Coated separator comprising at least one binder

Abstract

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

Description

Related Applications

[0001] This application claims priority to U.S. Provisional Application No. 63 / 578,107, filed August 22, 2023, and entitled 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 Application Records, or 1.71(d). BACKGROUND

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

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

[0005] In certain battery cell designs, it is required to laminate an adhesive-coated separator to the electrode. The benefits of applying an adhesive to the separator include faster material handling, faster air speed during battery cell assembly, and tighter contact between the separator and the electrode.

[0006] New electrode chemistries and battery cell designs require advanced coated separators that have thermal stability, the ability to be laminated to electrodes at higher lamination strength than conventional laminable separators, while still maintaining low impedance to allow lithium ions to pass through the separator. The uniqueness of this work is the ability to provide superior safety features, excellent rate capability, and excellent ability to be laminated to electrodes using water-based coating formulations. BRIEF DESCRIPTION OF DRAWINGS

[0007] The accompanying drawings illustrate several embodiments of the disclosure, wherein the same reference numerals in different drawings represent the same or similar elements or features.

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

[0009] Figure 2A and Figure 2B illustrates an exemplary dip coating process for forming a coated separator according to an embodiment.

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

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

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

[0013] The coated separator can be formed using any suitable technique. In an example, a microporous polyolefin base film (e.g., a pre-separator film) can be provided or formed. Microporous films generally have a pore size range of about 10 nanometers to several micrometers, with an average pore size of less than about 1 micrometer. Such films are generally opaque because the pore size and polymer matrix are large enough to scatter visible light. The term “microporous film” as used includes other descriptions used in the scientific and patent literature, such as “microporous membrane,” “microporous sheet,” and “microporous web.” The microporous polyolefin film can also exhibit free-standing properties and have interconnected pores extending throughout the film. “Free-standing” means that the film has sufficient mechanical properties that allow for handling, such as winding and unwinding in sheet form, for use in an energy storage device assembly.

[0014] The microporous polyolefin base film includes a first base surface and a second base surface. A first aqueous base dispersion can be disposed on at least a portion of the at least first base surface. The first aqueous base dispersion includes a plurality of inorganic particles. The first aqueous base dispersion on the first base surface can be dried to form a first inorganic coating layer. A second aqueous base dispersion can then be disposed on at least a portion of the first inorganic coating layer. The second aqueous base dispersion includes at least one binder. The second aqueous base dispersion can be dried to form a first binder coating layer.

[0015] In particular embodiments, the first aqueous-based dispersion can be disposed on the first substrate surface substantially simultaneously with disposing the first aqueous-based dispersion on the second substrate surface. For example, a microporous polyolefin-based substrate film can be dip-coated or otherwise moved through the first aqueous-based dispersion, thereby disposing the first aqueous-based dispersion on both the first substrate surface and the second substrate surface. Thereafter, the first aqueous-based dispersion can be dried to form the first and second inorganic coatings. Similarly, in particular embodiments, the second aqueous-based dispersion can be disposed on the first and second inorganic coatings substantially simultaneously. For example, the coated microporous polyolefin-based substrate film including the first and second inorganic coatings can be dip-coated or otherwise moved through the second aqueous-based dispersion, thereby disposing the second aqueous-based dispersion on both the first inorganic coating and the second inorganic coating. Thereafter, the second aqueous-based dispersion on the second inorganic coating can be dried to form the first and second adhesive coatings.

[0016] The coated separators disclosed herein are an improvement over conventional coated separators. For example, separators used in batteries need to exhibit properties such as good melt integrity, good temperature dimensional stability, and the ability to be laminated to electrodes. At least some conventional separators used in batteries are not able to exhibit these properties. For example, some conventional separators can include an adhesive configured to attach the separator to an electrode. The adhesive is able to adhere the conventional separator to the electrode with sufficient strength to successfully laminate the conventional separator to the electrode. However, the bulk between different layers of the electrode can be weaker than the attachment between the adhesive and the electrode, such that the entire conventional separator is not sufficiently laminated to the electrode. Furthermore, the presence of the adhesive in the conventional separator can limit or degrade the 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 be laminated to electrodes, and other properties that are beneficial to separators.

[0017] Figure 1is a cross-sectional schematic view of a coated separator 100 for an energy storage device according to an embodiment. The coated separator 100 includes a microporous polyolefin base film 102. The microporous polyolefin base film 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 can include a first inner inorganic surface 110 affixed to the first base surface 104 and a first outer inorganic surface 112 opposite the first inner inorganic surface 110. The coated separator 100 additionally includes a first binder coating 114 disposed on at least a portion of the first inorganic coating 108. For example, the first binder coating 114 includes a first inner binder surface 116 affixed to at least a portion of the first outer inorganic surface 112 and a first outer binder surface 118 opposite the first inner binder surface 116.

[0018] The coated separator 100 can 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 can include a second inner inorganic surface 122 affixed 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 binder coating 126 disposed on at least a portion of the second inorganic coating 120. For example, the second binder coating 126 includes a second inner binder surface 128 affixed to at least a portion of the second outer inorganic surface 124 and a second outer binder surface 130 opposite the second inner binder surface 128.

