Coated separators including at least one adhesive

Abstract

A coated separator includes a microporous polyolefin base membrane having a first base surface and a second base surface opposite the first base surface. The coated separator includes a first inorganic coating disposed on at least a portion of the first base surface and, optionally, a second inorganic coating disposed on at least a portion of the second base surface. Each of the first inorganic coating and the optional second inorganic coating includes a plurality of inorganic particles. The coated separator also includes a first adhesive coating disposed on at least a portion of the first inorganic coating and, optionally, a second adhesive coating disposed on at least a portion of the optional second inorganic coating. Each adhesive coating includes at least one adhesive.

Description

COATED SEPARATORS INCLUDING AT LEAST ONE ADHESIVERELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application No. 63 / 578,107, filed on August 22, 2023, and titled COATED SEPARATORS INCLUDING AT LEAST ONE ADHESIVE, which is incorporated herein by reference in its entirety.COPYRIGHT NOTICE

[0002] © 2024 Amtek Research International LLC. A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 37 CFR § 1.71(d).BACKGROUND

[0003] Separators are an integral part of the performance and safety of lithium-ion and rechargeable lithium metal batteries. During normal operation, the separator’s role is to prevent electronic conduction (i.e., shorts or direct contact) between the anode and cathode while permitting ionic conduction via the electrolyte. Nearly all lithium-ion battery separators contain polyethylene as part of a single- or multi-layer construction so that shutdown begins at ~130°C, near the melting point of polyethylene.

[0004] Large format lithium-ion cells designed for electric vehicle applications typically require heat-resistant ceramic coating layers to be applied to the base separator. The main reasons for applying ceramic coatings to the base separator are to 1) improve the safety of the battery by reducing shrinkage in the plane of the separator (mitigating the potential for direct contact between anode and cathode due to separator shrinkage); 2) improve voltage oxidation resistance, thus allowing for battery designs with higher energy density and extended cycle life; and 3) improve wetting of the interface between the separator and the electrodes.

[0005] In certain cell designs, an adhesive coated separator is required to laminate to electrodes. Benefits of applying an adhesive to the separator include faster material handling, faster wind speed during cell assembly, and more intimate contact between the separator and electrodes.

[0006] New electrode chemistries and cell designs require advanced coated separators with thermal stability, ability to laminate to electrodes with higher lamination strength than conventional laminable separators, while still maintaining low impedance to allow for lithium ions to pass through the separator. The uniqueness of this work lies in the ability to provide exceptional safety features, excellent rate performance, and superior ability to laminate to electrodes using water-based coating formulations.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The drawings illustrate several embodiments of the present disclosure, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings.

[0008] FIG. 1 is a cross-sectional schematic of a coated separator for an energy storage device, according to an embodiment.

[0009] FIGS. 2A and 2B illustrate an exemplary dip-coating process used to form the coating separator, according to an embodiment.

[0010] FIG. 3 illustrates an exemplary dip-coating process that combines the two-step process illustrated in FIGS. 2A and 2B into a single step.DETAILED DESCRIPTION

[0011] Embodiments disclosed herein relate to coated separators for energy storage devices, energy storage devices including the same, and methods of making the same. An exemplary coated separator includes a microporous polyolefin base membrane having a first base surface and a second base surface opposite the first base surface. The coated separator includes a first inorganic coating disposed on at least a portion of the first base surface and, optionally, a second inorganic coating disposed on at least a portion of the second base surface. Each of the first inorganic coating and the second inorganic coating includes a plurality of inorganic particles. The coated separator also includes a first adhesive coating disposed on at least a portion of the first inorganic coating and, optionally, a second adhesive coating disposed on at least a portion of the optional second inorganic coating. In other words, the coated separator may comprise a 3-layer or 5-layer coated separator. The adhesive coating includes at least one adhesive.

[0012] The coated separators may exhibit one or more properties that make the coated separators effective separators for batteries, such as lithium-ion batteries. As an example, prior to lamination, the coated separator may exhibit a free-standing machine and a transversedirection shrinkage of about 5% or less in each direction (e.g., machine direction and transverse direction) after exposure to a temperature of 180 °C. As another example, the coated separator may exhibit a lamination strength, tested using a 180° peel test at room temperature (i.e., 23° C), of about 75 gf / 25 mm or greater. As used herein, lamination strength may refer to the strength of the coated separator laminated to itself after laminating at 80 °C and 1.4 MPa for 20 seconds. In another example, the coated separator may exhibit a Gurley number of about 250 s / 100 cc air or less. In another example, the coated separator may exhibit a MacMullin number of 9 or less. In yet another example, the coated separator may exhibit two or more of the properties listed above. In still another example, the coated separator may exhibit each of the properties listed above.

[0013] The coated separator may be formed using any suitable technique. In an example, a microporous polyolefin base membrane (e.g., pre-manufactured separator membrane) may be provided or formed. The pore size range for microporous membranes is generally from about 10 nanometers to several microns, with an average pore size less than about 1 micrometer. Such membranes are generally opaque because the pore size and polymer matrix are of sufficient size to scatter visible light. The term “microporous membrane” as used, is inclusive of other descriptions used in the scientific and patent literature such as “microporous films,” “microporous sheets,” and “microporous webs.” The microporous polyolefin membranes can also exhibit free-standing properties, and have interconnected pores that extend throughout the membrane. “Free-standing” refers to a membrane having sufficient mechanical properties that permit manipulation such as winding and unwinding in sheet form for use in an energy storage device assembly.

[0014] The microporous polyolefin base membrane includes the first base surface and the second base surface. A first aqueous-based dispersion may be disposed on at least a portion of at least the first base surface. The first aqueous-based dispersion includes a plurality of inorganic particles. The first aqueous-based dispersion on the first base surface may be dried to form the first inorganic coating. A second aqueous-based dispersion may then be disposed on at least a portion of the first inorganic coating. The second aqueous-based dispersion includes at least one adhesive. The second aqueous-based dispersion may be dried to form the first adhesive coating.

[0015] In a particular embodiment, the first aqueous-based dispersion may be disposed on the first base surface substantially simultaneously with disposing the first aqueous-based dispersion on the second base surface. For example, the microporous polyolefin base membrane may be dip coated in or otherwise move through the first aqueous-baseddispersion thereby disposing the first aqueous-based dispersion on both the first and second base surfaces. The first aqueous-based dispersion may thereafter be dried to form the first and second inorganic coatings. Similarly, in a particular embodiment, the second aqueousbased dispersion may be disposed on the first and second inorganic coatings substantially simultaneously. For example, the coated microporous polyolefin base membrane including the first and second inorganic coatings may be dip coated in or otherwise move through the second aqueous-based dispersion thereby disposing the second aqueous-based dispersion on both of the first and second inorganic coatings. The second aqueous-based dispersion on the second inorganic coating may thereafter be dried to form the first and second adhesive coatings.

