Multilayer porous membrane with incompatible resins

Abstract

The present invention is a single-layer, two-layer, three-layer, or multi-layer porous membrane having at least one layer comprising a thermoplastic resin and a polymer that is incompatible with the thermoplastic resin. [Solution] One structure is a multilayer porous membrane in which at least one inner layer of the multilayer porous membrane comprises a thermoplastic resin and a polymer incompatible with the thermoplastic resin. A large amount of the incompatible polymer can be used in the inner layer. This structure has improved properties, including improved puncture strength. Another structure includes at least one layer comprising polyethylene and a polymer incompatible with polyethylene. The at least one layer comprising polyethylene and a polymer incompatible with polyethylene can be an inner layer or an outer layer. The inner layer can comprise more of the incompatible polymer than the outer layer. This porous membrane can be used as a battery separator.

Description

[Technical Field]

[0001] According to at least selected embodiments, the present application, disclosure, or invention relates to membranes, separator membranes, separators, battery separators, lithium secondary battery separators, multilayer membranes, multilayer separator membranes, multilayer separators, battery separators, lithium secondary battery separators, batteries, capacitors, fuel cells, lithium batteries, lithium ion batteries, lithium secondary batteries, and / or lithium ion secondary batteries, and / or methods of making and / or using such membranes, separator membranes, separators, battery separators, lithium secondary battery separators, batteries, capacitors, fuel cells, lithium batteries, lithium ion batteries, lithium secondary batteries, fabrics, filters, HVAC, materials for personal protective equipment, and / or lithium ion secondary batteries, and / or devices, vehicles, or products comprising same, and / or methods of making, testing, quantifying, characterizing, and / or analyzing such membranes, separator membranes, separators, battery separators, etc. According to at least certain embodiments, the present disclosure or invention relates to membrane layers, membranes or separator membranes, battery separators comprising such membranes, and / or related methods. According to at least certain embodiments, the present disclosure or invention relates to porous polymer membranes or separator membranes, battery separators comprising such membranes, and / or related methods. According to at least certain embodiments, the present disclosure or invention relates to microporous polyolefin membranes or separator membranes, microlayer membranes, multilayer membranes comprising one or more microlayers or nanolayer membranes, battery separators comprising such membranes, and / or related methods. According to at least certain embodiments, the present disclosure or invention relates to microporous polymer membranes or separator membranes having one or more outer and / or inner layers, microlayer membranes, multilayer microporous membranes or separator membranes having outer and inner layers, some of which layers or sublayers are produced by coextrusion and then laminated together to form the membrane or separator membrane.In some embodiments, a layer, microlayer, or nanolayer may comprise a homopolymer, copolymer, block copolymer, elastomer, and / or polymer blend. In selected embodiments, at least some layers, microlayers, or nanolayers may comprise different or separate polymers, homopolymers, copolymers, block copolymers, elastomers, and / or polymer blends. In selected embodiments, at least some layers, microlayers, or nanolayers comprise a thermoplastic resin and a first polymer that is incompatible with the thermoplastic resin. The present disclosure or invention also relates to methods of making and / or using such membranes, separator membranes, or separators, for example, as separators for lithium batteries. According to at least selected embodiments, the present application or invention is directed to multilayer and / or microlayer porous or microporous membranes, separator membranes, separators, composites, electrochemical devices, and / or batteries, and / or methods of making and / or using such membranes, separators, composites, devices, and / or batteries. According to at least certain selected embodiments, the present application or invention is directed to multi-layer separator membranes in which one or more layers of the multi-layer structure are produced in a multi-layer or micro-layer co-extrusion die using multiple extruders. [Background technology]

[0002] Batteries such as lithium-ion batteries may incorporate multilayer separator membranes to separate electrodes, retain electrolyte, enhance charge transfer, and perform other functions.

[0003] One separator membrane design is a tri-layer polyolefin-based separator. While these tri-layer designs have traditionally been effective in conventional lithium batteries, improvements are constantly being sought to fully optimize the balance of strength and / or performance characteristics for newer applications of certain primary and / or secondary batteries, such as lithium rechargeable batteries. This is especially true as battery separator requirements become more demanding as consumers desire thinner and stronger separators. For example, microporous tri-layer membranes formed by coextrusion of three layers may, in some cases, exhibit reduced strength when made to thinner specifications than conventional separators. Separators formed by lamination of single layers may also, in some cases, be unable to meet the ever-increasing demand for thinner and stronger separators in newer applications. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, there is a need for new and improved multi-layer microporous membranes, base films, or battery separators that offer various improvements over previous membranes, base films, or battery separators. [Means for solving the problem]

[0005] Applicant has addressed some of the deficiencies of previous multilayer battery separators by incorporating an incompatible resin into the thermoplastic resin of the inner layer of the multilayer structure. The multilayer structures described herein have three or more layers, including at least two outer layers and at least one inner layer. In some embodiments, the at least one inner layer may have a thickness of 0.1 to 10 microns, 0.1 to 5 microns, 0.1 to 4 microns, 0.1 to 3 microns, 0.1 to 2 microns, 0.1 to 1 micron, or 0.1 to 0.5 microns.

[0006] In one embodiment, a multi-layer porous membrane that can be used as a battery separator for a secondary battery is disclosed, wherein at least one inner layer of the multi-layer porous membrane comprises a thermoplastic resin and a first polymer that is incompatible with the thermoplastic resin.

[0007] In some preferred embodiments, the thermoplastic resin is a polyolefin, for example, the polyolefin may be polypropylene, polyethylene, a mixture thereof, a copolymer thereof, or a terpolymer thereof.

[0008] In some embodiments, the first polymer may be a copolymer. In other embodiments, the first polymer may be a block copolymer. The block copolymer may be a block copolymer comprising one or more hard blocks and one or more soft blocks. For example, the block copolymer may have the following chemical structure: [CH2-CHR] x -[Soft Block] y In the above formula, R is an aromatic or non-aromatic C5 to C10 ring, x is greater than 1, and y is greater than 1.

[0009] In some embodiments, the block copolymer is a styrenic block copolymer. For example, the block copolymer may be at least one of styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS) styrenic block copolymer, styrene-ethylene-ethylene-propylene-styrene (SEEPS) block copolymer, styrene-ethylene-propylene (SEP) block copolymer, and a triblock copolymer having styrene end blocks and a midblock that can be hydrogenated or unhydrogenated.

[0010] In some embodiments, the block copolymer is at least one selected from polyethylene-polybutylene (C2-C4), polyethylene-polypropylene (C2-C3), polyethylene-polypentene (C2-C5), polyethylene-polyhexene (C2-C6), polyethylene-polyheptene (C2-C7), polyethylene-polyoctene (C2-C8), polyethylene-polynonene (C2-C9), and polyethylene-polydecene (C2-C10) block copolymers.

[0011] In some embodiments, at least one inner layer can include the first polymer in an amount of 1 wt % or more, 3 wt % or more, 5 wt % or more, or 10 wt % or more.

[0012] In some embodiments, the glass transition temperature (T g ) is lower than that of thermoplastic resins.

[0013] In some embodiments, the multi-layer porous membrane is a dry-process porous membrane.

[0014] In some embodiments, the multi-layer porous membrane does not include a compatibilizer, and in particular does not include any compatibilizer that compatibilizes the thermoplastic resin and the first polymer. A compatibilizer is not used in the inner layer that includes the thermoplastic resin and the incompatible first polymer.

[0015] In some embodiments, the multi-layer porous membrane has a puncture strength of 350 gf or greater, 360 gf or greater, 370 gf or greater, or 380 gf or greater at a thickness of 14 microns or less.

[0016] In some embodiments, the multi-layer porous membrane may have a coating on one or both sides thereof.

[0017] In another aspect, disclosed herein are single-layer, bi-layer, tri-layer, or multi-layer porous membranes, in which at least one layer of the membrane comprises polyethylene and a polymer incompatible with polyethylene. In some embodiments, the at least one layer containing polyethylene and a polymer incompatible with polyethylene is an inner layer, and in some embodiments, an outer layer. In some embodiments, both the inner and outer layers comprise polyethylene and a polymer incompatible with polyethylene. For the inner layer, the amount of the incompatible polymer may be greater than 1 wt%, greater than 3 wt%, greater than 5 wt%, greater than 7 wt%, greater than 10 wt%, greater than 15 wt%, or greater than 20 wt%. For the outer layer, the amount of the incompatible polymer is less than 10 wt%, less than 7 wt%, less than 5 wt%, less than 3 wt%, or less than 1 wt%.

[0018] In another aspect, a battery separator is described that includes at least one multilayer porous membrane or at least one porous membrane described herein. In some embodiments, the multilayer porous membrane of the battery separator has a coating on one or both sides thereof.

[0019] In another aspect, a secondary battery is described that includes the battery separator described herein. [Effects of the Invention]

[0020] The membranes, separator membranes, or separators described above may demonstrate improved puncture strength, improved shutdown, improved strength, improved dielectric breakdown strength, and / or reduced tendency to tear. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a TEM image of some embodiments described herein. [Figure 2] FIG. 2 is a TEM image of some embodiments described herein. [Figure 3] FIG. 3 is a TEM image of some embodiments described herein. [Figure 4] FIG. 4 is a TEM image of some embodiments described herein. [Figure 5] FIG. 5 is a TEM image of some embodiments described herein. [Figure 6A] FIG. 6A is a TEM image of some embodiments described herein. [Figure 6B] FIG. 6B is a TEM image of some embodiments described herein. [Figure 7] FIG. 7 is a schematic diagram of a membrane according to some embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0022] The embodiments described herein may be more readily understood by reference to the following detailed description and examples. However, the elements, devices, and methods described herein are not limited to the specific embodiments shown in the detailed description and examples. It should be recognized that these embodiments merely illustrate the principles of the present disclosure. Many modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the present disclosure.

