Composite membranes, electrochemical separators, and electrochemical devices

Abstract

A composite membrane comprising: a microporous polymer scaffold having a polymer scaffold matrix and 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; and wherein the composite membrane comprises a metalized surface region. Also described is an electrochemical device for use in electrolysis comprising: an anode, a cathode and an electrochemical separator, wherein the electrochemical separator is the composite membrane disclosed herein.

Description

3240 woolCOMPOSITE MEMBRANES, ELECTROCHEMICAL SEPARATORS, AND ELECTROCHEMICAL DEVICES FIELD OF THE INVENTION

[0001] This disclosure relates to composite membranes, electrochemical separators for use in water electrolysis and electrochemical devices comprising electrochemical separators.BACKGROUND

[0002] Electrochemical separators prevent electrical contact between the anode and the cathode within an electrochemical cell, 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.

[0003] It is desirable to use microporous polymer scaffolds as supports for zero-gap alkaline electrolysis separators due to their high specific tensile strength, fine pore structure, and chemical stability. However, these materials tend to have low surface energy, which encourages product gas bubbles from the electrolysis reaction to stick on the surface of the diaphragm adjacent to the electrodes. This can result in a loss of performance of the electrolyser because the bubbles reduce the area available for electrochemical catalysis and / or the area available for ion transport through the separator.

[0004] Thus, there is a need for improved membranes for use as electrochemical separators.

[0005] SUMMARY

[0006] According to a first aspect of the present disclosure, there is provided a composite membrane comprising: a microporous polymer scaffold having a polymer scaffold matrix and a plurality of scaffold pores having a scaffold pore volume, and a continuous ceramic phase of ceramic particles within the scaffold pore volume; wherein the continuous ceramic phase comprises an interconnected ceramic phase pore volume defined by inter-particle pores between ceramic particles; and wherein the composite membrane comprises a metalized surface region.

[0007] The metalized surface region may comprise a metalized region of the surface area of the composite membrane that is coated with metal or metal oxide. The metalized surface region may be metalized region that is limited to at least a portion of the microporous polymer scaffold matrix.

[0008] The continuous ceramic phase may comprise a three-dimensional packing arrangement of ceramic particles, and wherein the inter-particle pores may be defined at least3240 woolin part by an inter-particle distance within the packing arrangement, and wherein the interparticle distance is from about 0.5 times to about 3 times the ceramic particle diameter or effective diameter.

[0009] The three-dimensional packing arrangement of ceramic particles 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.

[0010] The three-dimensional packing arrangement of ceramic particles may exhibits at least one structure factor peak in Lorentz-corrected small angle X-ray scattering spectra of the composite membrane.

[0011] The electrochemical separator may comprises a ceramic phase yield strain and a composite membrane break strain, and wherein the composite membrane break strain is greater than the ceramic phase yield strain.

[0012] The three-dimensional packing arrangement may be characterized by at least one of: a packing density of the ceramic particles of from about 0.40 to about 0.85; a pore size (d) to inter-particle distance (ID) ratio (d / ID) from 0.2 to 2.0, or an inter-particle distance that is from 0.5 to about 3 times the ceramic particle diameter.

[0013] The ceramic particles may be selected from silicon dioxide, aluminum oxide, titanium dioxide, cerium oxide, zirconium dioxide, yttria stabilized zirconium dioxide, other oxides, and other classes of ceramics including carbides, nitrides, sulfides, borides, phosphides, selenides, titanates, carbonates, nitrates, sulfates, borates, and phosphates, or combinations thereof.

[0014] The ceramic particles may have a particle diameter of about 1 nm to about 1 pm.

[0015] The microporous polymer scaffold may be selected from at least one of a nonfluorinated polymer, a partially fluorinated polymer, a perfluorinated polymer, and any combination thereof.

[0016] The microporous polymer scaffold may comprise any one selected from polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), expanded polyethylene (ePE), expanded polytetrafluoroethylene (ePTFE), or combinations thereof.

[0017] The microporous polymer scaffold may have a bubble point pressure of equal to or greater than 0.5 bar.

[0018] The composite membrane may have a contact thickness of from about 1 pm to about 150 pm.

[0019] The metalized surface region may be a first metalized surface region, and the microporous polymer scaffold may further comprise a second metalized surface region.

[0020] The first metalized surface region and / or the second metalized surface region may comprise a region of polymer scaffold matrix that is covered with a metal or metal oxide.3240 wool

[0021] The metal may be selected from at least one of: copper, nickel, chromium, zirconium, titanium, ruthenium, rhodium, palladium, platinum, gold, osmium, iridium, or mixtures thereof, alloys thereof.

[0022] The metal oxide may be selected from at least one of: nickel oxide, chromium oxide, zirconium dioxide, titanium dioxide, ruthenium (IV) oxide, rhodium (III) oxide.

[0023] The first metalized surface region may extend from a first major surface of the microporous polymer scaffold to a depth of about 1 pm to about 5 pm into the microporous polymer scaffold.

[0024] The second metalized surface region may extend from a second major surface of the microporous polymer scaffold to a depth of about 1 pm to about 5 pm into the microporous polymer scaffold.

[0025] The first and / or second metalized surface region may be formed by one of sputtering metal onto the microporous polymer scaffold; evaporation deposition of metal onto the microporous scaffold; electroless plating of metal onto the microporous polymer scaffold.

[0026] According to a second aspect of the present disclosure there is provided an electrochemical device for use in water electrolysis comprising: an anode, a cathode and an electrochemical separator, wherein the electrochemical separator is a composite membrane according to the first aspect.

[0027] According to a third aspect, there is provided a method of making a composite membrane, the method comprising:a) obtaining a microporous polymer scaffold, wherein the microporous polymer scaffold has a polymer scaffold matrix and a plurality of scaffold pores, the microporous polymer scaffold having a scaffold pore volume;(b) incorporating ceramic particles into the scaffold pore volume of the microporous polymer scaffold;(c) forming a continuous ceramic phase in the scaffold pore volume, wherein the continuous ceramic phase comprises an interconnected ceramic phase pore volume defined by inter-particle pores between ceramic particles; and(d) metalizing a surface region of the composite membrane.

[0028] The method may further comprise comprises at least one of: sputtering metal onto the microporous polymer scaffold or composite membrane; evaporation deposition of metal onto the microporous polymer scaffold or composite membrane; electroless plating of metal onto the microporous polymer scaffold or composite membrane.3240 wool

[0029] The method step (d) may be performed before method step (c) such that the microporous polymer scaffold is provided with a metalized surface region. Or the method steps (b) and (c) may be performed before step (d).BRIEF DESCRIPTION OF FIGURES

[0030] The present disclosure will be better understood in view of the following figures. 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 be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the figures should not be construed as limiting.

[0031] Figure 1 depicts a simplified schematic diagram of a known liquid alkaline water electrolyzer.

[0032] 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;

[0033] Figure 2b is a schematic illustration depicting a portion of a composite membrane according to at least one embodiment of the present disclosure.

