Coated separator for a lithium battery

Abstract

The present disclosure relates to coated separators and methods of producing such coated separator for a lithium battery, wherein coated separators comprise at least one polymer layer on at least one surface of a porous substrate, wherein the polymer layer comprises at least one Polymer of Intrinsic Microporosity (PIM). Preferably, the polymer layer has a hierarchical pore structure, comprising macropores, mesopores and / or micropores. The present invention also relates to electrochemical cells comprising such coated separators.

Description

Attorney Docket No.: 052981-517001WOCOATED SEPARATOR FOR A LITHIUM BATTERYCROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 697,978 filed on September 23, 2024, and U.S. Provisional Patent Application No. 63 / 792,836 filed on April 22, 2025, which are incorporated by reference in their entirety.BACKGROUND OF THE INVENTION

[0002] Electrical vehicles (EV) adoption increased from 100,000 in 2013 to 800,000 in 2022, in large part due to reductions in battery costs and increases in energy density (Michalek, J.J., et al., PNAS, 120 (2023), 23, doi.org / 10.1073 / pnas.2219396120). Advances in materials, focused on high-nickel cathodes, helped facilitate that transition. A report from late 2022 by Proc. Nat. Acad. Sci predicted that EV adoption would approach 50% by 2030 - assuming the EV price premium approaches zero and manufacturers offer EV models for every platform (Sabata, J., IEEE, 11 (2023), 2, doi.org / 10.1109 / MELE.2023.3264889). EV adoption is still limited in large part by the battery due to cost, energy density, and charging (Garsten, E., EV Sales Pace is Running Short of Power Going into 2024, Forbes, 2023, available at: https: / / www.forbes.com / sites / edgarsten / 2023 / 12 / 14 / ev-sales-pace-is-running-short-of-power- going-into-2024 / ?sh=43600c8d7985). Solving this deadlock requires further advances in materials, guided primarily by cost and charge efficiency. Advanced cathode / anode materials such as high-voltage NMC (Guo, Y., et al., Energy Storage Materials, 2024, doi.org / 10.1016 / j.ensm.2024.103258), LMFP (Hu, H., et al., J. Energy Storage, 73 (2023), Part B, 109006, doi.org / 10.1016 / j.est.2023.109006), and majority silicon anodes (Man, Q., et al., .1. Energy Chem., 76 (2023), 576-600, doi.org / 10.1016 / j.jechem.2022.09.020) may help solve portions of the problem, but suffer from technical challenges limiting adoption, such as manganese dissolution (Xu, Y., et al., Energy & Environmental Materials, 6 (2022), 6, el2575, doi.org / 10. 1002 / eem2.12575) and poor interfacial effects (e.g., impedance, wetting) (Liu, J., J. Energy Chem., 91 (2024), 73-98, doi.org / 10.1016 / j.jechem.2023. 12.011 and Thakur, A.K., et al., J. Energy Storage, 73 (2023), Part A, 108873, doi.org / 10.1016 / j.est.2023.108873). For the ever-increasing performance desires of new EV’ s a separator must be able to deliver low resistance at fast cycling rates (charging in 1 h or less), and new cathode technologies would benefit from that can inhibit metal transport. With next generation lithium batteries potentially years from commercialization, it is critical these challenges be solved in today’s lithium-ion system.

[0003] Battery separators are a critical component of lithium batteries, including lithium ion (Li- ion) batteries since they isolate the electrodes, providing ion transport through large pores filled withAttorney Docket No.: 052981-517001WO electrolyte and insulating electronic conductivity that would otherwise induce a short circuit. Whereas separators are not involved directly in cell reactions, their physical properties play a key role in determining the performance of the battery including energy density, power density, and safety. Importantly, separators’ mechanical integrity throughout the entire lifetime of the battery cell is critical for fast cycling rates and prevention of internal short circuit.

[0004] Several porous membrane separator materials and composites are currently utilized in Li- ion batteries, such as separators made of polyolefin, as well as ceramic-coated separators. As described in US 6,432,583 (Celgard Inc.), the ceramic composite layer is intended to block dendrite growth, enable fast cycling rates, and to prevent electronic shorting.

[0005] The use of Polymers of Intrinsic Microporosity (PIMs) as a selective battery membrane has been investigated. PIMs are composed of fused rings providing rigidity and sites of contortion, which may be provided by spiro-centers, by bent or bridged ring moieties, or by similar structural components which serve as a barrier preventing conformational relaxation of polymer chains. PIMs have been described and studied since 2006, as they create continuous networks of interconnected voids used as gas separation membranes, hydrogen storage materials, adsorbents and heterogeneous catalysts. The intrinsic microporosity of PIMs is defined as a network of interconnected intermolecular voids, which form as a direct consequence of the shape and rigidity of the component macromolecules. Notably, the article of Li, et al. (Nano Lett. 2015, 15, 5724-5729) describes the use of PIMs as a membrane platform for achieving high-flux, ion-selective transport in nonaqueous electrolytes.

[0006] As lithium battery electrodes are highly reactive, a solid-electrolyte-interphase (SEI) forms at the interface of the electrode and the adjacent electrolyte-filled separator. The composition and morphology of the SEI impacts the performance of the electrochemical cell. On one hand, the consumption of part of the lithium inventory inherent to the in situ SEI formation process reduces the coulombic efficiency of the electrochemical cell. On the other hand, optimal SEI limits the further decomposition of electrolyte components and improves lithium-ion transport at the electrodeseparator interface, improving the cycling performance and service life of the batteries.

[0007] Artificial SEI layers have been investigated to limit lithium inventory and electrolyte component depletion processes at the surface of anode materials. One of the approaches is based on the use of a layer of PIMs which is coated on porous supports. Notably, WO 2020 / 037246 Al (The Regents of the University of California) describes microporous ladder polymer according to the formula -[A-AB-B]- containing amine-functionalized monomer segments, amidoxime functionalized monomer segments, or a combination thereof, such microporous polymers being used in the separator which may comprise one or more support material such as glass fibers. Thin films of microporous polymers on porous supports, such as a polyolefin battery separator (e.g., Celgard) are described in the examples. The article of Chengyin Fu, et al. (Nature Materials, April 2020) describes a lithium electrode laminated with a TBAF@PIM-1 coated polyolefin separator, i.e., a separator coated withAttorney Docket No.: 052981-517001WO microporous polymer host (e.g., PIM-1) in combination with tetrabutylammonium fluoride (TBAF), with the separator (Celgard 2325). The coated separator was then assembled in either Li-Li or Li- NMC-622 cells along with a carbonate electrolyte containing an ionizable lithium salt (e.g., LiPF6). The composites are described as dendrite-suppressing solid-ion conductors (SICs) in lithium metal batteries.BRIEF SUMMARY OF THE INVENTION

[0008] The present disclosure relates to coated separators and methods of producing such coated separator for a lithium battery, which coated separator comprises at least one polymer layer on at least one surface of a porous substrate, wherein the polymer layer comprises at least one Polymer of Intrinsic Microporosity (PIM). The coated separator has the following properties:- a coat weight less than about 0.8 g / m2, preferably less than about 0.75 g / m2, more preferably less than about 0.7 g / m2, less than about 0.5 g / m2, less than about 0.4 g / m2, more preferably less than about 0.3 g / m2, more preferably less than about 0.2 g / nr;- a Gurley value less than about 400 s / 100 cm3air, preferably ranging from about 100 s / 100 cm3air and 400 s / 100 cm3air, more preferably ranging from about 100 s / 100 cm3air and 300 s / 100 cm3air, when measured on an Oken-type air permeability tester (EG Series, Asahi Seiko).

[0009] In some embodiments, the polymer layer is coated on both surfaces of the porous substrate. In some other embodiments, the polymer layer is coated on one surface of the porous substrate. In some other embodiments which can be combined, the coated separator may comprise at least one additional layer. This additional layer may comprise ceramic and / or aramid. Alternatively, it may comprise at least one PIM, which is distinct or identical to the PIM of the polymer layer.

[0010] In some embodiments, the separator has a heat shrinkage (measured at 150°C, 1 h) of less than 65% on a single-sided PIM coated separator, or less than 10% on a PIM / ceramic hybrid coated separator.

[0011] In some embodiments, the separator is such that:(1) the diffusion coefficient DPIM of the PIM coating with respect to Mn is in the range of about 0.1 x 10'10cm2 / s to about 9.0 x 10'9cm2 / s, and / or(2) the diffusion coefficient DPIM of the PIM coating with respect to Fe is in the range of about 0.1 x 10'11cm2 / s to about 9.0 x 10'8cm2 / s, wherein the diffusion coefficient DPIM of the PIM coating is defined the following equation:wherein xPIMis the thickness (cm) (or coat weight in g / m2) of the PIM coating the thickness (cm) of the separatorAttorney Docket No.: 052981-517001WO xTis the thickness (cm) of the coated separatorDSEPis the diffusion coefficient (cnf / s) of the separatorDTis the diffusion coefficient (cm2 / s) of the coated separator

[0012] In some embodiments, the polymer layer has a hierarchical pore structure, preferably comprising macropores, mesopores and / or micropores. In these embodiments, the pores may be as follows:- macropores and / or mesopores preferably have an average size comprised between about 10 and about 500 nanometers, between about 10 and about 400 nanometers, or between about 10 and about 300 nanometers; and- micropores preferably have an average size comprised between about 10 nm and about 0.3 nm, between about 10 nm and about 0.5 nm, or between about 10 nm and about 1 nm.

[0013] In some embodiments, the coated polymer is such that:- the thickness of the porous support is less than about 25 micrometers, less than about 20 micrometers, less than about 18 micrometers, less than about 17 micrometers, less than about 16 micrometers, or preferably less than 15 micrometers, and / or the thickness of the porous support is more than about 1 micrometer, more than about 2 micrometers, or preferably more than about 5 micrometers;- the polymer layer has a homogeneous or a heterogeneous average thickness of less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers or less than about 1 micrometer, and / or the average thickness of the polymer layer is more than about 50 nanometers, more than about 0.1 micrometers, more than about 0.3 micrometers or more than about 0.4 micrometers; and / or- if present, the additional layer has a homogeneous or a heterogeneous average thickness of less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers or less than about 1 micrometer, and / or the average thickness of the polymer layer is more than about 50 nanometers, more than about 0.1 micrometers, more than about 0.3 micrometers or more than about 0.4 micrometers.

[0014] In some embodiments, the coated separator is a ceramic-coated separator; preferably, a PP, PE or multilayer porous substrate with at least one surface coated with a ceramic layer; comprising the polymer layer described herein.

[0015] The present invention also relates to a method of producing a coated separator for a lithium battery, wherein the coated separator comprises at least one polymer layer coated on a porous substrate, wherein the method comprises the steps of:(a) preparing a coating dispersion comprising at least one Polymer of Intrinsic Microporosity (PIM), at least one solvent, or solvent mixture, and optionally at least one additive;(b) applying the dispersion of step (a) on at least one surface of the porous substrate, preferably using a dip coating method, a spray coating method, a casting method, a knife coater method, a gravureAttorney Docket No.: 052981-517001WO coater method, a Mayer bar / rod method, a slot die coater method, a reverse roll coater method, a roll coater method, a screen printing method or an inkjet method; and(c) optionally removing the solvent from the coated separator of step (b) and / or drying the coated separator of step (b).

[0016] The present invention also relates to electrochemical cells comprising such coated separators.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] It is to be understood that the thicknesses of the various layers depicted in the figures are illustrative only and are not drawn to scale or in proportion to one another.

[0018] FIG. 1 - Schematic of a coated separator wherein the polymer layer comprising PIMs is uniformly applied on one surface of the porous substrate

[0019] FIG. 2 - Schematic of a coated separator illustrating a polymer layer (e.g., comprising PIMs) uniformly applied to one surface of the porous substrate, while the opposite surface is coated with a different layer, such as an additional polymeric layer (e.g., comprising PIMs).

[0020] FIG. 3 - Schematic of a coated separator illustrating a polymer layer (e.g., comprising PIMs) uniformly applied to one surface of the porous substrate, while a different layer, such as an additional polymeric layer (e.g., comprising PIMs), is coated on top of the polymer layer.

[0021] FIG. 4 - Schematic of a coated separator illustrating a layer uniformly applied to one surface of the porous substrate, while a layer (e.g., a polymer layer) is coated on top of the polymer layer.

[0022] FIG. 5 - Schematic of a coated separator illustrating a polymer layer comprising PIMs 1 applied to one surface of the porous substrate 2, with the polymer layer partially contained within the pores of the porous substrate and creates an interface 3 where the polymer layer has penetrated into the pores of the porous substrate.