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

[0020] The microporous polyolefin base film 102 includes one or more polymers or polyolefins. For example, the microporous polyolefin base film 102 can include a polyethylene, such as ultra-high molecular weight polyethylene (UHMWPE), very-high molecular weight polyethylene (VHMWPE), high-density polyethylene (HDPE), or mixtures thereof. UHMWPE generally corresponds to a range between about 3,100,000 g / mol to about 10,000,000 g / mol, and VHMWPE generally corresponds to a range between about 500,000 g / mol to about 3.1 g / mol. In another embodiment, the microporous polyolefin base film 102 includes a polyethylene having a molecular weight greater than 300,000 g / mol (such as between about 300,000 g / mol and about 10,000,000 g / mol) and exhibits a measurable melt flow index. The microporous polyolefin base film 102 can also include one or more polymers different from or in addition to polyethylene, such as polypropylene, polyester, polystyrene, polyester, polyphenylene sulfide, or polyethylene terephthalate (PET).

[0021] In embodiments, the microporous polyolefin-based substrate film 102 is manufactured by combining one or more polymers with a plasticizer (e.g., mineral oil). The mixture is then blended and extruded to form a uniform viscous mass. The mass can be processed using blown film, cast film, or calendering methods to yield an oil-extended sheet of reasonable thickness (about 250 pm or less). The oil-extended sheet can be further biaxially oriented to reduce its thickness and achieve its mechanical properties. In an extraction operation, the plasticizer (e.g., mineral oil) is removed with a solvent, followed by evaporation of the solvent to produce a microporous polyolefin film, which is then coated with an inorganic surface layer.

[0022] The plasticizer employed is a non-evaporative solvent for the polymer and is preferably liquid at room temperature. The plasticizer has little or no solvency for the polymer at room temperature; it exerts its solvency at or above the softening temperature of the polymer. It is preferred to use a process oil, such as a paraffinic oil, a naphthenic oil, an aromatic oil, or a mixture of two or more such oils. Examples of suitable process 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 an annular die, and then biaxially oriented to form a thin oil-extended sheet. Any solvent compatible with the oil can be used for the extraction step, provided that the boiling point of the solvent makes it feasible to separate the solvent from the plasticizer by distillation. Such solvents include 1,1,2 trichloroethene; perchloroethylene; 1,2-dichloroethane; 1,1,1-trichloroethane; 1,1,2-trichloroethane; dichloromethane; chloroform; 1,1,2-trichloro-1,2,2-trifluoroethane; isopropyl alcohol; diethyl ether; acetone; hexane; heptane; and toluene. Other solvents can also be used, including those identified in PCT / US 2023 / 060674 entitled Microporous Polyolefin Membranes from Bespoke Solvents, which is incorporated by reference herein in its entirety. In some cases, it is desirable to select a process oil such that any residual oil in the polyolefin film after extraction is electrochemically inactive.

[0024] In embodiments, the microporous polyolefin-based base film 102 can include a plurality of inorganic particles uniformly dispersed within the polymer. Disposing the inorganic particles in the microporous polyolefin-based base film 102 can help keep the pores of the microporous polyolefin-based base film 102 open and minimize shrinkage of the coated separator 100 when the coated separator 100 is heated to a temperature greater than the melting temperature or glass transition temperature of the polymer.

[0025] The inorganic particles can include at least one of an inorganic oxide, carbonate, or hydroxide, such as aluminum oxide, silicon dioxide, zirconium oxide, titanium dioxide, mica, boehmite, magnesium hydroxide, calcium carbonate, another suitable inorganic acid, or a mixture thereof. One or more hydrotalcites can also be used, either alone or in combination with another type of inorganic particle. The inorganic material can include colloidal or fumed inorganic particles. The inorganic particles can exhibit an average particle size (e.g., average particle diameter) that is less than the thickness of the microporous polyolefin-based base film 102. In examples, the inorganic particles can exhibit an average particle size that is about 50% or less than the thickness of the microporous polyolefin-based base film 102.

[0026] In embodiments, the inorganic particles can be mixed with the polymer of the microporous polyolefin-based base film 102 prior to forming the microporous polyolefin-based base film 102. For example, the inorganic particles can be mixed with the polymer prior to extruding the polymer. In embodiments, the inorganic particles can be dispersed in the microporous polyolefin-based base film 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 greater detail below, the first inorganic coating 108 and the second inorganic coating 120 can be formed from a first aqueous-based dispersion. The first inorganic coating 108 and the second inorganic coating 120 include a plurality of inorganic particles. Any of the above-identified inorganic particles can be used. At high temperatures, the pores within the microporous polyolefin-based base film 102 can begin to collapse or close, thereby changing its permeability and reducing ion conduction. This, in turn, closes the battery cell. The inorganic particles of the first inorganic coating 108 and the second inorganic coating 120 are configured to maintain the planar dimensional stability of the microporous polyolefin-based base film 102. This prevents contact between the electrodes when the battery cell is closed due to loss of ion conduction.

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

[0029] In embodiments, the inorganic particles are selected to include nanoparticles or to include substantially only nanoparticles (e.g., about 90 wt% or more nanoparticles). It has been found that reducing the surface roughness of the first inorganic coating 108 and the second inorganic coating 120 increases the maximum laminate strength of the coated separator 100. The surface roughness of the first inorganic coating 108 and the second inorganic coating 120 is dependent, in part, on the average particle size of the inorganic particles that form the first inorganic coating 108 and the second inorganic coating 120. In particular, reducing the average particle size of the inorganic particles of the first inorganic coating 108 and the second inorganic coating 120 reduces the surface roughness of the first inorganic coating 108 and the second inorganic coating 120. It is presently believed that the reduced surface roughness of the first inorganic coating 108 and the second inorganic coating 120 increases the strength of the interfacial bonding between the microporous polyolefin base membrane 102 and the first inorganic coating 108 and the second inorganic coating 120. As such, selecting the inorganic particles of the first inorganic coating 108 and the second inorganic coating 120 to include nanoparticles increases the maximum laminate strength of the coated separator 100. The increased maximum laminate strength of the coated separator 100 can allow for a reduction in the amount of adhesive present in the coated separator 100, thereby allowing for a reduction in the thickness of the coated separator 100, a reduction in materials and costs associated with forming the coated separator 100, and avoidance of issues caused by the adhesive (e.g., loss of dimensional stability at high temperatures).