[0016] The coated separators disclosed herein are an improvement over the conventional coated separators. For example, separators used in batteries need to exhibit good melt integrity, good temperature dimensional stability, and the ability to laminate to electrodes, among other properties. At least some conventional separators used in batteries are unable to exhibit these properties. For example, some conventional separators may include an adhesive configured to attach the separator to an electrode. The adhesive may be able to bond the conventional separator to an electrode with sufficient strength to successfully laminate the conventional separator to the electrode. However, the body between the different layers of the electrode may be weaker than the attachment between the adhesive and electrode such that the entire conventional separator is not sufficiently laminated to the electrode. Further, the presence of the adhesive in the conventional separator may limit or deteriorate melt integrity and temperature dimensional stability of the conventional separator. The coated separators disclosed herein are an improvement over such conventional separators because the coated separators disclosed herein include an adhesive while also exhibiting good melt integrity, good temperature dimensional stability, the ability to laminate to electrodes, and other properties beneficial for separators.

[0017] FIG. 1 is a cross-sectional schematic of the coated separator 100 for an energy storage device, according to an embodiment. The coated separator 100 includes a microporous polyolefin base membrane 102. The microporous polyolefin base membrane 102 includes a first base surface 104 and a second base surface 106 opposite the first base surface 104. The coated separator 100 also includes a first inorganic coating 108 disposed on at least a portion of the first base surface 104. For example, the first inorganic coating 108 may include a first inner inorganic surface 110 attached to the first base surface 104 and a first outer inorganic surface 112 opposite the first inner inorganic surface 110. The coatedseparator 100 additionally includes a first adhesive coating 114 disposed on at least a portion of the first inorganic coating 108. For example, the first adhesive coating 114 includes a first inner adhesive surface 116 attached to at least a portion of the first outer inorganic surface 112 and a first outer adhesive surface 118 opposite the first inner adhesive surface 116.

[0018] The coated separator 100 may optionally include a second inorganic coating 120 disposed on at least a portion of the second base surface 106. For example, the second inorganic coating 120 may include a second inner inorganic surface 122 attached to the second base surface 106 and a second outer inorganic surface 124 opposite the second inner inorganic surface 122. The coated separator 100 additionally includes a second adhesive coating 126 disposed on at least a portion of the second inorganic coating 120. For example, the second adhesive coating 126 includes a second inner adhesive surface 128 attached to at least a portion of the second outer inorganic surface 124 and a second outer adhesive surface 130 opposite the second inner adhesive surface 128.

[0019] In an embodiment, as shown, the coated separator 100 may exhibit a five layer structure that includes the microporous polyolefin base membrane 102, the first inorganic coating 108, the first adhesive coating 114, the second inorganic coating 120, and the second adhesive coating 126. In another embodiment, the coated separator 100 may exhibit a three layer structure including the microporous polyolefin base membrane 102, the first inorganic coating 108, and the first adhesive coating 114. In other words, the second inorganic coating 120 and the second adhesive coating 126 may be omitted from the coated separator 100. In another embodiment, the coated separator 100 may include four layers (e.g., only one of the second inorganic coating 120 or the second adhesive coating 126 is omitted from the coated separator 100). For example, the coated separator 100 may exhibit a four layer structure including the microporous polyolefin base membrane 102, the first inorganic coating 108, the first adhesive coating 114, and the second adhesive coating 126 (in which case the second adhesive coating 126 is disposed on the microporous base membrane 102 without a second inorganic coating 120). In still another embodiment, the coated separator 100 includes six or more layers. For simplicity, the coated separator 100 will be discussed below as exhibiting the five layer structure.

[0020] The microporous polyolefin base membrane 102 includes one or more polymers or polyolefins. For example, the microporous polyolefin base membrane 102 may include a polyethylene, such as ultrahigh molecular weight polyethylene (UHMWPE), very high molecular weight polyethylene (VHMWPE), high density polyethylene (HDPE), or mixtures thereof. UHMWPE generally corresponds to a range of between about 3.1 million g / mol toabout 10 million g / mol, and VHMWPE generally corresponds to a range of between about 500,000 g / mol to about 3.1 g / mol. In another embodiment, the microporous polyolefin base membrane 102 comprises a polyethylene having a molecular weight greater than 300,000 g / mol (such as between about 300,000 g / mol and about 10 million g / mol) and exhibiting a measurable melt flow index. The microporous polyolefin base membrane 102 may also include one or more polymers other than or in addition to polyethylene, such as polypropylene, polyester, polystyrene, polyester, polyphenylene sulfide, or polyethylene terephthalate (PET).

[0021] In an embodiment, the microporous polyolefin base membrane 102 is manufactured by combining one or more polymers and a plasticizer (e.g., mineral oil). The mixture is then blended and extruded to form a homogeneous, cohesive mass. The mass can be processed using blown film, cast film, or calendering methods to give an oil-filled sheet of a reasonable thickness (about 250 pm or less). The oil-filled sheet can be further biaxially oriented to reduce its thickness and affect its mechanical properties. In an extraction operation, the plasticizer (e.g., mineral oil) is removed with a solvent that is subsequently evaporated to produce a microporous polyolefin membrane that is subsequently coated with an inorganic surface layer.

[0022] The plasticizer employed is a non-evaporative solvent for the polymer and is preferably a liquid at room temperature. The plasticizer has little or no solvating effect on the polymer at room temperature; it performs its solvating action at temperatures at or above the softening temperature of the polymer. It is preferred to use a processing oil, such as a paraffinic oil, naphthenic oil, aromatic oil, or a mixture of two or more such oils. Examples of suitable processing oils include: oils sold by Shell Oil Company, such as Gravex™ 942; oils sold by Calumet Lubricants, such as Hydrocal™ 800; and oils sold by Nynas Inc., such as HR Tufflo® 750.

[0023] The polymer / oil mixture is extruded through a sheet die or annular die, and then it is biaxially oriented to form a thin, oil-filled sheet. Any solvent that is compatible with the oil can be used for the extraction step, provided it has a boiling point that makes it practical to separate the solvent from the plasticizer by distillation. Such solvents include 1,1,2 trichloroethylene; perchloroethylene; 1,2-di chloroethane; 1,1,1 -tri chloroethane; 1,1,2- tri chloroethane; methylene chloride; chloroform; l,l,2-trichloro-l,2,2-trifluoroethane; isopropyl alcohol; diethyl ether; acetone; hexane; heptane; and toluene. Other solvents can also be used, including those identified in PCT / US2023 / 060674 titled Microporous Polyolefin Membranes from Bespoke Solvents which is incorporated herein by reference inits entirety. In some cases, it is desirable to select the processing oil such that any residual oil in the polyolefin membrane after extraction is electrochemically inactive.