[0034] Figure 2c is an SEM image of a surface of a composite membrane having a continuous ceramic phase.

[0035] Figure 3 is an SEM image of a surface of a microporous scaffold for use in Example 1 , accordance with embodiments of the present disclosure.

[0036] Figure 4 is an SEM image of a surface of a microporous scaffold having a metalized surface region for use in Example 1 , in accordance with embodiments of the present disclosure.

[0037] Figure 5a is an SEM image of a surface of a composite membrane of Example 1 having a metalized surface region and continuous ceramic phase in accordance with the present disclosure.

[0038] Figure 5b is an SEM image of a surface of a composite membrane of Comparative Example having a continuous ceramic phase as described herein.

[0039] Figure 6 is a plot of high frequency resistance from electrochemical impedance spectroscopy for comparative example 1 and example 1.

[0040] Figure 7 is the slope of the ohmic region of the polarization curve comparing performance of comparative example 1 and example 1.

[0041] Figure 8 is a schematic depiction of parameters associated with the continuous ceramic phase overlaying an SEM of a representative example of the continuous ceramic phase (i.e. , an opaloid).3240 wool

[0042] Figure 9a is a schematic depiction of a cross-section of a neat opaloid comprising monodisperse sub-micron particles in a three-dimensional packing arrangement;

[0043] Figure 9b is a schematic depiction of two adjacent particles, each having a diameter (D) that are elements of a particle packing arrangement within an opaloid as is shown in Figure 9a;

[0044] Figure 10a depicts a comparison of specific surface area (SSA) measured by BET with expected particle size,

[0045] Figure 10b is a graphical illustration of a comparison of particle diameter calculated with SSA to the nominal sub-micron particle diameters reported by manufacturers;

[0046] Figure 11a 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.

[0047] Figure 11b is a graphical illustration of inter-particle distance (ID) determined from SAXS data as a function of nominal particle diameter (D) for opaloids prepared from silica submicron particles.

[0048] Figure 12 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)).

[0049] Figure 13 depicts a representative pore size distribution from BET / BJH analysis of an opaloid prepared from silica sub-micron particles having a diameter of approximately 12 nanometers.

[0050] Figure 14 is a schematic depiction of expected values of the ratio of pore diameter to particle diameter (d / D) for different tightly packed arrangements of sub-micron particles where the coordination number, n, is 3, 4, 6, or 8.DETAILED DESCRIPTION

[0051] Throughout the description and claims, the terms take the meanings explicitly defined herein, unless the context clearly dictates otherwise.

[0052] 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.3240 wool

[0053] The terms “comprises” and “comprising” mean to include, but are not limited to, such that further features may be present.

[0054] 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.

[0055] Figure 1 depicts a simplified schematic of a known electrochemical device 10 for use in liquid alkaline water electrolysis. The electrochemical device 10 includes an anode 12, a separator 14, and a cathode 16. All of the components in the electrochemical device 10 are, in use, partially or fully saturated with liquid electrolyte 18 (e.g., aqueous KOH) to enable ion conduction. Water may be fed to the electrochemical device 10 on the cathode 16 side. An exemplary half-cell reaction for the anode 12 is as follows: 2OH~ - O2+ H2O + 2e~. An exemplary half-cell reaction for the cathode 16 is as follows: 2H2O + 2e~ H2+ 2OH~.

[0056] The electrochemical separator 14 has a first major surface 13 that is near to the anode 12 and a second major surface 15 that is near to the cathode 16. In some embodiments, the first major surface 13 can be near to or adjacent the anode 12 and the second major surface 15 can be near to or adjacent to the cathode 16. In some embodiments, the first major surface 13 can be in direct contact with the anode 12 and the second major surface 15 can be in direct contact with the cathode 16. The electrochemical separator 14 has a thickness (T) which is measured as the distance from the first major surface 13 to the second major surface 15.

[0057] During use of the electrochemical device 10 in liquid alkaline water electrolysis, the concentration profile of oxygen across the electrochemical separator 14 may be at a maximum at the first major surface 13, whilst the concentration profile of hydrogen across the electrochemical separator 14 may be at a maximum at the second major surface 15. The concentration of oxygen decays down through the separator 14 towards the cathode 16 and the concentration of hydrogen decays down through the separator 15 towards the anode 12. The concentration profile will typically follow a characteristic first order decay throughout the thickness of the separator 14, assuming that the separator 14 has a uniform internal morphology. During use of the electrochemical device 10, gas bubbles may form at or on the first major surface 13 and second major surface 15. It is desirable to minimize the formation of gas bubbles because their presence on the first and second major surfaces can negatively3240 woolaffect the performance of the electrolyzer by reducing the surface area available for electrochemical catalysis and / or the area available for ion transport through the separator 14.

[0058] The present disclosure is directed at composite membranes which may have many advantageous properties for use in electrochemical separators. Through a unique balance of properties, the composite membranes may enable improvements over state-of-the-art separators in multiple ways (“improvement vectors”). For example, they may simultaneously enable some or all of the following improvements:1) Make the separator thinner and thereby reduce ionic resistance and improve the volumetric and gravimetric energy density of the electrochemical device.2) Increase the compressive pressure the separator can withstand without short circuiting, e.g., to improve the safety of the electrochemical device, or to enable higher compressive loads and thereby improve the performance of the electrochemical device by reducing contact resistances within the electrochemical cell.3) Reduce unwanted crossover of reactive species or other materials through the separator and thereby improve the safety of the electrochemical device and enhance the operational flexibility of the electrochemical device.4) Improve the handleability of the separator e.g., to enable efficient processing, shipping, handling, storage, and installation of the separator in the final application (i.e., in the electrochemical cell in the electrochemical device), simplifying logistics and thereby facilitating scale-up and cost-reduction of the electrochemical device.5) Enhance the operable temperature range of the separator and thereby improve the performance of the electrochemical device by enabling higher-temperature operation (resulting in e.g., faster electrode kinetics and / or higher electrolyte conductivity within the electrochemical cell).6) Improve the dimensional stability of the separator at high temperature and thereby improve the safety of the electrochemical device by preventing catastrophic failure during e.g., a puncture of the electrochemical cell.

[0059] These improvement vectors are often in tension, in particular item #1 may conflict with items #2 - #4. These tensions result in so-called “engineering trade-offs” between separator attributes, which may be embodied in ratios for a given separator, such as the ratio of ionic conductance to degree of protection against short circuits, or the ratio of ionic conductance to gas or liquid permeance, which the separators disclosed herein may improve.