[0030] The inorganic particles of the first inorganic coating 108 and the second inorganic coating 120 can form about 75 wt% or more, such as about 80 wt% to about 90 wt%, of the first inorganic coating 108 and the second inorganic coating 120. The weight percentage of the inorganic particles present in the first inorganic coating 108 and the second inorganic coating 120 can depend on whether the first inorganic coating 108 and the second inorganic coating 120 include other components (e.g., hydrogen bonding components and / or crosslinking agents) and the composition of the other components. In embodiments, when the first inorganic coating 108 and the second inorganic coating 120 include hydrogen bonding components and crosslinking agents, the inorganic particles of the first inorganic coating 108 and the second inorganic coating 120 can form about 80 wt% to about 90 wt% of the first inorganic coating 108 and the second inorganic coating 120. The weight percentage of the inorganic particles in the first inorganic layer 108 and the second inorganic layer 120 can 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 embodiments, the first inorganic coating 108 and the second inorganic coating 120 can include a hydrogen bonding component. The hydrogen bonding component can form a binder that binds the inorganic particles together and binds the first inorganic coating 108 and the second inorganic coating 120 to adjacent layers of the coated separator 100. In this way, the hydrogen bonding component can increase the laminate strength and high temperature dimensional stability of the coated separator 100. The hydrogen bonding component can also cause the coated separator 100 to exhibit low Gurley (i.e., high air permeability) values.

[0032] In embodiments, the hydrogen bonding component can include a low molecular weight water-soluble polymer. In embodiments, the hydrogen bonding component can include at least one polymer or small molecule having multiple hydrogen bonding sites to minimize the weight percentage of the hydrogen bonding component in the first inorganic coating 108 and the second inorganic coating 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), polyvinyl pyrrolidone (PVP), carboxymethyl cellulose (CMC), polyacrylic acid, polyethylene oxide, or combinations thereof.

[0033] The hydrogen bonding component can form about 2 wt% to about 25 wt%, such as about 10 wt% to about 20 wt%, of the first inorganic coating 108 and the second inorganic coating 120. The weight percentage of the hydrogen bonding component can be selected for a variety of reasons. In examples, the weight percentage of the hydrogen bonding component can be selected based on the average particle size of the inorganic particles. As previously discussed, the laminate strength of the coated separator is partially dependent on the average particle size of the inorganic particles. When the inorganic particles are relatively coarse, the weight percentage of the hydrogen bonding component can be increased to compensate for the weaker laminate strength provided by the coarse inorganic particles, and vice versa. In examples, the weight percentage of the hydrogen bonding component can be selected based on the number of hydrogen bonding sites of the hydrogen bonding component. In examples, the weight percentage of the hydrogen bonding component can be selected based on whether the first inorganic coating 108 and the second inorganic coating 120 include a crosslinking agent.

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

[0035] The crosslinking agent can include any agent that can react with the hydrogen bonding component. Examples of crosslinking agents include boric acid, glycerol glycidyl ether, citric acid, succinic acid, glutaraldehyde, maleic acid, sodium borate, a polyfunctional aziridine, other suitable crosslinking agents, or combinations thereof. Specific examples of polyfunctional aziridines include XAMA-7 (C 20 H 33 O7N3) and pentaerythritol tris(3-(1-aziridinyl)propionate). In specific embodiments, the hydrogen bonding component includes polyvinyl alcohol and the crosslinking agent includes at least one polyfunctional aziridine. It has been found that polyvinyl alcohol in combination with at least one polyfunctional aziridine allows the coated separator 100 to exhibit a laminate strength greater than about 75 gf / 25 mm, or greater than about 100 gf / 25 mm, tested at room temperature (i.e., 23 °C) using a 180° peel test.

[0036] The cross-linking agent can form greater than 0 wt% to about 10 wt%, such as about 2 wt% to about 4 wt%, of the first inorganic coating 108 and the second inorganic coating 120. The weight percentage of the cross-linking agent in the first inorganic coating 108 and the second inorganic coating 120 can be selected based on a variety of factors. Generally, increasing the weight percentage of the cross-linking agent in the first inorganic coating 108 and the second inorganic coating 120 increases the percentage of cross-linked hydrogen-bonding components, thereby increasing the strength of the first inorganic coating 108 and the second inorganic coating 120. However, increasing the weight percentage of the cross-linking agent in the first inorganic coating 108 and the second inorganic coating 120 also increases the likelihood that the cross-linking agent remains unreacted after the formation of the first inorganic coating 108 and the second inorganic coating 120, which results in the cross-linking agent adversely affecting the strength of the first inorganic coating 108 and the second inorganic coating 120. In other words, there can be a weight percentage of the cross-linking agent in the first inorganic coating 108 and the second inorganic coating 120 that maximizes the cross-linking of the hydrogen-bonding components while minimizing the unreacted cross-linking agent. The weight percentage of the cross-linking agent that maximizes the cross-linking of the hydrogen-bonding components while minimizing the unreacted cross-linking agent can depend on the composition of the hydrogen-bonding components and the composition of the cross-linking agent.

