Electrochemical separators, electrochemical devices and related methods

Abstract

A battery separator for an alkali-metal or an alkali metal-ion rechargeable battery is described. The separator comprises a composite membrane having a microporous polymer scaffold and a continuous ceramic phase disposed within the scaffold pore volume, the continuous ceramic phase comprising a three-dimensional packing arrangement of sub-micron ceramic particles. Also described is a rechargeable battery comprising the separator, a method of manufacturing the battery separator and a method of manufacturing the rechargeable battery.

Description

[0001] ELECTROCHEMICAL SEPARATORS, ELECTROCHEMICAL DEVICESAND RELATED METHODS

[0002] FIELD OF THE INVENTION

[0003]

[0001] This disclosure relates to electrochemical separators for use in alkali metal and alkali metal-ion rechargeable batteries and to rechargeable batteries comprising the electrochemical separators. The disclosure also relates to methods of manufacturing electrochemical separators for alkali metal and alkali metal-ion rechargeable batteries and methods of manufacturing alkali metal and alkali metal-ion rechargeable batteries.

[0004] BACKGROUND

[0005]

[0002] Alkali metal and alkali metal-ion rechargeable batteries (e.g., lithium metal rechargeable batteries, lithium-ion batteries and sodium-ion batteries) comprise electrochemical cells that store energy via reversible changes in the oxidation state of an alkali metal. The electrochemical cells comprise at least one electrode comprising the alkali metal. For clarity, the term “alkali metal rechargeable batteries” refers to rechargeable batteries that comprise one metallic electrode, which are distinguished from “alkali metal-ion” rechargeable batteries that do not comprise a metallic electrode; however when the term “alkali metal” is used in other contexts herein, such as when an electrode or electrolyte is said to “comprise an alkali metal,” it refers to members of Group 1 of the Periodic Table of Elements with an atomic number larger than 1 (e.g., comprising Li and Na) and does not specify their oxidation state (e.g., such a reference could include an electrolyte comprising LiPFe or an electrode comprising LiCoCh or an electrode comprising Li metal). Alkali metal and alkali metal-ion rechargeable batteries are used in a wide variety of applications, and research is ongoing to improve aspects such as energy density, power density, and cost. However, the stabilities and lifetimes of these cells are reduced by failure mechanisms.

[0006]

[0003] Electrochemical separators prevent electrical contact between the anode and the cathode within a battery, thus reducing the risk of a short circuit, while allowing ion conduction between the anode and cathode by means of an electrolyte. Electrochemical separators may perform other vital functions as well, for example they may prevent reactive species (e.g., gases or ions) from the anode and cathode sides of the device from freely mixing.

[0007]

[0004] Electrochemical separators for alkali metal and alkali metal-ion rechargeable batteries (herein referred to as “battery separators”) may be produced via many processes comprising many materials. However, microporous polyolefin membranes, such as “wet processed” polyethylene or “dry processed” polypropylene are presentlythe most widely adopted by industry, due in part to their high specific tensile strength, fine pore structure, chemical stability, and low cost. However, these materials are hydrophobic, and the battery formation process requires long wetting times for the electrolyte to completely wet the separator. Therefore, there is a need for improved separator wettability to minimize formation time and / or improve yields and / or enable the use of preferred electrolyte formulations. In addition, the microporous polyolefin membranes are often coated on one or both sides with a surface layer of inorganic particles (e.g., alumina or boehmite) to improve dimensional stability at high temperature and thereby reduce the likelihood of short circuits during high-temperature events. However, due in part to the low melting point of the polyolefin layer, the dimensional stability at elevated temperatures is still lower than desired for many applications. Therefore, there is a need to improve the dimensional stability of separators at elevated temperatures to minimise shrinkage and prevent short circuits. Thinner and / or lighter separators are also desirable to maximise the energy density and / or power density within batteries.

[0008]

[0005] Alternative battery separators have been widely investigated, such as those based on more thermally stable non-wovens or on inorganic particles glued together with polymeric binders. While these alternative battery separators have shown improvements in some attributes, they have not gained a large market share due in part to high switching costs, and the significant installed base of capital equipment for making the incumbent battery separators based on microporous polyolefin membranes.

[0009]

[0006] Thus, there is a need for improved electrochemical separators for use in alkali metal and alkali metal-ion rechargeable batteries.

[0010] SUMMARY

[0011]

[0007] A battery separator for an alkali-metal or an alkali metal-ion rechargeable battery having an electrode comprising an alkali metal, the separator comprising a composite membrane, the composite membrane comprising:

[0012] a microporous hydrocarbon polymer scaffold having a scaffold matrix and a plurality of scaffold pores having a scaffold pore volume, and

[0013] a continuous ceramic phase disposed within the scaffold pore volume, wherein the continuous ceramic phase extends within the scaffold pore volume a distance of at least 1 mm in each of two orthogonal directions;wherein the continuous ceramic phase comprises a three-dimensional packing arrangement of sub-micron ceramic particles,

[0014] wherein the three-dimensional packing arrangement of sub-micron ceramic particles exhibits at least one structure factor peak in Lorentz-corrected SAXS data.

[0015]

[0008] The submicron ceramic particles may comprise aluminum.

[0016]

[0009] The submicron ceramic particles may comprise AI2O3, boehmite (AIO(OH)), core-shell particles comprising ceramic particles coated with an aluminum-containing shell, or combinations thereof.

[0017]

[0010] The submicron ceramic particles may have a particle diameter or effective diameter of from about 5 nanometers to about 200 nanometers.

[0018]

[0011] The microporous hydrocarbon polymer scaffold may comprise any one selected from polyethylene (PE), polypropylene (PP), or combinations thereof.

[0019]

[0012] A largest pore of the plurality of scaffold pores, may have a pore diameter, as determined by bubble point, which is from about 3 to about 15 times the primary mode particle diameter or effective particle diameter of the submicron ceramic particles on a volume basis.

[0020]

[0013] The inter-particle pores between the sub-micron ceramic particles may be defined by an inter-particle distance within the three-dimensional packing arrangement of sub-micron ceramic particles. The inter-particle distance may be from about 0.5 times to about 3 times the particle diameter or effective particle diameter of the submicron ceramic particles.

[0021]

[0014] The continuous ceramic phase disposed within the scaffold pore volume may have a ratio (d / D) of an inter-particle pore size, d, to particle diameter or effective diameter, D, of from about 0.2 to about 1.2.

[0022]

[0015] A packing density of the ceramic particles may be from about 0.40 to about 0.85.

[0023]

[0016] The porosity of composite membrane may be from about 30% to about 70%.

[0024]

[0017] The volume ratio of sub-micron ceramic particles to scaffold matrix in the composite membrane may be from about 0.5 to about 3.

[0025]

[0018] The continuous ceramic phase may extend substantially through the entire thickness of the scaffold.

[0026]

[0019] The bubble point of the battery separator may be at least about 10 bar.

[0027]

[0020] The contact thickness of the composite membrane may be from about 1 microns to about 25 microns.

[0028]

[0021] The microporous hydrocarbon polymer scaffold may comprise a metalized surface region.

[0022] The metalized surface region may comprises copper or aluminum.

[0029]

[0023] The battery separator may comprise a surfactant.

[0030]

[0024] The battery separator may comprise an integrated ionic transport layer on one or both sides of the battery separator, wherein the integrated ionic transport layer comprises one or more anion exchange polymers, one or more cation exchange polymers, one or more polymers of intrinsic microporosity (PIMs), one or more ionsolvating polymers, or combinations thereof.

[0031]

[0025] The battery separator may comprise a sorbent or a reactive material configured to absorb, capture, scavenge, or deactivate species detrimental to battery operation.

[0032]

[0026] The battery separator may comprise a hydrophobic electrolyte additive.

[0033]

[0027] The hydrophobic electrolyte additive may be fluoroethylene carbonate (FEC).

[0034]

[0028] In a second aspect of the invention there is provided a rechargeable battery comprising:

[0035] an anode,

[0036] a cathode,

[0037] the battery separator of the first aspect, and

[0038] an electrolyte comprising an alkali metal;

[0039] wherein at least one of the anode or the cathode includes the alkali metal.

[0040]

[0029] The alkali metal may be selected from lithium or sodium.

[0041]

[0030] The electrolyte may be a solvent-in-salt electrolyte.

[0042]

[0031] The hydrocarbon polymer scaffold may comprise a metalized surface region.

[0043]

[0032] The metallized surface region may be electrically isolated from both the anode and the cathode, and it may be electrically connected to a third terminal.

[0044]

[0033] The battery separator may comprise a surfactant having a cationic portion and an anionic portion, and wherein the cationic portion of the surfactant is the same as the alkali metal of the electrolyte and the anode or the cathode.

[0045]

[0034] According to a third aspect of the invention, there is provided a method of making a battery separator according to the first aspect, the method comprising: a) obtaining a microporous hydrocarbon polymer scaffold, wherein the microporous hydrocarbon polymer scaffold comprises a polyolefin and has a polymer scaffold matrix and a plurality of scaffold pores, the microporous polymer scaffold having a scaffold pore volume and having a porosity from about 70% to about 96%;(b) incorporating sub-micron ceramic particles into the scaffold pore volume of the microporous polymer scaffold; and

[0046] (c) consolidating the sub-micron ceramic particles such that they form a continuous ceramic phase disposed within the scaffold pore volume, wherein the continuous ceramic phase extends within the scaffold pore volume a distance of at least 1 mm in each of two orthogonal directions;

[0047] wherein the continuous ceramic phase comprises a three-dimensional packing arrangement of sub-micron ceramic particles; and

[0048] wherein the three-dimensional packing arrangement of sub-micron ceramic particles exhibits at least one structure factor peak in Lorentz-corrected SAXS data.

[0049]

[0035] The microporous hydrocarbon polymer scaffold may have an absolute tensile strength in the Machine Direction (MD) of from about 0.3 N / mm to about 2.0 N / mm.

[0050]

[0036] The microporous hydrocarbon polymer scaffold may have a mass-per-area of between 0.5 g / m2and 3 g / m2.

[0051]

[0037] The microporous hydrocarbon polymer scaffold may have a bubble point of X at least 2 bar.

[0052]

[0038] According to a fourth aspect of the present invention, there is provided a method of manufacturing a rechargeable battery, the method comprising:

[0053] a. providing a battery separator according to the first aspect;

[0054] b. wetting the battery separator;

[0055] c. forming a stack by disposing the wet battery separator between an anode, and a cathode and inserting the stack in a battery housing; wherein at least one of the anode and the cathode comprises the alkali-metal.

[0056]

[0039] The wetting step may be performed with a fluid that is an electrolyte of the battery or that comprises a solvent present in the electrolyte of the battery.

[0057]

[0040] The alkali metal may be selected from lithium or sodium.

[0058] BRIEF DESCRIPTION OF FIGURES

[0059]

[0041] The present disclosure will be better understood in view of the following figures.

[0060] In the figures, identical reference numerals have been used for the same or equivalent features of the composite membrane, supported liquid membrane, and processes disclosed therein. The figures are not necessarily drawn to scale but may beexaggerated to illustrate various aspects of the present disclosure, and in that regard, the figures should not be construed as limiting.

[0061]

[0042] Figure 1 depicts a schematic representation of an alkali metal or alkali metalion rechargeable battery.

[0062]

[0043] Figure 2a is a schematic illustration of a cross-section of a representative microporous polymer scaffold according to at least one embodiment of the present disclosure;

[0063]

[0044] Figure 2b is a schematic illustration depicting a portion of a composite membrane according to at least one embodiment of the present disclosure.

[0064]

[0045] Figure 2c is an SEM image of a composite membrane having a continuous ceramic phase.

[0065]

[0046] Figure 3a is a schematic depiction of a cross-section of a neat opaloid (composite membrane) comprising monodisperse sub-micron particles in a three- dimensional packing arrangement;

[0066]

[0047] Figure 3b is a schematic depiction of two adjacent particles, each having a diameter (D) that are elements of a particle three-dimensional packing arrangement within a continuous ceramic phase (i.e. an opaloid) as is shown in Figure 3a;

[0067]

[0048] Figure 4 is a schematic depiction of parameters associated with a continuous ceramic phase (i.e. an opaloid) overlaying an SEM of a neat opaloid;

[0068]

[0049] Figure 5a depicts representative Small-Angle X-ray Scattering (SAXS) data sets for opaloids prepared from silica sub-micron particles having diameters of approximately 7 nanometers, 12 nanometers, 22 nanometers, 45 nanometers, and 100 nanometers;

[0069]

[0050] Figure 5b is a graphical illustration of inter-particle distance (ID) determined from SAXS data as a function of nominal particle diameter (D) for continuous ceramic phases (opaloids) prepared from silica sub-micron particles;

[0070]

[0051] Figure 6 is a graphical illustration of representative SAXS data for a material comprising aggregates of monodisperse spherical particles, showing the Guinier, fractal, and Porod scattering regimes and an absence of the structure factor peaks characteristic of opaloids. This figure was reproduced from Bushell et al. (”On techniques for the measurement of the mass fractal dimension of aggregates,” Advances in Colloid and Interface Science, 95, 1-50 (2002))

[0071]

[0052] Figure 7 depicts a representative pore size distribution from BET / BJH analysis of a continuous ceramic phase (i.e. an opaloid) prepared from silica submicron particles having a diameter of approximately 12 nanometers;

[0053] Figure 8 is a schematic depiction of expected values of the ratio of pore diameter to particle diameter (d / D) for different tightly packed arrangements of submicron particles where the coordination number, n, is 3, 4, 6, or 8;

[0072]

[0054] Figure 9a depicts a comparison of specific surface area (SSA) measured by BET with expected particle size,

[0073]

[0055] Figure 9b is a graphical illustration of a comparison of particle diameter calculated with SSA to the nominal sub-micron particle diameters reported by manufacturers;

[0074]

[0056] Figure 10 is a graphical illustration depicting the relationship between volumespecific pore volume and porosity;

[0075] DETAILED DESCRIPTION

[0076]

[0057] Throughout the description and claims, the terms take the meanings explicitly defined herein, unless the context clearly dictates otherwise.

[0077]

[0058] The phrases “in one embodiment”, “in an embodiment” and “in some embodiments” etc. as used herein do not necessarily refer to the same embodiment(s), though they may. Furthermore, the phrases “in another embodiment” and “in some other embodiments” as used herein do not necessarily refer to a different embodiment, though they may. All embodiments of the disclosure are intended to be combinable.

[0078]

[0059] The terms “comprises” and “comprising” mean to include, but are not limited to, such that further features may be present.

[0079]

[0060] It is to be noted that all ranges described herein are exemplary in nature and include any and all values in between. Measurements that are reasonably close to the stated measurement deviate from the stated measurement by a reasonably small amount as understood and readily ascertained by individuals having ordinary skill in the relevant arts. In the event it is determined that individuals having ordinary skill in the relevant arts would not readily ascertain values for such reasonably small differences, the terms “substantially,” “approximately,” and “about” can be understood to mean plus or minus 10% of the stated value.

[0080]

[0061] Composite membranes (for use as electrochemical separators)

[0081]

[0062] The present disclosure is directed at composite membranes which may have many advantageous properties for use in electrochemical separators for alkali metal and alkali metal-ion rechargeable batteries (i.e., “battery separators” as used herein). Through a unique balance of properties, the composite membranes may enable improvements over state-of-the-art battery separators in multiple ways (“improvementvectors”). For example, they may simultaneously enable some or all of the following improvement vectors:

[0082]

[0063] 1 ) Enable thinner battery separators by providing sufficient thermal stability and protection against short circuits without the need for 1 or more additional coated layers of inorganic particles, and thereby reduce ionic resistance and improve the volumetric and gravimetric energy density of the alkali metal or alkali metal-ion rechargeable battery device.

[0083]

[0064] 2) Increase the compressive pressure the battery separator can withstand without short circuiting, e.g., to improve the safety of the alkali metal or alkali metal-ion rechargeable battery device, or to enable higher compressive loads and thereby improve the performance of the electrochemical device by reducing contact resistances within the electrochemical cell.

[0084]

[0065] 3) Reduce unwanted crossover of reactive species or other materials through the battery separator and thereby improve the safety of the alkali metal or alkali metalion rechargeable battery device and enhance the operational flexibility of the alkali metal or alkali metal-ion rechargeable battery device.

[0085]

[0066] 4) Improve the handleability of the battery separator e.g., to enable efficient processing, shipping, handling, storage, and installation of the separator in the final alkali metal or alkali metal-ion battery device, simplifying logistics and thereby facilitating scale-up and cost-reduction of the alkali metal or alkali metal-ion rechargeable battery device.

[0086]

[0067] 5) Enhance the operable temperature range of the battery separator and thereby improve the performance of the alkali metal or alkali metal-ion rechargeable battery device by enabling e.g., higher-temperature operation (resulting in e.g., faster electrode kinetics and / or higher electrolyte conductivity within the electrochemical cell).

[0087]

[0068] 6) Improve the dimensional stability of the battery separator at high temperature and thereby improve the safety of the alkali metal or alkali metal-ion rechargeable battery by preventing catastrophic failure during e.g., a puncture of the alkali metal or alkali metal-ion rechargeable battery device.

[0088]

[0069] 7) Improve the wettability of the battery separator and thereby reduce the time required for electrolyte wetting and formation during production of the alkali metal or alkali metal-ion rechargeable battery device, resulting in lower costs and / or enhanced productivity.

[0089]

[0070] These improvement vectors are often in tension, in particular improvement vector #1 may conflict with improvement vectors #2 to #4. These tensions result in so- called “engineering trade-offs” between separator attributes, which may for examplebe embodied in ratios for a given separator, such as the ratio of thickness to degree of protection against short circuits, or the ratio of thickness to dimensional stability at high temperature, which the battery separators disclosed herein may improve.

[0090]

[0071] The composite membranes may be readily wettable with liquid electrolyte to enable high ionic conductance. Furthermore, the composite membranes may be dimensionally stable under very high temperature conditions. Accordingly, when combined with a suitable electrolyte arrangement (e.g. having alkali metal ions), the inventors have shown that the systems of the present disclosure are particularly effective for use as electrochemical separators for alkali metal and alkali metal-ion rechargeable batteries.

[0091]

[0072] Furthermore, the inventors believe that the composite membranes of the present invention may be suitable for mass production leveraging the existing, installed base of capital equipment for making the incumbent battery separators based on microporous polyolefin membranes coated with a surface layer of inorganic particles. This compatibility with the existing supply chain may significantly reduce the switching costs associated with the composite materials of the present invention.

[0092]

[0073] Alkali metal and alkali metal-ion rechargeable batteries may comprise a negative electrode and a positive electrode. During discharge, the active material of the negative electrode is oxidized while the active material of the positive electrode is reduced. During charge the situation is reversed: the active material of the negative electrode is reduced while the active material of the positive electrode is oxidized. By convention, the negative electrode is typically called the “anode” and the positive electrode is typically called the “cathode.” The terms “anode” and “cathode” will be used herein according to this convention.