[0023] Additionally, all ranges disclosed herein should be understood to encompass any and all subranges subsumed therein. For example, a range stated as "1.0 to 10.0" should be considered to include any and all subranges beginning with a minimum value of 1.0 or greater and ending with a maximum value of 10.0 or less, such as 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.

[0024] Additionally, all ranges set forth herein are intended to include the endpoints of the range unless expressly stated otherwise. For example, the ranges "between 5 and 10," "from 5 to 10," or "5-10" should generally be considered to include the endpoints 5 and 10.

[0025] Furthermore, when the phrase "up to" is used in connection with an amount or quantity, it should be understood that the amount is at least a detectable amount or quantity. For example, a material present in an amount "up to" a specified amount may be present from a detectable amount up to and including the specified amount.

[0026] I. Membrane In some embodiments, single-layer, double-layer, triple-layer, or multi-layer porous membranes are disclosed. In some embodiments, single-layer, double-layer, triple-layer, or multi-layer microporous membranes are disclosed. While the term "membrane" is used throughout this specification for simplicity, it should be understood that this term also refers to a "thin film" or "separator." Additionally, the term "multilayer" is generally used to describe a porous membrane having two or more layers, unless explicitly stated otherwise.

[0027] In preferred embodiments, the membrane is a multilayer membrane comprising two outer layers and at least one inner layer, hi some embodiments, the multilayer membrane may have 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, 19 or more, or 20 or more inner layers.

[0028] In some embodiments, the porous membrane comprises a thermoplastic resin and a polymer incompatible with the thermoplastic resin. The porous membrane can be microporous, nanoporous, or a mixture of both. The porous membrane can be a single-layer, bilayer, trilayer, or multilayer porous membrane. For example, examples of multilayer membranes are described in International Publication No. 2018 / 089748, assigned to Celgard Corporation and incorporated herein by reference. Examples of trilayer membranes are described in U.S. Pat. No. 6,080,507, assigned to Celgard Corporation and incorporated herein by reference in its entirety.

[0029] Each layer can be monoextruded, meaning that the layer is extruded by itself as a single layer and does not have any sublayers. Alternatively, each layer can include multiple coextruded sublayers. For example, coextruded two-, three-, or multi-sublayer films are each collectively considered to be a "layer." A coextruded two-layer film has two sublayers, a coextruded three-layer film has three layers, and a coextruded multi-layer film has two or more, three or more, four or more, five or more, etc. The exact number of sublayers in a coextruded layer is determined by the die design and not necessarily by the coextruded materials that form the coextruded layer. For example, a coextruded two-, three-, or multi-sublayer film can be formed using the same material in each of the two, three, or four or more sublayers, and these sublayers are still considered separate sublayers, even though they are made of the same material. Each layer comprising the coextruded bi-, tri-, or sub-multilayer film can have a pre-orientation thickness of 1.2 mils or less, 1.1 mils or less, 1 mil or less, 0.9 mils or less, 0.8 mils or less, 0.75 mils or less, 0.5 mils or less, 0.4 mils or less, 0.3 mils or less, or 0.2 mils or less.

[0030] In some embodiments, the multilayer microporous membranes or multilayer microporous films described herein comprise two, three, four, or more coextruded layers. A coextruded layer is a layer formed by a coextrusion process. In some cases, the layers may be formed by the same or separate coextrusion processes. Successive layers can be formed by the same coextrusion process, or two or more layers can be coextruded by a single process. Two or more layers can be coextruded by separate processes, and two or more layers formed by a single process can be laminated to two or more layers formed by separate processes, so that in combination there are four or more consecutive coextruded layers. In some embodiments, the coextruded layers are formed by the same coextrusion process. For example, two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, fifteen or more, twenty or more, twenty-five or more, thirty-five or more, thirty-five or more, forty-five or more, forty-five or more, fifty or more, fifty-five or more, or sixty or more coextruded layers can be formed by the same coextrusion process. The extrusion process can be carried out by extruding a mixture of two or more polymers, which can be the same or different, with or without a solvent. In a preferred embodiment, the coextrusion process is a dry process, such as the Celgard® dry process, and does not use a solvent. In other cases, the coextrusion process is a wet process. In other embodiments, the process can be a dry process other than the Celgard® dry process. For example, the pores can be formed using a pore-forming or nucleating agent. In the Celgard® dry process, the pores are formed by stretching.

[0031] In some embodiments, the multilayer films described herein are made by forming a coextruded bilayer (two coextruded layers), trilayer (three coextruded layers), or multilayer (two, three, four, or more coextruded layers) film and then laminating the bilayer, trilayer, or multilayer film with at least one or two other films, including other coextruded bilayers, trilayers, and multilayers. The other films can be nonwoven or woven films, monoextruded films, or other coextruded films. In some embodiments, the other films are coextruded films having the same number of coextruded layers as the coextruded bilayer, trilayer, or multilayer film. Furthermore, each coextruded layer can have two, three, four, or more sublayers, as described herein above.

[0032] Laminating a bi-, tri-, or multi-layer coextruded film to at least one other mono-, tri-, or multi-layer coextruded film may involve the use of heat, pressure, or heat and pressure, and the lamination is not intended to be broken and forms a bond that does not easily break.

[0033] In some embodiments, one or more layers of a bi-layer, tri-layer, or multi-layer film comprise a thermoplastic resin and a first polymer, and in some cases, all layers of a bi-layer, tri-layer, or multi-layer film comprise a thermoplastic resin and a first polymer.

[0034] In preferred embodiments, at least one inner layer of the multilayer film comprises a thermoplastic resin and a first polymer that is incompatible with the thermoplastic resin. In some embodiments, all inner layers of the multilayer film comprise a thermoplastic resin and a first polymer that is incompatible with the thermoplastic resin, and in some embodiments, some but not all of the inner layers are included when the multilayer film comprises a thermoplastic resin and a first polymer that is incompatible with the thermoplastic resin.

[0035] The thermoplastic resin can be any thermoplastic resin not inconsistent with the objectives of the present disclosure. Generally, the thermoplastic resin should be extrudable.

[0036] In some embodiments, the thermoplastic resin is a polyolefin. In preferred embodiments, the polyolefin includes polypropylene, polyethylene, mixtures thereof, and / or copolymers thereof. In some embodiments, the polyolefin includes, but is not limited to, polyethylene, polypropylene, polybutylene, polymethylpentene, copolymers thereof, and blends thereof. In some embodiments, the copolymer may be a copolymer of polyethylene and polypropylene, where the amount of polyethylene is up to 20%, up to 15%, up to 10%, up to 5%, or up to 3%. In some embodiments, the polyolefin may be an ultra-low molecular weight, low molecular weight, medium molecular weight, high molecular weight, or ultra-high molecular weight polyolefin, such as, for example, medium or high molecular weight polyethylene (PE) or polypropylene (PP). For example, ultra-high molecular weight polyolefins can have a molecular weight of 450,000 (450k) or more, such as 500k or more, 650k or more, 700k or more, 800k or more, 1 million or more, 2 million or more, 3 million or more, 4 million or more, 5 million or more, 6 million or more, etc. High molecular weight polyolefins can have a molecular weight in the range of 250k to 450k, such as 250k to 400k, 250k to 350k, or 250k to 300k. Medium molecular weight polyolefins can have a molecular weight of 150 to 250k, such as 100k, 125k, 130k, 140k, 150k to 225k, 150k to 200k, 150k to 200k, etc. Low molecular weight polyolefins can have molecular weights in the range of 100k to 150k, such as 100k to 125k. Ultra-low molecular weight polyolefins can have molecular weights less than 100k. These values ​​are weight average molecular weights. In some embodiments, higher molecular weight polyolefins can be used to improve the strength or other properties of microporous multilayer membranes or batteries, including those described herein. In some embodiments, lower molecular weight polymers, such as medium, low, or ultra-low molecular weight polymers, can be beneficial.For example, without wishing to be bound by any particular theory, it is believed that the crystallization behavior of lower molecular weight polyolefins can result in microporous multilayer membranes with smaller pores resulting from at least one MD stretching process that forms the pores.

[0037] In some cases, the thermoplastic resin may include a non-polyolefin polymer. Exemplary non-polyolefin thermoplastic resins include, but are not limited to, polyacetal (or polyoxymethylene), polyamide, polyester, polysulfide, polyvinyl alcohol, polyvinyl ester, and polyvinylidene, such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF:HFP), polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and the like. Polyamides (nylons) include, but are not limited to, polyamide 6, polyamide 66, nylon 10,10, polyphthalamide (PPA), copolymers thereof, and blends thereof. Polyesters include, but are not limited to, polyester terephthalate, polybutyl terephthalate, copolymers thereof, and blends thereof. Polysulfides include, but are not limited to, polyphenyl sulfide, copolymers thereof, and blends thereof. Polyvinyl alcohols include, but are not limited to, ethylene vinyl alcohol, copolymers thereof, and blends thereof. Polyvinyl esters include, but are not limited to, polyvinyl acetate, ethylene vinyl acetate, copolymers thereof, and blends thereof. Polyvinylidenes include, but are not limited to, fluorinated polyvinylidenes (e.g., polyvinylidene chloride, polyvinylidene fluoride, etc.), copolymers thereof, and blends thereof. Various materials can be added to polymers. These materials are added to modify or enhance the performance or properties of individual layers or the entire membrane. Such materials include, but are not limited to, materials that can be added to lower the melting temperature of the polymer. For example, when the multilayer membrane is a battery separator, the multilayer membrane separator contains layers designed to close its pores at a predetermined temperature to block the flow of ions between the battery electrodes. This function is commonly referred to as shutdown.

