Monolithic composite membrane with continuous interpolymer phase

Abstract

Embodiments relate to composite membranes having a microporous polymer structure, and ion exchange materials that form a continuous ionomer phase within the composite membrane. A continuous ionomer phase refers to the absence of any internal interfaces in the ionomer layer or between any number of coatings of ion exchange material that are layered on top of one another. The composite membrane has a haze change of 0% or less after a blister test procedure. No blisters or bubbling is formed on the composite membrane after the blister test procedure. The composite membrane has a haze value between 5% and 95%, between 10% and 90%, or between 20% and 85%. The composite membrane can have a thickness greater than 17 microns at 0% relative humidity.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201880095988.0, entitled "Integral Composite Membrane with Continuous Ionomer Phase". The parent application is the Chinese national phase of international application PCT / US2018 / 044104, with an international filing date of January 30, 2020. Invention Field

[0002] This invention relates to integral composite membranes, and more particularly to composite membranes having a continuous ionomer phase. Background of the Invention

[0003] Composite membranes, such as anion exchange, cation exchange, and amphoteric composite membranes, can be used in a variety of applications. For example, composite membranes are a component of polymer electrolyte fuel cells, where they are located between the cathode and anode and transport protons formed near the catalyst at the hydrogen electrode to the oxygen electrode, thereby extracting current from the polymer electrolyte fuel cell. These polymer electrolyte fuel cells are particularly advantageous because they operate at lower temperatures than other fuel cells. Moreover, these polymer electrolyte fuel cells do not contain any of the corrosive acids found in phosphoric acid fuel cells.

[0004] Composite membranes can also be used in electrochemical devices to separate liquids contained within the device, such as electrolytic cells or flow batteries, like redox flow batteries. Flow batteries are charged and discharged via a reversible reduction-oxidation reaction between two liquid electrolytes. Ion exchange (i.e., the flow of current) occurs through the composite membrane, while the two liquid electrolytes circulate in their respective spaces within the flow battery. Flow batteries are scalable systems that can operate under a variety of conditions. For example, they can be integrated into smart grids and are advantageous for storing energy from wind or solar farms. Flow batteries are also characterized by their long lifespan (lasting several years), ease of maintenance, and overall energy efficiency.

[0005] Composite membranes incorporated into fuel cells, as well as those used in redox flow batteries, chlor-alkali electrolyzers, water electrolysis, diffusion dialysis, electrodialysis, pervaporation, and steam permeation applications, typically comprise ionomer membranes. These ionomer membranes have a discontinuous ionomer phase composed of multiple ionomer coatings. However, these ionomer thin-film composite membranes may experience premature structural failure in flow battery applications. During flow battery operation, the primary failure mode for these ionomer thin-film composite membranes is the formation of bubbles or blistering within the membrane, either within the ionomer layers or between multiple ionomer coatings. Therefore, there is a need for improved composite membranes with a continuous ionomer phase, high ionic conductivity, low reactant permeation, high mechanical strength, and low in-plane swelling. Summary of the Invention

[0006] In one embodiment, the present invention relates to a composite membrane for a redox flow battery. The composite membrane comprises a microporous polymer structure and an ion exchange material at least partially embedded within the microporous polymer structure and causing at least a portion of the microporous polymer structure to become closed. The ion exchange material forms a continuous ionomer phase within the composite membrane. After a foaming test procedure, the haze change of the composite membrane is 0% or less. The foaming test procedure may include: in a first step, immersing the composite membrane in a 6 mol / L sulfuric acid aqueous solution at 80°C for 3 minutes; in a second step, removing the composite membrane from the sulfuric acid aqueous solution; in a third step, immersing the composite membrane in deionized water under ambient conditions for one minute; in a fourth step, removing the composite membrane from the deionized water; repeating the cycle from the first step to the fourth step at least twice; in a fifth step, drying the composite membrane under ambient conditions; and in a sixth step, counting the bubbles or bubbling formed on the composite membrane. According to various embodiments, no bubbles or bubbling are formed on the composite membrane after the foaming test procedure (i.e., zero bubbles or bubbling are counted on the composite membrane). In some embodiments, the haze value of the composite membrane is between 5% and 95%, between 10% and 90%, or between 20% and 85%.

[0007] In some embodiments, the composite membrane comprises a single coating of ion exchange material. The thickness of the composite membrane can be 7 to 100 micrometers at 0% relative humidity, 17 to 50 micrometers at 0% relative humidity, or 25 to 40 micrometers at 0% relative humidity. Composite membranes according to various embodiments can have a thickness greater than 17 micrometers at 0% relative humidity.

[0008] In some embodiments, the composite membrane comprises multiple coatings of ion exchange material. In such embodiments, a first coating of ion exchange material is formed on the second coating of ion exchange material without performing a drying step on the second coating. The thickness of the composite membrane can be 10 to 150 micrometers at 0% relative humidity, 15 to 80 micrometers at 0% relative humidity, or 20 to 60 micrometers at 0% relative humidity.

[0009] According to various implementation methods, the equivalent of the ion exchange material can be between 500 and 2000 g / mol equivalent, between 700 and 1500 g / mol equivalent, between 900 and 1200 g / mol equivalent, or between 810 and 1100 g / mol equivalent.