[0023] FIG. 6 - Schematic of a coated separator illustrating a polymer layer comprising PIMs 1 applied to one surface of the porous substrate 2, with the polymer layer partially contained within the pores of the porous substrate and creates an interface 3 where the polymer layer has penetrated into the pores of the porous substrate, with a layer 4 (e.g., a polymer layer) is coated on top of the polymer layer.

[0024] FIGs. 7A and 7B - Contour maps of cell resistance (7 A) and metal blocking (7B) responses when modeled as a function of solids content (SC) or as a function of wet thickness (WT).

[0025] FIGs. 8A and 8B - Contour maps of metal blocking (8A) and cell resistance (8B), after overlaying.

[0026] FIGs. 9A and 9B - Scanning electron microscopy (SEM) cross-section images of the separator obtained in comparative example 7A and in inventive example 7B.Attorney Docket No.: 052981-517001WO

[0027] FIG. 10 - 1C,1D Cycling data for example 7B showing 3 replicate cells reaching 1400 cycles with improved capacity retention over a ceramic-coated that is used in today’s lithium ion (Li- ion) batteries.DETAILED DESCRIPTION OF THE INVENTION

[0028] In the present application:- the expression “comprised between ... and ...” should be understood as including the limits;- any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present invention;- where an element or component is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components; any element or component recited in a list of elements or components may be omitted from such list; and- any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents.

[0029] Definitions

[0030] The abbreviations used herein have their conventional meaning within the chemical and biological arts.

[0031] Unless specifically stated or obvious from context, as used herein, the term “about” in reference to a number or range of numbers is understood to mean the stated number and numbers + / - 10% thereof, or 10% below the lower listed limit and 10% above the higher listed limit for the values listed for a range. For example, "about 75" means 67.5-82.5, inclusive.

[0032] A lithium battery may include a lithium ion (Li-ion) battery, lithium metal battery, lithium polymer battery, solid-state lithium battery, lithium-air battery, or another battery with lithium is the primary transport ion.

[0033] PIMs are intended to be deposited onto a substrate from a liquid “ink” or "dispersion". "Dispersion" here represents any system that is substantially fluid-based from which materials, such as PIMs, may be deposited onto a separator or substrate. The dispersion is a homogeneous mixture or heterogeneous single-phase or multiphase mixture, either permanently or for a time scale at least sufficient for ink to be prepared and deposited onto the substrate. A dispersion as defined herein is comprised of one or more solutes, one or more solvents, and (optionally) one or more dispersion agents.

[0034] The dispersion may be dispersed over long time scales (requiring no agitation to maintain the dispersion), or may require agitation to remain dispersed. Methods of agitation may includeAttorney Docket No.: 052981-517001WO stirring, shaking, ultrasonication, mixing, or other methods. Methods that require mechanical agitation may use high-shear or low-shear mixing. Some dispersions may not require any agitation.

[0035] The term “solute" as used herein refers to a component of the dispersion mixture that is distributed through the dispersion. The solute may change when introduced to the solvent(s) and dispersal agent(s) of the dispersion; it may fully dissolve, change phase, swell, absorb solvent, or undergo other changes. After dispersal, the solute or solutes are deposited onto the separator as the coating. PIMs are examples of solutes used in dispersions.

[0036] The term “solvent” as used herein refers to a substance that is substantially fluid-based and, either alone or collectively with other co-solvents and / or dispersion agents, and with or without agitation, disperses the solute. The solvent functions to bring ink components together into a homogeneous mixture or heterogeneous single-phase or multiphase mixture. The use of the term “solvent” should not be interpreted narrowly to mean that the solute is strictly “dissolved”; rather, a “solvent” may be viewed as the majority carrier in the dispersion. Solvents can be polar or non-polar, protic or aprotic. The following provides examples of solvents. Polar solvents typically have a dielectric constant greater than about 5 or a dipole moment below about 1.0. Protic solvents are characterized by having a proton available for removal, such as by having a hydroxyl or carboxy group. Aprotic solvents lack such a group. Representative polar protic solvents include alcohols (methanol, ethanol, propanol, isopropanol, etc.), acids (formic acid, acetic acid, etc.) and water. Representative polar aprotic solvents include dichloromethane, chloroform, tetrahydrofuran, diethyl ether, acetone, ethyl acetate, dimethylformamide, dimethylacetamide, acetonitrile, and dimethyl sulfoxide. Representative non-polar solvents include alkanes (pentanes, hexanes, etc.), benzene, toluene, and 1,4-dioxane. Other solvents useful in the present invention are described herein. The dispersion may resemble aspects of one or more of many potential forms, such as suspension, emulsion, colloid, slurry, solution, or any other phase in which a material is dispersed, either homogeneously or heterogeneously, into a material that is substantially fluid. In some embodiments, the term “dispersion” refers to a system in which at least one substance, the dispersed phase, is distributed in discrete units throughout at least one second substance, the continuous phase or vehicle.

[0037] For example, the dispersion may contain a single dispersed component in a single solvent, it may contain a multicomponent dispersed mixture in a single solvent, it may contain a single dispersed component in a multicomponent solvent mixture, or multi-component dispersed phase in a multicomponent solvent mixture. The size of the dispersed phase can vary, ranging from nanometer-scale particles to multiple microns in size. In battery coatings, the dispersed phase typically consists of polymers, solid active materials, conductive agents, or additives, while the continuous phase is generally a liquid binder, polymeric binder, or solvent. In some embodiments, the slurry may include a solid active material as the dispersed phase and a polymer binder as the continuous phase, or alternatively, both phases may contain different solid components.Attorney Docket No.: 052981-517001WO

[0038] The term “separator” as used herein refers to an electrically insulating membrane between the positive and negative electrodes to prevent electrical shorts, i.e., provides electronic isolation. The separator also allows the ions to move between the positive and anode electrodes. The separator can include any suitable polymeric or inorganic material that is electrically insulating. The separator can include several layers including one or more membrane layers, and a porous substrate material for the membrane layers.

[0039] The term “coated separator” as used herein refers to a separator with at least one layer of material or polymer coated on at least one of its surfaces.

[0040] The term “porous support” or “porous substrate”, refers to any suitable material that is capable of supporting at least one material layer or polymer layer as described in the present invention, and is permeable to the electrolyte.

[0041] The term “microporous polymer” refers to a polymer having interconnected pores with an average diameter of less than about 12 nm, or less than about 10, less than about 5, less than about 4, less than about 3, less than about 2, or less than about 1 nm, or comprised between about 12 nm and about 0.1 nm, comprised between about 11 nm and about 0.2 nm or comprised between about 10 nm and about 0.3 nm.

[0042] The term “microporosity” or “intrinsic microporosity” refers to a polymer providing a continuous network of interconnected intermolecular voids (e.g., suitably of less than or equal to 4 nm in size), which forms as a direct consequence of the shape and rigidity of at least a proportion of the component monomers of the polymer. As will be appreciated by a person skilled in the art, intrinsic microporosity arises due to the rotationally constrained bond structure of the polymer backbone and, as the term suggests, it is an intrinsic property of a polymer formed from such monomers.

[0043] The term “hierarchical pore structure” as used herein refers to a system of interconnected pores that vary in size and organization and this pore system may be fully interconnected, partially interconnected, or contain areas or segments that are partially or not fully connected to the pore network. This structure is characterized by multiple levels of porosity, including micro-, meso-, and macropores. Micropores are defined as spaces or voids in a material with a diameter of less than about 2 nm by the International Union of Pure and Applied Chemistry (IUPAC). Mesopores are defined as spaces or voids in a material with a diameter of less than about 2 - 50 nm by IUPAC. Macropores are defined as spaces or voids in a material with a diameter greater than about 50 nm by IUPAC. Pore size distributions may have some overlap of the IUPAC definitions for a material. The rotationally constrained polymer backbones of PIMs lead to microporosity in these coated separators. Mesoporous and macroporous structures arise due to solvent evaporation after the PIM is deposited onto a separator. Careful ink composition design and selection of solvents and additives can allow pore structures and resulting morphologies of the pore network to be tailored and optimized. In an ink, single solvents, with a low vapor pressure, will vaporize quickly and produce a mix of macropores and mesopores. Morphology and interconnectedness of the pore structure will be highly dependent onAttorney Docket No.: 052981-517001WO ink composition, vaporization rates of components, and PIM affinity for the solvents or additives. Alternatively, solvent mixtures or the use of liquid additives can alter this evaporation process, such that the PIM is still soluble in strong solvent that is higher boiling or the PIM precipitates faster if a strong anti-solvent, high boiling antisolvent is used in the ink.

[0044] The air permeability of a separator is measured by a Gurley apparatus and may be correlated to properties like pore network tortuosity or ion transport in a battery. The term “Gurley value” or “Gurley number” (air permeability) as used herein refers to the time, measured in seconds, required for 100 cm3of air to pass through a defined area of the separator at a defined pressure difference. More precisely, it is the number of seconds needed for 100 cm3of air to flow through 6.45 cm2of the material (i.e., separator herein) at a pressure difference of 1.22 kPa, as determined using a Gurley densometer in accordance with the T460 standards (Technical Association of the Pulp and Paper Industry - TAPPI). Gurley number may be assessed in accordance with ASTM D726, or alternatively TAPPI T-536-88.

[0045] The term “coat weight” (CW) or “areal density”_as used herein refers to the weight of a coating material applied to the porous substrate, expressed per unit area in g / m2. It quantifies the amount of coating present on the surface area (e.g., 12 cm2or 100 cm2) of the porous substrate. Coat weight can be determined gravimetrically by first weighing the coated material, then stripping the coating using an appropriate solvent, and weighing the separator again after the coating has been removed. The coat weight is determined by subtracting these two values and normalizing the result to the surface area of the test sample. The coat weight may also be determined by UV-vis spectrophotometry, wherein a sample of the coated separator (e.g. ceramic coating) is dissolved, the polymer absorbance measured, and the coated mass calculated using a calibration curve and the Beer- Lambert law.

[0046] The term “thickness” as used herein in reference to the coated separator, the polymer layer or any layer present on at least one surface of the substrate, refers to the measurement of the total vertical distance from the top to the bottom of the coated separator, typically measured in micrometers (pm). This measurement includes the thickness of the porous substrate and any coating material applied to its surface. The thickness may be determined by using a micrometer, for example a Mitutoyo micrometer or a Mahr thickness gauge and averaging 10 thickness measurements along the length of the separator.

[0047] The term “wet thickness” (WT) or “wet film thickness” (WFT) as used herein refers to the thickness of the ink or dispersion layer that is applied to the separator immediately after the coating die head, or the coating roller, or the coating blade. Wet thickness is calculated as the ratio of the ink solids concentration to the resulting coat weight of the dry film. The equation used to calculate wet thickness is WT = SC / (CW • solvent density), wherein SC is the solids content. It is a critical quality control measurement in R2R coating as it directly relates to the thickness of the dry film.Attorney Docket No.: 052981-517001WO

[0048] The term "shrinkage" or "heat shrinkage" or “thermal shrinkage” as used herein in reference to the separator, refers to the reduction in the dimensions of the coated separator when exposed to elevated temperatures. More precisely, it is determined as the dimensional change in the machine direction (MD) expressed as a percentage, measured at a temperature of 150°C, according to ASTM D1204. The shrinkage is calculated by comparing the length of the separator before and after exposure to the specified temperature, with the resulting change normalized to the initial length.

[0049] The term “resistance” or “electrical resistance (ER)” or discharge area-specific resistance (ASR) as used herein refers to the ability of the separator material to resist the flow of electric current. It is determined by measuring the electrical resistance across the separator material under a specified voltage, typically following the guidelines set in ASTM D257. The ER may be determined by running electrochemical impedance spectroscopy on separator layers, wetted with electrolyte, between two polished, stainless steel electrodes. The discharge ASR is determined by pulsed discharged experiments in a full Li-ion pouch cell (NMC-631 cathode, graphite anode, electrolyte, and separator).

[0050] The term "MacMullin number" or "MacMullin value" as used herein, refers to a quantification of the ionic conductivity of the separator, used to assess the separator's performance in facilitating ion transport between the anode and cathode of a battery. It is determined by measuring the resistance of the separator to the flow of ions in a given electrolyte, and is calculated as the product of the resistance and the electrolyte conductivity.