[0038] In some embodiments, each layer or sublayer of a multilayer membrane comprises, consists of, or consists essentially of a different thermoplastic resin, polymer, or copolymer, or blend of polymers or copolymers. In some embodiments, each layer comprises, consists of, or consists essentially of the same thermoplastic resin, polymer, or copolymer, or blend of polymers or copolymers. In some embodiments, alternating layers of a multilayer microporous membrane or multilayer membrane comprise, consist of, or consist essentially of the same thermoplastic resin, polymer, or copolymer, or blend of polymers or copolymers. In other embodiments, some layers and / or sublayers of a multilayer membrane or multilayer microporous membrane comprise, consist of, or consist essentially of the same thermoplastic resin, polymer, or copolymer, or blend of polymers or copolymers, while some do not. In some embodiments, each layer or sublayer further comprises a first polymer. In other embodiments, the first polymer is present in some, but not all, of the layers or sublayers.

[0039] In some embodiments, a layer or sublayer of the multilayer film comprises, consists of, or consists essentially of a polyolefin (PO), such as, for example, PP, or PE, or a blend, mixture, or copolymer of PE+PP, and further comprises a first polymer (PY), additives, agents, materials, fillers, and / or particles (M), and / or the like that can be added or used and form a layer or microlayer of PP+PY, PE+PY, PP+M, PE+M, PP+PE+PY, PE+PP+M, PP+PY+M, PE+PY+M, PP+PE+PY+M, or blends, mixtures, copolymers, etc. thereof.

[0040] The same, similar, separate, or different PP or PE or PE+PP polymers, homopolymers, copolymers, molecular weights, blends, mixtures, copolymers, or the like can also be used. For example, the same, similar, separate, or different molecular weight PP, PE, and / or PP+PE polymers, homopolymers, copolymers, multipolymers, blends, mixtures, and / or the like can be used in each layer or sub-layer. Thus, the structure can include various combinations and sub-combinations of PP, PE, PP+PE, PP1, PP2, PP3, PE1, PE2, PE3, PP1+PP2, PE1+PE2, PP1+PP2+PP3, PE1+PE2+PE3, PP1+PP2+PE, PP+PE1+PE2, PP1 / PP2, PP1 / PP2 / PP1, PE1 / PE2, PE1 / PE2 / PP1, PE1 / PE2 / PE3, PP1+PE / PP2, or other combinations or structures.

[0041] Including the first polymer in an inner layer is beneficial because it avoids some of the problems associated with including the first polymer in an outer layer. For example, it has been found that including the first polymer in an outer layer can cause the film to become tacky, causing the film to stick to itself and negatively affecting pin removal force, an important property when the film is used as a battery separator. When used in an inner layer, more of the first polymer can be added to improve the film's physical properties without making the film too tacky. In some embodiments, the first polymer may be included in at least one outer layer, but in an amount that does not cause the film to become too tacky.

[0042] As described above, a multilayer film can include two outer layers (a first outer layer and a second outer layer) and one or more inner layers. In some cases, a multilayer film can include multiple inner layers. The inner layers can be mono-extruded or co-extruded layers. A laminate barrier can be formed between each inner layer and / or between each of the outer layers and one of the inner layers. A laminate barrier is formed when two surfaces, such as two surfaces of different films or layers, are laminated together using heat, pressure, or heat and pressure. In some embodiments, the layers of the film area have the following non-limiting structures of thermoplastic resins: PP, PE, PP / PP, PP / PE, PE / PP, PE / PE, PP / PP / PP, PP / PP / PE, PP / PP / PE, PP / PE / PP, PE / PP / PP, PP / PP / PP / PP, PP / PE / PE / PP, PP / PP / PP / PP, PP / PE / PE / PP, PE / PE / PP, PP / PP / PP / PP, PP / PE / PP / PP, PE / PE / PP / PP, PE / PP / PE / PP, PE / PP / PE / PP, PE / PP / PE / PP, PP / PE / PE / PE / PP, PE / PP / PP / PP / PE, PP / PP / PE / PP / PP, PE / PE / PP / PP / PE / PE, PP / PE / PP / PE / PP, PP / PP / PE / PE / PP / PP, PE / PE / PP / PP / PE / PE, PE / PP / PE / PP / PE / PP, PP / PE / PP / PE / PP / PE, PP / PP / PP / PE / PP / PP / PP, PE / PE / PE / PP / PE / PE / PE, PP / PE / PP / PE / PP / PE / PP, PE / PP / PE / PP / PE / PP / PE, PE / PP / PE / PP / PE / PP / PE / PP, PP / PE / PP / PE / PP / PE / PP / PE, PP / PP / PE / PE / PP / PP / PE / PE, PP / PE / PE / PE / PE / PE / PE / PP, PE / PP / PP / PP / PP / PP / PP / PE, PP / PP / PE / PE / PEPE / PP / PP, PP / PP / PP / PP / PE / PE / PE / PE, PP / PP / PP / PP / PE / PP / PP / PP / PP, PE / PE / PE / PE / PP / PE / PE / PE / PE, PP / PE / PP / PE / PP / PE / PP / PE / PP, PE / PP / PE / PP / PE / PP / PE / PP / PE, PE / PE / PE / PE / PE / PP / PP / PP / PP, PP / PP / PP / PP / PP / PE / PE / PE / PE, PP / PP / PP / PP / PP / PE / PE / PE / PE / PE,PE / PE / PE / PE / PE / PP / PP / PP / PP / PP, PP / PE / PP / PE / PP / PE / PP / PE / PP / PE, PE / PP / PE / PP / PE / PP / PE / PP / PP / PE / PP, PE / PP / PP / PP / PP / PP / PP / PP / PP / PP / PP / PP / PE, PP / PE / PE / PE / PE / PE / PE / PE / PE / PE / PE / PP, PP / PP / PE / PE / PE / PP / PP / PP / PP / PP / PP / PP, PE / PE / PE / PE / PE / PE / PE / PE / PE / PP / PP, PP / PP / PE / PP / PP / PP / PP / PP / PP / PP / PP / PE, PP / PP / PE / PP / PP / PP / PP / PP / PP / PP / PE, PP / PP / PP / PE / PP / PP / PP / PP / PP / PP / PE, PE / PE / PE / PP / PP / PP / PP / PP / PE / PE / PE / PP / PP. For purposes of presentation herein, PE refers to a single layer or sublayer within a multilayer film comprising, consisting of, or consisting essentially of PE. Similarly, PP refers to a single layer or sublayer within a multilayer film that comprises, consists of, or consists essentially of PP.

[0043] The PE or PP composition in each of the different layers can be the same or different from the PE or PP composition in the other layers. For example, the coextrusion precursor can have the structure (PP1 / PP2 / PP3), (PP3 / PP2 / PP1), (PP3 / PP3 / PP2 / PP1 / PP1), (PP3 / PP3 / PP2 / PP2 / PP1 / PP1), (PP3 / PP3 / PP3 / PP2 / PP2 / PP2 / PP1 / PP1 / PP1), etc. PP1 is made from homopolymer PP and additives for modifying the surface friction coefficient, including optional anti-slip or anti-block additives, such as polysiloxane or siloxane. PP2 can be made from the same or different PP homopolymer as PP1 and a copolymer of PP. The PP copolymer can be any propylene-ethylene or ethylene-propylene random copolymer, block copolymer, or elastomer. PP3 can be made from the same or a different homopolymer PP as PP1 and PP2, and further contains an additive to modify the surface coefficient of friction, which can be the same or different from that used in PP1. In other words, a multilayer film having the general structure PP / PE / PP / PE / PP can include PP1 / PE1 / PP2 / PE2 / PP3, where each PP layer has a different polypropylene structure than the other two PP layers, and similarly for the two PE layers.

[0044] In another embodiment, the coextrusion precursor can have the structure (PP1 / PP2 / PP3), (PP3 / PP2 / PP1), (PP3 / PP3 / PP2 / PP1 / PP1), (PP3 / PP3 / PP2 / PP2 / PP1 / PP1), (PP3 / PP3 / PP3 / PP2 / PP2 / PP2 / PP1 / PP1), (PP3 / PP3 / PP3 / PP2 / PP2 / PP1 / PP1 / PP1), etc. PP1 can be any polypropylene blend. PP2 can be made from any polypropylene block copolymer, including those described herein. PP3 can be made from the same or a different polypropylene block copolymer as used in PP2.

[0045] Individual layers of the multilayer film can include multiple sublayers and can be formed by coextrusion or bonding the individual sublayers to form the individual layers of the multilayer film. Using a multilayer film with a PP / PE / PP / PE / PP structure, each individual PP or PE layer can have two or more coextruded sublayers. For example, when each individual PP or PE layer includes three sublayers, each individual PP layer can be represented as PP = (PP1, PP2, PP3), and each individual PE layer can be represented as PE = (PE1, PE2, PE3). Thus, the PP / PE / PP / PE / PP structure can be represented as (PP1, PP2, PP3) / (PE1, PE2, PE3) / (PP1, PP2, PP3) / (PE1, PE2, PE3) / (PP1, PP2, PP3). The composition of each of the PP1, PP2, and PP3 sublayers can be the same, or each sublayer can have a different polypropylene composition from one or both of the other polypropylene sublayers. Similarly, the composition of each of the PE1, PE2, and PE3 sublayers can be the same, or each sublayer can have a different polyethylene composition than one or both of the other polyethylene sublayers. This principle applies to other multilayer membranes having more or fewer layers than the exemplary five-layer membrane described above.