[0093]

[0074] Figure 1 shows an alkali metal or alkali metal-ion rechargeable battery cell 10 having a housing or enclosure 13 hosting a cathode 12 and an anode 16. At least one of the cathode 12 or the anode 16 includes an active material comprising an alkali metal species (preferably lithium, sodium, or a combination thereof). For example, the cathode 12 may comprise lithium nickel manganese cobalt oxide (NMC) or lithium iron phosphate (LFP); or the anode 16 may comprise lithium metal. The other one of the cathode 12 or the anode 16 may be any suitable electrode (e.g. graphite). The cathode 12 comprises a cathode active layer 12a and a cathode-side current collector 12b and is electrically connected to a positive terminal 11. The anode 16 comprise an anode active layer 16a, an anode-side current collector 16b and is electrically connected to a negative terminal 17. The battery 10 also includes electrolyte 18 having a cation of the same alkali metal as the cathode 12 or the anode 16. The alkali metal or alkalimetal-ion rechargeable battery 10 comprises a battery separator 14 between the cathode 12 and the anode 16. When the battery 10 is being discharged, electrons flow spontaneously through the external circuit from the anode 16 to the cathode 12 (i.e. , electrical current flows from cathode to anode) while alkali metal ions 15 move from the anode 16 to the cathode 12 through the battery separator 14 (i.e., towards the left in the figure). When the battery is being charged, an external power supply causes these processes to run in reverse: electrons flow through the external circuit from the cathode 12 to the anode 16 (i.e., electrical current flows from anode to cathode), and alkali metal ions move from the cathode 12 to the anode 16 through the separator 14 (i.e., towards the right in the figure).

[0094]

[0075] Figure 2a shows a schematic of a microporous polymer scaffold 30, for example a microporous polyethylene scaffold, comprising scaffold matrix 35, for example nodes interconnected by fibrils, and scaffold pores 36. The microporous polymer scaffold 30 may have a thickness, which is the distance between the first and second major exterior surfaces. Preferably, the thickness of the scaffold (prior to deposition of the opaloid) may be measured via a non-contact technique to avoid collapse of the scaffold structure during measurement

[0095]

[0076] The battery separator 14 of Figure 1 comprises a composite membrane 40 which is more clearly shown in Figure 2b. The composite membrane 40 includes a hydrocarbon microporous polymer scaffold comprising the scaffold matrix 35 and scaffold pores, and sub-micron ceramic particles 32 within the scaffold pore volume. The sub-micron ceramic particles 32 are in the form of a porous inter-connected ceramic phase 31 within the composite membrane 40. The porous inter-connected ceramic phase 31 can have a three-dimensional packing arrangement which has properties of an opaloid or continuous ceramic phase as discussed herein. The submicron ceramic particles in preferred embodiments may comprise aluminum. For example, the sub-micron ceramic particles mat be AI2O3, boehmite, or core-shell ceramic particles comprising aluminum in one or both of the core or the shell. As illustrated in Figure 2b and shown in Figure 2c, the inventors have shown that the porous inter-connected continuous ceramic phase 31 (e.g., the opaloid) comprising ceramic particles 32 has inter-particle pores 33 and can be formed within the scaffold pores 36 of the microporous polymer scaffold 30. Figure 2b further shows the composite membrane includes composite membrane pores 45, which comprise interparticle pores 33 of the ceramic phase 31 within the scaffold pores 36, and interfacial particle-scaffold pores 34 (i.e., pores whose boundaries are defined by both the structural elements of the scaffold and the constituent particles of the ceramic phase; in practice these are pores at the interface between the particle phase 31 and thescaffold matrix 35). Additionally, cracks or defects 37 may be present within the composite membrane 40. Such composite membranes may be referred to as composite membranes as disclosed herein or Membrane-Reinforced Opaloids (MROs).

[0096]

[0077] Opaloids (continuous ceramic phases as described herein) are solid materials comprising ceramic particles in tightly packed arrangements where the arrangements have a degree of order that may range from crystalline (e.g., so-called colloidal crystals) to nearly amorphous. As used herein, ceramic particles are intended to encompass a subset of inorganic particles comprising inorganic non-metallic, non- carbonaceous materials comprising metal, non-metal, or metalloid atoms held by ionic or covalent bonds, and wherein the ceramic particle structure is electrically neutral. Opaloids can have many interesting properties, such as a narrow distribution of pore sizes, relatively high porosity, crush resistance, stability at high temperatures, stability in many chemical environments, and wettability with various fluids (including water). A familiar example of a colloidal crystal is an opal, a naturally occurring gemstone comprising tightly packed arrangements of sub-micron particles of silica that may be highly ordered (e.g., comprising face-centered cubic (fee), and / or hexagonal close packed (hep) structures). For clarity, the term opaloid is inclusive of opals and other colloidal crystals, but is broader. Opaloids may be naturally-occurring or synthetic. Opaloids may comprise packing arrangements of sub-micron particles where the packing arrangements are crystalline, semi-crystalline, and / or nearly amorphous. Non-limiting examples of particle packing arrangements of opaloids include face -centered cubic packing (fee), hexagonal close packing (hep), bodycentered cubic (bcc), simple cubic, liquid-like packing, as well as arrangements that are substantially similar to the foregoing examples but that may differ, for example, due to structural imperfections or packing defects. Opaloids may be polycrystalline (e.g., they may comprise multiple crystalline or semi-crystalline domains that border each other, and / or that may be separated by nearly amorphous or amorphous domains). Packing arrangements that are polycrystalline or that comprise an intermediate degree of order may optionally be referred to as colloidal semicrystals. The composition of opaloids is not particularly limited (e.g., they may comprise materials other than silica and / or may not comprise silica). However, it is noted that sub-micron particles comprising ceramics and / or glasses may be particularly useful in the present disclosure, e.g., for high thermal stability, high chemical stability, high mechanical stability (e.g., crush resistance), and excellent wettability with various fluids including those with high surface tension.

[0078] The sub-micron particles may comprise a wide variety of materials including ceramics and glasses (noting that some common definitions of ceramics include glasses as a subset of ceramics). Sudha et al. describe ceramics as follows in “Corrosion of ceramic materials” (in Fundamental Biomaterials: Ceramics, Editor(s): Sabu Thomas, Preetha Balakrishnan, M.S. Sreekala, Woodhead Publishing Series in Biomaterials, Woodhead Publishing, 2018, Pages 223-250), “Ceramics materials can be defined as inorganic, nonmetallic materials comprising metal, nonmetal, or metalloid atoms held by ionic or covalent bonds. The ceramic structure is based on electric neutrality. They are generally prepared using clays and other minerals from the earth or chemically processed crystalline oxide, nitride, or carbide powders, i.e. , aluminium and oxygen (alumina — AI2O3), silicon and nitrogen (silicon nitride — Sisl^ ), silicon and carbon (silicon carbide — SiC), etc. Ceramic materials are typically categorized as traditional ceramic and advanced ceramic. Traditional ceramic materials include clay, porcelain, feldspar, silica, calcite, and nepheline... Advanced ceramics includes alumina, zirconia, silicon carbide, silicon nitride, and titania-based materials, which can replace the metals and plastics in the modern era due to their exceptional properties that make them highly resistant to melting, bending, stretching and possess unique individual properties in their own way... Ceramic materials are broadly classified into two types based on the arrangement of atoms that constitute the particular substance, (a) Crystalline ceramic materials: Most of the ceramic materials have crystalline structure and are more brittle than metals. The arrangement of atoms in the crystalline ceramic was highly ordered throughout the material. Crystalline ceramics were not amenable to set of processing / production. These materials were generally synthesized either by compacting powders into a body followed by sintering at higher temperature to form a solid desired shape or by the reaction “in situ.” The techniques adapted to form crystalline ceramics include slip casting, tape casting, injection molding, dry pressing, and so on. (b) Noncrystalline / Amorphous ceramic materials: The processing of glass is totally different from the crystalline ceramic preparation and involves several steps. Noncrystalline ceramic, being glasses, can be usually prepared from melts. The glasses were processed into desired shape either by casting them in the molten state or by blowing the toffee-like viscosity state into a mold. These noncrystalline ceramic materials were also called “Super cooled liquids” because the orientations of molecules are random and highly disordered in the frozen solid state...” The foregoing description of ceramics will define how the term ceramics is used herein. Examples of ceramics as defined herein may include silica, alumina, titania, ceria, zirconia, yttria- stabilized zirconia, other oxides, and other classes of ceramics including carbides,nitrides, sulfides, borides, phosphides, selenides, titanates, carbonates, nitrates, sulfates, borates, and phosphates, or combinations thereof.

[0097]

[0079] The continuous ceramic phase of the present disclosure (i.e. , also termed an opaloid) may be produced, for example, by producing a stable colloidal dispersion or colloidal suspension (e.g., one in which the colloidal particles are stabilized against aggregation by e.g., surface charge on the colloidal particles resulting in DLVO-type repulsion, by polymeric or oligomeric dispersing agents adsorbed on the surfaces of the colloidal particles resulting in steric stabilization, by some combination of these two approaches, or by other colloidal stabilization techniques as will be readily understood by one of ordinary skill in the art), concentrating the stable colloidal dispersion or colloidal suspension through the colloidal glass transition, and substantially drying the material to produce a consolidated solid structure within the scaffold pore volume. Accordingly, the continuous ceramic phase can also be referred to as a “colloidal condensed phase” and this refers to a phase or range of phases comprising the particulate material (i.e., the ceramic particles), in which the positions of the particles thereof are constrained by adjacent particles. The particles forming a colloidal condensed phase are comparatively close-packed in comparison to the colloid from which it is made. The degree of order present in a colloidal condensed phase can range from a nearly amorphous material to a relatively ordered “colloidal crystal” phase with close packing of particles having repeating order over multiple (e.g. more than around 5, more than around 10, more than around 100, more than around 500, or more than around 1000 unit cells in two or three unit cell axes). The term “colloidal condensed phase” includes the “opaloid” materials disclosed herein. The degree of order may vary within a region of the colloidal condensed phase, or between regions of colloidal condensed phase within different pores of the microporous polymer scaffold. The colloidal condensed phase may include regions or domains with different degrees of order.

[0098]

[0080] As known in the art, colloids may undergo a colloidal glass transition as a function of increased particle packing density. The nature of the phase change behaviour with particle concentration and the degree of order present in the resulting colloidal condensed phase (such as the continuous ceramic phase disclosed herein) depends inter alia on the particulate size, morphology and dispersity.

[0099]

[0081] As known to one skilled in the art, a colloidal crystal comprises crystal domains of particulate solid in a repeating three-dimensional packing arrangement, typically with cubic or hexagonal symmetry. The particles thereof may be arranged in a close packed array (such as cubic close packed or hexagonal close packed). An array will comprise a repeating unit cell, having two or three unit cell axes. The axes may, butneed not be, orthogonal. It will be understood that the size of crystal domains will be governed at least in part by the size and shape of the pores within which they are formed (e.g., the microporous polymer scaffolds described herein). The colloidal crystal regions of the colloidal condensed phases may form domains of at least 5 or 10, or 100 or more unit cells in one, two or three unit cell axes.

[0100]

[0082] Within the context of this disclosure, the continuous ceramic phase may be also be known as continuous inorganic phase of inorganic particles or inorganic submicron particles.

[0101]

[0083] The sub-micron particles that comprise a continuous ceramic phase (i.e. an opaloid) may be essentially monodisperse (e.g., as in the case of a colloidal crystal as described above), but may also be polydisperse because, for example, the high degree of uniformity that may be required to enable highly crystalline order is not required in the case of semi-crystalline or nearly amorphous opaloids. In addition, multiple populations of essentially monodisperse colloidal particles (e.g., 2, 3, or more populations) may by design coexist in the same opaloid. The particle size distribution of such an opaloid (e.g., as measured by quantitative image analysis of representative SEM images) may contain multiple peaks (i.e., it may be multi-modal), with each peak corresponding to a population of particles of that characteristic size. Such peaks in the particle size distribution may or may not partially overlap. Such a multi-modal particle size distribution (e.g., as measured by dynamic light scattering) may also be evident in the particle size distribution of the precursor colloid from which the opaloid was produced. For example, specific size ratios and volume fractions of different monodisperse particles may be combined to enable tight packing in specific crystalline or semi-crystalline arrangements. Examples of such size ratios and volume fractions were described, along with an algorithmic method of predicting them, in “Prediction of binary hard-sphere crystal structures” (L. Filion & M. Dijkstra, Physical Review E, 79, 046714, 2009). As another non-limiting example, mixed populations of sub-micron particles may comprise cases where each population of particles comprises different materials (e.g., a population of sub-micron particles of one ceramic blended with a population sub-micron particles of another ceramic, or a population of ceramic submicron particles blended with a population of polymer sub-micron particles). The shapes of the sub-micron particles are also not particularly limited, and may include spheres, spheroids, cylinders, and other shapes of both low and high aspect ratio as would be understood by one of ordinary skill in the art.

[0102]

[0084] The continuous ceramic phases referred to herein (i.e. opaloids) and sol-gel solids represent distinct classes of materials. The structure of opaloids is inherently more ordered than that of sol-gel solids. Furthermore, opaloids may have characteristicrepeating length scales comparable to the size of the particles, whereas sol-gel solids, if they exhibit any repeating structure at all, may have characteristic repeating length scales comparable to the size of the aggregates. Also, opaloids may have higher porosity than sol-gel solids while maintaining a narrow distribution of small pore sizes. Finally, without wishing to be bound by theory, opaloids may be more conducive to high-volume manufacturing because, for example, their formation does not require complex chemical steps such as hydrolysis or gelation.

[0103] Contrasting the Colloidal Glass Transition and Gelation

[0104]

[0085] Without wishing to be bound by theory, the characteristic structures and properties of opaloids, as well as the manner in which they differ from other materials such as sol-gel solids, may be clarified through a better understanding of the colloidal glass transition and gelation dynamics for the cases of opaloids and sol-gel solids, respectively.

[0105]

[0086] Colloidal glass transition dynamics enable ordered tight packing of colloidal particles, characteristic of opaloids. Unlike molecular glasses, which may undergo a transition from a liquid to a glass upon cooling, colloidal dispersions or colloidal suspensions may undergo a glass transition upon concentrating (i.e., when the packing density of the dispersed phase within the continuous phase increases to the point that it exceeds a critical threshold after which the colloidal particles are no longer able to move freely). This is the so-called colloidal glass transition, which was described as follows by E. Weeks in “Introduction to the Colloidal Glass Transition,” ACS Macro Lett., 6, 27-34 (2017), “Their glass transition is not as a function of temperature, but rather of concentration. At low concentration, particles undergo Brownian motion and diffuse through the sample freely. At higher concentrations, the particles pack together randomly (with a liquid-like structure), and macroscopically the sample viscosity grows dramatically as a function of concentration. Below the glass transition concentration, Brownian motion enables the sample to equilibrate, and the sample is still considered a liquid. Above the glass transition concentration, equilibration is no longer possible on experimental time scales, and macroscopically the sample has a yield stress like a regular elastic material.” More detailed dynamics of this process were described in “Dynamics of Colloidal Glasses and Gels” (Y. Joshi, Annu. Rev. Chem. Biomol. Eng. 2014. 5:181-202), using monodisperse, spherical particles as a case study, “...at low volume fractions (cpv), the suspension is in a fluid state. Upon increasing (pvslowly beyond 0.494, crystals with (pv= 0.545 start nucleating and coexist with the fluid phase. Beyond (pv= 0.545, only the crystalline state exists.With further increases in cpv, the crystals become compact up to (pv» 0.74, which is the maximum packing fraction associated with the face-centered cubic or hexagonal close packing. If (pvis increased quickly from the fluid state, thereby preventing nucleation of crystals, the suspension enters the so-called supercooled regime. In this regime, individual particles can be considered to be arrested in cages formed by their neighbors. Owing to thermal motion, the particle rattles inside the cage before escaping (diffusing). This cage-diffusion timescale, also known as a relaxation time (Ta), increases with (pvand diverges as (pv— > 0.58, the concentration associated with the colloidal glass transition. Monodispersed spherical particles can exist in the random disordered configuration up to only (pv= (prcp« 0.64, the random close-packing fraction. (prcpincreases with polydispersity. The elasticity of particulate glasses originates in caging... ” The Joshi reference further states, “For spherical particles with hard-sphere interactions, MCT [mode coupling theory] predicts an ideal glass transition at the volume fraction of 0.525.” Note that the volume fractions of particles stated in the quote from the Joshi reference were specific to the case study being examined, and these particle volume fractions may differ for other colloidal systems due to, for example, particles with different shapes or degrees of stabilization. For example, the volume fraction associated with the colloidal glass transition may be about 0.4, or about 0.45, or about 0.49, or about 0.5, or about 0.55, or about 0.58, or about 0.60, or about 0.65, or about 0.7, or about 0.75, or about 0.8, or about 0.85. The importance of the colloidal glass transition as the dividing line between low and high solids concentrations, the former of which requires long-range structures (e.g., gels) for rigidity, and the latter of which does not, was further clarified in “Colloidal Gelation” (Del Gado et al., Chapter 14 of Fluids, Colloids and Soft Materials: An Introduction to Soft Matter Physics, First Edition. Edited by Alberto Fernandez Nieves and Antonio Manuel Puertas.©2016 John Wiley & Sons, Inc. Published 2016 by John Wiley & Sons, Inc.), where the authors note that, “At larger concentrations, the formation of spacespanning networks is no longer a requirement for rigidity” and that above the colloidal glass transition, “the constituent of the system is permanently trapped in cages of nearest neighbors.” In summary, the foregoing passages describe the colloidal glass transition in detail and illustrate how it enables colloidal particles to consolidate into tightly packed structures (e.g., those in which the volume fractions of the constituent particles are greater than about 0.4) with high degrees of order, characteristic of opaloids.

[0106]

[0087] In contrast, sol-gel processes are characterized by gelation dynamics. As described in “Colloidal Sol-Gel: A powerful, low-temperature aqueous synthesis route of nano-sized powders and suspensions" (Open Ceramics 8, 100200 (2021)), a “sol”is a colloidal system comprising a discontinuous solid phase dispersed in a continuous liquid phase. Sols are typically produced through the hydrolysis of a precursor comprising a metal atom surrounded by ligands that do not contain metal. Depending on the hydrolysis conditions, the solid phase of the resulting sols may be categorized as either fine particles or polymerized molecules (e.g., oligomers), resulting in either a colloidal sol or polymeric sol, respectively, with the latter being significantly more common in the art. Upon gelation (i.e. , the “gel” transition step in the sol-gel process) the solid phase forms a network with long-range structure leading to a gel that typically has high viscosity and may be described as comprising a solid phase and a liquid phase that are co-continuous. Gelation occurs at low concentrations (i.e., below the colloidal glass transition, most typically far below it, e.g., as illustrated by the extremely high porosity characteristic of silica aerogels) and is usually induced through chemical means (e.g., through neutralization of surface charges in the sol), resulting in particle gelation and aggregation, as well as poorly-ordered fractal and aggregate structures. As described by Schmidt (Journal of Non-Crystalline Solids 100 (1998) 51-64.), "For stable colloids (which in general remain stable due to the surface charge of their colloidal particles) the neutralization of surface charges (isoelectric point) leads to gelation, including the following basic reactions: neutralisation of surface charges, aggregation, further condensation by reactive surface groups, gelation (accompanied by a strong viscosity increase) to a solid gel." The poor degree of order of fractal gel structures and methods of characterizing the structure are well-established in the literature, for example, by Sinko et al. (Journal of Non-Crystalline Solids 354 (2008) 5466-5474), “The structure of ill-ordered materials, such as amorphous glasses, fractal systems, or aggregate structures is difficult to describe in direct pictures, these structures can well be characterized by scattering experiments.” The authors further describe how “The aggregate structure defines a random packing of colloidal particles.” In summary, the foregoing passages describe the gelation dynamics of the sol-gel process in detail and illustrate how they result in poorly ordered fractal and aggregate structures characteristic of sol-gel solids.