[0024] In an embodiment, the microporous polyolefin base membrane 102 may include a plurality of inorganic particles homogenously dispersed within the polymer. Disposing the inorganic particles in the microporous polyolefin base membrane 102 may help maintain the pores of the microporous polyolefin base membrane 102 open and minimize shrinkage of the coated separator 100 when the coated separator 100 is heated to temperatures greater than the melting temperature or glass transition temperature of the polymer.

[0025] The inorganic particles may include an inorganic oxide, carbonate, or hydroxide, such as at least one of alumina, silica, zirconia, titania, mica, boehmite, magnesium hydroxide, calcium carbonate, another suitable inorganic acid, or mixtures thereof. One or more hydrotalcites can also be used either alone or in combination with another type of inorganic particle. The inorganic material may include colloidal or fumed inorganic particles. The inorganic particles may exhibit an average particle size (e.g., average particle diameter) that is smaller than a thickness of the microporous polyolefin base membrane 102. In an example, the inorganic particles may exhibit an average particle size that is about 50% or less than the thickness of the microporous polyolefin base membrane 102.

[0026] In an embodiment, the inorganic particles may be mixed with the polymer of the microporous polyolefin base membrane 102 prior to forming the microporous polyolefin base membrane 102. For example, the inorganic particles may be mixed with the polymer before the polymer is extruded. In an embodiment, the inorganic particles may be dispersed in the microporous polyolefin base membrane 102 after extruding the polymer.

[0027] As previously discussed, the coated separator 100 includes a first inorganic coating 108 and a second inorganic coating 120. As will be discussed in more detail below, the first inorganic coating 108 and the second inorganic coating 120 may be formed from a first aqueous-based dispersion. The first and second inorganic coatings 108, 120 include a plurality of inorganic particles. Any of the above-identified inorganic particles may be used. At high temperatures, the pores within the microporous polyolefin base membrane 102 may begin to collapse or shut down, thereby modifying its permeability and reducing ionic conduction. This in turn shuts down the battery cell. The inorganic particles of the first and second inorganic coatings 108, 120 are configured to maintain in-plane dimensional stability of the microporous polyolefin base membrane 102. This prevents contact between the electrodes while the battery cell is shutting down due to loss of ionic conduction.

[0028] In an embodiment, the inorganic particles of the first and second inorganic coatings 108, 120 exhibit a ratio of nanoparticles to microparticles at a threshold coating ratio that minimizes the thickness of the first porous layer while maintaining high temperature stability of the coated separator 100. As used herein, “nanoparticles” refers to individual particles or multi-particle aggregates with a mean size less than or equal to about 100 nm. The term “microparticles” refers to individual particles, multi-particle aggregates, or multiaggregate agglomerates with a mean size larger than 100 nm to about 1 pm. Similarly, “nanoporous” indicates pores are present with a mean size of about 100 nm or less and “microporous” indicates pores are present with a mean size of greater than about 100 nm to about 1 pm. In an example, the ratio of nanoparticles to microparticles is selected such that the thermal shrinkage in each of the machine direction and traverse direction is about 6% or less, or about 5% or less after exposure to a temperature of 180 °C. It is noted that the higher surface area particles retain more moisture than the low surface area particles (z.e., larger size particles). One approach to address the moisture retention is to use a blend of high and low surface area particles. Low surface area particles (“microparticles”) do not tend to retain as much moisture as the high surface area particles (“nanoparticles”).

[0029] In an embodiment, the inorganic particles are selected to include nanoparticles or substantially only nanoparticles (e.g., about 90 wt% or greater nanoparticles). It has been found that decreasing surface roughness of the first and second inorganic coatings 108, 120 increases the maximum lamination strength of the coated separator 100. The surface roughness of the first and second inorganic coatings 108, 120 depends, in part, on the average particle size of the inorganic particles that form the first and second inorganic coatings 108, 120. In particular, decreasing the average particle size of the inorganic particles of the first and second inorganic coatings 108, 120 decreases the surface roughness of the first and second inorganic coatings 108, 120. It is currently believed that the decreased surface roughness of the first and second inorganic coatings 108, 120 increases the strength of the interfacial bond between the microporous polyolefin base membrane 102 and the first and second inorganic coatings 108, 120. As such, selecting the inorganic particles of the first and second inorganic coatings 108, 120 to include nanoparticles increases the maximum lamination strength of the coated separator 100. The increased maximum lamination strength of the coated separator 100 may allow the quantity of adhesive present in the coated separator 100 to be decreased thereby allowing the thickness of the coated separator 100 to be decreased, the material and cost associated with forming the coated separator 100 to bedecreased, and avoids issues caused by the adhesive (e.g., losing dimensional stability at high temperatures).

[0030] The inorganic particles of the first and second inorganic coatings 108, 120 may form about 75 wt% or more of the first and second inorganic coatings 108, 120, such as about 80 wt% to about 90 wt%. The weight percent of the inorganic particles that are present in the first and second inorganic coatings 108, 120 may depend on whether the first and second inorganic coatings 108, 120 include other components e.g., a hydrogen bonding component and / or a cross-linking agent) and the composition of the other components. In an embodiment, the inorganic particles of the first and second inorganic coatings 108, 120 may form about 80 wt% to about 90 wt% of the first and second inorganic coatings 108, 120 when the first and second inorganic coatings 108, 120 include a hydrogen bonding component and a cross-linking agent. The weight percent of the inorganic particles in the first and second inorganic layers 108, 120 may be selected for other reasons, such as the composition of the inorganic particles, whether the inorganic particles include surface groups, and the surface roughness of the inorganic particles.

[0031] In an embodiment, the first and second inorganic coatings 108, 120 may include a hydrogen bonding component. The hydrogen bonding component may form a binder that binds the inorganic particles together and binds the first and second inorganic coatings 108, 120 to the adjacent layers of the coated separator 100. As such, the hydrogen bonding component may increase the lamination strength and the high temperature dimensional stability of the coated separator 100. The hydrogen bonding component may also cause the coated separator 100 to exhibit low Gurley (i.e., high air permeability) values.

[0032] In an embodiment, the hydrogen bonding component may include a low molecular weight, water-soluble polymer. In an embodiment, the hydrogen bonding component may include at least one polymer or small molecule with multiple hydrogen bonding sites to minimize the weight percent of the hydrogen bonding component in the first and second inorganic coatings 108, 120 while achieving a robust, microporous inorganic surface layer that does not easily shed inorganic particles. Examples of hydrogen bonding components that are polymers include polyvinyl alcohol (PVOH), polyvinylpyrrolidone (PVP), carboxymethyl cellulose (CMC), polyacrylic acid, polyethylene oxide, or combinations thereof.