[0046] The maximum average thickness of the film may be 50 microns, less than 40 microns, less than 30 microns, less than 25 microns, less than 20 microns, less than 19 microns, less than 18 microns, less than 17 microns, less than 16 microns, less than 15 microns, less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, or less than 2 microns. This is the thickness of the multilayer film or film before any coatings or treatments are applied.

[0047] The average thickness of a layer or sublayer may be less than 15 microns, less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, less than 1 micron, less than 500 nm, less than 400 nm, less than 300 nm, less than 200 nm, or less than 100 nm.

[0048] As used herein, microporous means having an average pore size of 2 microns or less, 1 micron or less, 0.9 microns or less, 0.8 microns or less, 0.7 microns or less, 0.6 microns or less, 0.5 microns or less, 0.4 microns or less, 0.3 microns or less, 0.2 microns or less, 0.1 microns or less, 0.09 microns or less, 0.08 microns or less, 0.07 microns or less, 0.06 microns or less, 0.05 microns or less, 0.04 microns or less, 0.03 microns or less, 0.02 microns or less, or 0.01 microns or less. In some embodiments, the pores can be formed by subjecting the precursor membrane to an expansion process, such as that performed in the Celgard® dry process.

[0049] In some embodiments, one or more layers of the multilayer membrane comprise, consist of, or consist essentially of microporous PE, and the average pore size of the PE layer is 0.03-1, 0.05-0.09, 0.05-0.08, 0.05-0.07, or 0.05-0.06.

[0050] In some embodiments, one or more layers of the multilayer film comprise, consist of, or consist essentially of microporous PP, and the average pore size of the PP layer is 0.02-0.06, 0.03-0.05, or even 0.04-0.05 or 0.03-0.04.

[0051] In examples where a multilayer microporous membrane or film includes a layer comprising, consisting of, or consisting essentially of PP and another layer comprising, consisting of, or consisting essentially of PE, the average pore size of the PP layer is smaller than that of the PE layer.

[0052] The porosity of the multilayer microporous membrane can be any porosity consistent with the goals of the present disclosure. For example, any porosity that can form an acceptable battery separator is acceptable. In some embodiments, the porosity of the membrane or membranes can be 10-80%, 10-60%, 20-60%, 30-60%, or 40-60%.

[0053] In addition to the thermoplastic resin, each layer or sublayer of the porous membrane can contain an incompatible first polymer, or the incompatible first polymer can be present in some, but not all, of the layers or sublayers. In other embodiments, the incompatible first polymer is present only in the inner layers or sublayers of the porous membrane. Incompatibility, when referring to polymer blends, is understood in the art. Incompatible polymer blends are heterogeneous. The morphology of an incompatible polymer blend depends on various factors, including the degree of dispersion of the two phases and the shape and size of the dispersed particles. These factors are determined by the rheological properties of the two components and the mixing conditions.

[0054] In some embodiments, the incompatible first polymer may be a copolymer. In a preferred embodiment, the copolymer is a block copolymer. Block copolymers generally contain two or more chains, known as "blocks," of different polymers chemically attached to one another. The properties of these polymers depend on the chemical composition of the blocks, the sequence of copolymer distribution in the polymer chain, and the molecular weight distribution of the blocks and copolymers. In some cases, the copolymers described herein contain two or more block systems with different physical properties. For example, in some embodiments, the block copolymers described herein contain one or more hard blocks and one or more soft blocks. The terms "hard" and "soft" refer to the relative elastic properties of the blocks. Generally, a "hard" block comprises a polymer or copolymer sequence that exhibits a harder structure at room temperature. In contrast, a "soft" block comprises a polymer or copolymer sequence that exhibits a higher elasticity at room temperature than the "hard" block. In other words, a hard block has a higher hardness than a soft block, as measured by Rockwell or Shore hardness testing.

[0055] The incompatible first polymer can be present in any layer or sublayer in any amount consistent with the objectives of the present disclosure. In some embodiments, any layer or sublayer of the porous membrane contains 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less of the first polymer. In some cases, any layer or sublayer of the porous membrane contains 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, or 15% or more of the first polymer. In some embodiments, the porous membrane is a tri-layer or multi-layer membrane, an inner layer or sublayer of the porous membrane contains 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, or 15% or more of the first polymer. In some embodiments, the outer layer contains 5% or less of the first polymer. While not wishing to be bound by any particular theory, it is believed that adding more than 5% to the outer layer may make the film sticky or increase the pin removal force too much, making the membrane undesirable for use as a battery separator in some applications.

[0056] In some embodiments, the block copolymer is a styrenic block copolymer, such as a hydrogenated styrenic block copolymer (HSBC). In some cases, the styrenic block copolymer has a two- or three-block structure, such as an AB, ABA, or BAB structure, where A is the hard block and B is the soft block. In some cases, the styrenic block copolymer has a styrenic hard block and a diene soft block. The styrenic block copolymer may have a hydrogenated two- or three-block styrenic copolymer, which exhibits elastomeric properties over a wide temperature range. Compared to non-hydrogenated styrenic block copolymers, hydrogenated styrenic block copolymers exhibit better tensile strength, better heat resistance, weather resistance, and ozone resistance, and better compatibility with polyolefins. Before processing, the polystyrene end blocks form hard domains that act as crosslinking points below the glass transition temperature (Tg) of the polystyrene, while the soft blocks provide elasticity. In the presence of heat and shear during processing, the polystyrene domains soften, allowing for flow. After cooling, the polystyrene domains reform and harden, locking the rubber network in place. This physical phenomenon gives the block copolymer its high tensile strength and elasticity. In some cases, due to its thermoplastic properties, styrene block copolymers are recyclable.

[0057] In some embodiments, styrene block copolymers enhance elongation properties when blended with thermoplastic resins such as polypropylene or polyethylene. The styrene block copolymers are incompatible with thermoplastic resins, meaning that they do not easily disperse within the thermoplastic resin during mixing. Instead, the styrene block copolymers separate and orient in the machine direction (MD) within the extruded film. In some embodiments, the styrene block copolymers form rod-like domains in the MD. In some cases, the styrene block copolymers maintain the same morphology after annealing the extruded film, and individual styrene block copolymers may melt together to form larger domains. In some cases where each layer contains three or more sublayers, the styrene block copolymers may form larger melted domains within the inner sublayers than within the outer sublayers.

[0058] Styrene block copolymers are 5-70%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42% The styrene block copolymer may have a total styrene content of 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, or 75%. The styrene block copolymer may have an A-type hardness of 30 to 98, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, 100, or greater than 100.

[0059] An example of a diblock (AB) styrene copolymer is shown in the following chemical formula (1), and examples of a triblock (ABA) styrene copolymer are shown in the following chemical formulas (2), (3), and (4).

[0060] [ka]

[0061] Examples of random block copolymers are shown in the following chemical formulas (5), (6), (7) and (8).

[0062] [ka]

[0063] In some embodiments, the first polymer is a polyethylene / poly(1-butylene) copolymer, a polyethylene / poly(1-hexene) copolymer, or a polyethylene / poly(1-octene) copolymer. These polymers may be random or block copolymers, or may be blocked polymers having polystyrene and polyethylene / poly(1-butene) copolymer components (e.g., SEBS). The polyethylene / poly(1-butylene) copolymer, polyethylene / poly(1-hexene) copolymer, or polyethylene / poly(1-octene) copolymer components have the advantage of the high interfacial adhesion of polypropylene, allowing for fine dispersion of the polymer. That is, these copolymer components are high molecular weight components that are oriented parallel to the MD direction of the microporous membrane. In other embodiments, the first polymer may be a block copolymer of styrene, ethylene, and propylene (e.g., SEP, SEPS, SEEPS, or SEEPS-OH). In some embodiments, the first polymer may be a block copolymer of styrene and butadiene (e.g., SBS) or a block copolymer of styrene and isoprene (e.g., SIS).

[0064] The glass transition temperature (Tg) of the incompatible first polymer is sometimes lower than that of the thermoplastic resin. Without wishing to be bound by any particular theory, it is believed that the combination of hard and soft blocks of the incompatible first polymer together dissipates energy and essentially acts as a shock absorber, resulting in improved puncture strength.

[0065] In some cases, porous membranes in which one or more layers or sublayers include a combination of a thermoplastic resin and an incompatible first polymer may have improved puncture strength compared to microporous membranes in which all sublayers or layers include only a thermoplastic resin. In some cases, porous membranes having layers or sublayers including the combination have puncture strengths increased by 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 20%, 21%, 23%, 25%, or more than 25% compared to porous membranes in which the incompatible first polymer is absent. In some embodiments, the porous membranes described herein have puncture strengths of 350 gf or greater, 360 gf or greater, 370 gf or greater, 380 gf or greater, 400 gf or greater, 410 gf or greater, 420 gf or greater, 430 gf or greater, 440 gf or greater, or 450 gf or greater. Puncture strengths are normalized to a thickness of about 14 microns. Normalization is necessary due to the fact that thicker but identical membranes have higher puncture strengths than thinner but identical membranes.

[0066] In some embodiments, the porous membranes described herein do not require a compatibilizer. As understood in the art, a compatibilizer is an ingredient or compound that can make incompatible polymers compatible.

[0067] The porous membranes described herein can further include a second polymer incompatible with the thermoplastic resin, where the second polymer is different from the first polymer. The second polymer can be a second copolymer, such as a second block copolymer. In some embodiments, the block copolymer includes one or more hard blocks and one or more soft blocks. The second polymer can be used in combination with the first polymer, for example, in the same layer or sublayer of the porous membrane as the first polymer. Alternatively, the second polymer can be used solely in combination with the thermoplastic resin in a layer or sublayer, where the second polymer is present in one or more layers or sublayers and the first polymer is present in one or more layers or sublayers. The second polymer can be any of the block copolymers described herein for the first polymer.