[0051] The present invention relates to a coated separator for a lithium battery, comprising a porous substrate and at least one polymer layer on at least one surface of the porous substrate, wherein the polymer layer comprises at least one PIM. The coated separator has the following properties:- a coat weight less than about 0.8 g / m2, preferably less than about 0.75 g / m2, more preferably less than about 0.7 g / m2, less than about 0.5 g / m2, less than about 0.4 g / m2, more preferably less than about 0.3 g / m2, more preferably less than about 0.2 g / m2; and- a Gurley value less than about 400 s / 100 cm3air, preferably ranging from about 100 s / 100 cm3air and 400 s / 100 cm3air, more preferably ranging from about 100 s / 100 cm3air and 300 s / 100 cm3air. For reference, Celgard 2400 has a Gurley value of about 200 s / 100 cm3when measured by an Oken type Gurley densometer (Asahi Seiko).

[0052] The inventors have realized that separators comprising at least one polymer layer can exhibit excellent battery performance when characterized by the combination of such properties, thereby ensuring long-term cycling stability in a battery. With the combination of such properties, the ability of the separator to facilitate fast charge rates (<lh) and discharge rates (<lh) is of interest for development of batteries for EV applications.

[0053] The addition of a separator to a battery improves electrochemical performance of the battery by preventing electrical shorts, while the porous structure of the separator also contributes to ionic resistance. The resistance of the separator must be minimized to enable ionic conductivity and moderate charging rates in a battery. In order to measure the resistance or ionic conductivity of theAttorney Docket No.: 052981-517001WO separator, the MacMullin number (NM) was introduced as the ratio of the ionic conductivity of the pure electrolyte to the ionic conductivity of the separator filled with electrolyte, as described in R Raccichini, L Furness, J W Dibden, J R Owen, and N Garcia- Araez, “Impedance Characterization of the Transport Properties of Electrolytes Contained within Porous Electrodes and Separators Useful for Li-S Batteries”, Journal of the Electrochemical Society, 165, 11, A2741-A2749, 2018. MacMullin number is measured by stacking 1, 2, 3, 4, etc. separator layers in a battery cell and measuring the high frequency resistance intercept by electrochemical impedance spectroscopy, then calculating the slope of the resistance vs #separator layers plot. The addition of a polymer layer on the surface of a porous separator (also called porous substrate herein) is not evident. The polymer layer must also be porous. Its porosity creates complex pathways through the separator that resist air flow and allow ion transport in the battery to facilitate fast charge rates (<lh) and discharge rates (<lh). Air permeability of the separator is thus reduced, which correlates with an increase in ionic resistance and affects the overall electrochemical performance of the battery. Air permeability of the coated separator can be measured using a Gurley densometer, and is expressed as the Gurley value.

[0054] Gurley values are measured on a digital Oken-type air permeability tester (EG series, Asahi Seiko) using a procedure in which a 10 cm x 10 cm sample of the separator is clamped, a weight is applied, and the time required for 100 mL of air to pass through the sample is recorded.OR as measured on a 4150N Gurley densometer (Gurley Precision Instruments) using the same procedure. The claimed Gurley values are measured on an Oken-type air permeability tester (EG Series, Asahi Seiko).

[0055] J Landesfeind, J Hattendorff, A Ehrl, W A Wall, and H A Gasteiger, “Tortuosity Determination of Battery Electrodes and Separators by Impedance Spectroscopy”, Journal of the Electrochemical Society, 163, 7, A1373-A1387, 2016, or in K K Jana, S J Luc, A Huang, J F Soesanto, and K-L Tung, “Separator Membranes for High Energy Density Batteries”, ChemBioEng Rev, 6, 1-27, 2018, discusses resistance and Gurley value of the separator.

[0056] The coated separators of the invention, with the specific thickness and Gurley value disclosed herein, show improved battery performance. Without wishing to be bound by theory, it is believed that the controlled porosity and tortuosity of the polymer coating layer of the present invention comprising at least a PIM, maintain sufficient ionic transport while preventing shortcircuiting. As a result, coated separators of the invention not only cycle reliably in batteries, but also maintain stable performance over repeated fast charge rates (<lh) and fast discharge rates (<lh). It is also important that the coated separators of the invention maintain mechanical properties and structural integrity similar to or better than the incumbent ceramic-coated separators that are used in Li-ion batteries, today. Through modelling and optimization of the coating weight, Gurley, discharge ASR, and PIM diffusion coefficients, the coated separators of the invention demonstrate superior properties for fast battery cycling over the incumbent ceramic-coated separators, improved diffusion coefficients that block transition metal diffusion that leads to early cell failure when compared toAttorney Docket No.: 052981-517001WO incumbent ceramic coated separators, while maintaining mechanical properties like incumbent ceramic-coated separators to resist puncture and shrinkage under adverse conditions and the ability of incumbent separators to perform fast charge rates (<lh) and discharge rates (<lh). These properties can be achieved through the selection of a complex set of specific features characterizing the polymer layer composition, the porous substrate, the coating process, and the electrolytes, as described herein.

[0057] Another important characteristic of the coated separator of the invention resides in its heat shrinkage. The polymer layer may influence the dimensional stability of the separator under elevated temperatures, thereby reducing the risk of internal short circuits and improving the overall safety of the battery.

[0058] In some embodiments of the present invention, the separator comprises a porous substrate, one polymer layer coated on one surface of the porous substrate and has a heat shrinkage (measured at 150°C, 1 h) of less than about 65% on a single-sided PIM coated separator, preferably less than about 60%, less than about 55% or even less than about 50%.

[0059] In some embodiments of the present invention, the separator comprises a ceramic-coated porous substrate, one polymer layer coated on one surface of the porous substrate, and has a heat shrinkage (measured at 150°C, 1 h) of less than 10%, preferably less than 9% or even less than 8%.

[0060] In the examples, the heat shrinkage of the separator was measured by cutting samples of defined size, marking a smaller rectangle on the samples, recording the rectangle initial dimensions, and placing them in an oven at 150 °C for 1 hour, according to ASTM D1204 (with A4 white paper as a substrate). After cooling to room temperature, the final dimensions were recorded. Heat shrinkage (%) was calculated as (Lo-L)ZLoxlOO, Lo is the initial dimension and Lis the final dimension, determined separately for both length and width.

[0061] Another important feature of the separators of the invention is their ability to block metal transport, such as Mn, Fe and Ni, in a battery. The polymer layer, optionally in combination with the porous structure of the separator, can prevent dendrite growth or metal shorting, thereby enhancing the safety and long-term stability of the battery. With the target of fast charge rates (<lh) and discharge rates (<lh), any improvement to metal transport blocking properties of a new separator is desired over the incumbent separators used in lithium ion batteries today.

[0062] In some embodiments, the coated separator is such that:(1) the diffusion coefficient DPIM of the PIM coating with respect to Mn is in the range of about 0.1 x IO10cm2 / s to about 9.0 x 10‘9enf / s and / or(2) the diffusion coefficient DPIM of the PIM coating with respect to Fe is in the range of about 0.1 x 10'11cm2 / s to about 9.0 x 10‘8enf / s, wherein the diffusion coefficient DPIM of the PIM coating is defined the following equation:whereinAttorney Docket No.: 052981-517001WO xPIMis the thickness (cm) (or coat weight in g / m2) of the PIM coating xSEPis the thickness (cm) of the separator xTis the thickness (cm) of the coated separator DSEPis the diffusion coefficient (cm2 / s) of the separator DTis the diffusion coefficient (cm2 / s) of the coated separator

[0063] In some embodiments, the diffusion coefficient DPIM of the PIM coating with respect to Mn ranges from about 0.5 x IO10cm2 / s to about 5.0 x 10'9cm2 / s , from about 0.7 x IO10cm2 / s to about 4.0 x 10'9cm2 / s, from about 0.9 x IO10cm2 / s to about 3.0 x 10'9cm2 / s, or from about 1.0 x IO10cm2 / s to about 2.7 x 10' cm2 / s.

[0064] In some embodiments, the diffusion coefficient DPIM of the PIM coating with respect to Fe ranges from about 0.1 x I O10cm2 / s to about 8.0 x 10'8cm2 / s , from about 0.1 x 10'9cm2 / s to about 7.0 x 10'8cm2 / s, from about 0.1 x 10'8cm2 / s to about 6.0 x 10'8cm2 / s, or from about 0.5 x 10'8cm2 / s to about 5.0 x 10'8cm2 / s.

[0065] Polymer layer composition

[0066] Reference is made herein to the polymer layer, or polymer layer composition, which may also be referred to as a coating dispersion, depending on whether the discussion concerns the coating as applied to the substrate or the dispersion (or slurry or ink) used to form the coating on the substrate during the coating process. The descriptions and embodiments set forth in the following paragraphs arc applicable to both the polymer layer in its applied form on the substrate and the corresponding coating dispersion used during the coating process.

[0067] The polymer layer composition comprises at least one PIM. Polymers of intrinsic microporosity useful in the present invention include those described in Neil B. McKeown (International Scholarly Research Network, volume 2012, article ID 513986, 16 pages, doi: 10.5402 / 2012 / 513986); WO 2016 / 161367 Al; WO 2018 / 106957 Al; and / or WO 2020 / 264386 Al, US 10,710,065, US 11,318,455, US 11,545,724, US 11,394,082, US 2021 / 0309802, and US 2019 / 0326578, US 2024 / 0262960, each of which is incorporated herein by reference in its entirety. In some examples, the polymer of intrinsic microporosity can comprise PIM-1, PIM-2, PIM- 3, PIM-4, PIM-5, PIM-6, PIM-7, PIM-8, PIM-9, PIM- 10, KAUST-PI-X (e.g., KAUST-PI-1, KAUST PI-2), triptycene based polymers of intrinsic microporosity, derivatives thereof, or combinations thereof. Preferably, the polymer of intrinsic microporosity comprises PIM-1 and / or PIM-13, or derivatives thereof.

[0068] PIMs can be prepared by reacting any combination of monomers that lead to a rigid polymer within which there are sufficient structural features to induce a contorted structure. For example, PIMs can he prepared by reacting a first monomer unit having a site of contortion with a second monomer.Attorney Docket No.: 052981-517001WO

[0069] In some embodiments, the polymer layer described herein comprises at least one PIM copolymer, preferably a PIM copolymer comprising recurring units of PIM-1 and / or PIM-13, or derivatives thereof.

[0070] The polymer layer may comprise several PIM polymers and / or PIM copolymers. If the coated separator comprises several polymer layers, each of these layers may comprise one or several PIM polymers or PIM copolymers (herein PIM (co)polymers). The PIM (co)polymers may be the same or different in each of the polymer layers.

[0071] The PIM may have a number average molecular weight (Mn) between 1,000 and 2,000,000g / mol (kDa), preferably between 15,000 and 500,000 g / mol (kDa) or between 20,000 and 200,000 g / mol (kDa). The number average molecular weight of the PIM is measured by Size Exclusion Chromatography (SEC), also known as Gel Permeation Chromatography (GPC). The measurements can be performed on a SEC equipment equipped with 2 columns connected in series: one covering a molecular weight range 20,000-400,000 g / mol (ACQUITY APC XT BEH Column, 450 A, 2.5 pm, 4.6 mm x 150 mm) and the other covering 3,000-70,000 g / mol (ACQUITY APC XT BEH Column, 200 A, 2.5 pm, 4.6 mm x 150 mm). Chloroform (HPLC grade, stabilized with ethanol) is used as the mobile phase. Approximately 10-15 mg of polymer sample is dissolved in 1 mL chloroform, filtered using 0.45 microns filters. The filtrate is used for analysis. Polystyrene standards with peak molecular weights (Mp) ranging from 200 to 130,000 g / mol are used to generate the calibration curve. All molecular weight values reported are relative to these polystyrene standards.

[0072] In some embodiments, the polymer layer comprises at least one additional polymer which preferably comprises at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co- hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), and polyacrylonitrile (PAN), cellulose, carboxymethyl cellulose, styrene -butadiene rubber, and / or polyacrylatc.

[0073] In some embodiments, the PIM(s) and the additional polymer(s) form a gel (also called swelled network) when in contact with the electrolyte.

[0074] In some embodiments, the domain size for the two polymers is between about 10 nm to about 1,000 nm, or between 500 nm and about 5,000 nm.

[0075] In some embodiments, the polymer layer comprises at least one additional component, or an additive, which preferably comprises at least one of inorganic particles, nanoparticles, solvent(s) (in particular electrolyte solvent(s)), salt(s) (in particular electrolyte salt(s)), nucleating agent(s) (or poreforming additive(s)), plasticizer(s), filler(s) and / or binder(s).

[0076] In some embodiments, the polymer layer comprises at least one ceramic-based compound.