[0060] The composite membranes may be readily wettable with aqueous liquid electrolyte to enable high ionic conductance. Furthermore, the composite membranes may be stable under extremely chemically aggressive conditions. Accordingly, when combined with a suitable electrolyte arrangement, the inventors have shown that the systems of the present disclosure are particularly effective for use as electrochemical separators.3240 wool

[0061] The composite membranes 40 of the present disclosure comprise a 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. Figure 2a is a schematic illustration of a cross-section of a representative microporous polymer scaffold 30 used in the composite membranes of the present disclosure. The microporous polymer scaffold 30 has a scaffold matrix 35 and scaffold pores 36. 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 (in the case of a tube these two surfaces correspond to the inner and outer diameters of the tube). The microporous polymer scaffold 30 may have a thickness, which is the distance between the first and second major exterior surfaces. 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 SEM image a composite membrane 40 having a continuous ceramic phase 31 formed from ceramic particles 32, where the microporous polymer scaffold is ePTFE and the ceramic particles 32 are silicon dioxide particles having a nominal diameter of 100nm.

[0062] 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. Agglomerations of particles extending outside the scaffold lack reinforcement and are subject to a wide range of mechanical problems (e.g. cracking, flaking). 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. In the case in which the polymeric scaffold matrix 35 remains exposed, the surface presented to the electrolyte and electrodes when the composite membrane 40 is used in an electrochemical separator may be significantly heterogenous with respect to surface energy, e.g. PTFE having a far lower surface energy than the continuous ceramic phase 31. Low surface energy regions of the surface will preferentially serve as bubble nucleation sites when the electrolyte is supersaturated with the product gases, as is the case adjacent to an active electrode. These3240 woolnucleation sites will accumulate a significant volume of gas in contact with the separator and electrode, impeding the flow of ions and reducing electrolyzer efficiency.

[0063] The composite membranes of the present disclosure comprise a microporous polymer scaffold having a metalized surface region, as shown in SEM images of Figures 3 to 5a. Figure 3 is an SEM image of a first major exterior surface of a microporous polymer scaffold for use in the composite membranes of the present disclosure (Example 1). The microporous polymer scaffold 30 comprises a surface deposited metalized region 47 shown in Figure 4. The porous polymeric scaffold matrix 35 is covered with metal or metal oxide 42 such that the scaffold matrix 35 (which in this particular example is fibrillated) is covered with metal or metal oxide 42. The scaffold matrix 35 in the surface region may be covered with metal or metal oxide 42 such that the metal or metal oxide 42 is cohesive with the scaffold matrix 35. In some embodiments, the metal or metal oxide 42 may be bonded or adhered to the scaffold matrix 35.

[0064] The depth of the metalized surface region 47 from the first major exterior surface of the scaffold into the thickness of the microporous polymer scaffold 30 will 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. For example, industrially relevant processes such as sputtering or evaporation are generally considered to apply only to the portion of the substrate in the “line of sight”. Typically, the metalized surface region extends from the first major exterior surface of the microporous polymer scaffold 30 to a depth of about 0.5 pm to about 5 pm, or about 1 pm to about 5 pm, 1 pm to about 4 pm, 1 pm to about 3 pm into the microporous polymer scaffold thickness.

[0065] The surface metalized microporous polymer scaffold is then used for the formation of a composite membrane 40 according to the present disclosure, and as shown in Figure 5a.

[0066] 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 the second major exterior surface of the microporous polymer scaffold 30 to a depth of about about 0.5 pm to about 5 pm, or about 1 pm to about 5 pm, 1 pm to about 4 pm, 1 pm to about 3 pm into the microporous polymer scaffold thickness.

[0067] In Example 1 (detailed below), the entire surface area of the first major exterior surface of the microporous polymer scaffold matrix 35 was coated with Nickel. Accordingly, after the manufacture of the composite membrane 40, any microporous polymer scaffold matrix 35 extending beyond the continuous ceramic phase 31 of the composite membrane 40 is covered with metal or metal oxide (metalized region 47) thus improving the homogeneity of surface energy across the first major exterior surface of the composite membrane 40. 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 the3240 wooltest methods disclosed herein). A hydrophilic surface is generally regarded as one having a water contact angle of less than 90°. The water contact angle of the metalized region 47 is less than 90 °. This in turn minimizes or eliminates bubble nucleation sites, when the composite membrane 40 is used as an electrochemical separator. In contrast, Figure 5b shows the composite membrane of Comparative Example 1 that does not comprise the metalized surface region according to the present disclosure, and the microporous scaffold 35 is clearly visible, protruding above the ceramic phase 31. The exterior surface of the composite membrane in Comparative Example 1 is therefore heterogenous in terms of surface energy. The exposed scaffold matrix 35 being more hydrophobic than the hydrophilic ceramic phase 31.

[0068] 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 provided with the surface deposited metalized region. For example, from about 50 - 100 % of surface area, by line sight, of the microporous polymer scaffold can be coated. It will be appreciated that when the composite membrane is formed comprising the metalized microporous polymer scaffold, then the portion of the surface area of the composite membrane that is metalized will be comparatively less since it is only the microporous polymer scaffold that is metalized. 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.

[0069] Figure 6 is a plot of high frequency resistance from electrochemical impedance spectroscopy for Comparative Example 1 and Example 1. The composite membrane of Comparative Example 1 (detailed below) did not comprise a microporous polymer scaffold matrix having a metalized surface region. The Y-axis corresponds to the total high frequency (ohmic) resistance observed at a given galvanostatic set point, which is on the X-axis. As the current increases, more and more hydrogen and oxygen product gases are formed, which can accumulate as bubbles on the surface of the electrodes and separators. The increase in (ohmic) resistance as a function of the presence of bubbles was significantly ameliorated in Example 1 due to the metal coating on the microporous polymeric scaffold. Figure 7 is a comparison of the slopes of the ohmic region of the polarization curves of Comparative Example 1 and Example 1. As shown, there is a 20% reduction in ohmic resistance in-situ for the composite membrane 40 of Example 1 compared to the composite membrane of the Comparative Example 1. This can be attributed to reduced surface inventory of bubbles across the first major surface of the composite membrane of Example 1.

[0070] The metal for forming the metalized surface region can be selected from at least one of copper, nickel, chromium, zirconium, titanium, ruthenium, rhodium, palladium, platinum,3240 woolgold, osmium, iridium, or mixtures thereof, alloys thereof. Where the composite membrane is intended to be used for an electrochemical separator in alkaline water electrolysis, it is desirable that the metal form an alkaline-stable coating. Accordingly, in these applications, the metal may be preferably at least one of nickel, chromium, zirconium, titanium or mixtures thereof, or alloys thereof.

[0071] The metal oxide for forming the metalized surface region can be selected from at least one of: nickel oxide, chromium oxide, zirconium dioxide, titanium dioxide, ruthenium (IV) oxide, rhodium (III) oxide. In the present disclosure, the metals deposited onto the microporous polymer scaffold (or the composite membrane) may be deposited in metal form and then converted to metal oxide form prior to or when used in electrochemical systems.

[0072] The metalized surface region (on one of both of the first or second major exterior surfaces) is 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. The metal or metal oxide substantially does not occlude the surface pores of the scaffold matrix, and therefore the scaffold matrix still comprises through-pores, and airflowthrough the scaffold is substantially maintained.