[0068] In some embodiments, the multilayer microporous membranes described herein may additionally include one or more additives in at least one layer of the multilayer microporous membrane. In some embodiments, at least one layer of the multilayer microporous membrane includes more than one additive, for example, two, three, four, five, or more. The additive may be present in one or both of the outermost layers of the multilayer microporous membrane, one or more inner layers, all inner layers, or both all inner and outermost layers. In some embodiments, the additive may be present in one or more outermost layers and one or more innermost layers. In such embodiments, the additive may be released from one or more outermost layers over time, and the additive supply in one or more outermost layers may be filled by migration of the additive from the inner layer to the outermost layer. In some embodiments, each layer of the multilayer microporous membrane may include a different additive or combination of additives than the conditioning layer or each layer of the multilayer microporous membrane.

[0069] In some embodiments, the additive comprises, consists of, or consists essentially of a functionalized polymer. As will be understood by those skilled in the art, a functionalized polymer refers to a polymer having a functional group attached to the polymer backbone. Exemplary functional groups include: In some embodiments, the functionalized polymer is a maleic anhydride functionalized polymer. In some embodiments, the maleic anhydride modified polymer is a maleic anhydride homopolymer polypropylene, copolymer polypropylene, high density polypropylene, low density polypropylene, ultra high density polypropylene, ultra low density polypropylene, homopolymer polyethylene, copolymer polyethylene, high density polyethylene, low density polyethylene, ultra high density polyethylene, or ultra low density polyethylene.

[0070] In some embodiments, the additive comprises, consists of, or consists essentially of an ionomer. As will be understood by those skilled in the art, an ionomer contains both ionic-containing repeating groups and non-ionic repeating groups. Sometimes, the ionic-containing repeating groups may be less than 25%, less than 20%, or less than 15% of the ionomer. In some embodiments, the ionomer may be a Li-based, Na-based, or Zn-based ionomer.

[0071] In some embodiments, the additive comprises cellulose nanofibers.

[0072] In some embodiments, the additive has inorganic particles with a narrow particle size distribution. For example, the difference in distribution between D10 and D90 is less than 100 nm, less than 90 nm, less than 80 nm, less than 70 nm, less than 60 nm, less than 50 nm, less than 40 nm, less than 30 nm, less than 20 nm, or less than 10 nm. In some embodiments, the inorganic particles are selected from at least one of SiO2, TiO2, or a combination thereof.

[0073] In some embodiments, the additive comprises, consists of, or consists essentially of a lubricant. The lubricants or lubricating oils described herein are not so limited. As will be understood by those skilled in the art, lubricants are compounds that function to reduce friction between a variety of different surfaces, including polymer:polymer; polymer:metal; polymer; organic materials; and polymer:inorganic materials. Specific examples of lubricants or lubricating oils described herein are compounds that contain siloxy functional groups, including siloxanes and polysiloxanes, and fatty acid salts containing metal stearates.

[0074] Compounds containing two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more siloxy groups can be used as lubricants as described herein. Siloxanes, as understood by those skilled in the art, are a class of molecules having a backbone of alternating silicon (Si) and oxygen (O) atoms, each of which may have attached hydrogen (H) or saturated or unsaturated organic functional groups, such as -CH or -CH. Polysiloxanes are polymerized siloxanes, typically with higher molecular weights. In some embodiments described herein, the polysiloxanes may have high molecular weights, such as ultra-high molecular weight polysiloxanes. In some embodiments, high molecular weight and ultra-high molecular weight polysiloxanes may have weight average molecular weights ranging from 500,000 to 1,000,000.

[0075] The fatty acid salts described herein are also not particularly limited and may be any fatty acid salt that functions as a lubricant. The fatty acid of the fatty acid salt may be a fatty acid having 12 to 22 carbon atoms. For example, the metal fatty acid may be selected from the group consisting of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, palmitoleic acid, behenic acid, erucic acid, and arachidic acid. The metal may be any metal consistent with the objectives of the present disclosure. In some cases, the metal is an alkali or alkaline earth metal, such as Li, Be, Na, Mg, K, Ca, Rb, Sr, Cs, Ba, Fr, and Ra. In some embodiments, the metal is Li, Be, Na, Mg, K, or Ca.

[0076] The fatty acid salt may be lithium stearate, sodium stearate, lithium oleate, sodium oleate, sodium palmitate, lithium palmitate, potassium stearate, or potassium oleate.

[0077] Lubricating oils containing the fatty acid salts described herein have melting points of 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, or 240°C or higher. For example, fatty acid salts such as lithium stearate (melting point 220°C) or sodium stearate (melting point 245-255°C) have such melting points. For example, fatty acid salts such as calcium stearate (melting point 155°C) do not. The inventors of the present application have found that calcium stearate may be less ideal from a processing standpoint than other fatty acid metal salts, such as metal stearates, which have higher melting points, especially at high loading levels. In particular, calcium stearate cannot be added in amounts greater than 800 ppm without causing wax separation and ubiquitous extrusion during the cooking process, a phenomenon known as "dusting." While not wishing to be bound by any particular theory, it is believed that using a fatty acid salt with a melting point above the cooking extrusion temperature solves this "dusting" problem. Fatty acid salts with higher melting points than calcium stearate, particularly those above 200°C, can be included in amounts greater than 1% or 1000 ppm without "chalking." Amounts of 1% or greater have been found to be important for obtaining desired properties such as improved wetting and improved pin removal.

[0078] In some embodiments, the additive may comprise, consist of, or consist essentially of one or more nucleating agents. As will be appreciated by those skilled in the art, in some embodiments, a nucleating agent is a material, an inorganic material, that aids, enhances, or promotes crystallization of a polymer, including a semi-crystalline polymer.

[0079] In some embodiments, the additive may comprise, consist of, or consist essentially of a cavitation promoter. As will be understood by those skilled in the art, a cavitation promoter is a material that forms, aids in, enhances, or promotes the formation of bubbles or voids in a polymer.

[0080] In some embodiments, the additive may comprise, consist of, or consist essentially of a fluoropolymer, which is not so limited and in some embodiments is PVDF.

[0081] In some embodiments, the additive may comprise, consist of, or consist essentially of a crosslinking agent.

[0082] In some embodiments, the additive may comprise, consist of, or consist essentially of an X-ray detectable material. The X-ray detectable material is not particularly limited and may be, for example, any of the materials disclosed in U.S. Pat. No. 7,662,510, the entire contents of which are incorporated herein by reference. Suitable amounts of X-ray detectable material or element are also disclosed in U.S. Pat. No. 7,662,510, but in some embodiments, up to 50 wt.%, up to 40 wt.%, up to 30 wt.%, up to 20 wt.%, up to 10 wt.%, up to 5 wt.%, or up to 1 wt.%, based on the total weight of the microporous membrane or membrane, may be used. In one embodiment, the additive is barium sulfate.

[0083] In some embodiments, the additive can comprise, consist of, or consist essentially of a lithium halide. The lithium halide can be lithium chloride, lithium fluoride, lithium bromide, or lithium iodide. The lithium halide can be lithium iodide, which is both ionically conductive and electrically insulating. In some cases, a material that is both ionically conductive and electrically insulating can be used as part of a battery separator.

[0084] In some embodiments, the additive comprises, consists of, or consists essentially of a polymer processing agent. As will be understood by those skilled in the art, polymer processing agents or additives are added to improve the processing efficiency and quality of polymer compounds. In some embodiments, the polymer processing agent is an antioxidant, stabilizer, lubricant, processing aid, nucleating agent, colorant, antistatic agent, polymerization agent, or filler.

[0085] In some embodiments, the additive comprises, consists of, or consists essentially of a high temperature melt index (HTMI) polymer, which may be any one selected from, without limitation, PMP, PMMA, PET, PVDF, aramid, syndiotactic polystyrene, and combinations thereof.

[0086] In some embodiments, the additive comprises, consists of, or consists essentially of an electrolyte additive. The electrolyte additives described herein are not particularly limited, so long as they are consistent with the goals of the electrolyte described herein. The electrolyte additive can be any additive typically added by battery manufacturers, particularly lithium battery manufacturers, to improve battery performance. The electrolyte additive must be compatible, e.g., miscible, with the polymer used in the polymeric microporous membrane or a polymer compatible with the coating slurry. Additive miscibility can be aided or improved by coating or partial coating of the additive. For example, exemplary electrolyte additives are disclosed in A Review of Electrolyte Additives for Lithium-Ion Batteries (J. of Power Sources, vol. 162, issue 2, 2006, pp. 1379-1394), the entire contents of which are incorporated herein by reference. In some embodiments, the electrolyte additive is at least one selected from the group consisting of a solid electrolyte interphase (SEI) improver, a cathode protectant, a flame retardant additive, a LiPF salt stabilizer, an overcharge protectant, an aluminum corrosion inhibitor, a lithium precipitation agent or improver, or a solvation promoter, an aluminum corrosion inhibitor, a wetting agent, and a thickener. In some embodiments, the additive can have more than one property, such as being a wetting agent and a thickener.