[0107]

[0088] Well-ordered continuous ceramic phases or opaloids (e.g., those comprising sub-micron particles that have gone through a colloidal glass transition), and sol-gel materials with a fractal structure can be further distinguished by their characteristic length scale. Opaloids exhibit repeating order on the length scale of individual particles and may show a narrow distribution of inter-particle distances, whereas sol-gel structures may exhibit repeating order on the aggregate length scale. This distinction is described in the following passage from “Dynamics of Colloidal Glasses and Gels” (Y. Joshi, Annu. Rev. Chem. Biomol. Eng. 2014. 5:181-202), "... the colloidal glassyand gel state can be distinguished based on the length scale beyond which the density becomes homogeneous. In particulate colloidal glasses [including e.g., opaloids), this length scale is close to the inter-particle distance, whereas in gels it is approximately the aggregate length scale."

[0108]

[0089] Due substantially to the gelation dynamics described above, sol-gel processes and the resulting sol-gel solids have several drawbacks that limit their utility. Secondary structure formed during the gelation process can limit the dynamics of packing, producing irregular and polydisperse void structures. Bonding or sintering between particles can result in brittle or inflexible materials, limiting the toughness or durability of produced articles. Porosity may become limited as additional precursor converts to solid during the gelation phase. Furthermore, sol-gel solids, being based primarily on hydrolyzable precursors as described above, represent a narrower set of materials than opaloids, which encompass but are not limited to the full gamut of ceramics and glasses. Sol-gel chemistry can also impose significant complexity as well as onerous time constraints on industrial manufacturing processes such as roll-to-roll manufacturing processes. It is an object of the present invention to overcome these deficiencies by developing improved materials and processes based on opaloids.

[0109]

[0090] Although concentrating a colloidal dispersion or colloidal suspension through the colloidal glass transition may be a preferred element of a process for fabricating opaloids, opaloids are not particularly restricted in their method of manufacture. If the appropriate arrangement of sub-micron particles (e.g., as described above in the Introduction to Opaloids Including Colloidal Crystals) can be made without the use of a colloidal dispersion or colloidal suspension, it may nevertheless be considered an opaloid as defined herein.

[0110]

[0091] For clarity, the use of the term “colloidal” may be interpreted depending on the context according to both meanings described in Slomkowski et al., “Terminology of polymers and polymerization processes in dispersed systems (IIIPAC Recommendations 2011)*” Pure Appl. Chem., Vol. 83, No. 12, pp. 2229-2259 (2011): a “state of subdivision such that the molecules or polymolecular particles dispersed in a medium have at least one dimension between approximately 1 nm and 1 pm, or that in a system discontinuities are found at distances of that order.” Consistent with the first part of this definition (the two parts of the definition being separated by a comma), the term “colloidal” in “colloidal dispersion” or “colloidal suspension” may be interpreted as comprising particles dispersed in a medium in which the particles are within the characteristic length scale from approximately 1 nm to approximately 1 pm in size. Consistent with the second part of this definition, the term “colloidal” as used in “colloidal crystal” or “colloidal semi-crystal” may beinterpreted as comprising sub-micron particles (e.g., nanoparticles) that are approximately 1 nm to approximately 1 pm in size, and / or as indicating that the interparticle distances (ID) and / or pore sizes (d) of opaloids are also typically in this size range.

[0111]

[0092] The term “colloidal glass” can be interpreted according to both parts of Slomkowski’s definition of “colloidal” quoted above. Consistent with the first part of Slomkowski’s definition, the term “colloidal glass” in the scientific literature typically refers to a colloidal dispersion or colloidal suspension that has undergone a colloidal glass transition and exhibits highly viscous, glass-like behavior as described by Weeks as quoted above, “macroscopically the sample viscosity grows dramatically as a function of concentration. Below the glass transition concentration, Brownian motion enables the sample to equilibrate, and the sample is still considered a liquid. Above the glass transition concentration, equilibration is no longer possible on experimental time scales, and macroscopically the sample has a yield stress like a regular elastic material.” However, the term colloidal glass can also be interpreted according to the second part of Slomkowski’s definition, meaning the sub-micron particles (including nanoparticles) of colloidal glasses are typically 1 nm to 1 pm in size, and the interparticle distances (ID) and / or pore sizes (d) of colloidal glasses are also typically in this size range. Thus, the term “colloidal glass” does not necessarily imply that the particles are dispersed or suspended in a fluid. Instead, it can refer more broadly to tightly packed arrangements of sub-micron particles that retain features or discontinuities on the colloidal length scale. It may also be interpreted as an acknowledgement that such arrangements of sub-micron particles are usually produced from a precursor that was itself a colloidal dispersion or colloidal suspension. The opaloids described in the present disclosure may therefore be considered a form of colloidal glass. However, for clarity, the inventors prefer the term “opaloid” to “colloidal glass” as a term to describe the broad class of materials that is the focus of the present disclosure.

[0112] Detailed Description of Neat Opaloid Morphology and Properties

[0113]

[0093] This section will establish basic nomenclature for describing opaloid structures without mechanical reinforcement. Such opaloids without mechanical reinforcement (e.g., without an integrated microporous polymer scaffold) may also be called “neat” opaloids. Material properties of neat opaloids will also be discussed.

[0114]

[0094] Figure 3a shows a schematic of a cross-section of a neat opaloid 9 comprising monodisperse sub-micron particles 10 in a three-dimensional packingarrangement. The sub-micron particles in Figure 3a are depicted as having a high degree of order (e.g., a substantially face-centered cubic arrangement), but as described above other packing arrangements are possible, for example more amorphous arrangements such as liquid-like packing. The neat opaloid may comprise large defects (e.g., cracks) 11 that extend through the entire thickness of the opaloid, and may comprise other defects (e.g., cracks) 12 that do not extend through the entire thickness.

[0115]

[0095] As described above, opaloids comprise tightly packed three-dimensional packing arrangements of sub-micron particles. Figure 3b shows two adjacent particles of diameter D that are elements of a particle packing arrangement within an opaloid. The tightness of the packing arrangement may be described by the interparticle distance (ID, typically expressed in units of nanometers), which is the distance between the centers of adjacent sub-micron particles (or if the particles are non- spherical, then between the centroids of adjacent particles). Inter-particle distance may be considered a population property that is inherently polydisperse and may be described by an ID distribution. In an opaloid, the ID may be of colloidal size. Further, the ID of two adjacent particles may be approximately the particle diameter D (note that for polydisperse particles the effective D is the sum of the radii of the two adjacent particles, and if a particle is irregularly shaped then its effective radius is the radius of a sphere that occupies the same volume, and analogously its effective diameter is the diameter of a sphere that occupies the same volume). However, even in a tightly packed arrangement the distance between two adjacent particles may be smaller or larger than the sum of their radii. Said distance may be smaller, for example, because particles with irregular shapes may enable tighter packing. Said distance may be larger, for example, because sub-micron particles in the opaloid may not pack in perfect crystalline arrangements or because they may be coated in a material such as a polymeric material (e.g., a dispersing agent). The ID may be, for example, greater than about 0.5 times the effective particle diameter D and less than about 3 times the effective particle diameter D. The ID may be, for example, greater than about 0.5 times the effective particle diameter D and less than about 2.5 times the effective particle diameter D. The ID may be, for example, greater than about 0.5 times the effective particle diameter D and less than about 2 times the effective particle diameter D. In some examples, the amount of material (e.g., polymeric material) between adjacent particles may be minimized or eliminated. In the latter case, for example, the submicron particles may have direct contact with each other. The opaloid may substantially lack an organic binding agent (e.g., a polymeric binder). The opaloid maycomprise sub-micron particles that are bonded together substantially by van der Waals forces, by inorganic bonds, or by a combination of the two.

[0116]

[0096] The inter-particle distance may be determined via microscopy in combination with Quantitative Image Analysis, for example using the method depicted on the scanning electron micrograph in Figure 4. As indicated by the subscripts in the figure (i.e. , Dnand I Dn), a sufficient number of particles (to measure D) and pairs of adjacent particles (to measure ID) may be analyzed to generate representative statistics for the opaloid. In the case of irregular particles, ID may be calculated as the average distance between adjacent particle centroids. _To obtain a high-quality microscopy image, the conditions must be appropriately tailored to the specific sample being examined (e.g., appropriate magnification, working distance, accelerating voltage, etc.). The practice of tailoring such observing conditions is well-known to those of ordinary skill in the art. Quantitative Image Analysis may be used for determining ID when the inter-particle distance is larger than about 80 nm or larger than about 100 nm. If the inter- particle distances are less than about 100 nm or less than about 80 nm, then Small Angle X-ray Scattering (SAXS) may be used to determine the interparticle distance. Figure 5a shows representative SAXS data sets for neat opaloids prepared with 5 different types of silica sub-micron particles with diameters of approximately 7 nm, 12 nm, 22 nm, 45 nm, and 100 nm. The peaks in the SAXS data are identified with triangles and correspond to structures of a given length scale, typically from 0.5 nm to 80 nm. For these data, peaks indicate nanoscale organization of particles (spherical in this case) and are observable due to the contrast between SiO2 and pores (vacuum). The peaks can be referred to as structure factor peaks. Peak positions are given by the scattering vector, q, and the average center- to-center inter-particle distance, ID, is obtained from the position of the primary peak, qi, or lowest q-value peak: ID = 2n7qi. As shown in Figure 5b, there is reasonable agreement between nominal particle diameters (D) and the inter-particle distance (ID) values determined by SAXS for neat (i.e. non-reinforced) packing arrangements of SiO2 sub-micron particles. The dashed line in Figure 5b is the 45° line passing through the origin and is included as a guide to the eye. For 7 nm and 45 nm silica sub-micron particle opaloids, weak, broad peaks indicate a more disordered structure and broader distribution of center-to-center IDs compared to the other data in the chart. In contrast, opaloids with 12, 22, and 100 nm silica sub-micron particles exhibited narrow peaks, corresponding to a narrow distribution of IDs. Narrow peaks also indicate greater long- range order, where particles exhibit more uniform symmetry over length scales greater than the nearest neighbors. Multiple higher order peaks may also signify long-range order. Higher order peaks may also result from larger particles and inter-particledistances, which shift the scattering pattern to lower q and allow higher order peaks to be detected within the instrument’s range. Higher-order scattering peaks are characterized by peak positions 92, 93, ... 9n. The packing arrangement can be deduced by comparing SAXS peak position ratios, 91 / 91 : 92 / 91 : 93 / 91 : ... 9n / 9i, to characteristic values for specific arrangements, where qncorresponds to the positions of the higher order peaks. Peak position ratios for common spherical packing geometries may include 1 : 1.41 : 1.73 : 2.00 : 2.24 : 2.45 : 2.83 (simple cubic packing), 1 : 1.41 : 1.73 : 2.00 : 2.24 : 2.45 : 2.65 (body-centered cubic packing), 1 : 1.15 : 1.63 : 1.91 : 2.00 : 2.31 : 2.52 : 2.58 : 2.83 : 3.00 (face-centered cubic packing), or 1 : 1.06 : 1.13 : 1.46 : 1.73 : 1.87: 1.92 (hexagonal close packing). In Figure 5a, peaks are observed at peak position ratios 91 / 91 : 92 / 91 : 93 / 91 : ... 9n / 9i of 1 : 1.64 : 2.34, 1 : 1.67 : 2.43, and 1 : 1.70 : 2.50 : 3.28 : 4.04 : 4.81, for neat opaloids with 12, 22, and 100 nm silica sub-micron particles, respectively. The SAXS peak position ratios are consistent with having substantially close-packed arrangements; however, deviations from reported peak position ratios indicate that these neat opaloids do not exhibit perfect crystalline order. Deviations from expected values may be due to, for example, packing defects or polydispersity. A given observed peak position ratio may be within about 1% , or within about 2 %, or within about 3 %, or within about 4 %, or within about 5% of the nearest characteristic peak position ratio and certain peak position ratios may not be observed, for example depending on the form factor scattering of the sub-micron particles.

[0117]

[0097] Structure factor peaks may be identified in the Lorentz-corrected data (intensity*q2) as will be understood by one of ordinary skill in the art. Opaloids may be characterized by the presence of 1 or more structure factor peaks in the SAXS data, or by the presence of 2 or more structure factor peaks in the SAXS data, or by the presence of 3 or more structure factor peaks in the SAXS data, or by the presence of 4 or more structure factor peaks in the SAXS data, or by the presence of 5 or more structure factor peaks in the SAXS data, or by the presence of from 1 to 5 structure factor peaks in the SAXS data, or by the presence of from 1 to 10 structure factor peaks in the SAXS data, or by the presence of from 2 to 5 structure factor peaks in the SAXS data, or by the presence of from 2 to 10 structure factor peaks in the SAXS data. For a material to be considered an opaloid, it is not required that the peak position ratios for the structure factor peaks correspond to the theoretical peak position ratios for known arrangements of particles. n contrast, the SAXS data depicted in Figure 6, which was reproduced from Bushell et al. (”On techniques for the measurement of the mass fractal dimension of aggregates,” Advances in Colloid andInterface Science, 95, 1-50 (2002)), shows an absence of the structure factor peaks characteristic of opaloids. Instead, it shows representative SAXS data for a material comprising aggregates of monodisperse spherical particles, illustrating the Guinier, Fractal, and Porod scattering regimes. These data are characteristic of the poorly ordered fractal and aggregate structures characteristic of sol-gel solids. When analyzing SAXS data, care must be taken not to misinterpret the features shown in Figure 6, such as the “knee” at the transition between the Guinier regime and the Fractal regime, or the q-4dependence of the scattering intensity in the Porod regime, as structure factor peaks. As described above, structure factor peaks may be preferably identified in the Lorentz-corrected data (intensity*q2).

[0118]

[0098] The spaces between and among the sub-micron particles in an opaloid (i.e., the inter-particle pores, collectively the inter- particle pore volume, typically expressed in units of cc / g or as a porosity in vol%) may define an interconnected pore volume that is characteristic of the opaloid. Figure 3a shows a schematic of a cross-section of a neat opaloid comprising monodisperse sub-micron particles 10 in a three- dimensional packing arrangement, having an inter-particle pore volume 13. The pore volume 13 may have a complex and / or irregular geometry. The challenge of quantitatively characterizing the pore size of porous materials with complex or irregular pore geometries is well-known. Pore size in this case may be considered a population property that is inherently polydisperse and may be described by a pore size distribution. A variety of standard evaluation methods are available to those of ordinary skill in the art, such as quantitative image analysis, BET / BJH analysis, capillary flow porometry (including bubble point analysis), liquid / liquid porometry, thermoporometry by differential scanning calorimetry, and mercury porosimetry. Each of these quantification methods makes simplifying assumptions about the pore geometry, and most produce a pore size distribution from which characteristic pore size parameters may be extracted, such as a median or mode pore size (via BET / BJH analysis), the largest through-pore (e.g., via bubble point determination), or the mean flow pore size (via capillary flow porometry). In some embodiments, the mode pore size(s) of opaloids may be characterized via BET / BJH analysis as a preferred method. Figure 7 shows a representative pore size distribution from BET / BJH analysis of a neat opaloid prepared from silica sub-micron particles with a diameter of approximately 12 nm. The mode pore size of the distribution shown in Figure 7 is approximately 5 nm. The three- dimensional packing arrangement of the neat opaloid may be further characterized by comparing the pore diameter (d) to the particle diameter (D), for example using the ratio d / D. Figure 8 shows the expected values of d / D for different tightly packed arrangements with different coordination numbers (n). For many opaloid packingarrangements, the pore diameter is expected to be smaller than the particle diameter (i.e. , d / D < 1). However, for the same reasons that the ID may be larger than D, d / D may be larger than 1, for example the opaloid may have d / D < 1.1 or d / D < 1.5 or d / D < 2.0.

[0119]

[0099] The challenge of characterizing the particle size (e.g., the particle diameter, D) of the sub-micron particles in an opaloid is also complex and well-known to those of ordinary skill in the art. A variety of standard tools are available, such as dynamic light scattering of the colloidal dispersion from which the opaloid is produced (in which case care must be taken to prevent agglomeration from skewing the data), or direct microscopy of the opaloid itself, such as in Figure 4. In the case of particles of known shape (e.g., spherical particles), and known level of surface roughness (e.g., essentially smooth), the specific surface area (SSA, in units of m2 / g, as measured by BET) may be measured, and if the density of the particles (p) is known (or if it can be measured, for example by helium pycnometry), then a representative particle size may be calculated using, for example, the standard equations for the volume and area of a sphere (Vsphereand Asphere, respectively) based on its diameter (£)). The relevant equations for a sphere are as follows:

[0120]

[0121] 6

[0122] D~ (SSA)p

[0123]

[0100] Figure 9 illustrates how SSA may be used to estimate the particle size of an opaloid. Five neat opaloids were produced from solid silica sub-micron particles with nominal diameters (as reported by the manufacturers) of 7 nm, 12 nm, 22 nm, 45 nm, and 100 nm. Figure 9a compares the SSA measured by BET (solid dots) to the expected values (open squares). The expected values were calculated assuming the sub-micron particles are perfectly smooth, solid spheres of the nominal diameter (based on inspection of the particles via SEM) and assuming a density of silica of 2.2 g / cc. Figure 9b compares the particle diameter calculated from the SSA data to the nominal diameters reported by the manufacturers. The dashed line in Figure 9b is the 45° line passing through the origin and is included as a guide to the eye. As shown inFigure 9b, the SSA method for determining particle size works well for particles that are essentially smooth, solid spheres and may be utilized in such relatively simple cases. However, this method may not be as accurate for particles with a large degree of internal porosity or high surface roughness. In such complex cases characterizing the particle size of the constituent sub-micron particles in an opaloid may be done with direct observation via scanning electron microscopy, which may be combined with quantitative image analysis. The calculations described in the foregoing paragraph, and illustrated in Figure 9, may be used to calculate the effective diameter of the submicron particles of the opaloid. In the case that the sub-micron particles contain intraparticle pores, then the density to be used in the calculation is the sub-micron particle apparent density. The sub-micron particle apparent density is the matrix density of the particle multiplied by the quantity [one minus the intra-particle porosity of the submicron particle],

[0124]

[0101] In the description of opaloid morphology above, many of the properties may be considered population properties, such as inter-particle distance (ID), pore diameter (d), and particle diameter (D). Such properties may be represented by distributions, which may be characterized using standard summary statistics known to those of ordinary skill in the art. Such summary statistics include the median value, the volume- weighted mode value, the volume-weighted average, the number-weighted mode value, the number-weighted average, and the related 10 / 25 / 75 / 90 percentile values. When comparing two different population properties (for example, when comparing pore diameter to particle diameter), consistent summary statistics may be used (for example, making the comparison using the mode value for both properties). In some cases, the volume-weighted mode value may be preferred.