[0073] In some embodiments, the composite membrane may be formed (i.e., comprising the continuous ceramic phase within the scaffold pore volume), and then be provided with the metalized surface region. In such cases, the surface area of the composite membrane including the exposed microporous scaffold matrix and the exposed ceramic particles are coated with metal or metal oxide in a similar manner to that described above. This has a similar effect in that the homogeneity of the composite membrane surface in terms of surface energy can be improved, thus reducing possible bubble nucleation sites. In such embodiments, care must be taken to ensure airflow is maintained through the composite membrane, which has comparatively a much smaller pore size than the microporous polymer scaffold prior to formation of the composite membrane.

[0074] The composite membrane has a first major exterior surface and a second major exterior surface. One or both of the first and second major exterior surfaces can be coated with metal or metal oxide. It will be appreciated that in other embodiments, only a portion of the first major exterior surface of the composite membrane and / or a portion of the second major exterior surface of the composite membrane may be provided with the surface deposited metalized region. For example, from about 50 - 100 % of surface area, by line sight, of the composite membrane can be coated. For example, the exposed portions of the microporous polymer scaffold of the composite membrane may be selectively coated with metal or metal oxide.

[0075] The composite membrane 40 of the present disclosure are membrane layers that comprise a microporous polymer scaffold comprising a plurality of scaffold pores having a3240 woolscaffold 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. Figure 2a is a schematic illustration of a cross-section of a representative microporous polymer scaffold 30 used in the composite membranes of the present disclosure. The microporous polymer scaffold 30 has a scaffold matrix 35 and scaffold pores 36.

[0076] The composite membranes 40 of the present disclosure may be highly porous (for example, from about 30 vol % to about 75 vol%) with low liquid permeance (for example, < 100 L / m2 / h / bar or < 50 L / m2 / h / bar or < 10 L / m2 / h / bar at a differential pressure in the range of from 1 to 50 bar and with isopropyl alcohol (I PA) as the challenge fluid). Conventional porous diaphragms typically have high liquid permeance, which requires careful control of the pressure gradient across the diaphragm during electrolyzer operation. However, the composite membranes 40 of the present disclosure have low liquid permeance despite being porous. These composite membranes therefore can prevent gas-crossover in multiple ways. By reducing liquid permeance compared to known porous diaphragms, there is little or no convection flow through the separators.

[0077] The composite membrane 40 of the present disclosure may be highly porous (for example, from about 30 vol % to about 75 vol%) with a high bubble point (for example, from about 1 bar to about 30 bar), and thus, have a very small pore size. Conventional electrochemical separators have relatively large pores with a low bubble point pressure. In comparison, the composite membrane 40 of the present disclosure are highly porous with a high bubble point pressure which makes it harder to expel the gas from the pores and more likely that the pores will retain liquid via capillary forces. This provides an extra level of safety.

[0078] The microporous polymer scaffold is selected from at least one of a non-fluorinated polymer, a partially fluorinated polymer, a perfluorinated polymer, and any combination thereof. The microporous polymer scaffold may comprise polyolefins, optionally polyethylene (PE) or polypropylene (PP). The microporous polymer may comprise any one selected from a polytetrafluoroethylene (PTFE), a polyethylene (PE), or a copolymer of PTFE and PE, expanded polyethylene (ePE), expanded polytetrafluoroethylene (ePTFE), or combinations thereof.

[0079] The microporous polymer scaffold 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 membrane 40.

[0080] 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”) in response to capillary forces during wetting and / or drying as a result of the process to produce the composite membrane 40 The characteristics of the microporous polymer scaffold described in the proceeding paragraphs relate to microporous polymer scaffold properties prior to subsequent processing or modification, such as, for example, formation of the composite membrane 40 of the present disclosure.

[0081] 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.

[0082] 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 90 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 83 vol% to about 91 vol%.

[0083] 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.

[0084] The bubble point pressure can provide a measure of the largest pore size according to the Young-Laplace equation:4ylvcos9d3240 woolwhere P is the pressure required to dewet a liquid from a cylindrical pore, ytvis the liquid surface tension, Q is the contact angle, and d is the pore diameter.

[0085] 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 ceramic particle diameter of the ceramic particle forming the continuous ceramic phase. This may permit the microporous polymer scaffold to provide sufficient reinforcement for the formation of the continuous ceramic phase, and may minimize the formation of cracks and defects in the ceramic phase during the manufacturing process. For example, the largest pore size may be from 3 to 15 times the ceramic particle diameter. The microporous polymer scaffolds used in the embodiments comprising more than one composite membrane 40 may be essentially identical, or they may be different. 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., ePTFE), and a second microporous polymer scaffold made of a second polymer (e.g., ePE). Incorporating composite membrane 40 from 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 much more thermally stable scaffold (e.g., ePTFE) to provide mechanical integrity at elevated temperature.

[0086] 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.

[0087] Opaloids are solid materials comprising sub-micron particles in tightly packed arrangements where the arrangements have a degree of order that may range from crystalline to nearly amorphous. 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). 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 characteristic repeating 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. Opaloids may have higher porosity than sol-gel solids while maintaining a narrow distribution of small pore3240 woolsizes. 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.

[0088] 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. Within the context of the present application, the continuous ceramic phase may be also be known as continuous inorganic phase of inorganic particles. Similarly, 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 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.

[0089] 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.

[0090] 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 hexagonal close packed). An array will comprise a repeating unit cell, having two or three unit cell axes. The axes may, but need 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.3240 wool

[0091] Colloidal glass transition dynamics enable ordered tight packing of colloidal particles, characteristic of the continuous ceramic phase of the present disclosure. 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). In contrast, sol-gel solids are solid materials characterized by poorly ordered fractal and aggregate structures. Sol-gel processes are characterized by gelation dynamics. These poorly ordered structures are an inherent result of the gelation dynamics characteristic of sol-gel processes. Such gelation produces aggregates at concentrations below the colloidal glass transition, which prevents the solids from consolidating into the tight, ordered packing arrangements characteristic of opaloids.

[0092] As illustrated in Figure 2b, the inventors have shown that the porous interconnected 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 inter-particle 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 the scaffold matrix 35). Additionally, cracks or defects 37 may be present within the composite membrane 40.

[0093] The ceramic phase 31 (e.g., an opaloid, or condensed colloidal phase) 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 at least about 1 mm to 1500mm 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. The continuous 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. Figure 9a shows a schematic of a cross-section of a neat opaloid 60 comprising monodisperse sub-micron3240 woolparticles 62 in a three-dimensional arrangement. The sub-micron particles in Figure 9a 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) 61 that extend through the entire thickness of the opaloid, and may comprise other defects (e.g., cracks) 63 that do not extend through the entire thickness. A neat opaloid is an opaloid (i.e., a continuous ceramic phase, or condensed colloidal phase) without mechanical reinforcement (i.e., the microporous polymer scaffold).