[0087] Exemplary SEI improvers include VEC (vinyl ethylene carbonate), VC (vinylene carbonate), FEC (fluoroethylene carbonate), and LiBOB (lithium bis(oxalato)borate). Exemplary cathode protectants include N,N'-dicyclohexylcarbodiimide, N,N-diethylaminotrimethylsilane, and LiBOB. Exemplary flame retardant additives include TTFP (tris(2,2,2-trifluoroethyl)phosphate), fluorinated propylene carbonate, and MFE (methyl nonafluorobutyl ether). Exemplary LiPF6 salt stabilizers include LiF, TTFP (tris(2,2,2-trifluoroethyl)phosphate), 1-methyl-2-pyrrolidinone, fluorinated carbamates, and hexamethylphosphoramide. Exemplary overcharge protectants include xylene, cyclohexylbenzene, biphenyl, 2,2-diphenylpropane, and phenyl-tert-butyl carbonate. Exemplary lithium deposition improvers include AlI3, SnI2, cetyltrimethylammonium chloride, perfluoropolyethers, and tetraalkylammonium chlorides with long alkyl chains. Exemplary ionic solvation promoters include 12-crown-4 and TFPPB (tris(pentafluorophenyl)). Exemplary Al corrosion inhibitors include LiBOB, LiODFB, e.g., borates, and the like. Exemplary wetting agents and viscosity reducers include cyclohexane and P2O5.

[0088] In some embodiments, the electrolyte additive is air stable or resistant to oxidation. Battery separators containing the electrolyte additives disclosed herein may have a shelf life of weeks to months, e.g., 1 week to 11 months.

[0089] In some embodiments, the additive comprises, consists of, or consists essentially of an energy-dissipating immiscible additive, meaning that the additive is not miscible with the polymers used to form the multi-layer microporous membrane or layers of the membrane containing the additive.

[0090] The multilayer film can be stretched in the machine direction to produce a multilayer microporous film. In some cases, the microporous film is produced by transverse stretching of an MD-stretched microporous film. In addition to sequential MD-TD stretching, the multilayer film can also undergo simultaneous biaxial MD-TD stretching. Furthermore, simultaneous or sequential MD-TD stretched microporous multilayer films can be followed by a calendaring step to reduce film thickness, decrease roughness, reduce % porosity, increase TD tensile strength, increase uniformity, and / or reduce TD tearing. In some embodiments, the multilayer film is TD stretched 1x, 2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x, 10x, or more than 10x.

[0091] In an embodiment, the multilayer membrane may be produced by exemplary processes including a post-stretching calendering process, e.g., after machine direction stretching and transverse direction stretching (with or without machine direction relaxation) to reduce the thickness of the thus stretched membrane, e.g., multilayer porous membrane, in a controlled manner, to reduce the % porosity of the thus stretched membrane, e.g., multilayer porous membrane, in a controlled manner, and / or to improve the strength, properties, and / or performance of such stretched membrane, e.g., multilayer porous membrane, in a controlled manner, such as the puncture strength, machine direction and / or transverse direction tensile strength, uniformity, wettability, coatability, runnability, compression, springback, tortuosity, permeability, thickness, pin removal force, mechanical strength, surface roughness, hot tip hole propagation, and / or combinations thereof, of such stretched membrane, e.g., multilayer porous membrane, and / or as a method for producing a unique structure, pore structure, material, membrane, base film, and / or separator.

[0092] In some cases, the TD tensile strength of a multilayer film can be further improved by adding a calendering step after TD stretching. The calendering process typically involves heat and pressure, which can reduce the thickness of the porous film. The calendering process can restore the loss of MD and TD tensile strength caused by TD stretching. Furthermore, the increase observed in MD and TD tensile strength by calendering can create a more balanced MD and TD tensile strength ratio, which can be beneficial to the overall mechanical performance of the multilayer film.

[0093] The calendering process selectively densifies the heat-sensitive material using uniform or non-uniform heat, pressure, and / or speed to impart uniform or non-uniform calendering conditions (e.g., by using smooth rolls, rough rolls, patterned rolls, micropatterned rolls, nanopatterned rolls, speed variations, temperature variations, pressure variations, humidity variations, double-roll processes, multiple-roll processes, or combinations thereof) to produce improved, desired, or unique structures, characteristics, and / or performance, and to create or control the resulting structures, characteristics, and / or performance. In some embodiments, calendering pressures of 50 to 200 psi may be used, along with calendering temperatures of 50 to 70°C and line speeds of 40 to 80 ft / min. Higher pressures can, in some cases, produce thinner separators, while lower pressures produce thicker separators.

[0094] In some embodiments, one or more coating layers can be applied to one or both sides of the multilayer membrane. In some embodiments, the one or more coatings can be a ceramic coating comprising, consisting of, or consisting essentially of a polymeric binder and organic and / or inorganic particles. In some embodiments, only the ceramic coating is applied to one or both sides of the microporous membrane. In other embodiments, a different coating can be applied to the microporous membrane before or after application of the ceramic coating. Different additional coatings can also be applied to one or both sides of the membrane or film. In some embodiments, the different polymer coating layers can comprise, consist of, or consist essentially of at least one of polyvinylidene fluoride (PVdF) or polycarbonate (PC).

[0095] In some embodiments, the coating layer has a thickness of 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.

[0096] 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 coating methods: extrusion coating, roll coating, gravure coating, printing, knife coating, air knife coating, spray coating, dip coating, or curtain coating. The coating method can be performed at room temperature or at an elevated temperature.

[0097] The coating layer may be non-porous, nanoporous, microporous, mesoporous, or macroporous. The coating layer may have a JIS Gurley of 700 or less, sometimes 600 or less, 500 or less, 400 or less, 300 or less, 200 or less, or 100 or less.

[0098] One or more layers, treatments, materials, or coatings (CT), and / or nets, meshes, mats, wovens, or nonwovens (NW) can be added onto or within one or both sides of the multilayer films or membranes (M) described herein, including, but not limited to, CT / M, CT / M / CT, NW / M, NW / M / NW, CT / M / NW, CT / NW / M / NW / CT, CT / M / NW / CT, etc.

[0099] II. Battery Separator In another embodiment, a battery separator comprises a porous membrane as described in Section I herein. The multilayer membrane itself, i.e., without any coatings or other additional components, exhibits the improved properties described above. The performance of the porous membrane can be further improved by the addition of selective coatings or other additional components to one or both sides of the membrane, or by the MD, MD-TD, or MD-TD stretching and calendering described.

[0100] III. Secondary battery In some aspects, a secondary battery includes a battery separator described in Section II of this specification. The secondary battery may exhibit improved properties compared to conventional secondary batteries. In some embodiments, the secondary battery is a lithium ion battery.

[0101] IV. Method for fabricating multilayer films The porous membrane according to Section I of this specification can be produced in the form of a film using a single extrusion device, a coextrusion device, or a lamination device. In one example, two or more layers of a resin composition having a specific component are laminated to form a raw film, and then two or more layers of the multilayer film are stretched to form holes to produce a porous membrane. In another example, at least one porous film containing a polypropylene resin as a main component and at least one porous film containing a polyethylene resin as a main component are laminated to form a raw film, and then two or more layers of the multilayer film are stretched to form holes to produce a porous membrane. In some cases, it is easier to obtain a porous membrane with higher strength by first laminating two or more layers of film to form a raw film, and then stretching the film to form holes to produce a porous membrane, rather than using a single-layer film to form a raw film and then stretching the film to form holes. From this perspective, in the case of a multilayer film having multiple polyolefin-based porous layers laminated thereto, it is preferable that three or more polyolefin-based porous layers are laminated, more preferably at least two porous layers (PP porous layers) containing polypropylene resin as a main component and at least one porous layer (PE porous layer) containing polyethylene resin as a main component are laminated thereto, and even more preferable is a three-layer film laminated in the order of PP porous layer / PE porous layer / PP porous layer. As mentioned above, each PP and PE layer can also contain an incompatible first polymer, even within a PP or PE layer or within a sublayer of a PP or PE layer. In some embodiments, the incompatible first polymer can be present in some, but not all, PP or PE layers or sublayers.

[0102] The method for producing the multilayer film that multiple polyolefin-based porous layers are laminated, or the method for producing the composite porous film that has polyolefin-based porous film and other resin porous film can adopt, for example, the method that each layer adheres to each other by co-extrusion, the lamination method that each layer is extruded separately and then adheres to each other, etc. As lamination method, both the dry lamination method that uses adhesive and the heat lamination method that applies heat to adhere multiple layers can be adopted.

[0103] The porous membrane is preferably produced by a dry stretching process in which the film is melt-kneaded in an extruder without using a solvent, then directly stretched to orient it, followed by an annealing step, a cold stretching step, and a hot stretching step in that order. Methods such as a circular die extrusion method in which a molten resin is extruded and then stretched to orient the resin may also be used. The circular die extrusion process is particularly preferred because it allows the membrane to be produced in the form of a thin film. The dry stretching method, particularly the method of orienting lamellar crystals and then opening holes by interfacial peeling of the crystals, is preferred because it facilitates the alignment of pores compared to wet methods, and the porous membrane obtained by this method can exhibit low air resistance related to porosity.

[0104] The perforation by stretching the film will be described in more detail. The monolayer or multilayer raw material film described above is subjected to a stretching treatment. Uniaxial stretching (MD stretching) can be used as the stretching state. The stretching temperature can be appropriately adjusted according to the processing characteristics of the microporous membrane layer (a) of polypropylene resin or the microporous membrane layer (b) of polyethylene resin, and also according to the type of voids formed in each layer. By such a stretching treatment, voids are formed in both the microporous membrane layer (a) of polypropylene resin and the polyethylene layer (b). Here, mechanisms (methods) for providing voids include, for example, a method of opening pores at the interface of lamellar crystals. Methods for perforating the crystal interface include, for example, melt-extruding a crystalline resin such as polyethylene with a high drawdown ratio, annealing the precursor film at a temperature range of 5 to 50°C lower than the crystalline melting point of the crystalline resin to form an annealed precursor film, uniaxially cold-stretching the annealed precursor film at a temperature range of -20°C to 70°C by a factor of 1.1 to 2, and then uniaxially stretching the annealed precursor film at a temperature range of 5 to 50°C lower than the crystalline melting point of the crystalline resin by a factor of 1.5 to 5 (i.e., providing voids in the film) to obtain a porous film, thereby producing a precursor film.