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

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

[0039] The first adhesive coating 114 and the second adhesive coating 126 can exhibit any suitable thickness. For example, each of the first adhesive coating 114 and the second adhesive coating 126 can exhibit a thickness of about 0.2 pm to about 2 pm, such as about 0.5 pm to about 1 pm. In embodiments, the thickness of the first adhesive coating 114 and the second adhesive coating 126 can be substantially the same or different. In embodiments, the thickness of the first adhesive coating 114 and the second adhesive coating 126 is selected to provide sufficient lamination strength to the coated separator 100 while minimizing any adverse impact of the first adhesive coating 114 and the second adhesive coating 126 on the high temperature stability of the coated separator 100.

[0040] The first adhesive coating 114 and the second adhesive coating 126 include an adhesive. The adhesive is configured to adhere the first adhesive coating 114 and the second adhesive coating 126 to an electrode, another separator, or another component of a battery. The adhesive of the first adhesive coating 114 and the second adhesive coating 126 can include any adhesive configured to adhere the coated separator 100 to any structure or any other suitable structure. The adhesive can 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 electrolytes and acids of a battery. In examples, the adhesive includes a fluoropolymer resin, such as the fluoropolymer resin of FMA-12 polymer emulsion manufactured by Arkema. It is presently believed that the fluoropolymer resin from the FMA-12 polymer emulsion provides the coated separator 100 with extremely high lamination strength that is stable when heated to temperatures of at least 180 °C and exposed to electrolytes and acids used in common lithium-ion batteries. Other types of adhesives can also be used. Generally, the first adhesive coating 114 and the second adhesive coating 126 include the same adhesive, although it is noted that the first adhesive coating 114 and the second adhesive coating 126 can include different adhesives.

[0041] The adhesive of the first adhesive coating 114 and the second adhesive coating 126 can form about 75 wt% or more, such as about 85 wt% to about 97 wt%, of the first adhesive coating 114 and the second adhesive coating 126. The weight percentage of the adhesive present in the first adhesive coating 114 and the second adhesive coating 126 can depend on whether the first adhesive coating 114 and the second adhesive coating 126 include other components, such as inorganic particles or hydrogen bonding components. In embodiments, when the first adhesive coating 114 and the second adhesive coating 126 include inorganic particles and hydrogen bonding components, the adhesive of the first adhesive coating 114 and the second adhesive coating 126 can form about 85 wt% to about 97 wt% of the first adhesive coating 114 and the second adhesive coating 126. The weight percentage of the adhesive in the first inorganic layer 108 and the second inorganic layer 120 can be selected for other reasons, such as the composition of the adhesive, whether the first adhesive coating 114 and the second adhesive coating 126 are partially disposed on at least the first inorganic coating 108 and the second inorganic coating 120, and the surface roughness of the first inorganic coating 108 and the second inorganic coating 120 and / or the surface roughness of the first inorganic coating 108 and the second inorganic coating 120.

[0042] In embodiments, the first adhesive coating 114 and the second adhesive coating 126 include inorganic particles. The inorganic particles of the first adhesive coating 114 and the second adhesive coating 126 can include any of the inorganic particles disclosed herein and can be the same or different than the inorganic particles of the first inorganic coating 108 and the second inorganic coating 120. The inorganic particles of the first adhesive coating 114 and the second adhesive coating 126 improve the high temperature stability of the first adhesive coating 114 and the second adhesive coating 126 and the overall coated separator 100. The inorganic particles in the first adhesive coating 114 and the second adhesive coating 126 also improve the adhesion between the first inorganic coating 108 and the first adhesive coating 114 and the adhesion between the second inorganic coating 120 and the second adhesive coating 126, respectively. The improved adhesion between the first inorganic coating 108 and the first adhesive coating 114 and the improved adhesion between the second inorganic coating 120 and the second adhesive coating 126 improve the laminate strength of the coated separator 100, respectively.

[0043] The inorganic particles of the first adhesive coating 114 and the second adhesive coating 126 can form less than about 25 wt% of the first adhesive coating 114 and the second adhesive coating 126, such as from about 7 wt% to about 15 wt%. The weight percentage of inorganic particles present in the first adhesive coating 114 and the second adhesive coating 126 can be selected based on a variety of factors. In examples, the weight percentage of inorganic particles can 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 examples, the weight percentage of inorganic particles can be selected to impart a desired high temperature stability to the first adhesive coating 114 and the second adhesive coating 126, where increasing the weight percentage of inorganic particles increases the high temperature stability of the first adhesive coating 114 and the second adhesive coating 126. In examples, the weight percentage of inorganic particles can be selected based on a desired lamination strength, as generally increasing the weight percentage of inorganic particles in the first adhesive coating 114 and the second adhesive coating 126 increases the lamination strength of the coated separator 100. For example, the weight percentage of inorganic particles can be selected to impart a lamination strength of about 75 gf / 25 mm or greater, or about 100 gf / 25 mm or greater, as tested using the 180° Peel Test at room temperature (i.e., 23 °C) to the coated separator 100.

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

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

[0046] In embodiments, 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 can include one or more components different from the components listed above. In examples, one or more layers of the coated separator can include a gel-forming material, examples of which are disclosed in U.S. Patent Application Publication No. 2019 / 0386274, filed March 14, 2017, the disclosure of which is incorporated herein by reference in its entirety. In examples, one or more layers of the coated separator 100 can include a reinforcing material, such as a plurality of glass fibers. In examples, the first adhesive coating 120 and / or the second adhesive coating 126 can include a crosslinking agent.