[0125]

[0102] Figure 2b further shows that the MROs (i.e. , the composite membranes 20) comprise composite membrane pores 22, which comprise inter-particle pores 13 of the opaloid 9 within the scaffold pores 16, and interfacial particle-scaffold pores 24 (i.e., pores whose boundaries are defined by both the structural elements of the scaffold and the constituent particles of the opaloid; in practice these are pores at the interface between the opaloid and the scaffold matrix). Additionally, cracks or defects 26 may be present. In an MRO, an opaloid may fill at least a portion of the pore volume of a microporous polymer scaffold. The opaloid may comprise a continuous opaloid phase (e.g., with a continuous pore volume defined by the inter-particle pores) that extends over a large area (meaning larger than between 1 millimeter or a few centimeters in extent in each of two orthogonal directions) within the pore volume of the microporous polymer scaffold.

[0103] Further, the inventors have surprisingly discovered that the quality of MROs may be dramatically improved when they the MROs comprise a microporous polymer scaffold characterized by extremely tight pores (i.e., a microporous polymer scaffold with a bubble point of greater than about 2 bar). Such MROs may be referred to as High-Integrity MROs. In High-Integrity MROs, cracks or defects 26 (as shown in Fig.

[0126] 2b) can be minimized or eliminated. The minimization or elimination of such cracks or defects may be demonstrated, for example, using capillary flow porometry of the MRO and / or direct visualization of the MRO via microscopy such as scanning electron microscopy, as will be shown below. Without wishing to be bound by theory, larger particles may result in weaker drying forces, and therefore tighter (higher bubble point pressure) microporous polymer scaffolds may not necessarily be required to prevent defects (e.g., cracks) within the membrane layer 40 during fabrication when such particles are used. Accordingly, microporous polymer scaffolds having a largest pore size (derived from bubble point pressure) less than about 15 times the particle diameter (D) may minimize the formation of large cracks during the drying process, and therefore may be considered High Integrity Membrane Reinforced Opaloids.

[0127]

[0104] The production of MROs with high integrity and high quality via the use of membrane reinforcements with extremely tight pores was surprising in numerous respects:

[0128]

[0105] The extremely tight structure and high surface area of the microporous polymer scaffold provided a large number of potential nucleation sites for defects within the opaloid. Nevertheless, through-plane defects (e.g., cracks) were surprisingly minimized (e.g., as measured by capillary flow porometry).

[0129]

[0106] The extremely tight structure and high surface area of the microporous polymer scaffold also provided a large number of interfaces with the potential to disrupt the formation and structure of the opaloid. Nevertheless, the MROs surprisingly and substantially retained both the narrow distribution of small pores (e.g., as measured by BET / BJH), and the tight particle packing arrangement (e.g., as measured by SAXS) associated with the neat opaloid.

[0130]

[0107] The rapid drying of the MROs under hot-air convection (e.g., in a few minutes or less, consistent with the needs of high-volume production), imposed turbulent surface forces and significant mechanical stresses on the MRO. Nevertheless, defects were surprisingly minimized (e.g., as measured by capillary flow porometry, BET / BJH, SAXS, and haze), and there was no obvious loss of particles during drying or subsequent handling despite the absence of a binder (e.g., a polymeric binder).

[0131]

[0108] The extremely tight structure and high surface area of the microporous polymer scaffold provided a high-surface-area matrix of hydrophobic material throughout thecomposite membrane. Nevertheless, the resulting MROs were surprisingly highly wettable with water.

[0132]

[0109] The extremely tight structure and high surface area of the microporous polymer scaffold provided a large number of interfaces to nucleate defects during mechanical stress testing, and the lack of a binder provided limited support to cohere the particles. Nevertheless, the resulting MROs were flexible and free-standing and able to survive significant handling and mechanical stress without significant loss of particles or desirable properties. In addition, the MROs showed exceptional robustness when subjected to liquid flow under very high trans-membrane pressures up to about 50 bar with no obvious change in liquid permeance after exposure to such high pressures.

[0133]

[0110] The use of reinforcements with extremely tight structures surprisingly produced a “step change” in the ability of the MROs to selectively separate small molecules from a solvent (e.g., as measured through organic solvent nanofiltration).

[0134]

[0111] The composite membranes 40 of the present disclosure comprise a hydrocarbon microporous scaffold comprising a plurality of scaffold pores having a scaffold pore volume, and a continuous ceramic phase of ceramic particles within the scaffold pore volume. The continuous ceramic phase comprises an interconnected ceramic phase pore volume defined by inter-particle pores between ceramic particles. The microporous polymer scaffold 30 may have a first major exterior surface (i.e., a first surface) and a second major exterior surface (i.e., a second surface) that opposes the first surface. Preferably, the hydrocarbon microporous polymer scaffold comprises a polyolefin, polyaramid, or cellulose. More preferably the microporous polymer scaffold comprises polyethylene (PE) or polypropylene (PP). In a preferred embodiment, the microporous polymer scaffold comprises “wet- processed” (or “gel- processed”) polyethylene (PE).

[0135]

[0112] As described above, a non-limiting method to produce porous polyethylene membranes is through a wet or gel process known in the industry. In this process, polyethylene may be mixed with a hydrocarbon liquid and other additives. This mixture may be heated above the polymer melt temperature and extruded into a sheet. This sheet can then be orientated biaxially before and / or after the hydrocarbon liquid is extracted, producing a microporous membrane. Various process details are known in literature as in U.S. Patent No. 5,248,461, U.S. Patent No. 4,873,034, U.S. Patent No.

[0136] 5051183, U.S. Patent No. 6566012, Casting and stretching of filled and unfilled UHMW-polyethylene films, Ir.F.H. Assinck, Centre for polymers and composites, Eindhoven University of Technology, Nov 1995 and Porous biaxially drawn ultra-high molecular weight polyethylene films, N.S.J.A. Gerrits, Department of MaterialsTechnology, DSM Research; and P.J. Lemstra, Department of Polymer Technology, Eindhoven University of Technology, October 1990.

[0137]

[0113] Figure 2b is a schematic illustration depicting a portion of the composite membrane 40 according to at least one embodiment of the present disclosure. The composite membrane 40 includes microporous polymer scaffold 30 comprising the scaffold matrix 35 and scaffold pores 36, and ceramic particles 32 within the scaffold pore volume. The schematic of Figure 2b shows the ceramic particles 32 within the scaffold pores 26. The ceramic particles 32 are in the form of a porous inter-connected ceramic phase 31 within the composite membrane 40. The porous inter-connected ceramic phase 31 can have a three-dimensional packing arrangement which has properties of an opaloid. Figure 2c is an SEM image of a composite membrane 40 having a continuous ceramic phase 31 formed from ceramic particles 32. In preferred embodiments, the ceramic particles are submicron ceramic particles comprising aluminum. For example, the continuous ceramic phase may comprise submicron ceramic particles selected from AI2O3, boehmite (AIO(OH)), core-shell particles comprising inorganic (e.g., ceramic) particles coated with an aluminum-containing shell, or combinations thereof.

[0138]

[0114] These composite membranes 40 may be manufactured by imbibing concentrated dispersions of ceramic particles 32 into microporous polymer scaffolds 30. It is desirable that the particles 32 are fully disposed within the volumetric envelope of the microporous polymer scaffold 30. As shown in the SEM image of Figure 2c, it is possible for the scaffold matrix 35 to extend beyond the particle imbibed region of the composite membrane 40, owing to, for example, surface tension mediated particle migration during the drying process.

[0139]

[0115] The battery separator 14 can be manufactured as follows. The composite membrane 40 is formed by providing a hydrocarbon polymer scaffold comprising a polyolefin having a polymer scaffold matrix and a plurality of scaffold pores, the microporous polymer scaffold having a scaffold pore volume and having a porosity from about 70% to about 96%; incorporating or imbibing sub-micron ceramic particles into the scaffold pore volume of the microporous polymer scaffold and heat treating to consolidate the sub-micron ceramic particles such that they form the continuous ceramic phase disposed within the scaffold pore volume. The continuous ceramic phase extends within the scaffold pore volume a distance of at least 1 mm in each of two orthogonal directions.

[0140]

[0116] Disclosed herein is a method of making a battery separator for a rechargeable battery (e.g. an alkali metal or an alkali metal-ion rechargeable battery). The method comprises producing a composite membrane 40 by obtaining a microporoushydrocarbon polymer scaffold having a polyolefin (preferably polyethylene or polypropylene) including a polymer scaffold matrix and a plurality of scaffold pores. The microporous polymer scaffold has a scaffold pore volume and a porosity from about 70% to about 96%; To produce a composite membrane 40 having a continuous ceramic phase within the scaffold pore volume, sub-micron ceramic particles are incorporated into the scaffold pore volume of the microporous polymer scaffold.

[0141] The composite membrane 40, may be produced by incorporating the ceramic particles into the microporous polymer scaffold via a method that comprises imbibing. As used herein, the term “imbibing” refers to a process of depositing a material within the pores of a microporous polymer scaffold using a liquid carrier, but not substantially incorporating the imbibed material into the matrix of the microporous polymer scaffold, such that the microporous polymer scaffold remains largely intact. For example, the microporous polymer scaffold may be wetted with an imbibing fluid, where the imbibing fluid comprises the ceramic particles and a liquid carrier. As used herein, a microporous polymer scaffold that is “wetted” with a fluid has some or all of its pores filled with the fluid. The wetted microporous polymer scaffold may then be dried, such that the liquid carrier is substantially removed, resulting in the ceramic particles being deposited within the pores of the microporous polymer scaffold. As the wetted microporous polymer scaffold is dried, the microporous polymer scaffold can collapse in response to capillary forces.

[0142]

[0117] To produce a composite membrane 40 having a continuous ceramic phase within the scaffold pore volume, a variety of imbibing conditions can be chosen so that the ceramic particles deposited in the pores comprises the disclosed interconnected porous structure (e.g., the concentration of ceramic particles in the liquid carrier within the pores, the packing density the ceramic particles in the scaffold pores (e.g., enabled in part by a high colloidal stability of a colloidal precursor), the ratio of the volume of ceramic particles in the scaffold pores to the skeletal and total volume of the microporous polymer scaffold, and the distribution of the imbibing fluid in the microporous polymer scaffold).

[0143]

[0118] The method then includes consolidating the sub-micron ceramic particles such that they form a continuous ceramic phase disposed within the scaffold pore volume, wherein the continuous ceramic phase extends within the scaffold pore volume a distance of at least 1 mm in each of two orthogonal directions. In order to achieve this condensation, the imbibed microporous polymer scaffold may be heat treated to form a composite membrane according to the present disclosure. The heat treatment may comprise exposing the imbibed microporous polymer scaffold to temperatures of around 65 °C until visibly dry (for example, around 10 minutes). The heat treatmentmay further comprise exposing the imbibed microporous polymer scaffold to temperatures of from about 115 °C to about 200°C, for example at about 120°C, for about 30 minutes. The heat treatment step is intended to transition colloidal ceramic particles imbibed into the scaffold beyond their colloidal glass transition point such that the ceramic particles are in the form of the interconnected porous ceramic phase (i.e., as an opaloid). Accordingly, the skilled person will appreciate that other temperatures and time frames for heat treating the imbibed scaffold may be applicable depending on the imbibing solution and drying conditions (e.g., in a convection oven). The resulting composite membrane comprises a continuous ceramic phase comprising a three-dimensional packing arrangement of sub-micron ceramic particles. The three- dimensional packing arrangement of sub-micron ceramic particles exhibits at least one structure factor peak in Lorentz-corrected SAXS data. As order increases in the continuous ceramic phase, the number, prominence, and / or narrowness of the more structure factor peaks in Lorentz-corrected SAXS data will increase.

[0144]

[0119] The submicron ceramic particles can have a particle diameter or effective diameter of from about 5 nanometers to about 200 nanometers, or from about 20 nanometers to about 200 nanometers, or from about 5 nanometers to about 100 nanometers, or from about 20 nanometers to about 200 nanometers, or from about 5 nanometers to about 50 nanometers, or from about 20 nanometers to about 50 nanometers, or from about 50 nanometers to about 150 nanometers, or from about 50 nanometers to about 100 nanometers, or from about 100 nanometers to about 200 nanometers. The submicron ceramic particles can have a particle diameter or effective diameter of from about 25 nanometers to about 200 nanometers, or from about 25 nanometers to about 150 nanometers, or from about 25 nanometers to about 100 nanometers, or from about 25 nanometers to about 50 nanometers, or from about 50 nanometers to about 100 nanometers, or from about 10 nanometers to about 150 nanometers, or from about 150 nanometers to about 200 nanometers. The submicron ceramic particles can have a particle diameter or effective diameter of about 200 nanometers, or about 150 nm, or about 100 nm.

[0145]

[0120] The liquid carrier in the imbibing fluid is not particularly limited, and any suitable liquid carriers known in the art may be used. Suitable liquid carriers may include water and organic liquids. Organic liquids may include alcohols and mixtures of alcohols (such as a C1-C5 alcohols), dimethyl sulfoxide, dimethyl acetamide, acetonitrile, toluene, dimethyacetamide (DMAc), methyl ethyl ketone (MEK), acetone, dimethylformamide (DMF), tetrahydrofuran (THF), and N-methyl-2-pyrrolidone (NMP). More than one liquid carrier may be used, such as two, or three, or four liquid carriers. The C1-C5 alcohol (e.g., isomers of methanol, ethanol, propanol, butanol,and pentanol) may be any one selected from methanol, ethanol, propan-1-ol, propan- 2-ol, butan-1-ol, pentan-1-ol, and a combination thereof.

[0146]

[0121] If the imbibing fluid does not spontaneously and readily wet the microporous polymer scaffold, then a variety of techniques may be employed to assist in achieving good wetting, such as by applying a differential pressure to force the liquid into the microporous polymer scaffold, raising the temperature of the liquid to lower its viscosity and surface tension, and / or pre-wetting the microporous polymer scaffold with another miscible liquid. As described above, imbibing microporous polymer scaffolds, especially low surface energy scaffolds, relies on good wetting. "Wetting" results when the contact angle, q, between the liquid and the solid is less than about 90 degrees. Spontaneous wetting occurs when the surface energy between the solid and liquid, gsL is less than the surface energy between the solid and air, gsA. The typical relationship between these parameters and the liquid-air surface energy, gi_A (i.e., the surface tension of the liquid), is given by the relationship below (Young’s equation):

[0147]

[0122] gSL= gsA - gLA*cos(q)

[0148]

[0123] The battery separator may comprise a surfactant. The surfactant may comprise a cationic portion and an anionic portion. The cationic portion of the surfactant may comprise the same alkali metal ion as the electrolyte and / or the electrode. To achieve good wetting, the surface tension of the imbibing fluid should be sufficiently low to penetrate the microporous polymer scaffold. For example, a surface tension of less than or equal to about 30 dynes / cm is typically required to penetrate expanded microporous PTFE. Higher surface tension imbibing fluids may accordingly be suitable for higher energy scaffolds such as microporous polyethylene or microporous polypropylene.

[0149]

[0124] Imbibing fluids that are aqueous or substantially aqueous are preferred in some cases, for example because of the availability of stable and highly concentrated colloidal dispersions, or because of safety and environmental reasons. For example, when the sub-micron particles comprise a ceramic or glass then an aqueous or substantially aqueous imbibing fluid may be preferred to minimize the need for oligomeric or polymeric dispersing agents. To enable an aqueous or substantially aqueous imbibing fluid to wet a microporous polymer scaffold with minimal dilution, a suitable wetting agent may be emulsified in the aqueous or substantially aqueous imbibing fluid with the aid of a surfactant. Suitable wetting agents include alcohols and mixtures of alcohols that exhibit a low water solubility, such as those alcohols having five to ten carbon atoms in the longest continuous chain, e.g., alcohols with C5-C10 linear chains, and the like. For example, pentanols, hexanols, octanols, and the like, are within the range of suitable wetting agents. Herein, these wetting agents may bereferred to as “insoluble alcohols.” Similarly, suitable wetting agents also include carboxylic acids and mixtures of carboxylic acids that exhibit a low water solubility, such as those carboxylic acids having five to ten carbon atoms in the longest continuous chain, e.g., carboxylic acids with C5-C10 linear chains, and the like. For example, pentanoic acids, hexanoic acids, octanoic acids, and the like, are within the range of suitable wetting agents. Herein, these wetting agents may be referred to as “insoluble carboxylic acids.” Such insoluble wetting agents are most effective when present in the imbibing fluid above their solubility limit so as to form an “oil phase” that may be emulsified. Further, the imbibing fluid can incorporate with the water insoluble alcohol(s) and / or carboxylic acid(s) other water insoluble organics, such as alkanes, etc. In some embodiments, the wetting agent may also exhibit a low gsL relative to the targeted low surface energy scaffold.

[0150]

[0125] The surfactant(s) can be a single surfactant or a combination of surfactants.

[0151] Suitable surfactants are defined as those that are able to emulsify the desired wetting agent. For example, for the alcohols described above, several classes of anionic surfactants can be used, including, but not limited to, those having a structure of R(EO)nOSO3- or ROSOs' where R can be any organic chain, "O" is oxygen, "S" is sulfur, "EO" is ethylene oxide and n>1. In an alternate embodiment, non-ionic surfactants having the structure R(EO)nOH, where n>1, are also suitable for this invention. In a preferred embodiment, nonionic surfactants and / or surfactants with hydrophilic- lipophilic balance ("HLB") values often or greater were found most effective to emulsify the wetting agents described above. The concentration of surfactant can be adjusted in order to achieve good emulsification of the desired wetting agent. For example, when 4% by weight of n-hexanol wetting agent (based on the total aqueous solution weight) is used, a concentration of about 2 wt% of sodium dodecyl ether sulfate was found to be suitable. In an alternate formulation, 6 wt% of an ethoxylated alcohol was able to emulsify 4 wt% n-hexanol wetting agent. Other examples of suitable surfactants include Tergitol™ TMN10 and Barlox™ 8S.