[0105] Polyolefin resin compositions containing a polyolefin resin and a desired incompatible first polymer can be produced by melt blending, for example, using a single-screw or twin-screw extruder. Relatively high shear strength and relatively high temperature are required to efficiently disperse the incompatible first polymer within the high molecular weight polyolefin resin. Chemical incompatibility between the first polymer and the polyolefin resin results in the first polymer blended and dispersed in the polyolefin resin with a non-uniform distribution, rather than a uniform distribution, forming distinct rod-like domains oriented in the MD.

[0106] The resulting resin composition is preferably used to produce a microporous membrane by a dry process. Dry processes include melt-extrusion of a polyolefin resin composition followed by direct die extrusion to form a highly oriented film, or circular die extrusion to form a highly oriented film, followed by annealing the raw film, cold stretching to create micropores, and hot stretching to separate the polyolefin lamellar crystal interfaces. In the circular die extrusion process, for example, a melt-extruded polypropylene resin composition is blown up through a circular die in the MD direction and wound up through a guide plate and nip rolls to obtain a highly crystalline, highly MD-oriented raw film. Furthermore, dry processes may use nucleating agents or pore-forming agents to form pores, but oils and solvents cannot be used. An exemplary dry process of this type is the beta-nucleation biaxial stretching process. Wet methods include a method in which a polyolefin resin composition and a pore-forming material such as oil or a solvent are kneaded and melted, and then stretched as necessary to form a sheet, from which the nucleation material is extracted; and a method in which a polyolefin resin composition is dissolved and then immersed in a poor solvent for the polyolefin, in which the polyolefin is solidified and the solvent is removed at the same time.

[0107] In addition to the incompatible first and / or second polymers, the polyolefin resin composition may contain additives other than polyolefin resins. Examples of additives include fluorine-based flow improvers, waxes, crystal nucleation materials, antioxidants, metal soaps such as metal salts of aliphatic carboxylic acids, UV absorbers, light stabilizers, antistatic agents, antifogging agents, and color pigments. Melting and kneading of the polyolefin resin composition can be carried out using a single- or twin-screw extruder, as well as a kneader, lab plastomill, kneading rolls, Banbury mixer, and the like. Furthermore, a direct mixing method can also be used, in which the resin composition is melt-mixed in the extruder and then directly formed into a film. Examples of useful plasticizers include hydrocarbons such as liquid paraffin and paraffin wax, esters such as dioctyl phthalate and dibutyl phthalate, and higher alcohols such as oleic alcohol and stearic alcohol.

[0108] The pore formation process can be carried out by known methods, such as dry or wet methods. In a dry stretching process, such as the Celgard® dry stretching process, pores can be formed in a cold stretching step and then opened in a subsequent stretching step. Alternatively, in a dry process using a nucleating or pore-forming agent, pores can be formed via the nucleating or pore-forming agent and then opened by stretching. In a wet process, pores can be formed during oil or solvent extraction. The stretching process can be carried out by uniaxial or biaxial stretching, but is preferably carried out by at least MD stretching. When the membrane is stretched in one direction, the other direction can be unconstrained or fixed at a fixed length.

[0109] To suppress shrinkage of the microporous membrane, heat treatment can be performed either after stretching or after pore formation to induce heat setting. Heat treatment can include a stretching operation performed at a predetermined temperature and a predetermined stretching degree to suit the physical properties, and / or a relaxation operation performed at a predetermined temperature and a predetermined relaxation degree to reduce stretching stress. The relaxation operation can also be performed after the stretching operation. Heat treatment can be performed using a tenter or roll stretching machine. A method for producing a microporous membrane using the dry lamellar pore-opening method is described as an example. In the dry lamellar pore-opening method, a non-porous precursor in which numerous lamellar structures are bonded via tie molecules is stretched to cleave the lamellar interfaces, thereby forming pores without using solvents such as water or organic solvents.

[0110] The dry lamellar pore-forming method involves (i) extruding a nonporous precursor (highly oriented material film) formed from a resin composition containing a polyolefin and a desired incompatible first polymer, (ii) annealing, and (iii) uniaxially stretching the extruded nonporous precursor to form pores. Stretching can also be biaxial. Furthermore, microporous films produced by the dry lamellar pore-forming method and the process comprising (i), (ii), and (iii) can also be functionalized after the coating, dipping, or impregnation steps.

[0111] Step (i) can be carried out by a conventional extrusion method (single-screw or twin-screw extrusion method). The extruder can be equipped with a T-die or a circular die having an elongated hole. The uniaxial stretching in step (iii) can be carried out by the method described above. The machine direction (MD) stretching can include both cold stretching and hot stretching. To suppress internal strain in the non-porous precursor, the non-porous precursor can be annealed during step (i), after step (iii), or before stretching in step (iii). Annealing can be carried out, for example, at a temperature between 50°C lower than the melting point of the polypropylene resin (A) and 10°C lower than the melting point of the polypropylene resin (A), or at a temperature between 50°C lower than the melting point of the polypropylene resin (A) and 15°C lower than the melting point of the polypropylene resin (A).

[0112] Some embodiments described herein are further illustrated in the following non-limiting examples.

[0113] Example Unless otherwise specified, all microporous membranes were formed using the same dry-stretching process, which included at least the extrusion, annealing, and stretching steps. The lamination step described below occurs after extrusion but before annealing. Figure 7 shows a schematic diagram of a membrane in which a block copolymer, such as a styrenic block copolymer, is added to a PP layer. While the membrane shown in Figure 7 is a coextruded trilayer, it may also be a coextruded bilayer or a coextruded multilayer with four or more coextruded layers.

[0114] The microporous membranes may be used as separators, fabrics, filters, components of personal protective equipment materials, or the like.

[0115] Fabrication of controlled multilayer microporous membranes A controlled multilayer microporous membrane (control example) with a (PP1 / PP1 / PP1) / (PE1 / PE1 / PE1) / (PP1 / PP1 / PP1) structure was prepared by coextruding PP1 to create a coextruded trilayer (PP1 / PP1 / PP1) and coextruding PE1 to form a coextruded trilayer of (PE1 / PE1 / PE1). The two coextruded trilayers of (PP1 / PP1 / PP1) were then laminated to a single coextruded trilayer (PE1 / PE1 / PE1) to form a (PP1 / PP1 / PP1) / (PE1 / PE1 / PE1) / (PP1 / PP1 / PP1) structure. Each of the three sublayers in the coextruded trilayer (PP1 / PP1 / PP1) contained the same polypropylene composition. The three sublayers in the PE layer contained the same polyethylene composition.

[0116] Preparation of the multilayer microporous membrane of the present invention A multilayer microporous membrane (Comp1) of the present invention having a structure of (PP2 / PP2 / PP2) / (PE1 / PE1 / PE1) / (PP2 / PP2 / PP2) was prepared by coextruding PP2 to create a coextruded trilayer (PP2 / PP2 / PP2) and coextruding PE1 to form a coextruded trilayer of (PE1 / PE1 / PE1). The two coextruded trilayers of (PP2 / PP2 / PP2) were then laminated to a single coextruded trilayer (PE1 / PE1 / PE1) to form a (PP2 / PP2 / PP2) / (PE1 / PE1 / PE1) / (PP2 / PP2 / PP2) structure. Each of the three sublayers in the coextruded trilayer (PP2 / PP2 / PP2) contained the same polypropylene composition. PP2 was identical to PP1, except that 5% of the composition of PP1 was replaced with a styrenic block copolymer that is incompatible with the PP1 composition. The three sublayers in the PE layer contained the same polyethylene composition.

[0117] Both the control example and Example 1 were formed using a dry process that included extrusion (coextrusion), lamination (of the coextruded layers), annealing, and stretching. No oil or solvent was used.

[0118] The physical properties of the membranes of the control example and Example 1 are shown in Table 1. As shown, the puncture strength of the membrane of Example 1 was nearly 20% higher than that of the membrane of the control example. In addition, although the pore size of the PE layer (PE1 / PE1 / PE1) in the control example was larger than that of the PP layer (PP1 / PP1 / PP1 or PP2 / PP2 / PP2), the membrane of Example 1 showed a reduced pore size difference between the PE layer and sublayer and the PP layer and sublayer.

[0119] [Table 1]

[0120] Example 2 Transmission electron microscopy of microporous films during annealing Transmission electron microscope (TEM) images were obtained at each processing stage of Example 1. Figure 1 shows a TEM image of Example 1 after (PP2 / PP2 / PP2) trilayer coextrusion, cross-sectioned along the MD. As shown, domains of the incompatible styrenic block copolymer separate within the extruded film and orient toward the MD, as evidenced by the dark rod-like domains extending toward the MD.

[0121] Figure 2 shows the morphology of Example 1 after annealing for 10 minutes at 120°C. As shown, the morphology of the styrenic block copolymer domains remains substantially unchanged in the PP layer.

[0122] Each PP layer in Example 1 includes three coextruded sublayers, designated PP2 in the coextruded trilayer PP2 / PP2 / PP2. Interestingly, the morphology of the styrenic block copolymer in each sublayer is different. As shown in the enlarged view in Figure 3 and the different cross-sectional views in Figure 4, the styrenic block copolymer in the outermost PP2 sublayer and the central PP2 sublayer still form rod-like domains, while the styrenic block copolymer in the central PP2 sublayer displays larger domains that are aggregates of smaller domains that have fused together after the annealing process.