[0094] As described above, opaloids comprise tightly packed three-dimensional arrangements of sub-micron particles. Figure 9b 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 inter-particle 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 submicron 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). 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 sub-micron particles may have direct contact with each other. The opaloid may substantially lack an organic binding agent (e.g., a polymeric binder). The opaloid may comprise sub-micron particles (e.g., the ceramic particles disclosed herein) that are bonded together substantially by van der Waals forces, by inorganic bonds, or by a combination of the two. The inventors have shown that the properties of a neat opoloid are comparable to the morphological properites of the continous ceramic phase of the present disclosure, i.e. within the microporous polymer scaffold.

[0095] 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 of the continuousceramic phase may be from about 0.5 times to about 3 times the ceramic particle diameter. The inter-particle distance of the continuous ceramic phase may be from about 0.6 times to about 3 times the ceramic particle diameter. The inter-particle distance of the continuous ceramic phase 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 1 times to about 1.5 times the ceramic particle diameter.

[0096] 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 8, which depicts a representative continuous ceramic phase (i.e., an example opaloid). 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 ceramic phase. 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. 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 (pp) 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 (Vsphere and Asphere respectively) based on its diameter (DD). The relevant equations for a sphere are as follows:3240 wool

[0097] Figure 10 illustrates how SSA may be used to estimate the particle size of an opaloid, and thus of continuous ceramic phase of the present disclosure. 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 10a 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 and assuming a density of silica of 2.2 g / cc. Figure 10b compares the particle diameter calculated from the SSA data to the nominal diameters reported by the manufacturers. The dashed line in Figure 10b is the 45° line passing through the origin and is included as a guide to the eye. As shown in Figure 10b, 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 10, may be used to calculate the effective diameter of the sub-micron particles of the opaloid. In the case that the sub-micron particles contain intra-particle 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 intra-particle porosity of the sub-micron particle.

[0098] 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 inter-particle distance.

[0099] The three-dimensional packing arrangement of the continuous ceramic phase 31, and ceramic-catalsyt phase 28 may comprise a packing arrangement selected from facecentered 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 composite membrane. A structure factor peak as used herein can be defined as in “SciPy find peaks”:(https: / / docs.scipy.org / doc / scipy / reference / generated / scipy.signal.find peaks.htmi, accessed 19 December 2024): “all local maxima by simple comparison of neighboring values". 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 thedetected peak. For example, composite membranes 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 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.

[0100] Figure 11a 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 SiC>2 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 = 277 / 91. As shown in Figure 11b, 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 SiC>2 sub-micron particles. The dashed line in Figure 11b 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-particle distances, 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 : q q-i : 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 : 2.583240 wool: 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 11a, peaks are observed at peak position ratios qi / qi : q2 / Qi : q3 / qi : ... qn / Qi 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.

[0101] 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. In contrast, the SAXS data depicted in Figure 12, which 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)), 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 12, 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).

[0102] 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 40. Tensile3240 wooltesting of the composite membrane 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 composite membrane will show a break strain of the composite membrane 40. The composite membrane 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.

[0103] The continuous ceramic phase 31 (e.g., an opaloid, or colloidal condensed phase) may extend substantially through the entire thickness of the microporous polymer scaffold 30.

[0104] The continuous ceramic phase 31 (e.g., an opaloid, or colloidal condensed phase) 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 (e.g., an opaloid without an integrated microporous polymer scaffold), 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.

[0105] The continuous ceramic phase 31 (e.g., an opaloid, or condensed colloidal phase) itself may be considered to have a ceramic phase pore volume and pore size (or a colloidal condensed 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 size range 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 composite membrane 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 composite membrane 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).3240 wool

[0106] 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 9a shows a schematic of a cross-section of a neat opaloid comprising monodisperse sub-micron particles 60 in a three-dimensional packing arrangement, having an inter-particle pore volume 64. The pore volume 64 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 13 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 13 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 14 shows the expected values of d / D for different tightly packed arrangements with different coordination numbers (n). For many opaloid packing arrangements, 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.

[0107] 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.

[0108] 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 2.0,3240 woolor 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.

[0109] In the description of the continuous ceramic phase 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.

[0110] The composite membrane may have a bubble point pressure of from about 1 bar and 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 composite membrane 40 in accordance with the test methods set out below.

[0111] The composite membrane 40 may have a porosity defined by the void spaces formed by the interconnected pore volume (e.g., the inter-particle pores as defined above) of the continuous ceramic phase, any intra-particle pore volume, any interfacial particle-scaffold pores, any defects (e.g., cracks), if any, in the continuous ceramic phase, 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 40 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 40 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 about3240 wool25 vol% to about 65 vol%, or from about 25 vol% to about 70 vol%, or from about 25 vol% to about 75 vol%.

[0112] The composite membrane 40 may have a low liquid permeance. The liquid permeance may be < 100 L / m2 / h / bar or < 50 L / m2 / h / bar or < 10 L / m2 / h / bar at a differential pressure in the range of from 1 to 50 bar and with isopropyl alcohol (I PA) as the challenge fluid. In some embodiments it may be preferable to substitute a different challenge fluid, for example if required for material compatibility, so long as the rheological properties are similar to I PA and the values of liquid permeance are adjusted for the viscosity of the new challenge fluid under the assumption that the liquid permeance is inversely proportional to the viscosity of the challenge fluid (i.e., for a challenge fluid with double the viscosity of IPA the permeance should be half of what would be measured with IPA).

[0113] The ceramic particles 32 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). As used herein, ceramic particles 32 are intended to encompass a subset of inorganic submicron 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. Accordingly, the ceramic particles may also be referred to as inorganic particles, or inorganic submicron particles. For example, see Sudha et al. describe who 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. These3240 woolmaterials 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...”.

[0114] The ceramic particles 32 may be comprise silicon dioxide, aluminium 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. When the composite membrane is for use in alkaline water electrolysis, the ceramic particles 32 may comprise comprise zirconium dioxide, titanium dioxide, magnesium hydroxide, barium sulfate, or combinations thereof.

[0115] The ceramic particles 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 500 nm, or about 1 nm to 100 nm, or about 1 nm to 80 nm, or about 5 nm to 70 nm, or about 4 nm to 50 nm, or about 5 nm to 50 nm, or about 5 nm to 75 nm, or about 2 nm to 60 nm, or about 2 nm to 50 nm, or about 2 nm to 25 nm. The ceramic particles 32 may have a particle diameter (or effective particle diameter) of up to and including 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. Without wishing to be bound by theory, it is hypothesized that 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 composite membrane 40 during fabrication when such particles are used.

[0116] 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.3240 wool

[0117] 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 40 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.