[0077] In some embodiments, the polymer layer comprises at least one particle selected from one or more of boehmite (y-AlOOH), alumina (AI2O3), barium sulfate (BaSO i), magnesium oxide (MgO), magnesium hydroxide (Mg / OHE), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconia (ZrOz), yttrium oxide (Y2O3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiOo, barium titanate (BaTiO . and magnesium fluorineAttorney Docket No.: 052981-517001WO(MgFz), graphene oxide, reduced graphene oxide, boron nitride (BN), silicon nitride (SisN^, silicon carbide (SiC), silicon (Si), lithium lanthanum zirconium oxide (LLZO), tetraboron carbide (B4C), silicon dioxide (SiCE), silicon disulfide (SiSz), phosphorus pentasulfide (P2S5), zirconium dioxide (ZrCE), aluminum oxide (AI2O3), titanium dioxide (TiOz), tin dioxide (SnCE), cerium dioxide (CeCE), magnesium oxide (MgO), nickel oxide (NiO), zinc oxide (ZnO), zinc trioxide (ZnCE), aluminum monoxide (A1O), lithium phosphate (LisPCE), and mixtures thereof, preferably present in the polymer layer in a weight ratio ranging from 5 to 25 wt.%, or from 10 to 20 wt.%, relative to the weight of the PIM in the polymer layer. The size range for these particles or mixtures or particles may be 1-100 nm and they may be considered nanoparticles, or they may have a size range of 100 - 1000 nm and they may be considered submicron particles, or they may have a size range of 1 pm to 1000 pm and they may be considered microparticles. These particles may be present as single particles, aggregates, or agglomerates.

[0078] In some embodiments, the polymer layer comprises at least one nanoparticle selected among

[0079] In some embodiments, the polymer layer comprises at least one nanoparticle, preferably at least one nanoparticle selected among ceramic nanoparticles, polyacrylamide nanoparticles or aramid particles.

[0080] In some preferred embodiments, the polymer layer comprises metal oxides.

[0081] In some preferred embodiments, the polymer layer comprises ceramic materials.

[0082] In some embodiments, the polymer layer comprises at least one binder selected among polybutadiene, polyacrylonitrile (polymer or copolymer), cellulose, a soluble PIM, polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (NaCMC), crosslinked cellulose, phosphorylated cellulose, acetylated cellulose, oxidized cellulose, sulfonated cellulose, cellulose nanocrystals, cellulose nanofibers, other functionalized cellulose materials, polyacrylic acid (PAA), polyimide (PI), styrene-butadiene rubber (SBR), fluorinated polymers (e.g., PTFE), polyamide (nylon), ethylene vinyl alcohol (EVOH), poly(vinyl alcohol) and mixtures thereof.

[0083] In some embodiments, the polymer layer comprises at least one salt, in particular electrolyte salt selected among lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPFe), lithium bis(trifluromethyl)tetrafluorophosphate (LiPF^CFsh), lithium bis(pentafluoroethyl)tetrafluorophosphate (LiPF^^Fsh), lithium tris(pentafluoroethyl)trifluorophosphate (LiPFs^Fsh), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, LiNICFsSChh), lithium bis(perfluoroethanesulfonyl)imide LiNICzFsSCEh, LiN^FsSCEh, lithium (fluorosulfonyl) (nonafluorobutanesulfonyl)imide, lithium bis(lluorosulfonyl)imide, lithium tetrafluoroborate (LiBFO, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium tetrachloroaluminate, lithium aluminate (LiA104), lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, lithium tris(trifluoromethanesulfonyl)methide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borateAttorney Docket No.: 052981-517001WO(LiDFOB), LizBizFiz-xHx where x is an integer equal to 0 to 8, and mixtures of lithium fluoride and anion receptors such as B(OC6Fs)3, and mixtures thereof.

[0084] In addition, the polymer layer may comprise organic salts such as tetrabutylammonium fluoride (TBAF), tetrabutylammonium hexafluorophosphate (TBAPFe), tetraethylammonium tetrafluoroborate (TEABF-O, tetra-n-butylammonium bis(trifluoromethanesulfonyl)imide (TBA- TFSI), or imidazolium-based salts including l-ethyl-3-methylimidazolium TFSI (EMI-TFSI) or EMI- BF4. While these salts are generally not primary lithium sources, they may serve as supporting electrolytes, additives, or ionic liquid components to modulate the properties of the polymer layer and improve battery performance.

[0085] In some embodiments, the polymer layer comprises at least one nucleating agent (or a poreforming additive), in particular a nucleating agent selected among glass fibers, carbon fibers, graphite fibers, silicon carbide fibers (SiC), aramide fibers, wollastonite, talc, mica, clays, calcium carbonate (CaCCE), potassium titanate ( KsTiO?). silica (SiCE), silicate, kaolin, chalk, alumina (AI2O3), aluminate, boron nitride (BN), aluminum oxide (AI2O3), titanium dioxide (TiCE), zinc sulfide (ZnS), zinc oxide (ZnO), magnesium oxide (MgO), barium sulfate (BaSCE), carbon black, cobalt phosphate (Co3(PC>4)2), cobalt titanate (CoTiCE), cadmium sulfoselenide (Cd(S,Se)), cadmium selenide (CdSe), copper phthalocyanine (CuPc), ultramarine, ultramarine violet, zinc ferrite (ZnFe2O4), magnesium ferrite (MgFe2O4), iron oxides (Fe2Os), or mixtures thereof.

[0086] In some embodiments, the polymer layer comprises at least one plasticizer.

[0087] In some embodiments, the polymer layer comprises at least one filler, in particular a filler selected mineral fillers (such as talc, mica, kaolin, calcium carbonate (CaCCE), calcium silicate (Ca2SiCE), magnesium carbonate (MgCCE)), glass fibers, carbon fibers, synthetic polymeric fibers, aramid fibers, aluminum fibers (Al), titanium fibers (Ti), magnesium fibers (Mg), boron carbide fibers (B4C), rock wool fibers, steel fibers (Fe), wollastonite (CaSiCE), or mixtures thereof.

[0088] In some embodiments, the polymer layer comprises at least one binder, in particular a polymeric binder selected among polybutadiene, polyacrylonitrile (polymer or copolymer), cellulose, a soluble PIM, poly vinylidene fluoride (PVDF), polyethylene oxide (PEO), poly(ethylene glycol) (PEG), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (NaCMC), polyacrylic acid (PAA), polyimide (PI), styrene-butadiene rubber (SBR), fluorinated polymers (e.g., PTFE), polyamide (nylon), ethylene vinyl alcohol (EVOH), poly(vinyl alcohol), sodium alginate, polyurethane, polyimide, sulfonated polyether ether ketone (SPEEK), polyacrylonitrile (PAN), polybenzimidazole (PBI), and mixtures thereof.

[0089] The coating may be formed from a coating dispersion comprising one or more solvents; however, reference to solvents herein relates to the dispersion used in preparing the coating layer, rather than to the final coating layer itself. In some cases, residual amounts of solvent may migrate into the surroundings, including into the electrolyte, during or after the coating process, or when the battery is cycling. In some cases, volatile solvents will quickly evaporate to form a hierarchical poreAttorney Docket No.: 052981-517001WO structure. The use of less volatile solvents that dissolve the PIM can lead to porous networks as they slowly vaporize during drying. The use of less volatile solvents that are poor solvents for PIM can cause fast precipitation or coagulation of the PIM to form more dense and less porous structures. The use of volatile solvents and solvent mixtures is an important aspect of creating a hierarchical pore structure in the final, coated separator. The formation of macropores and mesopores through evaporative mechanisms and engineering controls allows for facile Li transport through the PIM coating until the solvated lithium ion reaches the microporous restrictions from the PIM. At these smaller size ranges, the PIM coating appears to have an affinity for Li ion transport while impeding the transport of other metal ions like Mn, Fe, Ni, etc.

[0090] In some embodiments, the coating dispersion comprises at least one solvent, in particular an electrolyte solvent selected from aprotic organic compounds commonly used in lithium batteries. These may include cyclic esters (e.g., ethylene carbonate, propylene carbonate, ’ / -butyrolactone ). linear esters, cyclic ethers (e.g., 2-methyltetrahydrofuran, 1,3 -dioxolane), linear ethers (e.g., 1,2- dimethoxyethane), amides, sulfoxides, carboxylic acid esters, sulfones (e.g., tetramethylene sulfone, ethyl methyl sulfone, dimethylsulfone), sulfonamides, and mixtures thereof. Specific examples of solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), tetrahydrofuran (THF), 1,3-dioxolane, sulfolane, methyl ethyl ketone (MEK), dimethylacetamide (DMAC), propylene carbonate (PC), isophorone, N-methylpyrrolidone (NMP), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), acetone, or mixtures thereof. Preferably, the solvent is NMP, DMF, THF, 1,3-dioxolane, MEK, acetone, or a mixture of these.

[0091] In some embodiments, the coating dispersion comprises a solvent mixture, comprising two or more solvents, for example, two, three, four or five different solvents. It may for example be a binary or ternary solvent mixture. The solvent(s) used in the coating dispersion can influence the porosity of the resulting coating layer, for example by affecting the formation, size, and distribution of pores during the coating process, for example the drying step.

[0092] The inventors have realized that the solids content of the coating dispersion is a key parameter in preparing the polymer layer. In particular, they have found that a higher solids content generally leads to a thicker coating, whereas a lower solids content can produce a thinner layer. By judiciously adjusting the percentage of solids in the dispersion, it is possible to control critical features of the resulting coating, including thickness, porosity, and uniformity. This control, in turn, directly impacts separator properties such as ionic conductivity, air permeability, and metal-blocking performance, thereby enabling the coated separator to deliver superior battery performance.

[0093] In fact, the combination of selected solids content, coating thickness, and coating method makes it possible to precisely tailor the structure of the polymer layer, thereby optimizing key separator properties such as porosity, tortuosity, electrical resistance, and ionic resistance, while simultaneously enhancing fast rate cycling stability, metal transport blocking properties, and safety ofAttorney Docket No.: 052981-517001WO the battery, leading to the claimed properties, including Gurley values. These features are interrelated; only through the appropriate combination of solids content, coating thickness, and coating method is it possible to achieve superior separator performance as demonstrated in the examples. To balance these properties, metal blocking typically improves with a thicker coating, but this will translate to a coating with higher resistance that may not facilitate fast charge rates (<lh) and fast discharge rates (<lh). The thickness of the dry coating and the density of the dry coating were previously assumed to be to be interrelated however, modifying solids as demonstrated in the examples can yield coatings of varied thickness while modifying the WT and ink additives allows modification of the coating density or permeability, as outlined by differences in exemplified Gurley values. The prior art does not teach or suggest such a combination.

[0094] Conventional practice suggests maximizing solids content to reduce solvent handling, shorten drying times, and improve process efficiency. Conventional practice also suggests that increasing the diffusion coefficient of the coating layer requires higher solids content to block migration of metal ions (e.g. manganese, nickel, cobalt, iron, etc.) produced by cathode degradation during battery cycling that lead to cell failure. Contrary to these expectations, the inventors have demonstrated that optimized low solids content can be highly beneficial for controlling the porosity, and morphology of the resulting polymer layer, leading to improved separator properties, lithium battery capacity stability in long term cycling, and a better ability for the separator to facilitate fast charging rates To balance these properties, metal blocking typically improves with a thicker coating but this will translate to a coating with higher resistance that may not facilitate fast charge rates (<lh) and fast discharge rates (<lh) while maintaining some ability to block metal transport.

[0095] In some embodiments, the coating dispersion comprises a concentration of less than 40 wt.% of solids, less than 30 wt.% of solids, less than 20 wt.% of solids, less than 10 wt.% of solids or preferably less than 5 wt.% of solids, relative to the total weight of the dispersion. According to these embodiments, the terms “solids”, “solids content”, or “solids concentration” refer to the non-solvent component or components of the coating dispersion. For example:- in a coating dispersion comprising PIMs and THF, the solids refer to the PIMs in the ink;- in a coating dispersion comprising PIMs, silica nanoparticles and THF, the solids refer to the PIMs and silica nanoparticles;- in a coating dispersion comprising PIMs, DMC and THF, the solids refer to the PIMs in the ink.

[0096]

[0097] In some embodiments, the coating dispersion comprises, based on the total weight of the dispersion: from about 0.1 to about 40 wt.% of PIM, for example from about 0.5 to about 30 wt.%, about 0.7 to about 20 wt.%, about 1 to about 10 wt.%, about 1 to about 5 wt.%, from about 60 to about 99 wt.% of at least one solvent,Attorney Docket No.: 052981-517001WO optionally, from about 1 to about 40 wt.% of at least one additive or a filler, as described above, preferably from about 4 to about 20 wt.%.