[0123] Example 3 Transmission electron microscopy of microporous membranes during stretching TEM images were obtained of the cross section of the microporous membrane after stretching the annealed membrane of Example 2. As shown in Figure 5, the rod-like styrenic block copolymer domains are present only within the PP lamellae, but not in the interlamellar regions.

[0124] Figures 6A and 6B show TEM images of this product in the PP layer. It is believed that the disrupted domains A and B of the styrenic block copolymer on the lamella surface may contribute to the improved puncture strength by acting as shock absorbers when the membrane is compressed or stretched during puncture. During these events, the interlamellar spaces may be compressed, causing the crystalline PP lamellae to come into contact with each other. In the absence of the styrenic block copolymer, such contact would cause the crystalline PP lamellae to break, resulting in membrane failure, i.e., small holes. The presence of the styrenic block copolymer domains on the outer surface can absorb some of the force, rather than the crystalline PP lamellae, preventing membrane failure.

[0125] Example 4 Microporous membrane deformation In a variation of Example 1 described above, an embodiment (Example 2) similar to Example 1 was formed, except that the PP layers had a composition of PP2 / PP3 / PP3, and the final structure had the composition (PP2 / PP3 / PP3) / (PE1 / PE1 / PE1) / (PP3 / PP3 / PP2). In this embodiment, PP2 and PE1 were as described above in Example 1. PP3 was similar to PP2, except that 8% of the PP3 was replaced with a styrenic block copolymer.

[0126] In another variation of Example 1 above, an embodiment (Example 3) similar to Example 1 was formed, except that the PP layers had the composition PP2 / PP4 / PP4, and the final structure had the composition (PP2 / PP4 / PP4) / (PE1 / PE1 / PE1) / (PP4 / PP4 / PP2). In this embodiment, PP2 and PE1 were as described above in Example 1. PP4 was similar to PP2, except that 10% of the PP4 was replaced with a styrenic block copolymer.

[0127] In another variation of Example 1 above, an embodiment (Example 4) similar to Example 1 was formed, except that the PP layers had the composition PP2 / PP4 / PP4 and the final structure had the composition (PP2 / PP5 / PP5) / (PE1 / PE1 / PE1) / (PP5 / PP5 / PP2). In this embodiment, PP2 and PE1 were as described above in Example 1. PP5 was similar to PP2, except that 20% of the PP5 was replaced with a styrenic block copolymer.

[0128] In another variation, an embodiment similar to the control example (Example 5) was formed, except that the PE layers had the composition PE2 / PE2 / PE2 and the final structure had the composition (PP1 / PP1 / PP1) / (PE2 / PE2 / PE2) / (PP1 / PP1 / PP1). In this embodiment, PP1 was as described above in Example 1, and PE2 was similar to PE1, except that 10% of the composition was replaced with a styrenic block copolymer.

[0129] In another variation, a trilayer was formed having the structure PP1 / PE2 / PP1. The trilayer may be coextruded (Example 6) or laminated (Example 7). PP1 and PE2 are as described herein.

[0130] In another variation, a three-layer PP2 / PE1 / PP2 was formed. The three layers may be coextruded (Example 8) or laminated (Example 9). PP2 and PE1 are as described herein.

[0131] Another variation is an inverse tri-layer PE1 / PP3 / PE1. The tri-layers may be coextruded (Example 10) or laminated (Example 11). PE1 and PP3 are as described herein.

[0132] Another variation is an inverse tri-layer PE2 / PP1 / PE2. The tri-layers may be coextruded (Example 12) or laminated (Example 13). PE2 and PP1 are as described herein.

[0133] In another variation, a multilayer structure (PP1 / PP2 / PP2) / (PE2 / PE2 / PE2) / (PP2 / PP2 / PP1) was formed: two coextruded trilayer (PP1 / PP2 / PP2) films were laminated with one laminated trilayer (PE2 / PE2 / PE2) film to form the structure.

[0134] In another variation, bubble extrusion of PP1 / PP2 / PE2 was used to form the structure PP1 / PP2 / PE2 / PE2 / PP2 / PP1. The bubble is collapsed onto itself in a process called "collapse bubble," forming a bond between the two PE2 inner layers of the bubble.

[0135] In any of the above examples where a styrenic block copolymer is used in the inner layer, the styrenic block copolymer can be replaced with an ethylene-butene copolymer, etc. Also, ethylene-butene can be replaced with a styrenic block copolymer in the PE-containing layer.

Claims

1. a thermoplastic resin and a first polymer that is incompatible with the thermoplastic resin; and at least one inner layer comprising the first polymer is at least one of polyethylene-polybutylene (C2-C4), polyethylene-polypropylene (C2-C3), polyethylene-polypentene (C2-C5), polyethylene-polyhexene (C2-C6), polyethylene-polyheptene (C2-C7), polyethylene-polyoctene (C2-C8), polyethylene-polynonene (C2-C9), and polyethylene-polydecene (C2-C10) block copolymers; The multilayer porous membrane wherein the inner layer has a thickness of 0.1 to 10 microns, 0.1 to 5 microns, 0.1 to 4 microns, 0.1 to 3 microns, 0.1 to 2 microns, 0.1 to 1 micron, or 0.1 to 0.5 microns.

2. The multi-layer porous membrane of claim 1 , wherein the thermoplastic resin is a polyolefin.

3. The multi-layer porous membrane of claim 2 , wherein the polyolefin comprises polypropylene, polyethylene, a mixture thereof, a copolymer thereof, or a terpolymer thereof.

4. The multi-layer porous membrane of claim 1 , wherein the block copolymer comprises one or more hard blocks and one or more soft blocks.

5. The block copolymer has the following chemical structure: In the following chemical formula, R is an aromatic or non-aromatic C5-C10 ring, x is greater than 1, and y is greater than 1: The multilayer porous membrane of claim 4. [CH2-CHR]x-[soft block]y

6. 10. The multi-layer porous membrane of claim 1, wherein said at least one inner layer comprises said first polymer in an amount of 1 wt % or greater.

7. 10. The multi-layer porous membrane of claim 1, wherein said at least one inner layer comprises said first polymer in an amount of 3 wt% or greater.

8. 10. The multi-layer porous membrane of claim 1, wherein said at least one inner layer comprises said first polymer in an amount of 5 wt% or greater.

9. 10. The multi-layer porous membrane of claim 1, wherein said at least one inner layer comprises said first polymer in an amount of 10 wt% or greater.

10. 10. The multi-layer porous membrane of claim 1, wherein the glass transition temperature (Tg) of the first polymer is lower than the glass transition temperature of the thermoplastic resin.

11. The multi-layer porous membrane of claim 1 , wherein the multi-layer porous membrane is a dry-process porous membrane.

12. 7. The multilayer porous membrane of claim 6, wherein the multilayer porous membrane has a puncture strength of 350 gf or more, 360 gf or more, 370 gf or more, or 380 gf or more, based on a thickness of 14 microns.

13. The multilayer porous membrane according to any one of claims 1 to 12, wherein the multilayer porous membrane does not contain a compatibilizer that compatibilizes the first polymer in the thermoplastic resin.

14. The outer layer of the multilayer porous membrane also comprises a thermoplastic resin, a first polymer incompatible with the thermoplastic resin, and Including, the thermoplastic resin and the first polymer of the outer layer are the same as or different from the thermoplastic resin and the first polymer in the inner layer; The multilayer porous membrane according to any one of claims 1 to 12.

15. 15. The multi-layer porous membrane of claim 14, wherein the amount of the first polymer in the outer layer is less than the amount of the first polymer in the inner layer.

16. 16. The multi-layer porous membrane of claim 15, wherein the amount of the first polymer in the outer layer is less than 10 wt%, less than 7 wt%, less than 5 wt%, or less than 3 wt%.

17. The multilayer porous membrane according to any one of claims 1 to 12, a coating on one or both sides of the multilayer porous membrane; A battery separator comprising:

18. A secondary battery comprising the battery separator according to claim 17.

19. at least one layer containing polyethylene and a polymer incompatible with polyethylene; 10. A porous membrane, wherein the polymer is at least one of polyethylene-polybutylene (C2-C4), polyethylene-polypropylene (C2-C3), polyethylene-polypentene (C2-C5), polyethylene-polyhexene (C2-C6), polyethylene-polyheptene (C2-C7), polyethylene-polyoctene (C2-C8), polyethylene-polynonene (C2-C9), and polyethylene-polydecene (C2-C10) block copolymers.

20. 20. The porous membrane of claim 19, wherein the at least one layer comprising polyethylene and a polymer that is incompatible with polyethylene is an inner layer or an outer layer.

21. 21. The porous membrane of claim 20, wherein the layer is an inner layer and the amount of the incompatible polymer is greater than 1 wt%, greater than 3 wt%, greater than 5 wt%, greater than 7 wt%, greater than 10 wt%, greater than 15 wt%, or greater than 20 wt%.

22. 21. The porous membrane of claim 20, wherein the layer is an outer layer and the amount of the incompatible polymer is less than 10 wt%, less than 7 wt%, less than 5 wt%, less than 3 wt%, or less than 1 wt%.

23. 20. The porous membrane of claim 19, wherein the porous membrane is a single layer, a double layer, a triple layer, or a multilayer membrane.

24. A battery separator comprising the porous membrane according to any one of claims 19 to 23, wherein the porous membrane is coated on at least one side.

25. A secondary battery comprising the battery separator of claim 24.

26. A fabric, filter or material for personal protective equipment comprising the porous membrane of any one of claims 1 to 16.

27. A fabric, filter or material for personal protective equipment comprising the porous membrane of any one of claims 19 to 23.

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