[0033] The hydrogen bonding component may form about 2 wt% to about 25 wt% of the first and second inorganic coatings 108, 120, such as about 10 wt% to about 20 wt%. The weight percent of the hydrogen bonding component may be selected for numerous reasons. In an example, the weight percent of the hydrogen bonding component may be selected basedon the average particle size of the inorganic particles. As previously discussed, the lamination strength of the coated separator depends, in part, on the average particle size of the inorganic particles. The weight percent of the hydrogen bonding component may be increased when inorganic particles are relatively coarse to compensate for the weaker lamination strength provided by the coarse inorganic particles, and vice versa. In an example, the weight percent of the hydrogen bonding component may be selected based on the number of hydrogen bonding sites of the hydrogen bonding component. In an example, the weight percent of the hydrogen bonding component may be selected based on whether the first and second inorganic coatings 108, 120 include a cross-linking agent.

[0034] In an embodiment, the first and second inorganic coatings 108, 120 may include a cross-linking agent. The cross-linking agent is selected to react with the hydrogen bonding component. It has been found that including the cross-linking agent in the first and second inorganic coatings 108, 120 significantly increases the lamination strength of the coated separator 100. For example, it has been found that including the cross-linking agent in the first and second inorganic coatings 108, 120 may allow the coated separator 100 to exhibit a lamination strength, tested using a 180° peel test at room temperature (i.e., 23° C), that is greater than about 100 gf / 25mm which is a significantly high lamination strength, especially for a five layer coated separator, and may allow the coated separator 100 to be used in certain battery applications.

[0035] The cross-linking agent may include any agent that may react with the hydrogen bonding component. Examples of the cross-linking agent include boric acid, glycerol glycidyl ether, citric acid, succinic acid, glutaraldehyde, maleic acid, sodium borate, a polyfunctional aziridine, other suitable cross-linking agent, or combinations thereof. Specific examples of polyfunctional aziridine include XAMA-7 (C20H33O7N3) and Pentaerythritol tris(3-(l-aziridinyl)propionate). In a particular embodiment, the hydrogen bonding component includes polyvinyl alcohol and the cross-linking agent includes at least one polyfunctional aziridine. It has been found that polyvinyl alcohol combined with at least one polyfunctional aziridine allows the coated separator 100 to exhibit a lamination strength, tested using a 180° peel test at room temperature (i.e., 23° C), that is greater than about 75 gf / 25 mm, or greater than about 100 gf / 25 mm.

[0036] The cross-linking agent may form greater than 0 wt% to about 10 wt% of the first and second inorganic coatings 108, 120, such as from about 2 wt% to about 4 wt%. The weight percent of the cross-linking agent in the first and second inorganic coatings 108, 120 may be selected based on a number of factors. Generally, increasing the weight percent ofthe cross-linking agent in the first and second inorganic coatings 108, 120 increases the percentage of the hydrogen bonding component that is cross-linked thereby increasing the strength of the first and second inorganic coatings 108, 120. However, increasing the weight percent of the cross-linking agent in the first and second inorganic coatings 108, 120 also increases the likelihood that the cross-linking agent remains unreacted after forming the first and second inorganic coatings 108, 120 which causes the cross-linking agent to detrimentally affect the strength of the first and second inorganic coatings 108, 120. In other words, there may exist a weight percent of the cross-linking agent in the first and second inorganic coatings 108, 120 that maximizes the cross-linking of the hydrogen bonding component while minimizing the unreacted cross-linking agent. The weight percent of the cross-linking agent that maximizes the cross-linking of the hydrogen bonding component while minimizing the unreacted cross-linking agent may depend on the composition of the hydrogen bonding component and the composition of the cross-linking agent.

[0037] The first and second inorganic coatings 108, 120 may exhibit any suitable thickness. For example, each of the first and second inorganic coatings 108, 120 may exhibit a thickness that is about 0.5 pm to about 5 pm, such as from about 1 pm to about 2 pm. In an embodiment, the thickness of the first and second inorganic coatings 108, 120 may be substantially the same or different. In an embodiment, the thickness of the first and second inorganic coatings 108, 120 are selected to provide sufficient high temperature stability to the coated separator 100.

[0038] As previously discussed, the coated separator 100 includes a first adhesive coating 114 and a second adhesive coating 126. The first and second adhesive coatings 114, 126 are disposed on at least a portion of the first and second inorganic coatings 108, 120. For example, the first and second adhesive coatings 114, 126 may be disposed on all of or substantially all of the first and second adhesive coatings 114, 126, respectively. The first and second adhesive coatings 114, 126 disposed on the first and second adhesive coatings 114, 126 improve adhesion of the coated separator 100 to an electrode, another separator, or another component of a battery. In other words, the first and second adhesive coatings 114, 126 improve the lamination strength of the coated separator 100 after disposing the coated separator 100 on the electrode.

[0039] The first and second adhesive coatings 114, 126 may exhibit any suitable thickness. For example, each of the first and second adhesive coatings 114, 126 may exhibit a thickness that is about 0.2 pm to about 2 pm, such as from about 0.5 pm to about 1 pm. In an embodiment, the thickness of the first and second adhesive coatings 114, 126 may besubstantially the same or different. In an embodiment, the thickness of the first and second adhesive coatings 114, 126 are selected to provide sufficient lamination strength to the coated separator 100 while minimizing any detrimental effect the first and second adhesive coatings 114, 126 have on the high temperature stability of the coated separator 100.

[0040] The first and second adhesive coatings 114, 126 include an adhesive. The adhesive is configured to adhere the first and second adhesive coatings 114, 126 to an electrode, another separator, or another component of the battery. The adhesive of the first and second adhesive coatings 114, 126 may include any adhesive that is configured to adhere the coated separator 100 to any of the structures or any other suitable structure. The adhesive may also be configured to remain stable when heated to the maximum operating temperature of the coated separator 100 (e.g., 180 °C) and exposed to the electrolyte and acids of the battery. In an example, the adhesives include a fluoropolymer resin, such as the fluoropolymer resin of the FMA-12 polymer emulsion manufactured by Arkema. It is currently believed that the fluoropolymer resin from the FMA-12 polymer emulsion provides exceptionally high lamination strength to the coated separator 100 that is stable when heated to at least a temperature of 180 °C and exposed to the electrolyte and acids used in common lithium ion batteries. Other types of adhesives can also be used. Generally, the first and second adhesive coatings 114, 126 include the same adhesive, though it is noted that the first and second adhesive coatings 114, 126 may include different adhesives.

[0041] The adhesive of the first and second adhesive coatings 114, 126 may form about 75 wt% or more of the first and second adhesive coatings 114, 126, such as from about 85 wt% to about 97 wt%. The weight percent of the adhesive that are present in the first and second adhesive coatings 114, 126 may depend on whether the first and second adhesive coatings 114, 126 include other components, such as inorganic particles or a hydrogen bonding component. In an embodiment, the adhesive of the first and second adhesive coatings 114, 126 may form about 85 wt% to about 97 wt% of the first and second adhesive coatings 114, 126 when the first and second adhesive coatings 114, 126 include inorganic particles and a hydrogen bonding component. The weight percent of the adhesive in the first and second inorganic layers 108, 120 may be selected for other reasons, such as the composition of the adhesive, whether the first and second adhesive coatings 114, 126 are partially disposed in at least the first and second inorganic coatings 108, 120, and the surface roughness of the first and second inorganic coatings 108, 120 and / or the surface roughness of the first and second inorganic coatings 108, 120.

