight, any type of PEO, and combinations, blends, mixtures, or copolymers thereof.

[0125] Although inorganic particles 28 are normally considered non-conductive, these particles develop a conductive or superconductive surface that improves the conductivity (reducing resistance) of separator 20 when in contact with the electrolyte. The inorganic particles are selected from, for example, silicon dioxide (SiO2), aluminum oxide (Al2O3), boehmite, kaolin, clay, barium sulfate, calcium carbonate (CaCO3), titanium dioxide (TiO2), SiS2, SiPO4, and the like, or combinations, blends, or mixtures thereof. Preferred inorganic particles may be boehmite, kaolin, SiO2, Al2O3, barium sulfate, and / or CaCO3. 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. Layer 24 is a microporous polyolefin product manufactured by, for example, Asahi Kasei Corporation, Tokyo, Japan. Layer 24 may have a porosity ranging from 10 to 90%, preferably ranging from 20 to 80%. Layer 24 may have an average pore size ranging from 0.001 to 2 microns, preferably ranging from 0.05 to 0.5 microns. Layer 24 may have a Gurley number ranging from 5 to 150 seconds, preferably ranging from 10 to 80 seconds. (Gurley number refers to the time it takes for 10 cc of air to pass through 1 square inch of 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 present invention.

Claims

1. A coating composition comprising a polymeric binder, heat-resistant particles, and a crosslinking agent, the polymeric binder comprises a polymer derived from polyvinylpyrrolidone and a lactam selected from polyvinylcaprolactam and polyvinylvalerolactam; the heat-resistant particles include at least one selected from the group consisting of polyimide resin particles, melamine resin particles, phenolic resin particles, polymethyl methacrylate (PMMA) resin particles, polystyrene resin particles, polydivinylbenzene (PDVB) resin particles, carbon black particles, and graphite particles; A coating composition comprising, as the crosslinking agent, at least a component having an epoxy group of the polymer derived from the lactam.

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

3. A secondary lithium ion battery comprising a separator having a layer of the coating composition of claim 1 or 2.

4. A vehicle comprising the secondary lithium ion battery according to claim 3.

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