[0152]

[0126] Furthermore, in the production of battery separators, it is desirable for processing aids such as surfactants and wetting agents be either fugitive (i.e., essentially completely removed from the battery separator during processing), or else compatible with the battery chemistry so that residual processing aids in the separator do not harm the function of the battery. For production of the composite membranes of the present invention, a suitable class of separators may comprise a surfactant having a cationic portion and an anionic portion, and wherein the cationic portion of the surfactant is the same as the alkali metal of the electrolyte and the anode or the cathode. In addition to the aqueous delivery system provided by the surfactant and thewetting agent, a stabilizing agent can be added. A stabilizing agent is typically soluble in both the wetting agent and water, and it allows a greater amount of wetting agent to be stabilized in the aqueous system than without the stabilizer. In one embodiment, glycols were found to be effective stabilizers, such as but not limited to dipropylene glycol ("DPG"), and propylene glycol. A wide range of stabilizer concentrations can be used depending on the amount of additional stability desired. For instance, if a small increase in stability is desired, a small amount of the stabilizer should be used. Conversely, higher stabilizer concentrations generally further increase the emulsion stability. Exceptions to these general guidelines do however exist. For example, DPG may be an effective stabilizer when used in concentrations ranging from less than about 1% wt. up to about 10% wt. based on total aqueous emulsion weight for hexanolbased systems

[0153]

[0127] The imbibing fluid may contain additives such as dispersing agents to stabilize the colloidal dispersion or colloidal suspension. The purpose of such dispersing agents is typically to reduce viscosity, reduce or prevent agglomeration of particles, and / or reduce or prevent settling of particles. Preparation of the colloidal dispersion or colloidal suspension, and maintaining the particles as suspended or dispersed, may require the use of high-shear mixing. Various means of high-shear mixing for the preparation of colloidal dispersions and colloidal suspensions are available and are well-known to those of ordinary skill in the art, such as rotor-stators, Cowles mixers, wet jet mills, and media mills.

[0154]

[0128] The inter-particle pores between the sub-micron ceramic particles are defined by an inter-particle distance within the three-dimensional packing arrangement of submicron ceramic particles, and wherein the inter- particle distance is from about 0.5 times to about 3 times the particle diameter or effective particle diameter of the submicron ceramic particles. The position of the primary structure factor peak maximum may correspond to an inter-particle distance within about 0.5 to about 3 times the ceramic particle diameter or effective diameter.

[0155]

[0129] The continuous ceramic phase disposed within the scaffold pore volume may have a ratio (d / D) of an inter-particle pore size, d, to particle diameter or effective diameter, D, of from about 0.2 to about 2.0, preferably from about 0.2 to about 1.2.

[0156]

[0130] The packing density of the ceramic particles in the continuous ceramic phase may be from about 0.40 to about 0.85.

[0157]

[0131] The continuous ceramic phase may extend substantially through the entire thickness of the scaffold.

[0132] Battery separators 14 according to embodiments of the present disclosure may have a total separator (contact) thickness of about 2 pm to about 30 pm. Battery separators 14 according to each of the embodiments of the present disclosure may have a total separator thickness of about 2 pm to about 30 pm, or from about 2 microns to about 25 microns, or from about 2 microns to about 20 microns, or from about 2 microns to about 15 microns, or from about 2 microns to about 10 microns, or from about 2 microns to about 5 microns, or from about 10 microns to about 30 microns, or from about 15 microns to about 30 microns, or from about 20 microns to about 30 microns, or from about 5 microns to about 15 microns...

[0158]

[0133] The composite membrane 40 of the present disclosure comprises a microporous scaffold comprising a plurality of scaffold pores having a scaffold pore volume, and ceramic particles within the scaffold pore volume. As such, the composite membrane 40 has a plurality of composite membrane pores defined at least in part by the ceramic particles within the scaffold pore volume.

[0159]

[0134] The microporous polymer scaffold may comprise polyolefins, optionally polyethylene (PE) or polypropylene (PP). The microporous polymer may comprise any one selected from a a polyethylene (PE), polypropylene (PP), expanded polyethylene (ePE), polyamide (PA), or combinations thereof. The microporous polymer scaffold may also comprise cellulose. In preferred embodiments, the microporous polymer scaffold comprises a polyolefin selected from polyethylene or polypropylene (PP), most preferably polyethylene (PE).

[0160]

[0135] The microporous polymer scaffold 30 may have a non-contact thickness of from about 1 pm to about 1000 pm, or from about 2 pm to about 1000 pm, or from about 2 pm to about 500 pm, from about 2 pm to about 100 pm, from about 2 pm to about 50 pm, or from about 2 pm to about 25 pm. The non-contact thickness of the microporous polymer scaffold is measured as indicated in the test methods described herein. The thickness of the scaffold may decrease (i.e. , “collapse”) in response to capillary forces during wetting and / or drying, for example, during the formation of the composite composite membrane 40 shown in Figures 2b and 2c.

[0161]

[0136] The scaffold pore volume, where the scaffold pore volume is a characteristic of the microporous polymer scaffold (as a whole) and comprises the total pore volume of the microporous polymer scaffold (i.e., comprises the cumulative pore volume of all scaffold pores). The scaffold pore volume is not necessarily constant; for example, it may change as a result of the process to produce the composite membrane 40. For example, the microporous polymer scaffold may deform as a result of stresses during coating and / or drying, resulting in either an increase or decrease in its pore volume. For instance, the thickness of the scaffold may decrease (i.e., “collapse”) inresponse to capillary forces during wetting and / or drying as a result of the process to produce the composite membrane 40.

[0162]

[0137] The scaffold pores 36 may have a mean flow pore size (e.g., as measured by Capillary Flow Porometry) from about 0.01 to about 100 pm, e.g., from about 0.01 to about 1 pm, or about 0.02 to about 25 pm, or about 0.01 to about 10 pm, or about 0.05 to about 20 pm, or about 0.1 to about 80 pm, or about 0.1 to about 50 pm, or about 0.1 to about 30pm, or about 0.2 to about 60 pm, or about 0.5 to about 50 pm.

[0163]

[0138] The microporous polymer scaffold may have a porosity from about 40 vol% to about 98 vol%, or from about 40 vol% to about 91 vol%, or from about 40 vol %to about 90 vol%, or from about 40vol% to about 85 vol%, or from about 40 vol% to about 80 vol%, or from about 40 vol% to about 75 vol%, or from about 40 vol% to about 70 vol%, or from about 40 vol% to about 60 vol%, or from about 50 vol% to about 98 vol%, or from about 50 vol% to about 91 vol%, or from about 50 vol %to about 90 vol%, or from about 50 vol% to about 85 vol%, or from about 70 vol % to about 96 vol%, or from about 50 vol% to about 80 vol%, or from about 50 vol% to about 75 vol%, or from about 50 vol% to about 70 vol%, or from about 50 vol% to about 60 vol%. In some embodiments, the microporous polymer scaffold may have a porosity from about 70% to about 96%, or from about 75% to about 96%, or from about 80% to about 96%, or from about 90% to about 96%, or from about 70% to about 80%, or from about 70% to about 85%, or from about 70% to about 75%, or from about 75% to about 85%. In some embodiments, the microporous polymer scaffold may have a porosity from about 83 vol% to about 91 vol%.

[0164]

[0139] The microporous polymer scaffold may have a bubble point pressure of from about 0.5 bar to about 10 bar, or from about 1 bar to about 10 bar, or from about 2 bar to about 15 bar, or from about 2 bar to about 10 bar, or from about 2 bar to about 5 bar, or from about 3 bar to about 9 bar, or from about 3 bar to about 8 bar, or from about 4 bar to about 9 bar, or from about 4 bar to about 8 bar. In some embodiments, the bubble point of the battery separator may be at least about 10 bar. The bubble point of the battery separator may be from about 10 bar to about 20 bar. In embodiments of separators with bubble point of at least 10 bar the composite membrane may be of high quality with fewer defects. The bubble point pressure can provide a measure of the largest pore size according to the Young-Laplace equation:

[0165] 4ylvcos9

[0166] d

[0167]

[0140] where P is the pressure required to dewet a liquid from a cylindrical pore, yLvis the liquid surface tension, Q is the contact angle, and d is the pore diameter.

[0141] Typically, the largest pore size (from bubble point pressure) of the microporous polymer scaffolds used in embodiments of this disclosure does not to exceed 15 times the primary mode of the ceramic particle diameter of effective particle diameter of the submicron ceramic particles forming the continuous ceramic phase (on a volume base). This may permit the microporous polymer scaffold to provide sufficient reinforcement for the formation of the continuous ceramic phase. For example, the largest pore size may be from 3 to 15 times the primary mode on a volume basis of the ceramic particle diameter.

[0168]

[0142] In the manufacture method, the microporous hydrocarbon polymer scaffold may have an absolute tensile strength in the Machine Direction (MD) of from about 0.3 N / mm to about 2.0 N / mm. wherein the microporous hydrocarbon polymer scaffold has a mass-per-area of between 0.5 g / m2and 3 g / m2. The microporous hydrocarbon polymer scaffold may have a bubble point of at least 0.5 bar. The microporous hydrocarbon polymer scaffold may have a bubble point of from about 0.5 bar to about 2.0 bar, or from about 0.5 bar to about 1.8 bar, or from about 0.5 bar to about 1.5 bar, or from about 0.5 bar to about 1.2 bar, or from about 0.5 bar to about 1.0 bar, or from about 0.5 bar to about 0.8 bar, or from about 1.0 bar to about 2.0 bar, or from about 1.5 bar to about 2.0 bar, or from about 1.5 bar to about 2.0 bar, or from about 1.2 bar to about 1.7 bar. Note that for the microporous hydrocarbon polymer scaffold, not all values of absolute tensile strength are practically achievable for all values of the limitations of matrix tensile strength (e.g., a matrix tensile strength of about 10,000 psi, 20,000 psi, 30,000 psi, 40,ooo psi, and 50,000 psi).

[0169]

[0143] In some embodiments, the composite membrane 40 is a multi-layer composite membrane that contains multiple microporous polymer scaffolds. The potential combinations of microporous polymer scaffolds is not particularly limited. For example, the plurality of microporous scaffolds may comprise a first microporous polymer scaffold made of a first polymer (e.g., PP), and a second microporous polymer scaffold made of a second polymer (e.g., PE). Incorporating more than one type of microporous polymer scaffold may confer specific benefits. For example, a low-melting scaffold (e.g., ePE) may be combined with a more thermally stable scaffold (e.g., PA) to provide mechanical integrity at elevated temperature. At least one of the plurality of microporous polymer scaffolds may have a bubble point pressure of equal to or greater than two (2) bar, and the sub-micron particles incorporated within the scaffold pore volume.

[0170]

[0144] Figure 2b is a schematic illustration depicting a portion of the membrane layer 40 according to at least one embodiment of the present disclosure. The membrane layer 40 includes microporous polymer scaffold 30 comprising the scaffold matrix 35and scaffold pores 36, and ceramic particles 32 within the scaffold pore volume. The schematic of Figure 2b shows the sub-micron ceramic particles 32 within the scaffold pores 26. The ceramic particles 32 are in the form of a porous inter-connected ceramic phase 31 within the membrane layer 40. The porous inter-connected ceramic phase 31 can have a three-dimensional packing arrangement which has properties of an opaloid. An opaloid is a form of colloidal glass. It is to be appreciated that opaloids are not sol-gel materials.

[0171]

[0145] As illustrated in Figure 2b, the inventors have shown that the porous interconnected continuous ceramic phase 31 (e.g., the opaloid) comprising sub-micron ceramic particles 32 has inter- particle pores 33 can be formed within the scaffold pores 36 of the microporous polymer scaffold 30. Figure 2b further shows the composite membrane includes composite membrane pores 45, which comprise inter-particle pores 33 of the ceramic phase 31 within the scaffold pores 36, and interfacial particlescaffold pores 34 (i.e., pores whose boundaries are defined by both the structural elements of the scaffold and the constituent particles of the ceramic phase; in practice these are pores at the interface between the particle phase 31 and the scaffold matrix 35). Additionally, cracks or defects 37 may be present within the composite membrane 40.

[0172]

[0146] The ceramic phase 31 (e.g., an opaloid) may comprise a continuous interconnected porous ceramic phase (e.g., with a continuous pore volume defined by the inter-particle pores 33) that extends continuously over a large area (for example, from about 1 mm to about 1500 mm in extent in each of two orthogonal directions) within the pore volume of the microporous polymer scaffold 30. In this context, the term “extends continuously” (i.e. the extent of the continuous ceramic phase 31) is not intended to describe the distance along a continuous path of the particle phase 31 within the scaffold pores 36 (which may, for example, comprise a torturous or indirect path within the scaffold pore volume) but rather, the term “extends continuously” is intended to encompass the displacement between two points of the continuous ceramic phase 31 within the scaffold pores 36 that are connected by such a continuous path within the scaffold pore volume.

[0173]

[0147] The ceramic phase 31 (e.g., an opaloid) comprises a three-dimensional packing arrangement of ceramic particles 32, and the inter-particle pores 33 are defined at least in part by an inter-particle distance (ID) within the packing arrangement. As used herein, the inter-particle distance may be the distance between the centers of adjacent ceramic particles (or if the ceramic particles are non-spherical, then between the centroids of adjacent sub-micron particles). The inter-particle distance (as depicted in Figure 3a, 3b) may be from about 0.5 times to about 3 times the ceramic particlediameter. The inter-particle distance may be from about 0.6 times to about 3 times the ceramic particle diameter. The inter-particle distance may be from about 0.7 times to about 3 times the ceramic particle diameter. The inter-particle distance may be from about 0.8 times to about 2 times the ceramic particle diameter. The inter-particle distance may be from about 0.9 times to about 1.5 times the ceramic particle diameter. The inter-particle distance may be from about 0.5 times to about 1.5 times the ceramic particle diameter. The inter-particle distance may be from about 0.5 times to about 1 times the ceramic particle diameter. The inter-particle distance may be from about 0.5 times to about 1.5 times the ceramic particle diameter. The inter-particle distance may be from about 0.5 times to about 1 times the ceramic particle diameter._The interparticle distance may be from about 1 times to about 1.5 times the ceramic particle diameter. The inter-particle distance may be determined via microscopy in combination with Quantitative Image Analysis, for example using the method depicted on the SEM image in Figure 4, which depicts a representative continuous ceramic phase (i.e. , an example opaloid). As indicated by the subscripts in the figure (i.e., Dnand IDn), a sufficient number of particles (to measure D) and pairs of adjacent particles (to measure ID) may be analyzed to generate representative statistics for the ceramic phase. aA In the case of irregular particles, ID may be calculated as the average distance between adjacent particle centroids. To obtain a high-quality microscopy image, the conditions must be appropriately tailored to the specific sample being examined (e.g., appropriate magnification, working distance, accelerating voltage, etc.). The practice of tailoring such observing conditions is well-known to those of ordinary skill in the art. Quantitative Image Analysis may be used for determining ID when the inter-particle distance is larger than about 80 nm or larger than about 100 nm. If the inter-particle distances are less than about 100 nm or less than about 80 nm, then Small Angle X-ray Scattering (SAXS) may be used to determine the interparticle distance.

[0174]

[0148] The three-dimensional packing arrangement of the continuous ceramic phase 31 may comprise a packing arrangement selected from face-centered cubic packing hexagonal close packing, body-centered cubic packing, simple cubic packing, random close packing, liquid like packing, and combinations thereof. The three-dimensional packing arrangement of ceramic particles exhibits at least one structure factor peak in Lorentz-corrected small angle X-ray scattering spectra of the membrane layer. This is indicative of discrete monodisperse particle populations. A structure factor peak as used herein can be defined as in “SciPy find peaks” (https: / / docs.sdpy.org / doc / sdpy / reference / generated / sdpy.signai.find__peaks.htmi, accessed 19 December 2024): “all local maxima by simple comparison of neighboringvalues”. For example, a peak data point will have two neighboring values of lesser value. Structure factor peaks should have prominence of at least about 10 % greater than the minimum Lorentz corrected intensity in the region corresponding to interparticle distances larger than the detected peak. For example, membrane layers having a well-ordered, highly loaded continuous ceramic phase may have a Lorentz corrected intensity peak prominence of many times (e.g. 5 times, or 6 times or more) the minimum Lorentz corrected intensity in the region corresponding to interparticle distances larger than the detected peak. The position of the at least one primary structure factor peak maximum may correspond to an inter-particle distance within about 0.5 to about 3 times the ceramic particle diameter. The position of the at least one structure factor peak maximum may correspond to an inter-particle distance within about 0.5 to about 1.5 times the ceramic particle diameter. The position of the at least one structure factor peak maximum may correspond to an inter-particle distance within about 0.5 to about 1.0 times the ceramic particle diameter.

[0175]

[0149] Tensile testing (i.e. , measurement of absolute tensile strength in N / mm) may be used to assess the presence of continuous ceramic phase in composite membrane layer 40. Tensile testing of the composite membrane layer will show a first tensile peak (e.g., yield point) that may be associated with the yielding of a continuous ceramic phase with macroscopic extent. The strain associated with this peak may be referred to as the ceramic phase yield strain. Tensile testing of membrane layer will show a break strain of the membrane layer 40. The membrane layer break strain is greater than the ceramic phase yield strain. The ratio of the membrane break strain divided by the ceramic yield strain may be about 1.2 to about 20.

[0176]

[0150] The continuous ceramic phase 31 (e.g., an opaloid) within the scaffold pore volume may have a packing density of ceramic particles from about 0.4 to about 0.85, or from about 0.5 to about 0.85, or from about 0.4 to about 0.8, or from about 0.4 to about 0.75, or from about 0.5 to about 0.8. The continuous ceramic phase packing density may be calculated by taking a ratio where the numerator is the sum of the solid volume of the ceramic particles and the intra- particle void volume, and the denominator is the ceramic phase volume. The ceramic particles within the continuous ceramic phase may have a packing density within the scaffold pore volume that may be greater than or equal to the packing density of the corresponding neat opaloid, and / or greater than or equal to a colloidal glass transition packing density (or volume fraction) for the ceramic particles when in a colloidal system.

[0177]

[0151] The continuous ceramic phase 31 (e.g., an opaloid) itself may be considered to have a ceramic phase pore volume and pore size. The ceramic phase pores 33 may be described by considering the specific pore volume (cc / g) in a specific pore sizerange in the pore size distribution characterized by N2 sorption (as described by the test methods disclosed herein). In analyzing the pore size distribution of the membrane layer 40 there will be a peak in the specific pore volume, which may be associated with the inter-particle pore size (d) within the continuous ceramic phase 31. The peak may, in some embodiments, be the mode pore size (nm) with the highest specific pore volume (for example, in cases where the membrane layer 40 pore size is dominated by the inter-particle pores of the three-dimensional packing arrangement of the ceramic phase 31). In other embodiments, the peak may instead be one of several peaks, each of which indicates the contribution from, for example, any of any defects (e.g., cracks) in the ceramic phase 31, and any unfilled pore volume of the scaffold pore. The ceramic phase pore size (d) may be characterized by a mode pore size. The ceramic phase pore size (d) may be about 0.15 times to about 2 times the ceramic particle diameter (D). The ceramic phase pore size (d) may be about 0.25 times to about 0.75 times the ceramic particle diameter (D).