[0042] In an embodiment, the first and second adhesive coatings 114, 126 include inorganic particles. The inorganic particles of the first and second adhesive coatings 114, 126 may include any of the inorganic particles disclosed herein and may be the same as or different than the inorganic particles of the first and second inorganic coatings 108, 120. The inorganic particles of the first and second adhesive coatings 114, 126 improve the high temperature stability of the first and second adhesive coatings 114, 126 and the high temperature stability of the coated separator 100 as a whole. The inorganic particles in the first and second adhesive coating 114, 126 also improve adhesion between the first and second inorganic coatings 108, 120 and first and second adhesive coatings 114, 126, respectively. The improved adhesion between the first and second inorganic coatings 108, 120 and first and second adhesive coatings 114, 126, respectively, improves the lamination strength of the coated separator 100.

[0043] The inorganic particles of the first and second adhesive coatings 114, 126 may form less than about 25 wt% of the first and second adhesive coatings 114, 126, such as about 7 wt% to about 15 wt%. The weight percent of inorganic particles that are present in the first and second adhesive coatings 114, 126 may be selected based on the number of factors. In an example, the weight percent of inorganic particles may be selected based on the composition of the inorganic particles, the composition of the adhesive, and the interaction between the inorganic particles and the adhesive. In an example, the weight percent of the inorganic particles may be selected to give the first and second adhesive coatings 114, 126 a desired high temperature stability where in increasing weight percent of the inorganic particles increases the high temperature stability of the first and second adhesive coatings 114, 126. In an example, the weight percent of the inorganic particles may be selected based on the desired lamination strength since, generally, increasing the weight percent of inorganic particles in the first and second adhesive coatings 114, 126 increases the lamination strength of the coated separator 100. For instance, the weight percent of the inorganic particles may be selected to give the coated separator 100 a lamination strength, tested using a 180° peel test at room temperature (i.e., 23° C), of about 75 gf / 25 mm or greater, or about 100 gf / 25 mm or greater.

[0044] In an embodiment, the first and second adhesive coatings 114, 126 include at least one hydrogen bonding component. The hydrogen bonding component of the first and second adhesive coatings 114, 126 may include any of the hydrogen bonding components disclosed herein and may be the same as or different than the hydrogen bonding component of the first and second inorganic coatings 108, 120. The hydrogen bonding component of the first andsecond adhesive coatings 114, 126 improves bonding between the inorganic particles of the first and second adhesive coatings 114, 126. The hydrogen bonding component of the first and second adhesive coatings 114, 126 also improves adhesion between the first and second inorganic coatings 108, 120 and a first and second adhesive coatings 114, 126, respectively.

[0045] The weight percent of the hydrogen bonding component in the first and second adhesive coatings 114, 126 may be less than weight percent of the hydrogen bonding component in the first and second inorganic coatings 108, 120 since the first and second adhesive coating 114, 126 already include an adhesive. The weight percent of the hydrogen bonding component in the first and second adhesive coatings 114, 126 may be independently selected to be about 0 wt% to about 6 wt%, such as in a range of about 2 wt% to 4 wt%. The weight percent of the hydrogen bonding component in the first and second adhesive coating 114, 126 may be selected for a variety of reasons. In an example, the weight percent of the hydrogen bonding component in the first and second adhesive coating 114, 126 may be selected based on the adhesion between the adhesive and inorganic particles of the first and second adhesive coatings 114, 126 and the adhesion between the first and second inorganic coatings 108, 120 and the first and second adhesive coatings 114, 126. In an example, weight percent of the hydrogen bonding component in the first and second adhesive coatings 114, 126 may be selected based on the stability of the adhesive at or near the maximum operating temperature of the coated separator 100. For instance, the weight percent of the hydrogen bonding component in the first and second adhesive coatings 114, 126 may be increased when the adhesive begins to flow at or near maximum operating temperature of the coated separator 100 since the hydrogen bonding component may minimize the flow of the adhesive.

[0046] In an embodiment, at least one of the microporous polyolefin base membrane 102, the first inorganic coating 108, the first adhesive coating 114, the second inorganic coating 120, or the second adhesive coating 126 may include one or more components other than the components listed above. In an example, one or more layers of the coated separator may include a gel forming material, examples of which are disclosed in U.S. Patent Application Publication No. 2019 / 0386274 filed on March 14, 2017, the disclosure of which is incorporated herein in its entirety, by this reference. In an example, one or more layers of the coated separator 100 may include a reinforcement material, such as a plurality of glass fibers. In an example, the first adhesive coating 120 and / or the second adhesive coating 126 may include a cross-linking agent.

[0047] As previously discussed, the coated separator 100 may exhibit a high temperature stability which may prevent or inhibit the creation of an internal short-circuit in the batteryduring failure of the battery. As used herein, high temperature stability refers to the ability of the coated separator 100 to exhibit a shrinkage of about 10% or less in each of the machine direction and transverse direction after exposure to a temperature of about 180 °C. For example, the coated separator 100 may exhibit a shrinkage in each of the machine direction and transverse direction of about 5% or less after exposure to a temperature of about 180 °C. The high temperature stability of the coated separator 100 depends, in part, on the weight percent of the inorganic particles, hydrogen bonding component, and cross-linking agent in each of the layers of the coated separator 100.

[0048] In an embodiment, the coated separator 100 may exhibit an areal resistance of about 1.5 (1 cm2or less, such as about 0.9 (1 cm2or less. The areal resistance of the coated separator 100 depends, in part, on the composition of the microporous polyolefin base membrane 102 and the average pore size of the coated separator 100.

[0049] As previously discussed, the coated separator 100 may exhibit a high lamination strength. For example, the coated separator 100 may exhibit a lamination strength, tested using a 180° peel test at room temperature (i.e., 23° C), of about 75 gf / 25mm or more, such as from about 75 gf / 25mm to about 180 gf / 25mm. The lamination strength of the coated separator 100 may depend, in part, on the hydrogen bonding components present in the layers of the coated separator 100 and whether the first and second inorganic coatings 108, 120 include a cross-linking agent. It is noted that the lamination strength may refer to lamination strength of the coated separator 100 after laminating at 80 °C at 1.4 MPa for 20 seconds when attached to itself.

[0050] In an embodiment, the coated separator 100 may exhibit a Gurley number of about 50 s / lOOcc air to about 800 s / lOOcc air, such as about 80 s / lOOcc air to about 250 s / lOOcc air. The Gurley number of the coated separator 100 indicates the resistance to transport of coated separator 100. For example, the Gurley number may indicate at least one of the porosity, pore size, thickness, or tortuosity of the coated separator 100.