[0098] The coating dispersion of the invention may preferably comprise:- about 0.57 to about 7 wt.% of PIM, preferably PIM-1 and / or PIM-13, which are dissolved in a solvent or solvent mixture;- about 0.7 to about 5 wt.% of PIM, preferably PIM-1 and / or PIM-13.

[0099] The coating dispersion of the invention may preferably be such that the solvent or solvent mixture preferably comprise THF, NMP or DMF, alone or mixed together. One example is a mixture of THF with NMP (e.g. a 50 / 50, a 70 / 30, or a 80 / 20 THF / NMP wt. mixture). Another example is a mixture of THF with DMF (e.g. a 50 / 50, a 70 / 30, or a 80 / 20 THF / NMP wt. mixture).

[0100] In some embodiments, the porous substrate comprises woven and / or non-woven structures.

[0101] In some embodiments, the porous substrate comprises polyethylene (PE), polypropylene (PP), poly(tetrafluoroethylene) (PTFE), polylvinyl chloride) (PVC), poly(vinylidene difluoride) (PVDF), cellulose, a ceramic, an aramid or combinations thereof.

[0102] In some embodiments, the polymer layer is coated on at least about 50 % of at least one surface of the porous substrate, at least about 60 %, at least about 70 %, at least about 80 %, at least about 90 %, at least about 98 % or at least about 99 %. For example, the polymer layer may be coated on one surface / side of the porous substrate only, and on at least about 50 % of this surface, at least about 60 %, at least about 70 %, at least about 80 %, at least about 90 %, at least about 98 % or at least about 99 %.

[0103] The polymer layer may be applied uniformly across the surface of the porous substrate or may be non-uniform, covering only selected regions of the substrate as desired. Preferably, the polymer is applied uniformly across one surface of the porous substrate. In some embodiments, the polymer layer has a homogeneous or a heterogeneous average thickness of less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers or less than about 1 micrometer, and / or the average thickness of the polymer layer is more than about 50 nanometers, more than about 0.1 micrometers, more than about 0.3 micrometers or more than about 0.4 micrometers. Control of the polymer layer thickness is important, as it influences both the ionic transport through the separator and its ability to block metal penetration, thereby affecting overall battery performance and safety. The polymer layer thickness may be determined using a micrometer, for example a Mitutoyo micrometer or a Mahr thickness gauge and averaging 10 thickness measurements along the length of the separator.

[0104] In some embodiments, the thickness of the porous support is less than about 25 micrometers, less than about 20 micrometers, less than about 18 micrometers, less than about 17 micrometers, less than about 16 micrometers, or preferably less than 15 micrometers, and / or the thickness of the porous support is more than about 1 micrometer, more than about 2 micrometers, or preferably more than about 5 micrometers.Attorney Docket No.: 052981-517001WO

[0105] In some embodiments, the thickness of the separator is less than about 16 micrometers, less than about 13 micrometers, less than about 12 micrometers, or preferably less than 10 micrometers, or less than 5 micrometers.

[0106] In some embodiments, the polymer layer is physically separated from the porous substrate and / or does not substantially infiltrate the pore structure of the porous substrate.

[0107] In some embodiments, the polymer layer at least partially infiltrates the pore structure of the porous substrate, or totally infiltrates the pore structure of the porous substrate.

[0108] In some embodiments, at least about 10 % of the polymer layer infiltrates the pore structure of the porous substrate, at least about 50 %, at least about 70 %, at least about 80 %, at least about 90 %, at least about 98 % , at least about 99 %, as measured for example by visual inspection of the crosssection of the substrate under microscopy, indicating the extent of polymer layer penetration and distribution within the pore structure of the substrate.

[0109] In some embodiments, the polymer layer has an average pore diameter of less than about 12 nm, or less than about 10 nm, less than about 5 nm, less than about 4 nm, less than about 3 nm, less than about 2 nm, or less than about 1 nm, or comprised between about 12 nm and about 0.1 nm, comprised between about 11 nm and about 0.2 nm or comprised between about 10 nm and about 0.3 nm.

[0110] In some embodiments, the polymer layer has a hierarchical pore structure, preferably comprising macropores, mesopores and / or micropores, wherein:- macropores and / or mesopores preferably have an average size comprised between about 10 and about 500 nanometers, between about 10 and about 400 nanometers, or between about 10 and about 300 nanometers; and- microporcs preferably have an average size comprised between about 10 nm and about 0.3 nm, between about 10 nm and about 0.5 nm, or between about 10 nm and about 1 nm.

[0111] In these embodiments, the macropores and / or mesopores of the hierarchical pore structure may comprise tortuous, spherical and / or oblique shapes, and / or the negative space of a fibrous network.

[0112] Single-sided or double-sided polymer layer coating

[0113] In some embodiments, the polymer layer is coated on both surfaces of the porous substrate. In some other embodiments, the polymer layer is coated on one surface of the porous substrate. In some other embodiments which can be combined, the coated separator may comprise at least one additional layer.

[0114] In a preferred embodiment, the coated separator is such that it comprises one polymer layer comprising at least one PIM and at least one additional layer.

[0115] Possible embodiments include:- the polymer layer is coated on the porous substrate, and the additional layer is coated on the polymer layer;Attorney Docket No.: 052981-517001WO- the additional layer is coated on the porous substrate, and the polymer layer is coated on the additional layer;- the polymer layer is coated on one surface of the porous substrate, and the additional layer is coated on the opposite surface of the porous substrate; or- both surfaces of the porous substrate are coated with either the polymer layer, the additional layer or a combination of both.

[0116] In some embodiments, the additional layer comprises ceramic and / or aramid.

[0117] In some embodiments, the additional layer comprises at least one PIM, which is distinct or identical to the PIM of the polymer layer.

[0118] According to these embodiments, the additional layer has a homogeneous or a heterogeneous average thickness of less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers or less than about 1 micrometer, and / or the average thickness of the polymer layer is more than about 50 nanometers, more than about 0.1 micrometers, more than about 0.3 micrometers or more than about 0.4 micrometers.

[0119] In some embodiments, the porous substrate is a ceramic-coated separator; preferably, a PP, PE or multilayer porous substrate with at least one surface coated with a ceramic layer.

[0120] In some embodiments, the porous substrate is an aramid-coated separator; preferably, a PP, PE or multilayer porous substrate with at least one surface coated with an aramid layer.

[0121] In some embodiments, the coated separator comprises two distinct polymer layers, wherein one at least comprises a PIM (first polymer layer) and the other one comprises a polymer which may be a distinct PIM or another polymer (second polymer layer). Possible embodiments include:- the first polymer layer is coated on the porous substrate, and the second polymer layer is coated on the first polymer layer;- the second polymer layer is coated on the porous substrate, and the first polymer layer is coated on the second polymer layer;- the first polymer layer is coated on one surface of the porous substrate, and the second polymer layer is coated on the opposite surface of the porous substrate; or- both surfaces of the porous substrate are coated with either the polymer layer, the second polymer layer or a combination of both.

[0122] These embodiments are exemplified in Figures 1-6.

[0123] FIG. 1 illustrates a schematic representation of a coated separator, wherein a polymer layer comprising PIMs is uniformly applied to one surface of a porous substrate.

[0124] FIG. 2 illustrates a coated separator where the polymer layer (e.g., comprising PIMs) is applied to one surface of the porous substrate, while the opposite surface is coated with a different layer, such as an additional polymeric layer that may also comprise PIMs.Attorney Docket No.: 052981-517001WO

[0125] FIG. 3 further illustrates a coated separator where a polymer layer (e.g., comprising PIMs) uniformly applied to one surface of the porous substrate, with a different layer, such as an additional polymeric layer (e.g., comprising PIMs), coated on top of the polymer layer.

[0126] FIG. 4 illustrates a coated separator where a layer is uniformly applied to one surface of the porous substrate, and another layer (e.g., a polymer layer) is coated on top.

[0127] FIG. 5 illustrates a coated separator where a polymer layer comprising PIMs 1 is applied to one surface of the porous substrate 2. In this schematic, the polymer layer is shown to be partially contained within the pores of the porous substrate, creating an interface 3 where the polymer layer has penetrated the substrate's pores.

[0128] FIG. 6 illustrates a coated separator where the polymer layer comprising PIMs 1 is applied to one surface of the porous substrate 2, with the polymer layer partially contained within the pores and creating an interface 3. Additionally, this figure shows that a layer 4 (e.g., a polymer layer) is coated on top of the polymer layer, suggesting the potential for advanced multi-layer structures that can further optimize the separator's performance through enhanced chemical and physical properties.

[0129] It should be noted that, according to these figures, the polymer layer is shown as being evenly distributed on the porous substrate. However, the invention is not limited to this homogeneous representation and also encompasses embodiments where the polymer layer exhibits heterogeneous thickness, allowing for variations in thickness across the surface depending on specific application requirements or desired performance characteristics.

[0130] The present invention also relates to a method of producing a coated separator for a lithium battery. The method of the invention involves coating a dispersion comprising at least one PIM on at least one surfacc / sidc of the porous substrate. This method may notably involve any of a dip coating method, a spray coating method, a casting method, a knife coater method, a gravure coater method, a Mayer bar / rod method, a slot die coater method, a reverse roll coater method, a roll coater method, a screen printing method or an inkjet method.

[0131] In some embodiments, the present invention provides a method of producing a coated separator for a lithium battery, wherein the coated separator comprises at least one polymer layer coated on a porous substrate, wherein the method comprises the steps of:(a) preparing a coating dispersion comprising at least one Polymer of Intrinsic Microporosity (PIM), at least one solvent, or solvent mixture, and at least one additive;(b) applying the dispersion of step (a) on at least one surface of the porous substrate, preferably using a dip coating method, a spray coating method, a casting method, a knife coater method, a gravure coater method, a Mayer bar / rod method, a slot die coater method, a reverse roll coater method, a roll coater method, a screen printing method or an ink jet method; andAttorney Docket No.: 052981-517001WO(c) optionally removing the solvent from the coated separator of step (b) and / or drying the coated separator of step (b).

[0132] In some embodiments, these additives are intentionally left in the coating while proceeding with step (c). These additives may notably be selected to induce the formation of pores within the polymer layer, preferably to create a hierarchical pore structure in the polymer layer.

[0133] The creation of these pores may occur with or without the implementation of step (c).

[0134] The creation of these pores may also occur at a later stage, for example during the cell assembly and / or when the electrolyte is added to the cell assembly. The additive may be specifically selected for its ability to migrate from the polymer layer into the electrolyte, where it may then dissolve, such migration creating voids in the polymer layer and as a result a wider pore size distribution in the polymer layer.

[0135] Alternatively, the additive may be selected to create channels or other pathways for lithium ion transport to occur.

[0136] In some embodiments, the coating dispersion comprises at least one additive promoting phase separation during step (c).

[0137] In some embodiments, the additive(s) may be removed during step (c), e.g., drying of the coated separator.

[0138] In some other embodiments, the additive(s) may remain in the coating layer and migrate into the battery electrolyte after formation of the cell, or when the cell is in use.

[0139] In some embodiments, the coating dispersion comprises at least one battery electrolyte component which dissolves in the electrolyte when the cell is in use.

[0140] In some embodiments, the battery electrolyte component phase dissolves, phase separates, or crystallizes in the coating dispersion.

[0141] In some embodiments, the dispersion of step (a) comprises less than about 40 wt.% of PIM polymer(s), relative to the total weight of the dispersion, or less than about 30 wt.%, less than about 20 wt.%, less than 10 wt.% or less than 8 wt.%.

[0142] In some preferred embodiments, the dispersion of step (a) comprises about 4 to 7 wt.% of PIM, preferably PIM-1 and / or PIM- 13, which are dissolved in a solvent or solvent mixture. The dispersion of step (a) may for example comprise about 5 to 6 wt.% of PIM, preferably PIM-1 and / or PIM- 13. The solvent or solvent mixture preferably comprise THF, NMP or DMF, alone or mixed together. One example is a mixture of THF with NMP (e.g. a 50 / 50, a 70 / 30, or a 80 / 20 THF / NMP wt. mixture). Another example is a mixture of THF with DMF (e.g. a 50 / 50, a 70 / 30, or a 80 / 20 THF / NMP wt. mixture).