[0178]

[0152] The continuous ceramic phase 31 within the scaffold pore volume may have a pore size (d) to inter-particle distance (ID) ratio (d / ID) from within the scaffold pore volume from about 0.2 to about 2.0. The continuous ceramic phase 31 within the scaffold pore volume may have a pore size (d) to inter-particle distance (ID) ratio (d / ID) from about 0.2 to about 2.0, or from about 0.3 to about 2, or from about 0.4 to about 2, or from about 0.2 to about 1.75, or from about 0.4 to about 1.75, 0.2 to about 1.5, or from about 0.4 to about 1.5.

[0179]

[0153] The continuous ceramic phase 31 within the scaffold pore volume may have a ratio (d / D) of the inter-particle pore size, d, to particle diameter D of from about 0.20 to about 2.0, or from about 0.3 to about 2.0, or from about 0.2 to about 1.5, or from about 0.3 to about 1.5. The ratio d / D may be from about 0.2 to about 1.2.

[0180]

[0154] The continuous ceramic phase 31 within the scaffold pore volume may have a pore size (d) from about 3 nm to about 100 nm, or about 5 nm to about 80 nm, or about 10 nm to about 60 nm , or about 10 nm to about 40 nm , or about 10 nm to about 30 nm , or about 10 nm to about 20 nm.

[0181]

[0155] The composite membrane 40may have a bubble point pressure of from about 1 bar to about 15 bar, or about 1 bar and about 20 bar, or about 1 bar and about 25 bar, about 1 bar and about 27 bar, or about 1 bar and about 30 bar. As described above, with reference to the microporous polymer scaffolds, the bubble point pressure can be used to calculate the largest pore size of the membrane layer 40 in accordance with the test methods set out below.

[0182]

[0156] The composite membrane may have a porosity defined by the void spaces formed by the interconnected pore volume (e.g., the inter-particle pores as definedabove) of the opaloid, any intra-particle pore volume, any interfacial particle-scaffold pores, any defects (e.g., cracks), if any, in the opaloid, and, in some examples, any unfilled scaffold pores or unfilled scaffold pore volumes. The composite membrane may comprise a porosity of between about 10 vol% to about 45 vol%, or about 10 vol% to about 50 vol%, or about 10 vol% to about 55 vol%, or about 10 vol% to about 60 vol%, or about 10 vol% to about 65 vol%, or about 10 vol% to about 70 vol%, or about 10 vol% to about 75 vol%. The composite membrane may comprise a porosity from about 15 vol% to about 45 vol%, or from about 15 vol% to about 50 vol%, or from about 15 vol% to about 55 vol%, or from about 15 vol% to about 60 vol%, or from about 15 vol% to about 65 vol%, or from about 15 vol% to about 70 vol%, or from about 15 vol% to about 75 vol%. The composite membrane may comprise a porosity from about 20 vol% to about 45 vol%, or from about 20 vol% to about 50 vol%, or from about 20 vol% to about 55 vol%, or from about 20 vol% to about 60 vol%, or from about 20 vol% to about 65 vol%, or from about 20 vol% to about 70 vol%, or from about 20 vol% to about 75 vol%. The composite membrane may comprise a porosity from about 25 vol% to about 45 vol%, or from about 25 vol% to about 50 vol%, or from about 25 vol% to about 55 vol%, or from about 25 vol% to about 60 vol%, or from about 25 vol% to about 65 vol%, or from about 25 vol% to about 70 vol%, or from about 25 vol% to about 75 vol%.

[0183]

[0157] The composite membranes described herein may have a total surface area, where the total surface area comprises contributions from the microporous polymer scaffold and the sub-micron particles (e.g., the opaloid). The composite membranes of the present disclosure may have a surface area in which the contribution of the submicron particles (i.e. , the opaloid) within the pore volume of the microporous polymer scaffold comprises from about 10% to about 20%, or about 10% to about 30%, or about 10% to about 40%, or about 10% to about 50%, or about 10% to about 60%, or about 10% to about 70%, or about 10% to about 80%, or about 10% to about 90% of the surface area based on the total surface area of the composite membrane.

[0184]

[0158] The ceramic particles 32 may have a particle diameter (or effective particle diameter) of about 1 nm to about 1 pm. The ceramic particles 32 may have a particle diameter (or effective particle diameter) of about 1 nm to about 500 nm , or about 1 nm to about 200 nm, or about 10 nm to about 500 nm, or about 1 nm to about 100 nm, or about 1 nm to about 80 nm, or about 5 nm to about 70 nm, or about 4 nm to about 50 nm, or about 5 nm to about 50 nm, or about 5 nm to about 75 nm, or about 2 nm to about 60 nm, or about 2 nm to about 50 nm, or about 2 nm to about 25 nm or about 25 nm to about 200 nm or about 25 nm to about 100 nm or about 25 nm to about 80 nm or about 30 nm to about 60 nm or about 50 nm to about 100 nm. The ceramic particles 32 may have a particle diameter (or effective particle diameter) of up to andincluding 45 nm, or up to and including 25 nm, or up to and including 15 nm, or up to and including 10 nm, or up to and including 8 nm.

[0185]

[0159] As used herein, the particle diameter is also intended to encompass non- spherical particles, where such non-spherical particles may be regarded as having an effective particle diameter. As used herein, the effective particle diameter is the diameter of a hypothetical spherical particle of same composition that, using a given particle-size determination method, would give the same diameter as a substance composed of spherical or non-spherical particles at the same concentration.

[0186]

[0160] The ceramic particles 32 may be comprise silicon dioxide, aluminum oxide, titanium dioxide, cerium oxide, zirconium dioxide, yttria stabilized zirconium dioxide, other oxides, and other classes of ceramics including but not limited to carbides, nitrides, sulfides, borides, phosphides, selenides, titanates, carbonates, nitrates, sulfates, borates, and phosphates, or combinations thereof. In preferred embodiments, the ceramic particles 32 are sub-micron ceramic particles comprising aluminum. In further preferred embodiments, the submicron ceramic particles comprise AI2O3, boehmite (AIO(OH)), core-shell particles comprising ceramic particles coated with an aluminum-containing shell, or combinations thereof.

[0187]

[0161] Utilizing particles with a core / shell architecture may confer specific advantages to the composite membrane (i.e. membrane-reinforced opaloid). For example, a particle comprising a core that is made of a material with highly tunable shape and particle size distribution may confer the ability to tune the average size and / or to make relatively monodisperse particles. It may also confer superior control over particle shape (e.g., highly spherical or rod-like). The core may also be lighter (i.e., less dense) than other materials. However, the core material may lack sufficient chemical stability for the intended application. Further, a particle comprising a shell of another material may confer favorable properties such as improved chemical stability or enhanced colloidal stability. Thus, using core / shell particles can be a way to balance engineering trade-offs, such as combining favorable morphology (e.g., size, monodispersity, morphology) with favorable properties (e.g., chemical stability). Non-limiting examples of core / shell particles include those with a core of silica and a shell of alumina and / or boehmite.

[0188]

[0162] The sub-micron particles may be coated in a material, for example to aid in colloidal stabilization of the colloidal suspension or colloidal dispersion, and / or to aid in the formation of the continuous ceramic phase (i.e. the opaloid) within the scaffold pore volume. The material may comprise, for example, a polymeric material (e.g., a dispersing agent).

[0163] The sub-micron particles may be colloidal sub-micron particles. The submicron particles may be imbibed within the scaffold pore volume comprising the scaffold pores. The sub-micron particles may be suspended in a liquid as a colloidal precursor (e.g., a colloidal suspension or colloidal dispersion) at least during the imbibing process, where the colloidal precursor may comprise a fluid continuous phase and the sub-micron particles dispersed or suspended within the continuous phase. The composite membrane may comprise the fluid (or liquid) continuous phase in the interparticle pores within the continuous ceramic phase (i.e. opaloid). Such arrangements of sub-micron particles are usually produced from a colloidal precursor that was itself a colloidal dispersion or colloidal suspension. However, the sub-micron particles are not necessarily dispersed or suspended in a fluid (or the fluid continuous phase) within the scaffold pore volume. As such, the composite membrane may comprise a continuous ceramic phase (or opaloid) within the scaffold pores that is fully dried, i.e., the fluid between the sub-micron particles of the continuous ceramic phase (or opaloid) having been substantially removed. The three-dimensional packing arrangements of subLmicron particles described by the term “opaloids” or “continuous ceramic phase” within the scaffold pores, as used herein, are not particularly restricted in their method of manufacture, and if the same or similar arrangement of sub-micron particles is made without the use of a precursor that is a colloidal dispersion or colloidal suspension, it may nevertheless be considered an opaloid or continuous ceramic phase as defined herein.

[0189]

[0164] The sub-micron ceramic particles used in the embodiments comprising more than one composite membrane 40 may be essentially identical, or they may be different.

[0190]

[0165] The composite membrane 40 can have a contact thickness of about 0.5 pm to about 150 pm. The composite membrane 40 can have a contact thickness of about 1 pm to about 150 pm. The composite membrane 40 can have a contact thickness of about 1 pm to about 100 pm. The composite membrane can have a contact thickness of about 1 pm to about 60 pm. The composite membrane 40 can have a contact thickness of about 10 pm to about 100 pm. The composite membrane 40 can have a contact thickness of about 10 pm to about 60 pm. The composite membrane 40 can have a contact thickness of about 1 micron to about 25 microns, or from about 5 microns to about 25 microns, or from about 10 microns to about 25 microns, or from about 15 microns to about 25 microns, or from about 20 microns to about 25 microns, or from about 1 micron to about 10 microns, or from about 1 micron to about 5 microns, or from about 5 microns to about 10 microns, or from about 10 microns to about 15 microns.

[0166] The thickness of the separator layer can be determined optically using SEM.

[0191]

[0167] The microporous hydrocarbon polymer scaffold may comprise a metalized surface region. The metalized surface region may comprise copper or aluminum. The microporous hydrocarbon polymer scaffold 30 may comprises a surface deposited metalized region. The microporous hydrocarbon polymeric scaffold matrix may be coated with metal such that the scaffold matrix 35 (which may or may not be fibri Hated) is covered with metal. The scaffold matrix in the surface region may be covered with metal such that the metal is cohesive with the scaffold matrix. In some embodiments, the metal may be bonded or adhered to the scaffold matrix. In some embodiments, the metal or metal oxide does not occlude the surface pores of the scaffold matrix, and therefore the scaffold matrix still comprises through-pores.

[0192]

[0168] The depth of the metalized surface region from the first major exterior surface of the scaffold into the thickness of the microporous polymer scaffold 30 may be dependent on, for example, the type of metal or metal oxide, the surface deposition method, and the properties of the microporous scaffold itself, such as porosity. Typically, the metalized surface region extends from the first major exterior surface of the microporous polymer scaffold 30 to a depth of about 1 pm to about 5 pm into the microporous polymer scaffold thickness.

[0193]

[0169] The surface metalized microporous polymer scaffold is then used for the formation of a composite membrane 40 according to the present disclosure.

[0194]

[0170] The metalized surface region (on one of both of the first or second major exterior surfaces) may be formed by one of sputtering metal onto the microporous polymer scaffold; evaporation deposition of metal onto the microporous scaffold; selective deposition of metal onto the microporous polymer scaffold.

[0195]

[0171] In some embodiments, both major exterior surfaces of the microporous polymer scaffold 30 may comprise a metalized surface region. Typically, the metalized surface region extends from each major exterior surface of the microporous polymer scaffold 30 to a depth of about 1 pm to about 5 pm into the microporous polymer scaffold thickness. The metal or metal oxide forming the metalized surface region on the second major surface of the microporous polymer scaffold may be the same or different from the metal or metal oxide forming the metalized surface region on the first major surface of the microporous polymer scaffold.

[0196]

[0172] In embodiments in which all of the surface area of the first major exterior surface of the microporous polymer scaffold was coated with metal, accordingly any microporous polymer scaffold matrix extending beyond the continuous ceramic phase 31 of the composite membrane 40 may be covered with metal or metal oxide, thusimproving the homogeneity of surface energy across the first major exterior surface of the composite membrane 40.

[0197]

[0173] The metal for forming the metalized surface region can be selected from at least one of copper, aluminum, nickel, chromium, zirconium, titanium, ruthenium, rhodium, palladium, platinum, gold, osmium, iridium, (lithium) or mixtures, alloys thereof. For alkali metal or alkali metal-ion rechargeable battery applications, the metal for forming the metalized surface region is preferably aluminum or copper.

[0198]

[0174] The composite membrane may have a volume ratio of [sub-micron ceramic particles] to [microporous hydrocarbon polymer structure] from about 0.5 to about 3.0, or from about 0.5 to about 2, or about 0.5 to about 1.5, or about 0.7 to about 1.3. In a preferred embodiment, the composite membrane may have a volume ratio of [submicron ceramic particles] to [microporous hydrocarbon polymer structure] of about 1.

[0199]

[0175] The surface energy across the first major exterior surface and second major exterior surface of the composite membrane can be characterized based on water contact angle (as set out in the test methods disclosed herein). However, it will be appreciated that in other embodiments, only a portion of the first major exterior surface and / or a portion of the second major exterior surface of the microporous polymer scaffold may be provide with the surface deposited metalized region. For example, from about 50 - 100 % of the surface may be coated.

[0200]

[0176] The battery separator 14 may comprise an integrated ionic transport layer on one or both sides of the battery separator, wherein the integrated ionic transport layer comprises one or more anion exchange polymers, one or more cation exchange polymers, one or more polymers of intrinsic microporosity (PIMs), one or more ionsolvating polymers, or combinations thereof.

[0201]

[0177] The battery separator 14 may comprise a sorbent or a reactive material configured to absorb, capture, scavenge, or deactivate species detrimental to battery operation such as those known to one of ordinary skill in the art.

[0202]

[0178] The battery separator 14 may comprise a hydrophobic electrolyte additive, such as fluoroethylene carbonate (FEC).

[0203]

[0179] As shown in Figure 1, rechargeable battery 10 has an anode 12, a cathode 16, and a battery separator 14 as described above. At least one of the anode 12 or the cathode 16 has an alkali metal (e.g. Li or Na) as a component of the active material (e.g., in the metallic state, in a compound such as an oxide or phosphate, or other active materials as known to one of ordinary skill in the art). The battery has an electrolyte 18 having alkali metal ions (e.g Li+or Na+). The alkali metal ions of the electrolyte 18 may be the same metal as the alkali metal of the electrode 12, 16. Theelectrolyte 18 may be a solvent-in-salt electrolyte. The alkali metal may be selected from lithium or sodium.

[0204]

[0180] In embodiments in which the hydrocarbon polymer scaffold comprises a metalized surface region, the metalized surface region may be electrically isolated and disposed on the side of the battery separator that is located closest to the anode or, alternatively, on the side of the battery separator that is located closest to the cathode. The metallized surface region may be electrically isolated from both the anode 12 / 16 and the cathode 16 / 12, and be electrically connected to a third terminal. The electrochemical cell thus constructed may be configured to enable early detection of a short circuit, for example as in Wu et al. “Improving battery safety by early detection of internal shorting with a bifunctional separator,” Nature Communications, 5:5193 (2014). This embodiment is further described in Example 15.

[0205]

[0181] In a preferred embodiment, the composite membranes of the present invention may comprise a continuous ceramic phase that extends substantially through the entire thickness of a microporous polyolefin scaffold. This morphology is expected to result in two major benefits compared to incumbent battery separators. The first major benefit is improved battery cell safety. As shown in Examples 16 and 17, the continuous ceramic phase results in extraordinary dimensional stability even at temperatures of 200°C and 300°C, well above the melting point of the microporous polyolefin scaffold. Without wishing to be bound by theory, the presence of the continuous ceramic phase throughout the thickness of the battery separator is believed to essentially eliminate a potential failure mechanism of the incumbent separators: delamination of the layer of inorganic particles from the polyolefin layer once the polyolefin layer melts. Furthermore, the resulting reinforcement of the entire microporous polyolefin scaffold is believed to significantly reduce the risk that the electrodes will short circuit by restricting the ability of the electrodes to experience out- of-plane movement that could otherwise be enabled by a molten polyolefin layer. The second major benefit is improved wettability. Without wishing to be bound by theory, the presence of the continuous ceramic phase is expected to provide favorable wicking paths for the electrolyte throughout the composite membrane due to the high surface energy of the continuous ceramic phase combined with high capillary forces due to its small and uniform pores. The crush resistance of the continuous ceramic phase, combined with its ability to retain liquid in its pores due to high capillary forces, may also facilitate pre-wetting of the battery separator just before it is wound or stacked with the electrodes during cell assembly, further reducing wetting time.

[0206]

[0182] In a preferred embodiment, the benefits of the enhanced wettability of the composite membranes of the present invention may be even greater when used withan electrolyte that has particular difficulty wetting conventional battery separators, e.g., an electrolyte with a high surface tension. Such electrolytes include substantially aqueous electrolytes and so-called solvent-in-salt (including water-in-salt) electrolytes. Solvent-in-salt electrolytes are characterized by extremely high salt concentrations (e.g., greater than about 4 molar) the salt begins to dominate the weight and / or volume of the electrolyte, and virtually all solvent molecules are coordinated to cations such that virtually no free solvent molecules remain. Common electrolyte solvents at room temperature may have surface tensions (in dyne / cm) of, for example, about 29 (Ethyl Methyl Carbonate or EMC), about 32 (Dimethyl Carbonate or DMC), or about 44 (Propylene Carbonate or PC), or about 72 (water). Electrolytes with high surface tension may have surface tensions (in dyne / cm) of at least about 35, or at least about 40, or at least about 45, or at least about 50, or at least about 55, or at least about 60, or at least about 65, or at least about 70, or at least about 75, or at least about 80.

[0207] Test Methods

[0208] Non-Contact Thickness (e.g., of the Microporous Polymer Scaffold)

[0209]

[0183] A sample of a microporous polymer scaffold was placed over a flat smooth metal anvil and tensioned to remove wrinkles. The height of microporous polymer structure on anvil was measured and recorded using a non-contact Keyence LS- 7010M digital micrometer. Next, the height of the anvil without microporous polymer scaffold was recorded. The thickness of the microporous polymer scaffold was taken as a difference between micrometer readings with and without microporous polymer scaffold being present on the anvil.

[0210] Contact Thickness (e.g. of the Composite Membrane)

[0211]

[0184] A sample was analyzed with a Mitutoyo Litematic handheld micrometer with a measuring force of 0.01 Newtons to determine the contact thickness.

[0212] Mass per Area (e.g., of the Microporous Polymer Scaffold)

[0213]

[0185] A microporous polymer scaffold was strained to a point sufficient to eliminate wrinkles, and then a 10 cm2piece was cut out using a die. The 10 cm2piece was weighed on a conventional laboratory balance. The mass-per-area (M / A) was then calculated as the ratio of the measured mass to the known area.