[0051] In an embodiment, the coated separator 100 may exhibit a MacMullin number of less than about 15, such as less than about 9. The MacMullin number is the ratio of ionic conductivity of pure electrolyte and ionic conductivity of the coated separator 100 filled with the electrolyte.

[0052] The coated separator 100 exhibits an averaged thickness of about 5 pm to about 25 pm, such as about 9 pm to about 16 pm. The thickness t of the coated separator 100 depends on the thickness of each of the layers of the coated separator 100 and the number oflayers that form the coated separator 100. Generally, it is desirable to decrease the overall thickness of the coated separator 100 thereby increasing the energy density of the battery.

[0053] The coated separator 100 may be formed using any suitable process. FIGS. 2A and 2B illustrate an exemplary dip-coating process used to form the coating separator 100, according to an embodiment. Referring to FIG. 2A, the microporous base membrane 102 is wound on a cardboard core 201. The microporous base membrane 102 can also be fed directly from an extruder or cast film line. The microporous base membrane 102 is unwound from the unwinder (or otherwise fed) and dipped in a bath 202 of a first aqueous-based dispersion to form a first dipped microporous polyolefin base membrane 203. The first aqueous-based dispersion includes one or more solids and at least one liquid. The solids of the first aqueous-based dispersion form the first and second inorganic coatings 108, 120 and include the inorganic particles and, optionally, the hydrogen bonding component, the crosslinking agent, or other components of the first and second inorganic coatings 108, 120. The liquid may include water (e.g., deionized water), isopropanol, another alcohol, another suitable liquid, or combinations thereof.

[0054] After dipping the microporous polyolefin base membrane 102 in the first aqueousbased dispersion, Mayer rods may be used (e.g., two Mayer rods, one for each side of the coated microporous polyolefin base membrane 102) to control the thickness of the first aqueous-based dispersion coatings on the first dipped microporous polyolefin base membrane 203. The first dipped microporous polyolefin base membrane 203 may then be dried, for example, with a series of air knives (not shown) and transported through a vertical oven 204 to form the first and second inorganic coatings 108, 120 on the microporous polyolefin base membrane 102. The coated microporous polyolefin base membrane 205 (z.e., the microporous polyolefin base membrane 102 and the first and second inorganic coatings 108, 120) may then be wound onto a core 206.

[0055] Referring to FIG. 2B, the coated microporous polyolefin base membrane 205 is unwound from the core 206 and dipped in a bath 208 of a second aqueous-based dispersion to form a second dipped microporous polyolefin base membrane 210 (z.e., the first and second inorganic coatings 108, 120 are at least partially coated with the second aqueous-based dispersion). The second aqueous-based dispersion includes one or more solids and at least one liquid. The solids of the second aqueous-based dispersion form the first and second adhesive coatings 114, 126 and include the adhesive and, optionally, the inorganic particles, the hydrogen bonding component, or other components of the first and second adhesivecoatings 114, 126. The liquid may include water (e.g., deionized water), isopropanol, another alcohol, another suitable liquid, or combinations thereof.

[0056] After dipping the coated microporous polyolefin base membrane 205 in the second aqueous-based dispersion, Mayer rods may be used (e.g., two Mayer rods, one for each side of the second dipped microporous polyolefin base membrane 210) to control the thickness of the second aqueous-based dispersion coatings on the second dipped microporous polyolefin base membrane 210. The second dipped microporous polyolefin base membrane 210 may then be dried, for example, with a series of air knives (not shown) and transported through a vertical oven 204 to form the first and second adhesive coatings 114, 126. The coated separator 100 may then be wound onto a core 212.

[0057] FIG. 3 illustrates an exemplary dip-coating process that combines the two-step process illustrated in FIGS. 2A and 2B into a single step, according to an embodiment. The microporous polyolefin base membrane 102 is wound on a cardboard core 301. The microporous polyolefin base membrane 102 is unwound from the unwinder and dipped in a bath 302 of the first aqueous-based dispersion to form a first dipped microporous polyolefin base membrane 303. After dipping the microporous polyolefin base membrane 102 in the first aqueous-based dispersion, Mayer rods may be used (e.g., two Mayer rods, one for each side of the coated microporous polyolefin base membrane 102) to control the thickness of the first aqueous-based dispersion coatings on the first dipped microporous polyolefin base membrane 303. The first dipped microporous polyolefin base membrane 303 may then be dried, for example, with a series of air knives (not shown) and transported through a first vertical oven 304a to form the first and second inorganic coatings 108, 120 on the microporous polyolefin base membrane 102. The coated microporous polyolefin base membrane 305 (i.e., the microporous polyolefin base membrane 102 and the first and second inorganic coatings 108, 120) may then be dipped in a bath 308 of the second aqueous-based dispersion to form a second dipped microporous polyolefin base membrane 310. After dipping the coated microporous polyolefin base membrane 305 in the second aqueous-based dispersion, Mayer rods may be used (e.g., two Mayer rods, one for each side of the second microporous polyolefin base membrane 310) to control the thickness of the second aqueousbased dispersion coatings on the second dipped microporous polyolefin base membrane 310. The second dipped microporous polyolefin base membrane 310 may then be dried, for example, with a series of air knives (not shown) and transported through a second vertical oven 304b to form the first and second adhesive coatings 114, 126. The coated separator 100 may then be wound onto a core 312.

[0058] It is noted that the coated separator 100 may be formed using other techniques. Examples of other methods that may be used to form the coated separator 100 are disclosed in U.S. Patent Application Publication No. 2019 / 0386274 filed on March 14, 2017, the disclosure of which was previously incorporated herein.

[0059] Working Examples

[0060] The following working examples provide further detail about the coated separators disclosed herein.

[0061] Example 1

[0062] A 7 pm thick, microporous ultrahigh molecular weight polyethylene and fumed alumina-containing separator prepared at ENTEK (7 m CF, Membranes LLC, Oregon) was coated with an aqueous-based dispersion composed of the following:282.3 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids;Sekisui)237.7 g Deionized water40 g Isopropanol440 g CAB-O-SPERSE PG 003 (40wt% alumina in water; Cabot Corporation)

[0063] The coating dispersion contained 20wt% solids with 88 / 12 alumina / PVOH mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #9 Mayer rods. The wetted separator was then dried with a series of air knives and transported through a vertical oven set at 100° C and wound on a core, prior to testing and additional coating.

[0064] This separator was then coated again on both sides with an aqueous-based dispersion composed of the following:17.7 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids;Sekisui)348.2 g Deionized water30 g Isopropanol15 g W450ZX (50wt% alumina in water; Evonik)89.1 g FMA-12 (46wt% polymer emulsion in water; Arkema)

[0065] The coating dispersion contained 20wt% solids with 90 / 7 / 3 FMA-12 polymer / alumina / polyvinyl alcohol (PVOH) mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #4 Mayer rods. The wetted separator was then dried with aseries of air knives and transported through a vertical dryer and wound on a core, prior to testing.