[0047] As previously discussed, the coated separator 100 can exhibit high temperature stability, which can prevent or inhibit the creation of internal short circuits in a battery during a battery malfunction. 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 the cross direction after exposure to a temperature of about 180 °C. For example, the coated separator 100 can exhibit a shrinkage of about 5% or less in each of the machine direction and the cross direction after exposure to a temperature of about 180 °C. The high temperature stability of the coated separator 100 depends, in part, on the weight percentages of the inorganic particles, the hydrogen bonding component, and the crosslinking agent in each layer of the coated separator 100.

[0048] In embodiments, the coated separator 100 can exhibit an area resistance of about 1.5 Ω-cm 2 or less, such as about 0.9 Ω-cm 2 or less. The area resistance of the coated separator 100 depends, in part, on the composition of the microporous polyolefin base film 102 and the average pore size of the coated separator 100.

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

[0050] In embodiments, the coated separator 100 can exhibit a Gurley number of about 50 s / 100 cc air to about 800 s / 100 cc air, such as about 80 s / 100 cc air to about 250 s / 100 cc air. The Gurley number of the coated separator 100 is indicative of the transport resistance of the coated separator 100. For example, the Gurley number can be indicative of at least one of the porosity, the pore size, the thickness, or the tortuosity of the coated separator 100.

[0051] In embodiments, the coated separator 100 can exhibit a MacMichael number of less than about 15, such as less than about 9. The MacMichael number is the ratio of the ionic conductivity of a pure electrolyte to the ionic conductivity of the coated separator 100 filled with the electrolyte.

[0052] The coated separator 100 exhibits an average thickness of approximately 5 µm to approximately 25 µm, such as approximately 9 µm to approximately 16 µm. The thickness t of the coated separator 100 depends on the thickness of each layer of the coated separator 100 and the number of layers forming the coated separator 100. Generally, it is desirable to reduce the total thickness of the coated separator 100, thereby increasing the energy density of the battery.

[0053] The coated diaphragm 100 can be formed using any suitable process. Figure 2A and Figure 2B An exemplary dip-coating process for forming the coated diaphragm 100 according to an embodiment is shown. Reference Figure 2A A micron-porous base membrane 102 is wound onto a cardboard core 201. The micron-porous base membrane 102 can also be fed directly from an extruder or a cast film production line. The micron-porous base membrane 102 is unwound from a unwinder (or otherwise fed) and impregnated in a bath 202 of a first aqueous dispersion to form a first impregnated micron-porous polyolefin base membrane 203. The first aqueous dispersion comprises one or more solids and at least one liquid. The solids of the first aqueous dispersion form a first inorganic coating 108 and a second inorganic coating 120 and comprise inorganic particles of the first inorganic coating 108 and the second inorganic coating 120, as well as optionally hydrogen-bonded components, crosslinking agents, or other components. The liquid may include water (e.g., deionized water), isopropanol, another alcohol, another suitable liquid, or a combination thereof.

[0054] After impregnating the micron-porous polyolefin base membrane 102 in a first aqueous dispersion, Mayer rods (e.g., two Mayer rods, one for each side of the coated micron-porous polyolefin base membrane 102) can be used to control the thickness of the first aqueous dispersion coating on the first impregnated micron-porous polyolefin base membrane 203. The first impregnated micron-porous polyolefin base membrane 203 can then be dried, for example, using a series of air knives (not shown) and passed through a vertical oven 204 to form a first inorganic coating 108 and a second inorganic coating 120 on the micron-porous polyolefin base membrane 102. The coated micron-porous polyolefin base membrane 205 (i.e., the micron-porous polyolefin base membrane 102 and the first inorganic coating 108 and the second inorganic coating 120) can then be wound onto a core 206.

[0055] refer to Figure 2BThe coated microporous polyolefin base film 205 is unwound from the core 206 and immersed in a bath 208 of a second aqueous-based dispersion to form a second immersed microporous polyolefin base film 210 (i.e., the first inorganic coating 108 and the second inorganic coating 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 and comprise the binder of the first adhesive coating 114 and the second adhesive coating 126 and, optionally, inorganic particles, hydrogen bonding components, or other components. The liquid can include water (e.g., deionized water), isopropyl alcohol, another alcohol, another suitable liquid, or combinations thereof.

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

[0057] Figure 3 Exemplary embodiments of a coated separator 100 are shown in FIGS. 2-4. The coated separator 100 includes a microporous polyolefin base film 205, a first inorganic coating 108, a second inorganic coating 120, a first adhesive coating 114, and a second adhesive coating 126. The microporous polyolefin base film 205 is coated with the first inorganic coating 108 and the second inorganic coating 120. The first inorganic coating 108 and the second inorganic coating 120 are coated with the first adhesive coating 114 and the second adhesive coating 126. Figure 2A and Figure 2BThe two-step process shown in FIG. 1 is combined into a single-step exemplary dip coating process. Microporous polyolefin-based substrate film 102 is wound on a paperboard core 301. Microporous polyolefin-based substrate film 102 is unwound from the unwinder and dipped in a bath 302 of a first aqueous-based dispersion to form a first dipped microporous polyolefin-based substrate film 303. After microporous polyolefin-based substrate film 102 is dipped in the first aqueous-based dispersion, a Meyer bar (e.g., two Meyer bars, one for each side of the coated microporous polyolefin-based substrate film 102) can be used to control the thickness of the first aqueous-based dispersion coating on the first dipped microporous polyolefin-based substrate film 303. The first dipped microporous polyolefin-based substrate film 303 can then be dried, for example, with a series of air knives (not shown) and transported through a first vertical oven 304a to form a first inorganic coating 108 and a second inorganic coating 120 on microporous polyolefin-based substrate film 102. The coated microporous polyolefin-based substrate film 305 (i.e., microporous polyolefin-based substrate film 102 and first inorganic coating 108 and second inorganic coating 120) can then be dipped in a bath 308 of a second aqueous-based dispersion to form a second dipped microporous polyolefin-based substrate film 310. After the coated microporous polyolefin-based substrate film 305 is dipped in the second aqueous-based dispersion, a Meyer bar (e.g., two Meyer bars, one for each side of the second microporous polyolefin-based substrate film 310) can be used to control the thickness of the second aqueous-based dispersion coating on the second dipped microporous polyolefin-based substrate film 310. The second dipped microporous polyolefin-based substrate film 310 can then be dried, for example, with a series of air knives (not shown) and transported through a second vertical oven 304b to form a first adhesive coating 114 and a second adhesive coating 126. The coated separator film 100 can then be wound onto a core 312.