[0143] The dispersion of the PIM polymer(s) and additives in the solvent(s) is preferably conducted using a mixer (e.g., stirrer, homogenizer, or high-shear mixer) to mix the PIM polymer! s), additives, and solvent(s). The intensity and duration of mixing is adjusted based on the concentration of the PIM polymer(s) and additives in the dispersion.Attorney Docket No.: 052981-517001WO

[0144] The PIM(s) and additive(s) may be mixed together before being added in the solvent(s), or they may be added to the dispersion independently.

[0145] In some embodiments, step (a) is carried out at a temperature ranging from about 10 and about 100°C, preferably a temperature ranging from about 15 and about 80°C, more preferably a temperature ranging from about 20 et about 50°C, most preferably a temperature of about 20-23°C.

[0146] Certain additives such as stabilizers and / or surfactants may be added during step (a) to, e.g., improve the stability of the dispersion during the method.

[0147] Step (b) may be repeated several times to create several coating layers.

[0148] In the gravure coating process, the dispersion is applied onto the porous substrate through a patterned roller. The engraved cells on the roller may be engineered to hold a specific volume of dispersion; they can hold a fixed amount of dispersion, which provides control of the thickness and pattern of the coating layer. As the roller rotates, the dispersion is deposited consistently across the surface of the porous substrate. This method is particularly well-suited for achieving consistent coating layers. The equipment usually provides the possibility to control the pressure applied on the substrate during the process and adjust based on the materials used.

[0149] In some preferred embodiments, the polymer layer is applied to the separator using a microgravure coating process. In this process, a microgravure roll with very fine, shallow engraved cells transfers a controlled amount of the coating dispersion onto the substrate. The use of microgravure allows for precise control over the thickness of the polymer layer, which is a key property of the coated separator of the invention. After ink application, the coated separator moves through a dryer where solvents are evaporated at elevated temperatures. Such technique enables the formation of thin coatings within the range of the invention. This precise control of layer thickness and distribution is particularly advantageous for optimizing separator properties such as porosity, tortuosity, ionic conductivity, and overall battery performance, and is made possible using microgravure coating process.

[0150] In the slot die coating method, the polymer is applied to the separator by using a die head with a very small opening that allows the ink to spread across the separator, during the R2R coating process, applying a thin layer of ink to the separator substrate. After ink application, the coated separator moves through a dryer where solvents are evaporated at elevated temperatures, producing the final coating morphology.

[0151] In the dip coating method, the porous substrate is submerged into the dispersion, allowing the coating material to penetrate the surface(s) of the porous substrate. Upon withdrawal, the substrate is dried, resulting in a uniform coating layer. This method is particularly well-suited for achieving deep and consistent coverage.

[0152] The spray coating involves atomizing the dispersion into fine droplets and spraying them onto the porous substrate. This method is particularly well-suited for applying thin, uniform layers across the porous substrate surface, especially for separators requiring lightweight coatings. TheAttorney Docket No.: 052981-517001WO spray parameters can notably be adjusted for even distribution of the dispersion on the porous substrate surface(s).

[0153] In the casting method, the dispersion is spread onto the surface of the porous substrate, using for example a blade or a spatula, where it forms a uniform layer.

[0154] The knife coater method applies the dispersion by moving a blade or knife across the surface of the porous substrate. The gap between the knife and the substrate determines the coating thickness. This method is particularly well-suited for producing controlled coating layers on the separator.

[0155] The dispersion may be applied to at least one surface of the porous substrate using a Mayer bar / rod, which is wire-wound metering equipment comprising a cylindrical metal rod with wire around it. The wire creates a series of grooves or channels along the rod’ s length, which contribute to controlling the thickness of the coating applied.

[0156] The dispersion may be applied to at least one surface of the porous substrate using a slot die coater. The dispersion is applied through a slit, which is adjustable in size, typically ranging from about 100 micrometers to several millimeters, depending on the desired coating thickness. This method is particularly well-suited for precise control over coating thickness and uniformity.

[0157] The dispersion may be applied to at least one surface of the porous substrate using roll coating. In roll coating, a rotating single roller collects the dispersion and transfers it onto the porous substrate. The thickness of the coating is controlled by the speed and pressure of the roller.

[0158] In some preferred embodiments, the polymer layer is applied to the separator using a slotdie coating process.

[0159] A reverse roll coater may be employed to apply the dispersion on the surface of porous substrate. The equipment usually comprises at least two counter-rotating rolls, wherein the first roll collects the dispersion, while the second roll transfers it to the porous substrate, providing an even coating layer. This method is particularly well-suited for large-scale applications requiring consistent results.

[0160] The dispersion may also be applied to at least one surface of the porous substrate using screen printing according to which the dispersion is forced through a mesh screen onto the porous substrate. This method is particularly useful for applying patterned or selective coatings, where only specific areas of the substrate require dispersion.

[0161] The dispersion may also be applied to at least one surface of the porous substrate using the inkjet method, also called inkjet printing method. This method uses equipment with nozzles to deposit the dispersion onto the porous substrate in a controlled manner, often assisted by computer systems for precise monitoring and adjustment of the deposition parameters.

[0162] Step (c) is optional. According to step (c), the solvent(s) may be removed from the coated separator, at least partially. Additionally or alternatively, the creation of pores, and notably of a hierarchical pore structure as described herein, may be activated during step (c).Attorney Docket No.: 052981-517001WO

[0163] Step (c) may for example be carried out by:- drying the coated separator to extract the solvent(s), preferably using an oven or a vacuum chamber;- applying heat to vaporize the solvent(s), preferably at a temperature of at least about 40°C, between about 30 and about 200°C or between about 35 and about 100°C;- rinsing the coated separator with a non-solvent;- passing the coated separator, while still wet with solvent, through an inline non-solvent bath; and / or- filtrating the solvent(s), preferably using vacuum suction.

[0164] In some preferred embodiments, the coated separator is transferred in an oven and dried at a temperature of from about 40 to about 80°C, or from about 50 to about 70°C, of about 60°C for less than about 10 minutes, less than about 2 minutes or less than 1 minute.

[0165] Unless otherwise specified, each step of the methods of the present invention can be performed at any suitable reaction temperature. Representative temperatures include, but are not limited to, below room temperature, at room temperature, or above room temperature. Other temperatures useful in the methods of the present invention include from about -40 °C to about 65 °C, or from about room temperature to about 40 °C, or from about 40 °C to about 65 °C, or from about 40 °C to about 60 °C.

[0166] The present invention also provides an electrochemical cell comprising an anode; a cathode; a separator as described herein; and an electrolyte. The electrolyte can have a variety of components, such as an alkyl carbonate, a fluorinated carbonate, a diisocyanate, a lithium salt, or combinations thereof.

[0167] Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, one of skill in the art will appreciate that certain changes and modifications may be practiced within the scope of the appended claims. In addition, each reference provided herein is incorporated by reference in its entirety to the same extent as if each reference was individually incorporated by reference. Where a conflict exists between the instant application and a reference provided herein, the instant application shall dominate.

[0168] Examples

[0169] The following examples illustrate the invention without limiting it.

[0170] Separators were prepared by applying coating polymer dispersions in suitable solvent(s) onto commercially available porous polyolefin substrates (9-16 pm thick). The compositions of the exemplified dispersions (also called ink, all homogenous) are detailed in Table 1.Attorney Docket No.: 052981-517001WOTabic 1

[0171] The coating dispersions of Table 1 were prepared by stirring the polymer in the solvent(s) for 24 hours, followed by filtration through a 1 -micron pore glass fiber syringe filter. The solids content of the dispersions was determined by drying a known mass of dispersion and collecting the mass of the residual solids. Ink compositions are crucial for preparing PIM coatings with a porous morphology, for electrochemical cell cycling. The polymer concentration in these inks is low to promote thin coatings when applied to a separator. The use of volatile solvents, like THF, allows for fast evaporation from the coating, when the coated segment reaches the dryer on the R2R coater. In some examples, the use of solvent mixtures facilitates slower drying of the coating and the options for solvent B can cause phase separation and polymer precipitation on the separator, solubilization and reorganization, or pore structure modification. In some examples, an ink containing NMP and THF (e.g., 4-20% NMP) is advantageous, as some NMP remains after THFAttorney Docket No.: 052981-517001WO evaporation. Since the PIM has low solubility in NMP, it resolubilizes the polymer and creates a dense PIM layer adjacent to the separator. In some other examples, the solvent comprises DMC and THF (e.g., 4-10% DMC). Since PIM-1 is more soluble in DMC, an ink containing DMC extends the drying time for the wet film, producing a network of hierarchical pores due to evaporation of the majority of the THF and DMC at different times in the R2R coating process.

[0172] The following methods were used to apply coating dispersions onto porous substrates: either Mayer rod, microgravure, or slot die coating methods to apply the polymer solutions onto the porous substrate and dried, method was used to apply the dispersions onto porous substrates:

[0173] The following properties were measured:

[0174] Coat weight

[0175] May determined gravimetrically, in which a 12 or 100 cm2area of coated material is weighed, the coating stripped using an appropriate solvent, and the separator is weighed again. The coat weight is determined by subtracting these two values and normalizing them to the surface area of the test sample. This method is used for PIM-coatings that were applied to base separators with uncoated polyethylene.

[0176] Determined by UV-vis spectrophotometer measurement for base separators with a ceramic coating. Four 14 mm punches are collected from a coating and dissolved in 4 mL of chloroform. The solution is filtered through a 10 pm syringe filter and added to a quartz cuvette. Polymer absorbance is measured at 435 nm and the coated mass of polymer is calculated using the Beer- Lambert law and a calibration curve to determine the molar absorptivity coefficient. This method is used for PIM-coatings that were applied to base separators with a ceramic coating on one side. PIM coatings were applied to the uncoated side of the single-sided ceramic coating.

[0177] Gurley

[0178] A 10 cm x 10 cm punch of separator was placed in the Gurley apparatus and clamped. The weight was raised, and the timer was started simultaneously to measure the time required for 100 mL (100 cm3) of air to pass through the separator. Two different instruments were used to determine the Gurley number: the digital Oken-type air permeability tester (EG series) from Asahi Seiko (Gurley EG) and the 4150N Gurley densometer from Gurley Precision Instruments (Gurley 4150N).

[0179] Machine Direction (MD) heat shrinkage

[0180] The MD heat shrinkage was used to measure the percentage of dimensional shrinkage in the machine direction (MD) when the material is exposed to 150°C. Heat shrinkage is key in assessing the thermal stability of battery separator materials. This measurement is conducted for dry separator samples with 10 cm x 10 cm dimensions and a 4.5 cm x 5.0 cm rectangle is drawn on the sample. The sample dimensions are measured at the top of the punch, bottom, and two measurements are taken in the middle in the machine direction (MD) and the transverse direction (TD). At least 3 replicate punches were prepared in this way for each coated separator. OnceAttorney Docket No.: 052981-517001WO premeasurements are taken, the separator samples are placed on top of five sheets of A4 white paper. Five sheets of A4 white paper are then placed on top of the separator samples. A4 paper with the same number of sheets must be used to replicate this test to replicate the coefficient of friction present between the paper and separator samples. For a separator with a single coating, the coating is placed facing up and the PE side is placed facing down. For a sample with a ceramic coating on one side and a Sepion PIM coating on the other side, the ceramic is placed facing down. This stack of paper and samples is placed in a pre-heated oven (preheated for at least 2h) and left in the oven for 60 min. After 60 min, the stack of paper and samples is removed from the oven and allowed to cool. Once cool, the upper 5 layers of paper are carefully removed so the samples are not disturbed. Then each sample has length measured in 4 areas again (top, 2 middle measurements, and bottom) in both the MD and TD. Heat shrinkage (%) was calculated as (Lo-L) / LoxlOO, Lo is the initial dimension and Lis the final dimension, determined separately for both machine direction (MD) and transverse direction (TD) of the sample. The heat shrinkage was calculated four times, for each length measurement (top, two middle, bottom) and averaged to determine the average heat shrinkage in the MD and in the TD separately.

[0181] Tensile strength at break (kgf / crm. ASTM D882)

[0182] Maximum stress the coated separator can withstand in the Instron tensile testing apparatus direction before breaking, expressed in kilogram-force per square centimeter.

[0183] Elongation at break (%, ASTM D882)

[0184] Percentage increase in length of the material can endure i n the In stro n te ns ile te s ting app arat u s before breaking under tensile stress, in order to assess the flexibility and ductility of the separator.

[0185] Puncture strength (kgf. ASTM F1306),

[0186] The force (in kilogram-force) required to puncture the separator in the Instron puncture testing apparatus, in order to assess the resistance to mechanical penetration.