[0118] The composite membrane 40 may have a bubble point pressure of from about 1 bar and 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. The composite membrane 40 may have a bubble point pressure of from about 5 bar and about 15 bar, or about 5 bar and about 20 bar, or about 5 bar and about 25 bar, about 5 bar and about 27 bar, or about 5 bar and about 30 bar. The composite membrane may have a bubble point pressure of from about 10 bar and about 15 bar, or about 10 bar and about 20 bar, or about 10 bar and about 25 bar, about 10 bar and about 27 bar, or about 10 bar and about 30 bar. The composite membrane 40 may have a bubble point pressure of from about 15 bar and about 20 bar, or about 15 bar and about 25 bar, about 15 bar and about 27 bar, or about 15 bar and about 30 bar. The composite membrane 40 may have a bubble point pressure of from_about 20 bar and about 25 bar, about 20 bar and about 27 bar, or about 20 bar and about 30 bar. The composite membrane 40 may have a bubble point pressure of from about 25 bar and about 27 bar, or about 25 bar and about 30 bar. The bubble point pressure of the composite membrane is measured as indicated in the test methods described herein.Test Methods

[0119] Non-Contact Thickness (e.g., of the Microporous Polymer Scaffold)

[0120] 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 scaffold 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.

[0121] Contact Thickness (e.g., of the composite membrane)3240 wool

[0122] Samples were analyzed with a Mitutoyo Litematic handheld micrometer with a measuring force of 0.01 Newtons to determine the contact thickness.

[0123] Electrochemical Test Method:

[0124] Test was conducted at Fraunhofer-IFAM, Dresden, Germany. Electrochemical Separator was placed in a custom 10cm2active area alkaline electrolysis cell in a zero-gap arrangement with circulating 30 weight % KOH at atmospheric pressure. Cell inlet electrolyte temperature was maintained at 80°C by use of a line heater. Nickel felt electrodes (Baekert) in contact with nickel current collectors were used on both the anode and cathode side. A preconditioning 15 minute galvanostatic hold of 0.15 A / cm2was applied before measurements.

[0125] Polarization Curve

[0126] Polarization Curves were generated by 10 minute galvanostatic holds at 0.01, 0.025, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.60, 0.70, 0.80, 0.90, and 1.00 A / cm2. An estimation of the resistance of the system may be made by taking the slope of the final 5 points.

[0127] Bubble Resistance from High Frequency Resistance from Electrochemical Impedance Spectroscopy:

[0128] Electrochemical Impedance Spectroscope was performed by imposing an AC voltage perturbation at 5% of the voltage of the galvanostatic setpoint being interrogated. Setpoints were 1.0V, where the water electrolysis reaction is not occurring and the system is bubble-free, 0.05 A / cm2, and 0.60 A / cm2. Higher galvanostatic set-points correspond to more gas production. The ohmic portion of the cell’s impedance was inferred from the minimum real-axis intercept of the Nyquist plot. An estimation of the bubble resistance may be made by subtracting the 0.60 A / cm2condition’s high frequency resistance from the high frequency resistance of the 1.0V condition.

[0129] Water Droplet Contact AngleWater droplet contact angle was assessed by used of a Kruss Goniometer (DSA100). The static contact angle of a 50 pL droplet was used, averaging each side of the droplet.

[0130] Mass per Area (e.q., of the Microporous Polymer Scaffold)

[0131] 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 on3240 woola conventional laboratory balance. The mass-per-area (M / A) was then calculated as the ratio of the measured mass to the known area.

[0132] Bulk Density (e.q., of the Microporous Polymer Scaffold)

[0133] The bulk density of the microporous polymer scaffold was calculated by dividing its mass-per-area by its non-contact thickness.

[0134] Skeletal Density (e.q., of the Microporous Polymer Scaffold)

[0135] 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.

[0136] Sample Skeletal Density = Sample Mass I Sample Volume

[0137] Sample Volume = Sample Chamber Volume - (Expansion Chamber Volume / ((Gauge Pressure After Fill / Gauge Pressure After Expansion) - 1))

[0138] Porosity (e.q., of the Microporous Polymer Scaffold)

[0139] 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:

[0140] Porosity = ((Skeletal Density - Bulk Density) / Skeletal Density)*100% [Vol%]

[0141] Absolute tensile strength (e.q., of the Microporous Polymer Scaffold) [first and second directions]

[0142] 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.

[0143] Matrix tensile strength (e.q., of the Microporous Polymer Scaffold) [firstand second directions]3240 wool

[0144] 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 was calculated 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:

[0145] Matrix Tensile Strength = (Absolute Tensile Strength / Non-Contact Thickness) / (Bulk Density / Skeletal Density) [MPa]

[0146] Scanning Electron Microscopy (SEM)

[0147] Samples of neat opaloids and composite membranes were carefully mounted to SEM stubs using double-sided conductive tape. Cross-sections of composite membranes were prepared using a Gatan® I Ilion2 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.

[0148] Small-Angle X-ray Scattering (SAXS)

[0149] 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, A according to the expression: q = 47rsin(0) . 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: " finds3240 woolall local maxima by simple comparison of neighboring values." For example, a peak data point will have 2 neighboring values of lesser value. 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).

[0150] N2 Sorption BET Specific Surface Area (SSA) and Pore Size Distributions

[0151] 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)”. For the data in the Figures, 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.

[0152] Volume-specific surface area (e.g., of the Microporous Polymer Scaffold)3240 wool

[0153] The specific surface area of the microporous polymer scaffold was normalized to account for differences in polymer densities by multiplying by the skeletal density of the microporous polymer scaffold:

[0154] Volume-specific surface area (m2SUrface / cc) = Specific surface area (m2SUrface / g) * Skeletal density (g / cc)

[0155] Area-normalized true surface area (e.g., of the Microporous Polymer Scaffold)

[0156] The area-normalized true surface area of the microporous polymer scaffold was calculated by multiplying its specific surface area by its mass per area:

[0157] Area-normalized true surface area (m2SUrface / m2) = Specific surface area (m2SUrface / g) * Mass per area (g / m2)

[0158] Capillary flow porometryCapillary flow porometry (CFP) measurements were performed using a Quantachrome capillary flow porometer. Adhesive backers (10 mm diameter) were applied to samples, which were die cut. Silicone oil (surface tension (yiv) about 19.75 mN / m) was applied and wet curves were collected over the full pressure range (about 0.25 to 392 psig or about 0.017 to 27 bar). Equivalent pore diameters were determined using the Young-Laplace equation with a contact angle value (0) of 0°.

[0159] Bubble Point Pressure

[0160] 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:4ylvcos9dwhere P is the pressure required to dewet a liquid from a cylindrical pore, ytvis the liquid surface tension, Q is the contact angle, and d is the pore diameter.

[0161] 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 between3240 woolthe 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).

[0162] Mean Flow Pore Diameter

[0163] 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.

[0164] Liquid Permeance (e.q. of a porous diaphragm for LA WE)

[0165] A 50 mm diameter sample was cut and placed inside a METcell 2-inch Crossflow cell from Evonik (parts METXF-2.5-136 and METXF-2.5-137) liquid flow cell shown in Figure 30. A layer of hydrophilic PVDF membrane (part GVWP04700 from Millipore Sigma) was placed in between the sample and the metal frit support to prevent damage to the sample. Isopropyl alcohol was pressurized to between 1-50 bar via a head of pressurized nitrogen and flowed through the sample for 30 minutes. The pressure was selected to provide a reasonable test time for a particular sample. The permeate alcohol was collected at the outlet of the cell in a flask and its mass measured on a conventional laboratory scale to determine the permeance of the sample per the following equation: Permeance = Permeate Mass / Permeate Density / ((Sample Diameter / 2)A2*pi) / Flow Time / Pressure.EXAMPLESExample 1

[0166] An ePTFE microporous polymer scaffold was produced following the teachings of U.S. Patent 3,953,566 to W. L. Gore & Associates. The ePTFE microporous polymer scaffold had the following properties: 3.3 bar bubble point, mass per area of 11.6 g / m2.