[0058] It should be noted that the coated separator film 100 can be formed using other techniques. Examples of other methods that can be used to form the coated separator film 100 are disclosed in U.S. Patent Application Publication No. 2019 / 0386274, filed March 14, 2017, the disclosure of which is hereby incorporated by reference in its entirety.

[0059] Working Examples

[0060] The following working examples provide additional details regarding the coated separators disclosed herein.

[0061] Example 1

[0062] A 7 pm thick microporous separator film containing ultra-high molecular weight polyethylene and fumed aluminum oxide (7 pm CF, Membranes LLC, Oregon) made at ENTEK was coated with an aqueous-based dispersion consisting of:

[0063] 282.3 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Sekisui)

[0064] 237.7 g deionized water

[0065] 40 g isopropyl alcohol

[0066] 440 g CAB-O-SPERSE PG 003 (40 wt% alumina in water; Cabot Corporation)

[0067] The coating dispersion contained 20 wt% solids with an alumina / PVOH mass ratio of 88 / 12. The separator was dip coated with the aqueous-based dispersion and a #9 Meyer bar was used to control the thickness of the wet layer on each side. The wet separator was then dried with a series of air knives and transported through a vertical oven set to 100 °C and wound onto a core before testing and additional coating.

[0068] The separator was then coated on both sides again with an aqueous-based dispersion consisting of:

[0069] 17.7 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Sekisui)

[0070] 348.2 g deionized water

[0071] 30 g isopropyl alcohol

[0072] 15 g W450ZX (50 wt% alumina in water; Evonik)

[0073] 89.1 g FMA-12 (46 wt% polymer emulsion in water; Arkema)

[0074] The coating dispersion contained 20 wt% solids with an FMA-12 polymer / alumina / polyvinyl alcohol (PVOH) mass ratio of 90 / 7 / 3. The separator was dip coated with the aqueous-based dispersion and a #4 Meyer bar was used to control the thickness of the wet layer on each side. The wet separator was then dried with a series of air knives and transported through a vertical dryer and wound onto a core before testing.

[0075] Example 2

[0076] A 7 pm thick microporous ultra-high molecular weight polyethylene and fumed alumina containing membrane (7 pm CF, Membrane Technology Limited, Oregon) prepared at ENTEK was coated with an aqueous-based dispersion consisting of:

[0077] 353 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Nippon Shokubai)

[0078] 182 g deionized water

[0079] 40 g isopropyl alcohol

[0080] 425 g CAB-O-SPERSE PG 003 (40 wt% alumina in water; Cabot Corporation)

[0081] The coating dispersion contained 20 wt% solids with an alumina / PVOH mass ratio of 85 / 15. The membrane was dip coated with the aqueous-based dispersion and the wet layer thickness on each side was controlled with a #9 Meyer bar. The wet membrane was then dried with a series of air knives and transported through a vertical oven set at 100 °C and wound onto a core before testing and additional coating.

[0082] The membrane was then coated on both sides again with an aqueous-based dispersion consisting of:

[0083] 35.3 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Nippon Shokubai)

[0084] 225 g deionized water

[0085] 30 g isopropyl alcohol

[0086] 14 g W450ZX (50 wt% alumina in water; Evonik)

[0087] 195.7 g FMA-12 (46 wt% polymer emulsion in water; Arkema)

[0088] The coating dispersion contained 20 wt% solids with an FMA-12 polymer / alumina / PVOH mass ratio of 90 / 7 / 3. The membrane was dip coated with the aqueous-based dispersion and the wet layer thickness on each side was controlled with a #4 Meyer bar. The wet membrane was then dried with a series of air knives and transported through a vertical dryer and wound onto a core before testing.

[0089] Example 3

[0090] A 7 pm thick microporous ultra-high molecular weight polyethylene and fumed alumina containing membrane (7 pm CF, Membrane Technology LLC, Oregon) prepared at ENTEK was coated with an aqueous-based dispersion consisting of:

[0091] 282.4 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Nippon Paper Industries)

[0092] 246.6 g deionized water

[0093] 40 g isopropyl alcohol

[0094] 425 g CAB-O-SPERSE PG 008 (40 wt% alumina in water; Cabot Corporation)

[0095] 6.0 g PZ-33 (pentaerythritol tri(3-(l-aziridinyl)propionate, PolyAziridine LLC)

[0096] The coating dispersion contained 20 wt% solids with an alumina / PVOH / aziridine mass ratio of 85 / 12 / 3. The membrane was dip coated with the aqueous-based dispersion and the thickness of the wet layer on each side was controlled with a #10 Meyer bar. The wet membrane was then dried with a series of air knives and transported through a vertical oven set to 100 °C and wound onto a core before testing and additional coating.