[0066] Example 2

[0067] A 7 pm thick, microporous ultrahigh molecular weight polyethylene and fumed alumina-containing separator prepared at ENTEK (7 m CF, Membranes LLC, Oregon) was coated with an aqueous-based dispersion composed of the following:353 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids; Sekisui)182 g Deionized water40 g Isopropanol425 g CAB-O-SPERSE PG 003 (40wt% alumina in water; Cabot Corporation)

[0068] The coating dispersion contained 20wt% solids with 85 / 15 alumina / PVOH mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #9 Mayer rods. The wetted separator was then dried with a series of air knives and transported through a vertical oven set at 100° C and wound on a core, prior to testing and additional coating.

[0069] This separator was then coated again on both sides with an aqueous-based dispersion composed of the following:35.3 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids; Sekisui)225 g Deionized water30 g Isopropanol14 g W450ZX (50wt% alumina in water; Evonik)195.7 g FMA-12 (46wt% polymer emulsion in water; Arkema)

[0070] The coating dispersion contained 20wt% solids with 90 / 7 / 3 FMA-12 polymer / alumina / PVOH mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #4 Mayer rods. The wetted separator was then dried with a series of air knives and transported through a vertical dryer and wound on a core, prior to testing.

[0071] Example 3

[0072] A 7 pm thick, microporous ultrahigh molecular weight polyethylene and fumed alumina-containing separator prepared at ENTEK (7 m CF, Membranes LLC, Oregon) was coated with an aqueous-based dispersion composed of the following:282.4 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids; Sekisui)246.6 g Deionized water40 g Isopropanol425 g CAB-O-SPERSE PG 008 (40wt% alumina in water; Cabot Corporation)6.0 g PZ-33 (Pentaerythritol Tris (3-(l-Aziridinyl) Propionate, Poly Aziridine LLC)

[0073] The coating dispersion contained 20wt% solids with 85 / 12 / 3 alumina / PVOH / aziridine mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #10 Mayer rods. The wetted separator was then dried with a series of air knives and transported through a vertical oven set at 100° C and wound on a core, prior to testing and additional coating.

[0074] This separator was then coated again on both sides with an aqueous-based dispersion composed of the following:17.7 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids; Sekisui)348.2 g Deionized water30 g Isopropanol15 g W450ZX (50wt% alumina in water; Evonik)89.1 g FMA-12 (46wt% polymer emulsion in water; Arkema)

[0075] The coating dispersion contained 10wt% solids with 85 / 12 / 3 FMA-12 polymer / alumina / PVOH mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #4 Mayer rods. The wetted separator was then dried with a series of air knives and transported through a vertical dryer and wound on a core, prior to testing.

[0076] Example 4

[0077] A 9 pm thick, microporous ultrahigh molecular weight polyethylene and fumed alumina-containing separator prepared at ENTEK (9pm CF, Membranes LLC, Oregon) was coated with an aqueous-based dispersion composed of the following:282.4 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids; Sekisui)246.6 g Deionized water40 g Isopropanol425 g CAB-O-SPERSE PG 008 (40wt% alumina in water; Cabot Corporation)6.0 g PZ-33 (Pentaerythritol Tris (3-(l-Aziridinyl) Propionate, Poly Aziridine LLC)

[0078] The coating dispersion contained 20wt% solids with 85 / 12 / 3 alumina / PVOH / aziridine mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #10 Mayer rods. The wetted separator was then dried with a series of air knives and transported through a vertical oven set at 100° C and wound on a core, prior to testing and additional coating.

[0079] This separator was then coated again on both sides with an aqueous-based dispersion composed of the following:35.3 g Selvol 09-325 (aqueous based PVOH solution; 98% hydrolyzed; 8.5wt% solids;Sekisui)225 g Deionized water30 g Isopropanol14 g W450ZX (50wt% alumina in water; Evonik)195.7 g FMA-12 (46wt% polymer emulsion in water; Arkema)

[0080] The coating dispersion contained 20wt% solids with 90 / 7 / 3 FMA-12 polymer / alumina / PVOH mass ratio. The separator was dip-coated through a bath containing the aqueous-based dispersion, and the thickness of the wet layer was controlled on each side with #4 Mayer rods. The wetted separator was then dried with a series of air knives and transported through a vertical dryer and wound on a core, prior to testing.

[0081] Summary of Data:

[0082] Thickness was measured using EMVECO micrometer (Model 200-A). Air permeability was measured using Asahi Seiki, Model EGO1-55-1MR. For shrinkage testing, coated separators were suspended in an oven at 180°C for 5 minutes. Shrinkage after 180°C exposure was measured in the machine and transverse directions. For lamination strength measurements, two sheets of coated separator were placed between PET release films. Samples were then placed in a Carver Laboratory Press (Model C) with temperature setpoint at 80°C, pressed at 210psi for 20 seconds. The lamination strength of the separators was then measured using a 180° peel test at room temperature (i.e., 23° C). Impedance measurements were measured at lOOKHz using a Gamry Impedance Analyzer (Interface 1000). Separators were soaked in IM LiPF6 in 1 : 1 EC:EMC, and impedance measurements were plotted for 1, 2, and 3 layers of separator; the slope of the plot gives the resistance for a single layer, which was used to calculate the MacMullin number of the separator.Table 1

[0083] As shown in Table 1, the coated separators disclosed herein exhibit good Gurley numbers, high temperature thermal stability, lamination strength, and MacMullin numbers. For example, at least some of the coated separators of Examples 1-4 may be used in lithium- ion batteries. It is noted that Table 1 demonstrates that the inclusion of the PVOH and the aziridine cross-linking agent in the inorganic coating significantly increases the lamination strength of the coated separator.

[0084] While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting.

[0085] References to approximations are made throughout this specification, such as by use of the terms “about” or “approximately.” For each such reference, it is to be understood that, in some embodiments, the value, feature, or characteristic may be specified without approximation. For example, where qualifiers such as “about,” “substantially,” and “generally” are used, these terms include within their scope the qualified words in the absence of their qualifiers. Further, all ranges include both endpoints.

[0086] The claims following this written disclosure are hereby expressly incorporated into the present written disclosure, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims. Moreover, additional embodiments capable of derivation from the independent and dependent claims that follow are also expressly incorporated into the present written description.

[0087] Without further elaboration, it is believed that one skilled in the art can use the preceding description to utilize the invention to its fullest extent. The claims and embodiments disclosed herein are to be construed as merely illustrative and exemplary, and not a limitation of the scope of the present disclosure in any way. It will be apparent to those having ordinary skill in the art, with the aid of the present disclosure, that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the disclosure herein. In other words, various modifications and improvements of the embodiments specifically disclosed in the description above are withinthe scope of the appended claims. The scope of the invention is therefore defined by the following claims and their equivalents.