[0214] Bulk Density (e.g., of the Microporous Polymer Scaffold)

[0215]

[0186] The bulk density of the microporous polymer scaffold was calculated by dividing its mass-per-area by its non-contact thickness.Skeletal Density (e.q., of the Microporous Polymer Scaffold)

[0216]

[0187] The skeletal density is the density of a solid calculated by excluding all open pores and internal void volume. A Micromeritics AccuPyc II 1340 Gas Pycnometer (Micromeritics Instrument Corp., Norcross, GA) using helium gas as the displacement medium was used to analyze the samples. The AccuPyc uses the theory of gas displacement to determine the volume occupied by a given sample. The sample was added to a 3.5 cm3sample cup and sealed in the analysis chamber. The sample was purged 50 times with helium gas at 19.5 psig and the gas expands into another precision internal volume. Once purged, the sample was then analyzed with 15 cycles of fill cycles at 19.5 psig, or until the sample volume equilibrium was detected (0.02% precision). The skeletal density was calculated by dividing the sample mass by the adjusted sample volume. The sample mass was determined by weighing on an analytical balance of + / - 0.1 mg sensitivity.

[0217] Sample Skeletal Density = Sample Mass I Sample Volume

[0218] Sample Volume = Sample Chamber Volume - (Expansion Chamber Volume / ((Gauge Pressure After Fill / Gauge Pressure After Expansion) - 1))

[0219] Porosity (e.q., of the Microporous Polymer Scaffold)

[0220]

[0188] The porosity of the microporous polymer scaffold was calculated by dividing the difference between skeletal density and bulk density of the membrane by the skeletal density of the membrane per the following formula:

[0221] Porosity = ((Skeletal Density - Bulk Density) / Skeletal Density)*100% [Vol%]

[0222] Absolute tensile strength (e.q., of the Microporous Polymer Scaffold) [first and second directions!

[0223]

[0189] The tensile strength was determined in each direction by measuring the maximum tensile load of a sample as described in ASTM D638-5, then dividing the load by the original gauge width of the sample.

[0224] Matrix tensile strength (e.q., of the Microporous Polymer Scaffold) [first and second directions!

[0225]

[0190] The absolute tensile strength (in units of N / mm or equivalent) was normalized to discount pore volume to determine the matrix tensile strength of the microporous polymer scaffold (in units of MPa or equivalent). The matrix tensile strength wascalculated by dividing the absolute tensile strength of the sample by a ratio of its bulk density to the skeletal as shown in the following formula:

[0226] Matrix Tensile Strength = (Absolute Tensile Strength / N on-Contact Thickness) / (Bulk Density / Skeletal Density) [MPa]

[0227] Scanning Electron Microscopy (SEM)

[0228]

[0191] Samples of the composite membranes were carefully mounted to SEM stubs using double-sided conductive tape. Cross-sections of composite membranes were prepared using a Gatan® Illion2 broad beam ion mill with ion beam accelerating voltages of 0.2-5kV at a milling temperature of -150°C to -160°C. The samples were then coated with a thin (2nm) conductive layer of platinum using a Cressington® 208HR sputter coater. SEM images were then obtained using a Hitachi® SLI8000 and SLI8230 FESEM at an accelerating voltage of 1-3kV, with working distances of 2-8mm, using upper and lower secondary electron detectors.

[0229] Small-Angle X-ray Scattering (SAXS)

[0230]

[0192] Small-angle X-ray scattering (SAXS) measurements were performed on a Xenocs Xeuss 2.0 instrument. Samples were probed with Cu K-a radiation (A = 0.154 nm). Typical operating conditions were 50kV and 0.6 mA. Sample-to-detector distances ranged from approximately 1200 to 6400 mm. Samples were held under vacuum during scattering experiments, which were performed directly on membrane- reinforced opaloids and neat opaloids. The collection time varied based on the sample- to-detector distance, sample thickness, and operating voltage. Data were calibrated using a silver behenate standard. SAXS data were collected on a 2-D detector, and the intensity distribution provided information about structural length scales and anisotropy. For isotropic structures, the intensity was uniform over 360° (azimuthal angle) and could be integrated over 360° to obtain 1-D SAXS profiles, membrane- reinforced opaloids and neat opaloids exhibited isotropic 2-D SAXS patterns. The scattering vector or peak position (i.e., the local maximum associated with the structure factor peak), q (in units of nm-1), is proportional to the sine of the scattering angle, Q, and inversely proportional to the wavelength, , according to the expression: q = 47Tsin(9) . Values of q can be converted to real space correlation distances with the relationship ID = 2n / q. Lorentz-corrected intensities can be calculated by multiplying intensity by q2. Primary inter-particle structural features may be identified by structure factor peaks in the Lorentz-corrected intensity spectra. A peak herein may be defined as in scipy.signal.find_peaks: " finds all local maxima by simple comparison of neighboring values." E.g. a peak data point will have 2 neighboring values of lesservalue. Structure factor peaks generally have a prominence of at least 20%, where prominence is the maximum value of the structure factor peak normalized by the minimum Lorentz corrected intensity in the adjacent region corresponding to interparticle distances larger than the detected peak. Structure factor peaks may also have a prominence of at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 75%, at least about 100%, at least about 200%, at least about 300%, at least about 400%, at least about 500%, or at least about 600%. Structure peaks may also be characterized by their full width at half-prominence. Full width at half prominence may be calculated as the width of the peak (i.e. , the length of the line that intersects the contours of the peak at a given Lorentz-corrected intensity) at half the prominence. Structure factor peaks may have a full width at half prominence of less than about 100%, or less than about 70%, or less than about 50%, of the structure peak Inter-particle Distance (ID). Inter-particle distances (ID) larger than 100nm, but smaller than 300nm may be evaluated by use of Ultra Small-Angle X-ray Scattering (USAXS).

[0231] N2 Sorption BET Specific Surface Area (SSA) and Pore Size Distributions

[0232]

[0193] This technique is also known as BET / BJH. N2 sorption was performed on a Quantachrome AutoSorb iQ MP-XR gas sorption instrument with nitrogen as the adsorbate at 77 K. A starting p / po of 1e-5 was used in order to assess the pore structure of the samples down to the lUPAC-designated micropore regime (< 2 nm). Degassing was performed on the AutoSorb iQ using a step heating profile up to 150 °C under vacuum for four hours. Isotherms were collected with either standard resolution (47 adsorption points, 14 desorption points) or high resolution (65 adsorption points, 38 desorption points). High-resolution runs were carried out by utilizing a delta Vmax of 10 cc / g in addition to a larger number of partial pressure targets. The specific surface area was determined from the nitrogen adsorption data using the Brunauer- Emmett-Teller (BET) method. The range of data points used for this analysis was selected using the Rouquerol method according to ISO 9277:2010, “Determination of the specific surface area of solids by gas adsorption — BET method.” Density functional theory (DFT) was utilized to calculate the pore size distribution over the lUPAC-designated micropore and mesopore regimes (pores < 50 nm). The kernel chosen for the DFT calculations was “N2 at 77 K on silica (cylinder pores, NLDFT adsorption branch)”. The mode pore size or primary pore size was the pore size (nm) with the highest specific pore volume (cc / g) in the pore size distribution.

[0233] Bubble Point Pressure

[0194] The bubble point pressure is a means to characterize the pore size of a porous support material and may be measured according to a bubble point measurement as further explained below. For a given fluid and pore size of a porous material (such as the microporous polymer scaffolds and composite membranes of the present disclosure) at constant wetting, the pressure required to force an air bubble through the pore is in inverse proportion to the size of the through-pore (hole). The bubble point pressure can provide a measure of the largest pore size according to the Young-Laplace equation:

[0234]

[0235] where P is the pressure required to dewet a liquid from a cylindrical pore, ytvis the liquid surface tension, 0 is the contact angle, and d is the pore diameter.

[0236]

[0195] The bubble point pressure was measured according to the general teachings of ASTM F316-03 using a Capillary Flow Porometer (Model 3G zh from Quantachrome Instruments). The sample holder comprised a porous metal plate (Part Number: 196450, Anton Paar), 25.4 mm in diameter and a plastic mask (Part Number ABF-300, Professional Plastics), 18mm inner diameter x 24.5 mm outer diameter. The sample was placed in between the metal plate and the plastic mask. The sample was then clamped down and sealed using an O-ring (Part Number: 193798, Anton Paar). The sample was wet with the test fluid (Silicone fluid, 10 cSt, having a surface tension of 19.75 dynes / cm).

[0237] Mean Flow Pore Diameter

[0238]

[0196] The mean flow pore diameter was measured according to the general teachings of ASTM F316-03 using a Capillary Flow Porometer (Model 3G zh from Quantachrome Instruments). The dry gas flow data were determined by loading the dry sample into the sample holder, applying gas pressure to the dry sample, and measuring gas flow rate vs. gas pressure. The wet flow data were measured by loading the sample into the sample holder, wetting the sample with test fluid, applying gas pressure to the wet sample, and measuring the gas flow rate vs. gas pressure. The one-half dry flow data was determined by plotting one-half times the dry gas flow data as a function of gas pressure. The mean flow pore diameter was determined by identifying the intersection point of the one-half dry flow data and the wet flow data, and then using the Young- Laplace equation to convert the corresponding gas pressure from the intersection point to a pore diameter value.

[0239] Electrolyte Wettability

[0197] Battery separator wettability with respect to electrolyte was quantified by placing a controlled quantity (e.g., a 20 microliter droplet) of a test fluid (e.g., propylene carbonate) onto the surface of a separator that was tensioned to remove wrinkles and configured to be level and positioned above the work surface (e.g., not in contact with a benchtop). This configuration enabled the behavior of the electrolyte droplet to be observed under conditions that are dominated by wetting into the separator pores and wicking within the separator pore volume. The response variables are the distance the test fluid wicks and the contact angle of the droplet at given time intervals (e.g., 60 seconds).

[0240] Residual Moisture via TGA

[0241]

[0198] The residual moisture content of the separator was quantified via thermogravimetric analysis (TGA) as the weight loss between 60°C and 120°C. Residual moisture was calculated in units of ppm (by weight) or as the mass per geometric area of separator.

[0242] Ex-situ Ionic Resistance

[0243]

[0199] The ionic resistance of a separator was measured via stainless steel disk electrodes, a portable potentiostat, and a conductivity standard. The technique was based on the technique shown in Landesfeind et al. “Tortuosity Determination of Battery Electrodes and Separators by Impedance Spectroscopy,” J. Electrochem Soc., 163(7) A1373-A1387 (2016). A 40 mm diameter battery separator sample was punched with a die, wet with isopropyl alcohol, and placed into a jar with an electrolyte of choice (e.g., a 10000 pS conductivity standard from Fisher Scientific 15-077-952) for a desired wetting time (e.g., at least 1 hour). The sample was then placed on the 50 mm bottom disk electrode, which has a 5 mm lip to hold a small pool of electrolyte. After 1 mL of additional electrolyte was added on the battery separator sample, the 20 mm diameter top electrode, encircled in about 5 mm thick PTFE, was placed on top, with an approximately a 1 kg cylindrical weight to hold the electrode in place. Leads from a portable potentiostat (PalmSens Sensit BT) were attached to the top and bottom electrode. Using PSTrace software, an Impedance Spectroscopy measurement was taken from 15 kHz to 150 kHz. In JMPOPro 16.1.0, a line was fit to the Zreaiand -Zimagto estimate the Zreaiintercept, which was recorded as the ex-situ ionic resistance.

[0244]

[0200] In the following examples, the microporous polymer scaffolds A-D are microporous polyethylene scaffolds that were produced via the wet (or “gel”) process. Properties of these microporous polyethylene scaffolds are shown in Tables 1a and 1b.EXAMPLES

[0245] Example 1

[0246]

[0201] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) was restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid was prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.2 g Lonza Barlox 8S, and 0.2 g 1 -hexanol arewere combined in a small sample vial and then shaken vigorously to emulsify the 1- hexanol. 1 g of the imbibing fluid was pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wet the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0247] Example 2

[0248]

[0202] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) was restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid was prepared by combining a silica-alumina core-shell nanoparticle (diameter of 12nm) dispersion (Ludox® CL, W. R. Grace) with an aqueous wetting package as follows. 10 g of Ludox® CL, 0.2 g Lonza Barlox 8S, and 0.2 g 1- hexanol arewere combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid was pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wet the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0249] Example 3

[0250]

[0203] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “B”) was restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid was prepared by combining a silica-alumina core-shell nanoparticle (diameter of 12nm) dispersion (Ludox® CL, W. R. Grace) with an aqueous wetting package as follows. 10 g of Ludox® CL, 0.2 g Lonza Barlox 8S, and 0.2 g 1- hexanol arewere combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid was pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wet thescaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0251] Example 4

[0252]

[0204] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “C”) was restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid was prepared by combining a silica-alumina core-shell nanoparticle (diameter of 12nm) dispersion (Ludox® CL, W. R. Grace) with an aqueous wetting package as follows. 10 g of Ludox® CL, 0.2 g Lonza Barlox 8S, and 0.2 g 1- hexanol arewere combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid was pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wet the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0253] Example 5

[0254]

[0205] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “D”) was restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid was prepared by combining a silica-alumina core-shell nanoparticle (diameter of 12nm) dispersion (Ludox® CL, W. R. Grace) with an aqueous wetting package as follows. 10 g of Ludox® CL, 0.2 g Lonza Barlox 8S, and 0.2 g 1- hexanol arewere combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid was pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wet the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0255] Example 6

[0256]

[0206] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “D”) was restrained in a 7” square cardboard frame and tensioned to removewrinkles. An imbibing fluid was prepared by combining a silica-alumina core-shell nanoparticle (diameter of 12nm) dispersion (Ludox® CL, W. R. Grace) with a wetting alcohol as follows. 5.6 g of Ludox® CL and 1.4 g Isopropyl Alcohol (I PA) arewere combined in a small sample vial and then shaken vigorously to mix. 1 g of the imbibing fluid was pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wet the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0257] Example 7

[0258]

[0207] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) was restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid was prepared by combining a silica nanoparticle (diameter of 50 nm) dispersion (Snowtex® ST-30LH, Nissan Chemical) with an aqueous wetting package as follows. 5 g of ST-30LH, 5 g DI H2O, 0.2 g Lonza Barlox 8S, and 0.2 g 1- hexanol arewere combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid was pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wet the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0259] Example 8

[0260]

[0208] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 7” square cardboard frame and tensioned to remove wrinkles. A silica nanoparticle (diameter of 50 nm, 30% solids by weight) dispersion (Snowtex® ST-30LH, Nissan Chemical) is modified to a core-shell SiO2 @ AI2O3 dispersion by the addition of aluminum chloride at a level of 2 % by weight on a dispersion basis. An imbibing fluid is prepared by combining the core-shell nanoparticle dispersion with an aqueous wetting package as follows. 5 g of modified ST-30LH, 5 g DI H2O, 0.2 g Lonza Barlox 8S, and 0.2 g 1-hexanol are combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid isremoved by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample is then dried with a heat gun set to 150°F until visibly dry.

[0261] Example 9

[0262]

[0209] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 6-inch PI_A hoop and tensioned to remove wrinkles. This hoop was placed in a Denton Vacuum Desktop Pro Sputtering Coater with a Copper Target (Plasmaterials). 25sccm Argon Plasma deposit at a power level of 25W (Direct Current mode) was applied for a period of 4 minutes, with an estimated coating thickness of 10nm (measured at same conditions on flat PET control coupon).

[0263]

[0210] An imbibing fluid is prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.2 g Lonza Barlox 8S, and 0.2 g 1-hexanol are combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0264] Example 10

[0265]

[0211] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid is prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.2 g Lonza Barlox 8S, and 0.2 g 1-hexanol are combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry.

[0212] A 3 mil drawdown bar is used to spread a mixture of 1% by weight PIM-1 (Millipore) dissolved in tetrahydrofuran evenly onto the top side of a polymer sheet substrate. The polymer sheet substrate (obtained from DAICEL VALUE COATING LTD., Japan) comprises PET and a protective layer of cyclic olefin copolymer (COC), and is oriented with the COC side on top. The sample sits in ambient air for 7 minutes before being dried at 100°C for 3 min. The polymer sheet substrate is removed and the composite Mmembrane is placed on top. A small amount of THF is added to the composite mMembrane, until fully wetted. A glass cover is added to the assembly and a 1kg weight is placed on top. Assembly is left to dry overnight.

[0266] Example 11

[0267]

[0213] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid is prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.2 g Lonza Barlox 8S, and 0.2 g 1-hexanol are combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry. The result is a composite membrane.

[0268]

[0214] A coating solution of Cab-o-sperse 1030K (30% 150nm fumed silica), with 0.6% Polyvinyl alcohol (10k MW, 90% Hydrolyzed) as binder is applied to the composite membrane and spread using a 3 mil drawdown bar. The assembly is placed in an oven and dried at 60 degrees C for 30 minutes.

[0269] Example 12

[0270]

[0215] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid is prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.2 g Lonza Barlox 8S, and 0.2 g 1-hexanol are combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of theimbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry. The result is a composite membrane.

[0271]

[0216] A coating slurry is formed by mixing 2 weight % polyvinylidene fluoride particles (Nanochemazone) in deionized water. On a PVDF weight basis, 5% polyvinyl alcohol, 2% Lithium dodecyl sulfate, and 5% triethyl phosphate are added to the slurry, which is then heated to 50°C and vigorously stirred. The slurry is cooled to room temperature and spread onto the composite membrane and spread using a 3 mil drawdown bar. The assembly is placed in an oven and dried at 60 degrees C for 30 minutes.

[0272] Example 13

[0273]

[0217] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 6-inch PLA hoop and tensioned to remove wrinkles. This hoop was placed in a Denton Vacuum Desktop Pro Sputtering Coater with a Copper Target (Plasmaterials). 25sccm Argon Plasma deposit at a power level of 25W (Direct Current mode) was applied for a period of 4 minutes, with an estimated coating thickness of 10nm (measured at same conditions on flat PET control coupon).

[0274]

[0218] An imbibing fluid is prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.2 g Lonza Barlox 8S, and 0.2 g 1-hexanol are combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry. The result is a composite membrane.

[0275]

[0219] A coating solution of Cab-o-sperse 1030K (30% 150nm fumed silica), with 0.6% Polyvinyl alcohol (10k MW, 90% Hydrolyzed) as binder is applied to the composite membrane and spread using a 3 mil drawdown bar. The assembly is placed in an oven and dried at 60 degrees C for 30 minutes.Example 14

[0276]

[0220] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 6-inch PI_A hoop and tensioned to remove wrinkles. This hoop was placed in a Denton Vacuum Desktop Pro Sputtering Coater with a Copper Target (Plasmaterials). 25sccm Argon Plasma deposit at a power level of 25W (Direct Current mode) was applied for a period of 4 minutes, with an estimated coating thickness of 10nm (measured at same conditions on flat PET control coupon).

[0277]

[0221] An imbibing fluid is prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.2 g Lonza Barlox 8S, and 0.2 g 1-hexanol are combined in a small sample vial and then shaken vigorously to emulsify the 1-hexanol. 1 g of the imbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample was then dried with a heat gun set to 150°F until visibly dry. The result is a composite membrane.