[0167] The ePTFE microporous polymer scaffold was placed on the stage of a Cressington 208HR vacuum sputtering unit equipped with a thickness monitor. A fresh nickel3240 woolsputtering target was used. A sputtering current of 80mA was used, until a thickness of 20nm on the first major exterior surface of the ePTFE microporous polymer scaffold was achieved.

[0168] The ePTFE microporous polymer scaffold was then flipped over to coat the second side, and the sputtering was repeated, with the same settings. Surface hydrophilicity was assessed visually by placing a 50pL water droplet on the surface with a micropipette. The metallized microporous polymeric scaffold is shown in Figure 4.

[0169] The nickel coated ePTFE microporous polymer scaffold was restrained in an 8-inch diameter metal hoop and tensioned by hand to remove wrinkles, resulting in a restrained the ePTFE microporous scaffold in the 8-inch hoop.

[0170] An imbibing fluid was prepared by combining a colloidal dispersion of yttria-stabilized zirconia nanoparticles (ZRYS3 available from Nyacol Nano Technologies, Inc.) with an aqueous wetting package as follows. The nanoparticles were nominally 3 mol% yttria, 32 nanometers in diameter (D), and the as-received colloidal dispersion was 52 mass% in water. To the as-received colloidal dispersion, 3 mass% 1 -hexanol and 3 mass% Tergitol TMN-10 were added, and the mixture was agitated vigorously to emulsify the 1 -hexanol. About 1 g of the mixture was pipetted onto a first surface of the restrained ePTFE microporous polymer scaffold and spread evenly using the side of a plastic rod until the mixture fully wetted the restrained ePTFE microporous polymer scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the ePTFE microporous polymer scaffold with a lint-free cloth. The 8-inch hoop was flipped over such that a second surface of the ePTFE microporous polymer scaffold was facing upwards. About 0.5 g of the mixture was pipetted onto the second surface of the restrained ePTFE microporous polymer scaffold and spread evenly using the side of the plastic rod (about 30 seconds). Excess imbibing fluid was carefully removed from both of the surfaces of the ePTFE microporous polymer scaffold by wiping them with a lint-free cloth. The imbibed ePTFE microporous polymer scaffold was then dried in an oven set to 65°C until visibly dry (about 10 minutes and then heat treated in a hot air convection oven at 150°C for an additional 30 minutes). The result was a composite membrane according to the present disclosure. The porosity of which is defined by a network of nanoparticles within the pores of the microporous membrane. The composite membrane is also referred to a membrane-reinforced opaloid (MRO).

[0171] This Example was assessed in an electrochemical test as described in the Test Methods section. An SEM of the final composite membrane is shown in Figure 5.Comparative Example

[0172] An ePTFE microporous polymer scaffold was produced following the teachings of U.S. Patent 3,953,566 to W. L. Gore & Associates. The ePTFE microporous polymer scaffold had the following properties: 3.3 bar bubble point, mass per area of 11.6 g / m2.

[0173] The ePTFE microporous polymer scaffold was restrained in an 8-inch hoop.3240 wool

[0174] An imbibing fluid was prepared by combining a colloidal dispersion of yttria-stabilized zirconia nanoparticles (ZRYS3 available from Nyacol Nano Technologies, Inc.) with an aqueous wetting package as follows. The nanoparticles were nominally 3 mol% yttria, 32 nanometers in diameter (D), and the as-received colloidal dispersion was 52 mass% in water. To the as-received colloidal dispersion, 3 mass% 1 -hexanol and 3 mass% Tergitol TMN-10 were added, and the mixture was agitated vigorously to emulsify the 1 -hexanol. About 1 g of the mixture was pipetted onto a first surface of the restrained ePTFE microporous polymer scaffold and spread evenly using the side of a plastic rod until the mixture fully wetted the restrained ePTFE microporous polymer scaffold (about 30 seconds). Excess imbibing fluid was removed by wiping the surface of the ePTFE microporous polymer scaffold with a lint-free cloth. The 8-inch hoop was flipped over such that a second surface of the ePTFE microporous polymer scaffold was facing upwards. About 0.5 g of the mixture was pipetted onto the second surface of the restrained ePTFE microporous polymer scaffold and spread evenly using the side of the plastic rod (about 30 seconds). Excess imbibing fluid was carefully removed from both of the surfaces of the ePTFE microporous polymer scaffold by wiping them with a lint-free cloth. The imbibed ePTFE microporous polymer scaffold was then dried in an oven set to 65°C until visibly dry (about 10 minutes and then heat treated in a hot air convection oven at 150°C for an additional 30 minutes, the result was a composite membrane a continuous ceramic phase. The composite membrane is also referred to a membrane-reinforced opaloid (MRO).Example 2

[0175] A sample of the ePTFE microporous scaffold as in Comparative example 1 was restrained in a 6-inch PLA hoop. This hoop was placed in a Denton Vacuum Desktop Pro Sputtering Coaterwith an 80 % Nickel, 20% Chromium Target (Plasmaterials). Plasma deposit at a power level of 100W was applied for a period of 5 minutes, with an estimated coating thickness of 20nm (measured at same conditions on flat PET control coupon). The sample was then imbibed as in example 1 and a composite membrane according to the present disclosure was formed using the same procedure as in example 1.Example 3

[0176] A gel-processed microporous polyethylene polymer scaffold having the following properties: 1.3 bar bubble point, mass per area of about 3.1 g / m2was restrained in a 6-inch PLA hoop. This hoop was placed in a Denton Vacuum Desktop Pro Sputtering Coater with an 80 % Nickel, 20% Chromium Target (Plasmaterials). Plasma deposit at a power level of 100W was applied for a period of 5 minutes, with an estimated coating thickness of 20nm (measured at same conditions on flat PET control coupon). The coated sample was then imbibed as in example 1 and a composite membrane according to the present disclosure was formed using the same procedure as in example 1.3240 woolExample 4

[0177] A sample of the ePTFE microporous scaffold as in Comparative example 1 was restrained in a 6-inch PLA hoop. This hoop was placed in the active chamber of the metal evaporator (Denton Vacuum DV-502A). The crucible (Alumina coated Tungsten - Kurt J Lesker) was filled with 80 / 20 Ni / Cr pellets (99.95% Pure, Kurt J Lesker). The crucible was heated to temperature for 2-3 minutes, with an expected coating thickness of 10nm (measured at same conditions on flat PET control coupon). The coated sample was then imbibed as in example 1 and a composite membrane according to the present disclosure was formed using the same procedure as in example 1.Example 5

[0178] A sample of the ePTFE microporous scaffold as in Comparative example 1 was restrained in a 6-inch PLA hoop. This hoop was placed in the active chamber of the metal evaporator (Denton Vacuum DV-502A). The crucible (Alumina coated Tungsten - Kurt J Lesker) was filled with Nickel pellets (99.95% Pure, Kurt J Lesker). The crucible was heated to temperature for 3-4 minutes, with an expected coating thickness of 20nm (measured at same conditions on flat PET control coupon). This process was repeated such that the ePTFE microporous scaffold was coated on each side. The coated sample was then imbibed as in example 1 and a composite membrane according to the present disclosure was formed using the same procedure as in example 1.