[0187] Electrical resistance (ER)

[0188] ER is determined by running electrochemical impedance spectroscopy on separator layers, wetted with electrolyte, between two polished, stainless steel electrodes. Separator layers are soaked in LP57 electrolyte for 0.5-4 h prior to the test. A number of separator layers from 1 to 5 are placed in the test fixture and topped up with excess electrolyte. EIS is run on the fixture and resistance at the Z’ axis intercept is measured. The Z’ intercepts (Ohm) are plotted against the number of separator layers and the slope of this line (multiplied by area of the separator punch) yields the area-specific ER.

[0189] Discharge resistance measurements (Area Specific Resistance ASR)

[0190] They are run on full lithium ion cells with NMC-631 cathode, graphite anode, the example separator number, and LP57 electrolyte. After formation, cells are charged for three hours,Attorney Docket No.: 052981-517001WO discharged for three hours then they enter a hybrid pulse power characterization (HPPC, Duong, T.Q., USABC and PNGV Test Procedures, Journal of Power Sources, 89 (2000), 244-248) protocol where the cell is charged to 100% SOC, then as the cell is discharged, 30 second 1C pulses are applied through the SOC range to measure resistance and power capabilities. Results are expressed as area-specific resistances and reported for the discharge pulse at 50% State-of-Charge (SOC).

[0191] Example 1

[0192] The results of this first set of experiments are provided in Table 2.Table 2 (NT = Not Tested)“I CCS on PE” = 1 -layer Ceramic-Coating on polyethylene Separator“2xCCS on PE” = 2-layer Ceramic-Coating on polyethylene Separator (one on each side)

[0193] Table 2 demonstrates a number of comparative examples with high coat weights and Gurley values (1A-1E) and properties for incumbent polyethylene and ceramic-coated polyethylene separators that are used in Li-ion batteries, today. These examples show the mechanical integrity of the incumbent separators and with excellent resistance to puncture, high tensile strength, and required heat shrinkage (150 °C) for Li-ion applications. The PIM-coating examples in this table show that replacing one of the ceramic coatings with a PIM coating does not adversely affect the mechanical integrity of the separator. These thick PIM coatings show some improvements to puncture strength and heat shrinkage. The incumbent separators have excellent ion transport, likely due to high porosity. When the PIM-coated examples from Table 2 are built into Li-ion pouch cells, they exhibit poor capacity retention and fail earlier than the incumbent PE or ceramic-coated separators.Attorney Docket No.: 052981-517001WO

[0194] Example 2

[0195] The compositions of the exemplified dispersions for this second set of experiments are detailed in Table 3 and the results in Table 4.Table 3Table 4 (NT = Not Tested)

[0196] Table 3 demonstrates a number of comparative examples with high coat weights and Gurley values (2A-2D) for PIM coatings containing solid fillers and additives. When these PIM-coated examples from Table 3 are built into Li-ion pouch cells, they exhibit poor capacity retention and fail earlier than the incumbent PE or ceramic-coated separators.

[0197] Example 3

[0198] The compositions and results for this third set of experiments are detailed in Table 5.Attorney Docket No.: 052981-517001WOTable 5

[0199] Table 5 shows the results of a development strategy to reduce the PIM coating CW and Gurley to bring Li-ion cell cycling performance in line with the incumbent PE, IxCCS and 2xCCS separator examples. The development target was reduction of the cell level resistance (discharge ASR), while maintaining mechanical integrity of the coated separator (as predicted in Table 5 withAttorney Docket No.: 052981-517001WOMD heat shrinkage measurements). Comparative example 3B was prepared with InkC (contains 80:20 THF:NMP). It is expected the NMP causes PIM precipitation and densification as the THF evaporates from the ink. The high Gurley values for this coating are indicative of a dense layer lacking mesopores or macropores, where transport through the PIM’ s microporous structure must facilitate all ion transport in the Li-ion cell. Example 2B has the highest discharge area-specific resistance (ASR) of all coatings in Table 5, suggesting that ion transport is impeded by this thick, high CW, high Gurley coating. Conversely, the on-market PE (IX), IxCCS (1Y), and 2xCCS (1Z) coatings have very low Gurley values and very low cell ASR values. Examples 2D-2Y were all coated with THF-only inks at 50-70 mg polymer / mL solvent. With these coatings, the solids concentration in the ink, and the target wet thickness on the R2R coater were modified to reduce Gurley and coat weight for the resulting coatings. Coat weight is proportional to coating thickness and initial efforts to lower discharge ASR in the cell focused on reducing coat weight. Example 3H (CW 0.49 g / m2, Gurley EG 653,000 s / 100 cm3) and example 3W (CW 0.52 g / m2, Gurley EG 4,920 s / 100 cm3) were two important coatings for further development and optimization of cell level resistance. These two coatings have a similar, thin coat weights and but very different Gurley values and the resulting decrease cell discharge ASR strongly correlates with this reduction in Gurley value and an increase in the porosity or hierarchical porosity of example 3W. Conversely, when the inventors considered example 3C (CW 1.41 g / m2, Gurley EG 653,400 s / 100 cm3) and 3H (CW 0.49 g / m2, Gurley EG 653,000 s / 100 cm3), these two coatings have similar Gurley values but the three times reduction in CW for example 3H does not translate to a proportional reduction in discharge ASR or cell resistance.

[0200] Example 4

[0201] The compositions and results for this set of experiments are detailed in Table 6 and Table 7.Attorney Docket No.: 052981-517001WOAttorney Docket No.: 052981-517001WOTable 6

[0202] The results in Table 6 show that separators coated with PIM-1 can achieve similar discharge ASR values to the incumbent PE and ceramic-coated separators, without significant loss or mechanical integrity (as measured by heat shrinkage). This was achieved by reducing the solids concentration in the ink, increasing the target wet thickness of the coating and all coatings in Table 6 were prepared by microgravure R2R coating method in order to apply thin coat weights. With optimization of both CW, Gurley, and the ink composition, examples like 41 (CW0.17 g / cm2, Gurley EG 304 s / 100 cm3) exhibit lower discharge ASR values than the 2xCCS comparative example while maintaining heat shrinkage lower than the IxCCS comparative example. Example 41 also shows good cell cycling performance in a Li-ion cell. Further optimization of CW and Gurley lead to very thin coatings like 4N (CW0.14 g / m2, Gurley EG 140 s / 100 cm3) and 40 (CW 0.10 g / m2, Gurley 132 s / 100 cm3) showing similar discharge ASR and heat shrinkage to the comparative 2xCCS (1 Y) example.

[0203] Attorney Docket No.: 052981-517001WOAttorney Docket No.: 052981-517001WOTable 7 (NT = Not Tested)

[0204] Despite acting as a strong barrier, the PIM- 1 coating does not significantly hinder ionic flow, as shown by the low discharge ASR values that have been achieved in Table 6. By examining the ASR and Mn diffusion coefficients for the separators in Table 7, it is obvious that coated separators with lower discharge ASR exhibit greater Mn diffusion, in the H-cell measurement method. Low ASR is best for cycling a Li-ion battery at fast rates but inhibiting Mn diffusion (or other transition metal diffusion) is desired by the battery industry to introduce new cathode technologies and prevent failure modes caused by Mn migration to the graphite anode. With this target for low metal diffusion (Mn, Fe, Ni, etc.) there must be an optimal ASR level for good cell cycling that minimizes the metal diffusion allowed by the coated separator. All of the PIM-coated separators exhibit lower Mn diffusion than the on-market separators listed in Table 7.

[0205] Example 6

[0206] When designing the PIM-coated separator, a balance of low resistance, high transition metal blocking capabilities, and good cycle life performance are desired.

[0207] High resistance of the coated separator can result in poor cycle life. Multiple linear regression (MLR) computational modelling approach was used to predict product properties in order to target a balance of metal transmission rate (proportional the diffusion coefficient), while maintaining a low cell discharge ASR. To utilize this MLR approach, linear equations are fitted for each design parameter of interest to the formulae yi = niixi + bi and yi = ni2X2 + b2. The general structure of multiple equations can be simplified using linear algebra, to the following general equation:Attorney Docket No.: 052981-517001WO y = bxx X (x + bz) X (z + / q )

[0208] Utilizing this rational design approach, the inventors fitted numerical functions based on solids content (SC), wet thickness (WT), coat weight (CW), and Gurley to predict the Mn transmission rate, the discharge ASR, and the separator electrical resistance. After evaluating significance and correlation of each input, it was determined SC and WT had the strongest correlation to Mn blocking rate and discharge ASR. CW and Gurley were removed from the MLR functions and correlation coefficients and mean squared error improved for the new MLR functions with only SC and WT input variables. It was also determined there was a weak correlation between the input variable measurements and separator electrical resistance (ER) and more work is being done to improve ER measurement quality. The final outputs of the MLR model gave a function relating SC and WT to the Mn blocking rate and a second function relating SC and WT to the discharge ASR, and these models were used to improve the PIM coating design. Contour maps of these parameters are shown in Figure 7A and 7B. The final goal of these modelling efforts is focused on developing a ink composition, and coating composition that have low discharge ASR to enable lithium battery charge rates in less than 1 h, and producing thinner and more porous coatings while maintaining metal blocking properties of the PIM coating.

[0209] FIG. 7A shows contour maps of metal blocking and cell resistance response when modeled as a function of solids content (SC).

[0210] The discharge ASR was modeled according to the following equation:Resistance (Discharge ASR, G em2) = 621.71 x SC - 0.43099 x WT + 22.547 (eq.l)

[0211] FIG. 7B shows contour maps of metal blocking and cell resistance response when modeled as a function of wet thickness (WT).

[0212] The metal transmission rate was modeled according to the following equation:Metal Transmission Rate (mmol Mn / min) = -0.10599 x SC - 0.00017226 x WT + 0.013818(eq.2)

[0213] When these contour maps are overlayed, limits can be applied to map the range of solids contents and wet thicknesses that produce low resistance, metal blocking coatings. Contour maps of these parameters are shown in Figure 8A (metal blocking) and 8B (cell resistance).

[0214] The light-shaded, uniform grey regions in the contour maps (FIGs. 8A-8B) correspond to combinations of solids content (SC) and wet thickness (WT) that meet the predefined performance requirements for metal blocking and cell resistance, whereas the light-shaded regions correspond to combinations that do not meet those requirements or represent impractical limits for the R2R coating equipment. In other words, samples falling within the combined dark grey areas exhibitAttorney Docket No.: 052981-517001WO acceptable cell resistance and metal transmission values for a battery cell, while samples in the dark areas show insufficient performance. Tables 6 and 7 establish that discharge ASR must be minimized. This modelling approach shows there are practical limits that do not allow minimization of the parameter due to restrictions to SC and WT in the metal blocking figure. Conversely, to maximize metal blocking properties (and minimize PIM diffusion coefficients), the discharge ASR must be maximized. This results in poor Li-ion cell cycling, as outlined in comparative example 3B. Accordingly, formulations compositions (SC) and coating conditions (WT) should be selected to fall within the light-shaded regions to ensure compliance with the specified performance criteria, restricting to a small area of working examples that encompasses the examples in Tables 6 and 7.

[0215] Example 7

[0216] In this example, roll-to-roll coating methods, such as slot-die coating or microgravure coating, were employed. The coating parameters were carefully controlled to achieve specific coating thickness of the polymer dispersion onto the porous substrate. The solid content of the dispersions (wt.%) as well as the wet thickness of the ink are detailed in Table 9.

[0217] In this example, roll-to-roll coating methods, i.e., slot die or microgravure, with control coating parameters, i.e., coating thickness, and controlling being applied to the substrate.Table 9*Note: Example 7B has retained a capacity of about 93% at the 1500 cycle mark, outperforming the 1Z comparative example in capacity retention and cycling ability.

[0218] When solids content and wet thickness parameters result in the formation of a dense coating, this coating allows little diffusion and exhibits high resistance, as observed in 7A.Attorney Docket No.: 052981-517001WOSuch coatings result in poor Li-ion battery performance. Separator design to minimize cell resistance focus on coating parameters and coating composition. Through modelling and careful selection of wet thickness and solids content targets, less dense coatings can be produced. These coatings have lower Gurley values, lower resistance, and allow for more diffusion through the coating. As observed in 7B and 7C, this approach to PIM-1 coating preparation yields a Li-ion cell that is capable of long cycle life, on a 1C (charge from 0% to 100% capacity in 1 h),lD (discharge from 100% to 0% capacity in 1 h) cycling protocol.

[0219] FIGs. 9A and 9B respectively show scanning electron microscopy (SEM) cross-section images of the separator obtained in comparative example 7A and in inventive example 7B.