[0278]

[0222] A coating slurry is prepared from aqueous solution of 2 wt% Nanocellulose (nanografi). On a cellulose solids weight basis, 3 wt% Carboxymethylcellulose (as a binder) and 1 wt% DLSS (as a surfactant) were then added and mixed vigorously. The coating slurry is then coated onto thean composite membrane using a 3mil drawdown bar, and the assembly is dried in a convection oven at 60 °C for 4 h.

[0279] Example 15

[0280]

[0223] An ultrahigh molecular weight PE microporous polymer scaffold (with attributes of scaffold “A”) is restrained in a 7” square cardboard frame and tensioned to remove wrinkles. An imbibing fluid is prepared by combining an alumina nanoparticle (diameter of 60-90 nm) dispersion (AL20, Nyacol) with an aqueous wetting package as follows. 10 g of AL 20, 0.1 g Lithium Dodecyl Sulfate powder, and 0.4 g 1-butanol are combined in a small sample vial and then shaken vigorously to emulsify the 1- butanol. 1 g of the imbibing fluid is pipetted onto the surface of the polymer scaffold and spread evenly using the side of a plastic rod until it fully wets the scaffold (about 30 seconds). Excess imbibing fluid is removed by wiping the surface of the polymer scaffold with a Kimwipe® tissue. The sample is then dried with a heat gun set to 150°F until visibly dry. The sample was subsequently heat treated at 120C for 1 hour to remove residual 1-butanol.Example 16

[0281]

[0224] Lithium-ion and lithium-metal battery cells are built in standard 2032 cell hardware (Shenzhen TICO Technology Co., Ltd., Shenzhen, China) as will be understood by one of ordinary skill in the art. The housing (i.e. , the positive can and negative can) is made of 316 stainless steel. A conical spring (316 stainless steel described by the manufacturer as “15.4x1.1 for 20 series battery”) and spacer (316 stainless steel disc that is 16 mm diameter and 1 mm thick) are incorporated between the cathode and the positive can to take up extra space in the cell and ensure good contact among the internal cell components. A grommet is integrated on the negative can to seal the cell and electrically isolate the two terminals once the cell is crimped.

[0282]

[0225] The separator for both lithium-ion and lithium-metal battery cells is the composite membrane made according to Example 1.

[0283]

[0226] The anode for lithium-metal battery cells is lithium foil that is 500 microns thick.

[0284]

[0227] The anode for lithium-ion battery cells has an active layer composition as follows (in dry mass fractions): 94% Superior Graphite SLC1520T graphite commercially available from Superior Graphite, United States; 1.5% C65 carbon black commercially available from Imerys S.A., Belgium; 1.5% BH1000 NaCMC (NaCMC = sodium carboxymethyl cellulose) commercially available from Wealthy Chemical Industry (Suzhou) CO, Ltd., Jiangsu, China.; 3% Styrene butadiene rubber (SBR), commercially available from MTI Corp., Richmond, CA. These anodes are prepared according to the following steps as will be understood by one of ordinary skill in the art: a) Dissolve NaCMC in deionized (DI) water and allow to equilibrate overnight (about 14 - 18 hours), b) Disperse C65 using 1.5” diameter Cowles blade at 2000 rotations per minute (RPM), c) Disperse SLC1520T graphite using 1.5” diameter Cowles blade at 2000 RPM, d) Dilute with DI water as needed to adjust viscosity to maintain a vortex for efficient mixing, e) Blend in SBR using 1.5” diameter Cowles blade at 1000 RPM, f) Cast via doctor blade on 10 pm copper foil, g) Dry at 35 °C in air on a large hot plate, h) To remove any residual solvent, transfer air-dried electrodes to vacuum oven, dry overnight at 110 °C under vacuum, i) Punch a 1” diameter piece of electrode, weigh it to determine the mass-per-area of the active layer (must subtract mass of the foil substrate), j) Use a drop micrometer to measure the thickness of the 1” diameter electrode to determine the thickness of the active layer (must subtract thickness of the foil substrate), and calender it so the active layer achieves a density of about 1.6 g / cc. The anode has an average mass-per-area (not including foil) of about 19.2 mg / cm2. The average final electrode thickness (with foil, after calendering) is about128 microns, corresponding to an average density of 1.63 g / cc, and an average porosity of 24%. Note that the electrode density is a so-called “envelope” density that is calculated by dividing the mass-per-area of the active layer by the thickness of the active layer.

[0285]

[0228] The cathode for lithium-ion and lithium-metal battery cells has an active layer composition as follows (in dry mass fractions): 93% NCM-111 (NCM-111 is Li1.05Ni0.33Mn0.33Co0.33O2) from MSE Supplies LLC, Tucson, AZ, USA; 3% Kynar® HSV- 900 PVDF (polyvinylidene fluoride) from Arkema inc., King of Prussia, PA, USA; 1.5% C65 carbon black from Imerys S.A., Belgium; 2.5% SFG6-L conductive graphite from Imerys S.A., Belgium. These anodes are prepared according to the following steps as will be understood by one of ordinary skill in the art: a) All mixing steps are carried out under argon blanket, b) Dissolve PVDF in dry NMP (NMP is N-methylpyrrolidone), c) Disperse C65 using 1.5” diameter Cowles blade at 2000 RPM, d) Disperse SFG6-L conductive graphite using 1.5” diameter Cowles blade at 2000 RPM, e) Disperse NCM- 111 using 1.5” diameter Cowles blade at 2000 RPM, f) Dilute with dry NMP as needed, g) Cast via doctor blade on 15 pm aluminum foil, h) Dry at 80 °C in air on a large hot plate, i) To remove any residual solvent, transfer air-dried electrodes to vacuum oven, dry overnight at 110 °C under vacuum, j) Punch a 1” diameter piece of electrode, weigh it to determine the mass-per-area of the active layer (must subtract mass of the foil substrate), k) Use a drop micrometer to measure the thickness of the 1” diameter electrode to determine the thickness of the active layer (must subtract thickness of the foil substrate), and calender it so the active layer achieves a density of about 3.0 g / cc. The average final electrode thickness (with foil, after calendering) is about 162 microns, corresponding to an average envelope density of 2.97 g / cc and an average porosity of 31%. Note that the electrode density is a so- called “envelope” density that is calculated by dividing the mass-per-area of the active layer by the thickness of the active layer.

[0286]

[0229] All battery cells are assembled in an argon-filled glove box configured for battery assembly. The lithium discs, electrolyte, and separators are stored in the argon glove box to minimize moisture content. Prior to cell assembly, the cell hardware (positive can, negative can, spacer, and conical spring), NMC cathode, graphite anode, and separators are dried overnight at 80°C under vacuum.

[0287]

[0230] When assembling battery cells, the following steps are followed: a) For lithium- metal cells only, brush both surfaces of the lithium foil with a stainless steel brush to clean the surfaces prior to assembly, b) Place anode in negative can - for lithium-ion cells, the anode is oriented such that the copper foil faces the negative can, and for lithium metal cells, the lithium disc is in direct contact with the negative can, c) Add 150 pL of electrolyte to negative can, d) Center 19 mm separator over negative can(note separator diameter is larger than negative can diameter), e) Center cathode on separator (active material side facing separator), f) Center spacer over cathode, g) Press cathode, separator, and spacer down into negative can (separator edge wraps up around the electrode and spacer, preventing shorting at separator edges), h) Center conical spring on top of spacer, with wide opening toward spacer, i) Place positive can on top, crimp to 7,500 - 9,000 kPa, cleaned residual electrolyte from cell surfaces, j) Place battery cells in an oven (at ambient pressure in an air environment) at 45°C for 16 hours to facilitate electrolyte wetting. Cells are then removed from the oven and allowed to equilibrate at room temperature. Cells then undergo formation (e.g., several charge / discharge cycles at C / 20), power testing (up to 3C charge and discharge rates), and extended cycling (between C / 5 and C / 2 for both charging and discharging) using a Neware battery cycler (CT-4008T-5V50mA-164-U Three Range Battery Testing Equipment; Neware Battery Testers I nt., Belleville, IL, USA) as will be understood by one of ordinary skill in the art.

[0288] Example 17

[0289]

[0231] Description of building a battery w / 3rd terminal for #7, with sensing (])A separator made according to the teachings of Example 13 is assembled into a 3- terminal lithium-ion pouch cell that is configured to detect early short circuits as follows. The pouch design is based on the teachings of Wu et al. in Nature Communications 5:5193 (2014). The cathode, anode, and electrolyte are produced and prepared for battery cell assembly as described Example 14. All materials are cut to size for the pouch cell. Battery cell assembly is done in an argon-filled glove box configured for battery assembly. Copper foil is used as the electrical leads to the anode and separator. Aluminum foil is used as the electrical lead to the cathode. Kapton tape is used to ensure the anode, cathode, and separator remain electrically isolated at the points the electrical leads make contact with the battery components. To configure the cell for early detection of short circuits, a first volt meter is connected between the anode and separator, and a second volt meter is connected between the anode and the cathode. During normal operation, the first and second volt meters measure similar voltages. For early detection of a short circuit (e.g., a lithium dendrite that has grown partially through the separator and made electrical contact with the metallized portion of the separator) the voltage measured by the first volt meter drops significantly, deviating from the second volt meter and approaching zero volts as the severity of the short increases.Example 18

[0290]

[0232] Samples were generated according to Examples 1, 2, 3, and 5. A 40 mm diameter disk was cut out of each example and place unrestrained into an open metal weighing dish. The weighing dishes with the 40 mm diameter disks were placed inside a convection oven at 200°C for 1 hour. After 1 hour, the samples were removed from the oven and measured. Example 1 still had a diameter of 40 mm, example 2 had a diameter of 38 mm, example 3 had a diameter of 38 mm, and example 5 had a diameter of 39 mm. Dimensional stability at 200C for 1 hour and 300C for 1 hour, preferably on #1 or #2 .

[0291] Example 19

[0292]

[0233] Samples were generated according to Examples 1, 2, 3, and 5. A 40 mm diameter disk was cut out of each example and place unrestrained into an open metal weighing dish. The weighing dishes with the 40 mm diameter disks were placed inside a convection oven at 300°C for 1 hour. After 1 hour, the samples were removed from the oven and measured. Example 1 still had a diameter of 40 mm, example 2 had a diameter of 38 mm, example 3 had a diameter of 38 mm, and example 5 had a diameter of 38 mm.

[0293]

[0234] The inventors have demonstrated that membrane reinforced opaloids are an excellent platform for preparing improved alkali metal and alkali metal-ion rechargeable battery separators. The separators disclosed herein are thinner and therefore maximise the energy density and power density of the battery without compromising its safety. A thinner separator, may allow for 5 or 10% more active materials in the cell

[0294]

[0235] The ceramic particles improve the wettability of the battery separator, thus reducing the current long soaking times and reducing costs of battery manufacture. After filling the housing with the battery components including the separator, the aging process takes 1-2 days for electrolyte wetting. Cells are getting larger, so wettability is much more important for these cells in order to increase the speed at which the electrolyte can be filled.

[0295]

[0236] The continuous ceramic phase formed throughout the thickness of the separator improves the thermal stability and therefore reduce the risk of thermal runaway by preventing catastrophic electrode contact during high-temperature events and minimizing change to existing supply chain & cell manufacturing processes unlikeconventional ceramic-coated polyolefins (even with aramids). Separator plays a key role in avoiding short circuits, by not shrinking.

[0296]

[0237] Increased wettability of the separator is particularly crucial to increase the cycle life of sodium-ion batteries (e.g. NATRON®) by increasing total ceramic surface area and minimizing change to existing supply chain & cell manufacturing processes unlike conventional ceramic-coated polyolefins. Natron are looking for high loadings of nanoparticles of 5-10 g / m2or more. Moisture is less of a concern... because our active materials have a high wt% water in their crystal structure. Adsorbed moisture on the separator is basically negligible.

[0297] Table 1a - Physical Properties of Microporous Polymer Scaffolds of the Examples

[0298]

[0299] Table 1b - Tensile Properties of Microporous Polymer Scaffolds of the Examples

[0300]

[0301] Table 2 - Membrane-Reinforced Opaloids

[0302]

Claims

CLAIMS1 - A battery separator for an alkali-metal or an alkali metal-ion rechargeable battery having an electrode comprising an alkali metal, the separator comprising a composite membrane, the composite membrane comprising:a microporous hydrocarbon polymer scaffold having a scaffold matrix and a plurality of scaffold pores having a scaffold pore volume, anda continuous ceramic phase disposed within the scaffold pore volume, wherein the continuous ceramic phase extends within the scaffold pore volume a distance of at least 1 mm in each of two orthogonal directions;wherein the continuous ceramic phase comprises a three-dimensional packing arrangement of sub-micron ceramic particles,wherein the three-dimensional packing arrangement of sub-micron ceramic particles exhibits at least one structure factor peak in Lorentz-corrected SAXS data.2 - The battery separator of claim 1, wherein the submicron ceramic particles comprise aluminum.3 - The battery separator of claim 2, wherein the submicron ceramic particles comprise AI2O3, boehmite (AIO(OH)), core-shell particles comprising ceramic particles coated with an aluminum-containing shell, or combinations thereof.4 - The battery separator of any preceding claim, wherein the submicron ceramic particles have a particle diameter or effective diameter of from about 5 nanometers to about 200 nanometers.5 - The battery separator of any preceding claim, wherein the microporous hydrocarbon polymer scaffold comprises any one selected from polyethylene (PE), polypropylene (PP), or combinations thereof.6 - The battery separator of any preceding claim, wherein a largest pore of the plurality of scaffold pores has a pore diameter, as determined by bubble point, is from about 3 to about 15 times the primary mode particle diameter or effective particle diameter of the submicron ceramic particles on a volume basis.7 - The battery separator of any preceding claim, wherein the inter-particle pores between the sub-micron ceramic particles are defined by an inter-particle distance within the three-dimensional packing arrangement of sub-micron ceramic particles, and wherein the interparticle distance is from about 0.5 times to about 3 times the particle diameter or effective particle diameter of the submicron ceramic particles.8 - The battery separator of any preceding claim, wherein the continuous ceramic phase disposed within the scaffold pore volume has a ratio (d / D) of an inter-particle pore size, d, to particle diameter or effective diameter, D, of from about 0.2 to about 1.2.9 - The battery separator of any preceding claim, wherein a packing density of the ceramic particles of from about 0.40 to about 0.85.10 - The battery separator of any preceding claim, wherein the porosity of the composite membrane is from about 30% to about 70%.11 - The battery separator of any preceding claim, wherein the volume ratio of sub-micron ceramic particles to scaffold matrix in the composite membrane is from about 0.5 to about 3.12 - The battery separator of any preceding claim, wherein the continuous ceramic phase extends substantially through the entire thickness of the scaffold.13 - The battery separator of any preceding claim, wherein the bubble point of the battery separator is at least about 10 bar.14 - The battery separator of any preceding claim, wherein the contact thickness of the composite membrane is from about 2 microns to about 25 microns.15 - The battery separator of any preceding claim, wherein the microporous hydrocarbon polymer scaffold comprises a metalized surface region.16 - The battery separator of claim 15, wherein the metalized surface region comprises copper or aluminum.17- The battery separator of any preceding claim, wherein the battery separator comprises a surfactant.18 - The battery separator of any preceding claim, wherein the battery separator comprises an integrated ionic transport layer_on one or both sides of the battery separator, wherein the integrated ionic transport layer comprises one or more anion exchange polymers, one or more cation exchange polymers, one or more polymers of intrinsic microporosity (PIMs), one or more ion-solvating polymers, or combinations thereof.19 - The battery separator of any preceding claim, wherein the battery separator comprises a sorbent or a reactive material configured to absorb, capture, scavenge, or deactivate species detrimental to battery operation.20- The battery separator of any preceding claim, wherein the battery separator comprises a hydrophobic electrolyte additive.21 - The battery separator of claim 20, wherein the hydrophobic electrolyte additive is fluoroethylene carbonate (FEC).22 - A rechargeable battery comprising:an anode,a cathode,the battery separator of any one of claims 1 to 21, andan electrolyte comprising an alkali metal;wherein at least one of the anode or the cathode includes the alkali metal.23 - The rechargeable battery of claim 22, wherein the alkali metal is selected from lithium or sodium.24 - A rechargeable battery according to claim 22 or 23, wherein the electrolyte is a solvent-in-salt electrolyte.25 - The rechargeable battery of any one of claims 22 to 24, wherein the hydrocarbon polymer scaffold comprises a metalized surface region, wherein the metallized surface region is electrically isolated from both the anode and the cathode, and is electrically connected to a third terminal.26 - The rechargeable battery of any one of claims 22 to 25, wherein the battery separator comprises a surfactant having a cationic portion and an anionic portion, and wherein the cationic portion of the surfactant is the same as the alkali metal of the electrolyte and the anode or the cathode.27 - A method of making a battery separator according to any one of claims 1 to 21, the method comprising:a) obtaining a microporous hydrocarbon polymer scaffold, wherein the microporous hydrocarbon polymer scaffold comprises a polyolefin and has a polymer scaffold matrix and a plurality of scaffold pores, the microporous polymer scaffold having a scaffold pore volume and having a porosity from about 70% to about 96%;(b) incorporating sub-micron ceramic particles into the scaffold pore volume of the microporous polymer scaffold; and(c) consolidating the sub-micron ceramic particles such that they form a continuous ceramic phase disposed within the scaffold pore volume, wherein the continuous ceramic phase extends within the scaffold pore volume a distance of at least 1 mm in each of two orthogonal directions;wherein the continuous ceramic phase comprises a three-dimensional packing arrangement of sub-micron ceramic particles; andwherein the three-dimensional packing arrangement of sub-micron ceramic particles exhibits at least one structure factor peak in Lorentz-corrected SAXS data.28 - The method of claim 27, wherein the microporous hydrocarbon polymer scaffold has an absolute tensile strength in the Machine Direction (MD) of from about 0.3 N / mm to about 2.0 N / mm.29 - The method of claim 27 or 28, wherein the microporous hydrocarbon polymer scaffold has a mass-per-area of between 0.5 g / m2and 3 g / m2.30 - The method of any one of claims 27 to 29, wherein the microporous hydrocarbon polymer scaffold has a bubble point of at least 2 bar.31 - A method of manufacturing a rechargeable battery, the method comprising:b. providing a battery separator according to any one of claims 1 to 21 ;c. wetting the battery separator;d. forming a stack by disposing the wet battery separator between an anode, and a cathode and inserting the stack in a battery housing; wherein at least one of the anode and the cathode comprises the alkali-metal.32 - The method of claim 32, wherein the wetting step is performed with a fluid that is an electrolyte of the battery or that comprises a solvent present in the electrolyte of the battery.33 - A method according to claim 32 or 33, wherein the electrolyte is a solvent-in-salt electrolyte.34 - A method according to any one of claims 31 to 33, wherein the alkali metal is selected from lithium or sodium.

Images