[0097] This membrane was then coated again on both sides with an aqueous-based dispersion consisting of:

[0098] 17.7 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Nippon Paper Industries)

[0099] 348.2 g deionized water

[0100] 30 g isopropyl alcohol

[0101] 15 g W450ZX (50 wt% alumina in water; Evonik)

[0102] 89.1 g FMA-12 (46 wt% polymer emulsion in water; Arkema)

[0103] The coating dispersion contained 10 wt% solids with a FMA-12 polymer / alumina / PVOH mass ratio of 85 / 12 / 3. The membrane was dip coated with the aqueous-based dispersion and the thickness of the wet layer on each side was controlled with a #4 Meyer bar. The wet membrane was then dried with a series of air knives and transported through a vertical dryer and wound onto a core prior to testing.

[0104] Example 4

[0105] A 9 pm thick microporous ultra-high molecular weight polyethylene and fumed alumina containing membrane (9 pm CF, Membrane Technology LLC, Oregon) prepared at ENTEK was coated with an aqueous-based dispersion consisting of:

[0106] 282.4 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Nippon Paper Industries)

[0107] 246.6 g deionized water

[0108] 40 g isopropyl alcohol

[0109] 425 g CAB-O-SPERSE PG 008 (40 wt% alumina in water; Cabot Corporation)

[0110] 6.0 g PZ-33 (pentaerythritol tri(3-(1-aziridinyl)propionate, Polyaziridine LLC)

[0111] The coating dispersion contained 20 wt% solids with an alumina / PVOH / aziridine mass ratio of 85 / 12 / 3. The membrane was dip coated with the aqueous-based dispersion and the thickness of the wet layer on each side was controlled with a #10 Meyer bar. The wet membrane was then dried with a series of air knives and transported through a vertical oven set to 100 °C and wound onto a core prior to testing and additional coating.

[0112] The two sides of this membrane were then coated again with an aqueous-based dispersion consisting of:

[0113] 35.3 g Selvol 09-325 (aqueous-based PVOH solution; 98% hydrolyzed; 8.5 wt% solids; Nippon Paper Industries)

[0114] 225 g deionized water

[0115] 30 g isopropyl alcohol

[0116] 14 g W450ZX (50 wt% alumina in water; Evonik)

[0117] 195.7 g FMA-12 (46 wt% polymer emulsion in water; Arkema)

[0118] The coating dispersion contained 20 wt% solids with a FMA-12 polymer / alumina / PVOH mass ratio of 90 / 7 / 3. The separator was dip coated with the aqueous based dispersion and the wet layer thickness on each side was controlled with a #4 Meyer bar. The wet separator was then dried with a series of air knives and transported through a vertical dryer and wound onto a core prior to testing.

[0119] Summary of data:

[0120] Thickness was measured using an EMVECO micrometer (Model 200-A). Air permeability was measured using an Asahi Seiki Model EGO1-55-1MR. For shrinkage testing, the coated separator was hung in an oven at 180°C for 5 minutes. The shrinkage after 180°C exposure was measured in the machine direction and the cross direction. For laminate strength measurements, two pieces of coated separator were placed between PET release film. The sample was then placed in a Carver laboratory press (Model C) with a temperature set point of 80°C and pressed at 210 psi for 20 seconds. The laminate strength of the separator was then measured at room temperature (i.e., 23°C) using a 180° peel test. Impedance measurements were measured using a Gamry impedance analyzer (Interface 1000) at 100 KHz. The separators were soaked in 1 M LiPF6in a 1 : 1 EC: EMC and the impedance measurements were plotted for 1, 2, and 3 layer separators; the slope of the plot gives the resistance of the single layer, which was used to calculate the MacM illan number of the separator.

[0121] Table 1

[0122]

[0123] As shown in Table 1, the coated separators disclosed herein exhibit good Gurley number, high temperature thermal stability, laminate strength, and MacM illan number. For example, at least some of the coated separators of Examples 1-4 can be used in lithium ion batteries. It is noted that Table 1 demonstrates that including PVOH and aziridine crosslinker in the inorganic coating significantly increases the laminate strength of the coated separator.

[0124] While a number of aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting.

[0125] Approximations are referred to throughout the specification, such as by use of the terms "about" or "approximately". For each such approximation, it should be understood that in some embodiments the value, feature, or characteristic can be specified without approximation. For example, where a qualifier such as "about," "substantially," and "approximately" is used, these terms include the qualified term without the qualifier within its range. Further, all ranges include both endpoints.

[0126] The claims following the written disclosure hereby expressly incorporated by reference into this written disclosure, wherein each claim is separately indicative of a separate embodiment. The disclosure includes all permutations of the independent claims and their dependent claims. Additionally, additional embodiments derived from the following independent and dependent claims are expressly incorporated into this written description.

[0127] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present application to its fullest extent. The claims and embodiments disclosed herein are to be construed as merely illustrative and not a limitation of the scope of the present disclosure. It will be apparent to one of ordinary skill in the art that changes can be made to the details of the above-described embodiments without departing from the essential principles of the disclosure disclosed herein. In other words, various modifications and improvements of the embodiments specifically disclosed in the above description are within the scope of the following claims. Thus, the scope of the present application should not be limited to the specific embodiments described herein, but only by the claims that follow.