[0220] The high Gurley value of comparative example 7 A shows a densified PIM layer adjacent to the separator surface. This dense layer is the root cause for high Gurley values, high resistance, and limitations to lithium transport during cell cycling at fast rates. Light and thin coatings, like Example 7B, do not have this dense layer due to selection of solids content and wet thickness targets that yield a less dense coating layer. It is expected the hierarchical pore structure is present throughout the entire thickness of example 7B, facilitating better lithium transport during fast cycling (1C, ID cycling rates) while still maintaining regular points to block transition metal (Mn, Fe, Ni) transport, and preventing early cell failure.

[0221] Example 8

[0222] Single sided ceramic separators were coated on the uncoated side with the battery-grade PIM-1 composition using a gravure roll method with a roll-to-roll coater, slitted to have 70 mm for cell build. The cells were built using a semi-automated line in a multilayer pouch cell comprising of 2 NMC631 cathodes and 3 graphite anodes layers. All materials were dried prior to cell assembly. After assembly and before electrolyte filling, the cells were further dried in a vacuum oven. After electrolyte filling, the cells were vacuum sealed, fixtured and placed into the cyclers to begin testing. Prior to cycling, the cells were put through a formation protocol to generate solid electrolyte interphase (SEI) onto the electrode surfaces. The formation protocol was comprised of 6 steps comprising a rest, a charge-discharge at C / 20 (charge from 0 to 100% capacity in 20 h, discharge from 100 to 0% capacity in 20 h) to 30% SOC, a charge-discharge at C / 20 to 100% SOC, a rest, a charge-discharge at C / 20 to 100% SOC, and a final rest. After formation, the nominal cell capacity is approximately 270 mAh.

[0223] Cell cycling at 1C rate

[0224] After formation, the cells were put into testing in 1C, ID cycling, in an oven at 30 °C. This is a cycling protocol that is charging in discharging at a fast rate, where the battery is charged from 0% to 100% capacity in 1 h and discharged from 100% to 0% in 1 h. Example 7B shown in FIG. 10 (3 replicate cells reaching 1400 cycles), the cycle life at 1C for the symmetric cell for the example 7B exceeded 500 cycles and continued cycling beyond that and therefore demonstrated significantly performant cycle life. Example 7B demonstrates by optimizing PIM coatingAttorney Docket No.: 052981-517001WO properties and ink compositions, the resulting coating can cycle at a fast rate and retain transition metal blocking properties with low Gurley and low CW.

Claims

Attorney Docket No.: 052981-517001WOWHAT IS CLAIMED IS:

1. A coated separator for a lithium battery, comprising a porous substrate and at least one polymer layer on at least one surface of the porous substrate, wherein the polymer layer comprises at least one Polymer of Intrinsic Microporosity (PIM), wherein the coated separator has the following properties:- a coat weight less than about 0.8 g / m2, preferably less than about 0.75 g / m2, more preferably less than about 0.7 g / m2, less than about 0.5 g / m2, less than about 0.4 g / m2, more preferably less than about 0.3 g / m2, more preferably less than about 0.2 g / m2;- a Gurley value less than about 400 s / 100 cm3air, preferably ranging from about 100 s / 100 cm3air and 400 s / 100 cm3 air, more preferably ranging from about 100 s / 100 cm3 air and 300 s / 100 cm3 air.

2. The coated separator of claim 1, wherein:(1) the diffusion coefficient DPIM of the PIM coating with respect to Mn is in the range of about 0.1 x 10'10cm2 / s to about 9.0 x 10' cm2 / s and / or(2) the diffusion coefficient DPIM of the PIM coating with respect to Fe is in the range of about 0.1 x 10’11cm2 / s to about 9.0 x 10'8cm2 / s, wherein the diffusion coefficient DPIM of the PIM coating is defined the following equation:_ xPIMPIM XSEp _ XTDSEP DTwherein xPIMis the thickness (cm) (or coat weight in g / m2) of the PIM coating xSEPis the thickness (cm) of the separator xTis the thickness (cm) of the coated separatorDSEPisthe diffusion coefficient (cm2 / s) of the separatorDTis the diffusion coefficient (cm2 / s) of the coated separator3. The coated separator of claim 1 or 2, wherein the polymer of intrinsic microporosity comprise at least one of PIM-1, PIM-2, PIM-3, PIM-4, PIM-5, PIM-6, PIM-7, PIM-8, PIM-9, PIM-10, KAUST- PI-X, triptycene based polymers of intrinsic microporosity, derivatives thereof, or combinations thereof; preferably, the polymer of intrinsic microporosity comprises PIM-1 and / or PIM- 13, or derivatives thereof.

4. The coated separator of any one of the preceding claims, wherein the polymer of intrinsic microporosity comprises at least one PIM copolymer, preferably a PIM copolymer comprising recurring units of PIM-1 and / or PIM- 13, or derivatives thereof.Attorney Docket No.: 052981-517001WO5. The coated separator of any one of the preceding claims, wherein the polymer of intrinsic microporosity has a number average molecular weight (Mn) between 1,000 and 2,000,000g / mol (kDa), preferably between 15,000 and 500,000 g / mol (kDa) or between 20,000 and 200,000 g / mol (kDa).

6. The coated separator of any one of the preceding claims, wherein the polymer layer is coated on at least about 50 % of at least one surface of the porous substrate, at least about 60 %, at least about 70 %, at least about 80 %, at least about 90 %, at least about 98 % or at least about 99 %.

7. The separator of any one of the preceding claims, wherein the polymer layer has a homogeneous or a heterogeneous average thickness of less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers or less than about 1 micrometer, and / or the average thickness of the polymer layer is more than about 50 nanometers, more than about 0.1 micrometers, more than about 0.3 micrometers or more than about 0.4 micrometers.

8. The separator of any one of the preceding claims, wherein the thickness of the porous support is less than about 25 micrometers, less than about 20 micrometers, less than about 18 micrometers, less than about 17 micrometers, less than about 16 micrometers, or preferably less than 15 micrometers, and / or the thickness of the porous support is more than about 1 micrometer, more than about 2 micrometers, or preferably more than about 5 micrometers.

9. The separator of any one of the preceding claims, wherein the thickness of the separator is less than about 14 micrometers, less than about 13 micrometers, less than about 12 micrometers, or preferably less than 10 micrometers.

10. The separator of any one of the preceding claims, wherein the polymer layer has an average pore diameter of less than about 12 nm, or less than about 10 nm, less than about 5 nm, less than about 4 nm, less than about 3 nm, less than about 2 nm, or less than about 1 nm, or comprised between about 12 nm and about 0.1 nm, comprised between about 11 nm and about 0.2 nm or comprised between about 10 nm and about 0.3 nm.

11. The separator of any one of the preceding claims, wherein the polymer layer has a hierarchical pore structure, preferably comprising macropores, mesopores and / or micropores, wherein:- macropores and / or mesopores preferably have an average size comprised between about 10 and about 500 nanometers, between about 10 and about 400 nanometers, or between about 10 and about 300 nanometers; and- micropores preferably have an average size comprised between about 10 nm and about 0.1 nm, between about 10 nm and about 0.5 nm, or between about 10 nm and about 1 nm.Attorney Docket No.: 052981-517001WO12. The separator of claim 11, wherein the macropores and / or mesopores of the hierarchical pore structure comprise tortuous, spherical and / or oblique shapes, and / or the negative space of a fibrous network.

13. The separator of any one of the preceding claims, wherein the polymer layer is coated on both surfaces (or sides) of the porous substrate.

14. The separator of any one of the claims 1-12, wherein the polymer layer is coated on one surface (or side) of the porous substrate.

15. The separator of any one of the preceding claims, comprising one polymer layer comprising at least one PIM and at least one additional layer.

16. The separator of claim 15, wherein:- the polymer layer is coated on the porous substrate, and the additional layer is coated on the polymer layer;- the additional layer is coated on the porous substrate, and the polymer layer is coated on the additional layer;- the polymer layer is coated on one surface of the porous substrate, and the additional layer is coated on the opposite surface of the porous substrate; or- both surfaces of the porous substrate are coated with either the polymer layer, the additional layer or a combination of both.

17. The separator of claim 15 or 16, wherein the additional layer comprises ceramic and / or aramid.

18. The separator of any one of the claims 15-17, wherein the additional layer has a homogeneous or a heterogeneous average thickness of less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers or less than about 1 micrometer, and / or the average thickness of the polymer layer is more than about 50 nanometers, more than about 0.1 micrometers, more than about 0.3 micrometers or more than about 0.4 micrometers.

19. The coated separator of any one of the preceding claims, wherein:- the separator comprises a porous substrate, one polymer layer coated on one surface of the porous substrate and has a heat shrinkage (measured at 150°C, 1 h) of less than about 65% on a single-sided PIM coated separator, preferably less than about 60 %;- the separator comprises a ceramic-coated porous substrate, one polymer layer coated on one surface of the porous substrate, and has a heat shrinkage (measured at 150°C, 1 h) of less than 10%, preferably less than about 9%.Attorney Docket No.: 052981-517001WO20. The separator of any one of the preceding claims, comprising two distinct polymer layers, wherein one at least comprises a PIM (first polymer layer) and the other one comprises a polymer which may be a distinct PIM or another polymer (second polymer layer), wherein:- the first polymer layer is coated on the porous substrate, and the second polymer layer is coated on the first polymer layer;- the second polymer layer is coated on the porous substrate, and the first polymer layer is coated on the second polymer layer;- the first polymer layer is coated on one surface of the porous substrate, and the second polymer layer is coated on the opposite surface of the porous substrate; or- both surfaces of the porous substrate are coated with either the polymer layer, the second polymer layer or a combination of both.

21. A method of producing a coated separator for a lithium battery, wherein the coated separator comprises at least one polymer layer coated on a porous substrate, wherein the method comprises the steps of:(a) preparing a coating dispersion comprising at least one Polymer of Intrinsic Microporosity (PIM), at least one solvent, or solvent mixture, and optionally at least one additive;(b) applying the dispersion of step (a) on at least one surface of the porous substrate, preferably using a dip coating method, a spray coating method, a casting method, a knife coater method, a gravure coater method, a Mayer bar / rod method, a slot die coater method, a reverse roll coater method, a roll coater method, a screen printing method or an inkjet method; and(c) optionally removing the solvent from the coated separator of step (b) and / or drying the coated separator of step (b).

22. The method of claim 21, wherein the coating dispersion comprises at least one solvent which is an electrolyte solvent; preferably at least one aprotic organic solvent; more preferably at least one of cyclic esters (e.g., ethylene carbonate, propylene carbonate, / -butyrolactone), linear esters, cyclic ethers (e.g., 2-methyltetrahydrofuran, 1,3-dioxolane), linear ethers (e.g., 1,2-dimethoxy ethane), amides, sulfoxides, carboxylic acid esters, additional sulfoxides, sulfones (e.g., tetramethylene sulfone, ethyl methyl sulfone, dimethylsulfone), sulfonamides, and mixtures thereof.

23. The method of claim 21 or 22, wherein the coating dispersion comprises a solvent mixture (e.g., a binary or ternary solvent mixture); preferably a solvent mixture promoting phase separation during step (c); more preferably a solvent mixture promoting phase separation during step (c) leading to a polymer layer having a hierarchical pore structure.

24. The method of any one of claims 21-23, wherein the coating dispersion comprises at least one battery electrolyte component which dissolves in the electrolyte when the cell is in use.Attorney Docket No.: 052981-517001WO25. The method of any one of claims 21-24, wherein the solvent is at least one of dimethyl sulfoxide (DMSO), dimethylformamide (DMF), tetrahydrofuran (THF), 1,3 -dioxolane, sulfolane, methyl ethyl ketone (MEK), dimethylacetamide (DMAC), propylene carbonate (PC), isophorone, N- methylpyrrolidone (NMP), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), acetone, or a mixture thereof; preferably, the solvent is NMP, DMF, THF, dioxolane, MEK, acetone, or a mixture thereof.

26. The method of any one of claims 21-25, wherein step (b) is repeated several times to create several coating layers on the surface(s) of the porous substrate.

27. The method of any one of claims 21-26, wherein the coating dispersion comprises less than 40 wt.% of solids, less than 30 wt.% of solids, less than 20 wt.% of solids, less than 10 wt.% of solids or preferably less than 5 wt.% of solids, relative to the total weight of the dispersion.

28. An electrochemical cell comprising an anode; a cathode; the coated separator of any of claims 1- 20; and an electrolyte.

29. The cell of claim 28, wherein the electrolyte comprises at least one of an alkyl carbonate, a fluorinated carbonate, a diisocyanate, a lithium salt, or combinations thereof.

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