[0179] The invention of this application has been described above both generically and with regard to specific embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments without departing from the scope of the disclosure. Thus, it is intended that the embodiments cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

3240 woolCLAIMS:

1. A composite membrane comprising:a microporous polymer scaffold having a polymer scaffold matrix and a plurality of scaffold pores having a scaffold pore volume, and a continuous ceramic phase of ceramic particles within the scaffold pore volume;wherein the continuous ceramic phase comprises an interconnected ceramic phase pore volume defined by inter-particle pores between ceramic particles; andwherein the composite membrane comprises a metalized surface region.

2. The composite membrane of claim 1 , wherein the metalized surface region comprises a metalized region of the surface area of the composite membrane that is coated with metal or metal oxide.

3. The composite membrane of claim 1 or 2, wherein the metalized surface region is a metalized region that is limited to at least a portion of the microporous polymer scaffold matrix.

4. The composite membrane of any one of claims 1 to 3, wherein the continuous ceramic phase comprises a three-dimensional packing arrangement of ceramic particles, and wherein the inter-particle pores are defined at least in part by an inter-particle distance within the packing arrangement, and wherein the inter-particle distance is from about 0.5 times to about 3 times the ceramic particle diameter or effective diameter.

5. The composite membrane of claim 4, wherein the three-dimensional packing arrangement of ceramic particles comprises a packing arrangement selected from facecentered cubic packing, hexagonal close packing, body-centered cubic packing, simple cubic packing, random close packing, liquid like packing, and combinations thereof.

6. The composite membrane of claim 4 or 5, wherein 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 composite membrane.

7. The composite membrane of any one of claims 1 to 6, wherein the electrochemical separator comprises a ceramic phase yield strain and a composite membrane break strain, and wherein the composite membrane break strain is greater than the ceramic phase yield strain.

8. The composite membrane of any one of claims 5 to 7, wherein the three-dimensional packing arrangement is characterized by at least one of:3240 woola packing density of the ceramic particles of from about 0.40 to about 0.85;a pore size (d) to inter-particle distance (ID) ratio (d / ID) from 0.2 to 2.0, oran inter-particle distance that is from 0.5 to about 3 times the ceramic particle diameter.

9. The composite membrane of any one of the preceding claims, wherein the ceramic particles are selected from silicon dioxide, aluminum oxide, titanium dioxide, cerium oxide, zirconium dioxide, yttria stabilized zirconium dioxide, other oxides, and other classes of ceramics including carbides, nitrides, sulfides, borides, phosphides, selenides, titanates, carbonates, nitrates, sulfates, borates, and phosphates, or combinations thereof.

10. The composite membrane of any one of the preceding claims, wherein the ceramic particles have a particle diameter of about 1 nm to about 1 pm.

11. The composite membrane of any one of the preceding claims, wherein the microporous polymer scaffold is selected from at least one of a non-fluorinated polymer, a partially fluorinated polymer, a perfluorinated polymer, and any combination thereof.

12. The composite membrane of any one of the preceding claims, wherein the microporous polymer scaffold comprises any one selected from polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), expanded polyethylene (ePE), expanded polytetrafluoroethylene (ePTFE), or combinations thereof.

13. The composite membrane of any one of the preceding claims, wherein the microporous polymer scaffold has a bubble point pressure of equal to or greater than 0.5 bar.

14. The composite membrane of any one of the preceding claims, wherein the composite membrane has a contact thickness of from about 0.5 pm to about 150 pm.

15. The composite membrane of any one of the preceding claims, wherein the metalized surface region is a first metalized surface region, and the microporous polymer scaffold further comprises a second metalized surface region.

16. The composite membrane of claim 15, wherein the first metalized surface region and / or the second metalized surface region comprises a region of polymer scaffold matrix that is covered with a metal or metal oxide.3240 wool17. The composite membrane of claim 16, wherein the metal is selected from at least one of: copper, nickel, chromium, zirconium, titanium, ruthenium, rhodium, palladium, platinum, gold, osmium, iridium, or mixtures therefore, or alloys thereof.

18. The composite membrane of claim 16, wherein the metal oxide is selected from at least one of: nickel oxide, chromium oxide, zirconium dioxide, titanium dioxide, ruthenium (IV) oxide, rhodium (III) oxide.

20. The composite membrane of any one of claims 15 to 18, wherein the first metalized surface region extends from a first major surface of the microporous polymer scaffold to a depth of about 1 pm to about 5 pm into the microporous polymer scaffold.

21. The composite membrane of any one of claims 15 to 18, wherein the second metalized surface region extends from a second major surface of the microporous polymer scaffold to a depth of about 1 pm to about 5 pm into the microporous polymer scaffold.

22. The composite membrane of any one of claims 15 to 18, wherein the first and / or second metalized surface region is formed by one of sputtering metal onto the microporous polymer scaffold; evaporation deposition of metal onto the microporous scaffold; electroless plating of metal onto the microporous polymer scaffold.

23. An electrochemical device for use in electrolysis comprising:an anode, a cathode and an electrochemical separator, wherein the electrochemical separator is a composite membrane according to any one of claims 1 to 22.

24. A method of making a composite membrane, the method comprising:a) obtaining a microporous polymer scaffold, wherein the microporous polymer scaffold has a polymer scaffold matrix and a plurality of scaffold pores, the microporous polymer scaffold having a scaffold pore volume;(b) incorporating ceramic particles into the scaffold pore volume of the microporous polymer scaffold;c) forming a continuous ceramic phase in the scaffold pore volume, wherein the continuous ceramic phase comprises an interconnected ceramic phase pore volume defined by inter-particle pores between ceramic particles; and(d) metalizing a surface region of the composite membrane.3240 wool25. The method of claim 24, wherein (c) comprises at least one of: sputtering metal onto the microporous polymer scaffold or composite membrane; evaporation deposition of metal onto the microporous polymer scaffold or composite membrane; electroless plating of metal onto the microporous polymer scaffold or composite membrane.26 The method of claim 24 or 25, wherein method step (d) is performed before method step (c) such that the microporous polymer scaffold is provided with a metalized surface region.

27. The method of claim 24 or 25, wherein the method steps (b) and (c) are performed before step (d).

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