Claims

1. A coated diaphragm for an energy storage device, comprising: A micron-sized porous polyolefin substrate membrane having a first substrate surface and a second substrate surface opposite to the first substrate surface; A first inorganic coating disposed on at least a portion of the surface of the first substrate, 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; The coated diaphragm, when attached to itself, exhibits a lamination strength of approximately 75 gf / 25 mm to approximately 170 gf / 25 mm after lamination for 20 seconds at 80°C and 1.4 MPa using a 180° peel test at 23°C, and the coated diaphragm exhibits the following before lamination: After exposure to a temperature of 180°C, the shrinkage rate is approximately 5% or less in both the machine direction and the transverse direction; or A McMarin number of 9 or less.

2. The coated separator of claim 1, wherein, Prior to lamination, the coated diaphragm further exhibits a Grylls number of approximately 250 s / 100 cc air or less.

3. The coated separator of claim 1 or claim 2, wherein, The micron-porous polyolefin substrate membrane comprises polyethylene with a molecular weight greater than 300,000 g / mol and exhibits a measurable melt flow index.

4. The coated separator of claim 1 or claim 2, wherein, The micron-sized porous polyolefin base membrane contains 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 particle includes inorganic oxides, carbonates, hydroxides, or mixtures thereof, or wherein the first inorganic particle includes alumina, silicon dioxide, zirconium oxide, titanium dioxide, mica, boehmite, magnesium hydroxide, calcium carbonate, hydrotalcite, or mixtures thereof.

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

7. The coated separator of claim 6, wherein, The first inorganic coating contains at least one crosslinking agent.

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

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

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

11. The coated separator of any one of claims 1-10, wherein, The coated diaphragm exhibits a shrinkage rate of approximately 5% or less in both the machine direction and the transverse direction after being exposed to a temperature of 180°C.

12. The coated separator of any one of claims 1-10, wherein, The coated diaphragm exhibits a McMurlin number of 9 or less.

13. The coated separator of any one of claims 1-12, wherein, The coated diaphragm exhibits the following characteristics: After exposure to a temperature of 180°C, the machine experiences a shrinkage rate of approximately 5% or less in both the directional and transverse directions; and The McMullin number is 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 surface of the second substrate, the second inorganic coating comprising 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: electrode; and The coated diaphragm as described in any one of claims 1-14 is attached to the electrode.

16. A method for forming a coated diaphragm for an energy storage device, the method comprising: At least a portion of a first substrate surface of a micron-porous polyolefin substrate membrane is coated with a first aqueous dispersion, the micron-porous polyolefin substrate membrane comprising a second substrate surface opposite to the first substrate surface, the first aqueous dispersion comprising a plurality of first inorganic particles; The first aqueous dispersion on the surface of the first substrate is dried to form a first inorganic coating on at least a portion of the surface of the first substrate of the micron-porous polyolefin substrate film. At least a portion of the first inorganic coating is coated with a second aqueous dispersion, the second aqueous dispersion comprising at least one binder; as well as The second aqueous dispersion is dried to form a first adhesive coating on at least a portion of the first inorganic coating to form the coated diaphragm; The coated diaphragm, when attached to itself, exhibits a lamination strength of approximately 75 gf / 25 mm to approximately 170 gf / 25 mm after lamination for 20 seconds at 80°C and 1.4 MPa using a 180° peel test at 23°C; and the coated diaphragm exhibits the following before lamination: After exposure to a temperature of 180°C, the shrinkage rate is approximately 5% or less in both the machine direction and the transverse direction; or A McMarin number of 9 or less.

17. The method of claim 16, wherein, Prior to lamination, the coated diaphragm further exhibited a Grylls number of approximately 250 s / 100 cc air or less.

18. The method of claim 16 or claim 17, wherein, The micron-porous polyolefin substrate membrane comprises polyethylene with a molecular weight greater than 300,000 g / mol and exhibits a measurable melt flow index.

19. The method of claim 16 or claim 17, wherein, The micron-sized porous polyolefin base membrane contains one or more of ultra-high molecular weight polyethylene, very high molecular weight polyethylene, or high-density polyethylene.

20. The method according to any one of claims 16 to 19, wherein, The first inorganic particle includes inorganic oxides, carbonates, hydroxides, or mixtures thereof, or wherein the first inorganic particle includes alumina, silicon dioxide, zirconium oxide, titanium dioxide, mica, boehmite, magnesium hydroxide, calcium carbonate, hydrotalcite, or mixtures thereof.

21. The method according to any one of claims 16-20, wherein, The first inorganic coating contains at least one hydrogen-bonded component.

22. The method of claim 21, wherein, The first inorganic coating contains at least one crosslinking agent.

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

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

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

26. The method according to any one of claims 16-25, wherein, The coated diaphragm exhibits a shrinkage rate of approximately 5% or less in both the machine direction and the transverse direction after being exposed to a temperature of 180°C.

27. The method according to any one of claims 16-26, wherein, The coated diaphragm exhibits a McMurlin number of 9 or less.

28. The method according to any one of claims 16-27, wherein, The coated diaphragm exhibits the following characteristics: After exposure to a temperature of 180°C, the machine experiences a shrinkage rate of approximately 5% or less in both the directional and transverse directions; and The McMullin number is 9 or less.

29. The method of any one of claims 16-28, further comprising: At least a portion of the second substrate surface of the micron-porous polyolefin substrate film is coated with the first aqueous dispersion; as well as The first aqueous dispersion on the surface of the second substrate is dried to form a second inorganic coating on at least a portion of the surface of the second substrate of the micron-porous polyolefin substrate film. At least a portion of the second inorganic coating is coated with the second aqueous dispersion; as well as The second aqueous dispersion is dried to form a second adhesive coating on at least a portion of the second inorganic coating.

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