Claims

CLAIMSWhat is claimed is:

1. A coated separator for an energy storage device, comprising: a microporous polyolefin base membrane having a first base surface and a second base surface opposite the first base surface; a first inorganic coating disposed on at least a portion of the first base surface, the first inorganic coating comprising a plurality of first inorganic particles; and a first adhesive coating disposed on at least a portion of the first inorganic coating, the first adhesive coating comprising at least one adhesive; wherein the coated separator exhibits a lamination strength, tested using a 180° peel test at 23° C, of about 75 gf / 25 mm to about 170 gf / 25 mm after laminating at 80 °C and 1.4 MPa for 20 seconds when attached to itself, and wherein the coated separator exhibits the following prior to lamination: a machine and traverse directional shrinkage of about 5% or less in each direction after exposure to a temperature of 180 °C; or a MacMullin number of 9 or less.

2. The coated separator of claim 1, wherein prior to lamination, the coated separator further exhibits a Gurley number of about 250 s / 100 cc air or less.

3. The coated separator of claim 1 or claim 2, wherein the microporous polyolefin base membrane comprises a polyethylene having a molecular weight greater than 300,000 g / mol and exhibiting a measurable melt flow index.

4. The coated separator of claim 1 or claim 2, wherein the microporous polyolefin base membrane comprises one or more of ultra-high molecular weight polyethylene, very high molecular weight polyethylene, or high density polyethylene.

5. The coated separator of any one of claims 1 to 4, wherein the first inorganic particles comprise an inorganic oxide, carbonate, hydroxide, or mixtures thereof, or wherein the first inorganic particles comprise alumina, silica, zirconia, titania, mica, boehmite, magnesium hydroxide, calcium carbonate, hydrotalcites, or mixtures thereof.

6. The coated separator of any one of claims 1-5, wherein the first inorganic coating includes at least one hydrogen bonding component.

7. The coated separator of claim 6, wherein the first inorganic coating comprises at least one cross-linking agent.

8. The coated separator of claim 6 or 7, wherein the at least one hydrogen bonding component comprises polyvinyl alcohol and the at least one cross-linking agent comprises at least one polyfunctional aziridine.

9. The coated separator of any one of claims 1-8, wherein the first adhesive coating comprises at least one hydrogen bonding component forming about 1.5 wt% to about 5 wt% of the first adhesive coating.

10. The coated separator of claim 9, wherein the at least one hydrogen bonding component comprises polyvinyl alcohol.

11. The coated separator of any one of claims 1-10, wherein the coated separator exhibits the machine and traverse directional shrinkage of about 5% or less in each direction after exposure to a temperature of 180 °C.

12. The coated separator of any one of claims 1-10, wherein the coated separator exhibits the MacMullin number of 9 or less.

13. The coated separator of any one of claims 1-12, wherein the coated separator exhibits: the machine and traverse directional shrinkage of about 5% or less in each direction after exposure to a temperature of 180 °C; and the MacMullin number of 9 or less.

14. The coated separator of any one of claims 1-13, further comprising a second inorganic coating disposed on at least a portion of the second base surface, the second inorganic coating including a plurality of second inorganic particles; and a second adhesive coating disposed on at least a portion of the second inorganic coating, the second adhesive coating comprising the at least one adhesive.

15. An energy storage device, comprising: an electrode; and the coated separator of any one of claims 1-14 attached to the electrode.

16. A method of forming a coated separator for an energy storage device, the method comprising: coating at least a portion of a first base surface of a microporous polyolefin base membrane with a first aqueous-based dispersion, the microporous polyolefin base membrane comprising a second base surface opposite the first base surface, the first aqueous-based dispersion comprising a plurality of first inorganic particles; drying the first aqueous-based dispersion on the first base surface to form a first inorganic coating on at least a portion of the first base surface of the microporous polyolefin base membrane; coating at least a portion of the first inorganic coating with a second aqueous-based dispersion, the second aqueous-based dispersion comprising at least one adhesive; and drying the second aqueous-based dispersion to form a first adhesive coating on at least a portion of the first inorganic coating to form the coated separator; wherein the coated separator exhibits a lamination strength, tested using a 180° peel test at 23° C, of about 75 gf / 25 mm to about 170 gf / 25 mm after laminating at 80 °C and 1.4 MPa for 20 seconds when attached to itself; and wherein the coated separator exhibits the following prior to lamination: a machine and traverse directional shrinkage of about 5% or less in each direction after exposure to a temperature of 180 °C; or a MacMullin number of 9 or less.

17. The method of claim 16, wherein prior to lamination, the coated separator further exhibits a Gurley number of about 250 s / 100 cc air or less.

18. The method of claim 16 or claim 17, wherein the microporous polyolefin base membrane comprises a polyethylene having a molecular weight greater than 300,000 g / mol and exhibiting a measurable melt flow index.

19. The method of claim 16 or claim 17, wherein the microporous polyolefin base membrane comprises one or more of ultra-high molecular weight polyethylene, very high molecular weight polyethylene, or high density polyethylene.

20. The method of any one of claims 16 to 19, wherein the first inorganic particles comprise an inorganic oxide, carbonate, hydroxide, or mixtures thereof, or wherein the first inorganic particles comprise alumina, silica, zirconia, titania, mica, boehmite, magnesium hydroxide, calcium carbonate, hydrotalcites, or mixtures thereof.

21. The method of any one of claims 16-20, wherein the first inorganic coating includes at least one hydrogen bonding component.

22. The method of claim 21, wherein the first inorganic coating comprises at least one cross-linking agent.

23. The method of claim 21 or 22, wherein the at least one hydrogen bonding component comprises polyvinyl alcohol and the at least one cross-linking agent comprises at least one polyfunctional aziridine.

24. The method of any one of claims 16-23, wherein the first adhesive coating comprises at least one hydrogen bonding component forming about 1.5 wt% to about 5 wt% of the first adhesive coating.

25. The method of claim 24, wherein the at least one hydrogen bonding component comprises polyvinyl alcohol.

26. The method of any one of claims 16-25, wherein the coated separator exhibits the machine and traverse directional shrinkage of about 5% or less in each direction after exposure to a temperature of 180 °C.

27. The method of any one of claims 16-26, wherein the coated separator exhibits the MacMullin number of 9 or less.

28. The method of any one of claims 16-27, wherein the coated separator exhibits:the machine and traverse directional shrinkage of about 5% or less in each direction after exposure to a temperature of 180 °C; and the MacMullin number of 9 or less.

29. The method of any one of claims 16-28, further comprising: coating at least a portion of the second base surface of the microporous polyolefin base membrane with the first aqueous-based dispersion; and drying the first aqueous-based dispersion on the second base surface to form a second inorganic coating on at least a portion of the second base surface of the microporous polyolefin base membrane; coating at least a portion of the second inorganic coating with the second aqueousbased dispersion; and drying the second aqueous-based dispersion to form a second adhesive coating on at least a portion of the second inorganic coating.

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