[0010] According to various embodiments, the composite membrane further includes an additional layer of ion exchange material disposed on the bottom surface of the composite membrane. In some embodiments, the microporous polymer structure includes at least two microporous polymer layers. In some embodiments, the composite membrane contains more than one ion exchange material, which is in the form of a mixture of ion exchange materials. In other embodiments, the composite membrane includes more than one layer of ion exchange material, such that the layers of ion exchange material are formed of the same ion exchange material or different ion exchange materials.

[0011] In another embodiment, the present invention relates to a composite membrane for a redox flow battery. The composite membrane comprises a microporous polymer structure and an ion exchange material at least partially embedded within the microporous polymer structure and effectively closing at least a portion of the microporous polymer structure. The ion exchange material forms a continuous ionomer phase within the composite membrane. The thickness of the composite membrane is greater than 17 micrometers at 0% relative humidity. For example, the thickness of the composite membrane can be 7 to 100 micrometers at 0% relative humidity, 17 to 50 micrometers at 0% relative humidity, or 25 to 40 micrometers at 0% relative humidity.

[0012] In another embodiment, the present invention relates to a composite membrane for a redox flow battery. The composite membrane comprises a microporous polymer structure and an ion exchange material at least partially embedded within the microporous polymer structure and effectively closing at least a portion of the microporous polymer structure. The ion exchange material forms a continuous ionomer phase within the composite membrane. The thickness of the composite membrane is greater than 17 micrometers at 0% relative humidity. For example, the thickness of the composite membrane can be 7 to 100 micrometers at 0% relative humidity, 17 to 50 micrometers at 0% relative humidity, or 25 to 40 micrometers at 0% relative humidity. After undergoing a bubbling test procedure, the haze change of the composite membrane is 0% or less. That is, the haze value of the composite membrane remains the same or decreases before and after the bubbling test procedure. According to various embodiments, the haze value of the composite membrane is between 5% and 95%, between 10% and 90%, or between 20% and 85%.

[0013] In another embodiment, a method for forming the aforementioned composite membrane is provided. The method includes providing a support layer and, in one step, applying an ion exchange material onto the support layer. The method further includes obtaining a microporous polymer structure comprising at least one microporous polymer layer. The method further includes laminating at least one microporous polymer layer onto the ion exchange material to form an impregnated microporous polymer structure having a continuous ionomer phase. The impregnated microporous polymer structure is then dried and thermally annealed to form the composite membrane.

[0014] In other embodiments, a flow battery comprising the aforementioned composite membrane is provided. The flow battery may include: a cathode reservoir comprising a positive electrolyte fluid; an anode reservoir comprising a negative electrolyte fluid; and an exchange region comprising the aforementioned composite membrane, located between a first side having a positive electrode and a second side having a negative electrode. The cathode reservoir is connected to the first side of the exchange region via a first pump, and the anode reservoir is connected to the second side of the exchange region via a second pump.

[0015] In other embodiments, a composite membrane is provided, wherein the composite membrane is prepared by a method comprising the steps of: obtaining an untreated microporous polymer structure; applying an impregnating agent solution containing an ion exchange material to the untreated microporous polymer structure to form a treated microporous polymer structure having a continuous ionomer phase; and drying and thermally annealing the treated microporous polymer structure to form a composite membrane, wherein the ion exchange material forms a continuous ionomer phase within the composite membrane, wherein the composite membrane exhibits a haze change of 0% or less after undergoing a foaming test procedure.

[0016] Other aspects and variations of the invention will become apparent in the following discussion. Brief description of the attached figures

[0017] The invention will be better understood based on the following non-limiting drawings, in which:

[0018] Figure 1A-1C A micrograph of a cross-section of a composite membrane containing bubbles or bubbling is shown;

[0019] Figure 2A and 2B A micrograph shows a cross-section of a composite film having a discontinuous ionomer phase containing bubbles or bubbling at the interface between two ionsomers.

[0020] Figure 3A A cross-sectional side view of a composite membrane according to some aspects of the present invention is shown;

[0021] Figure 3B-3D An exemplary flowchart of a method for constructing an exemplary composite membrane according to some aspects of the present invention is shown;

[0022] Figure 3E-3F Micrographs of composite membranes with porous substrates according to various embodiments are shown, the porous substrates being characterized by nodes interconnected by fibrils and a continuous ionomer phase.

[0023] Figure 4 A schematic diagram of a flow battery including a composite membrane according to some aspects of the present invention is shown;

[0024] Figure 5 shows a schematic diagram of a haze testing apparatus for measuring the total transmittance of a composite film according to some aspects of the present invention;

[0025] Figures 6A-6B Exemplary composite membranes and conventional ion exchange membranes prepared according to some aspects of the present invention before and after a foaming test are shown respectively; and

[0026] Figures 7A-7C Samples of composite films prepared according to some aspects of the present invention are shown after a foaming test according to some aspects of the present invention. Invention Details

[0027] I. introduction

[0028] In one embodiment, the present invention relates to a composite membrane comprising a porous substrate having an impregnating agent containing an ion-exchange material (e.g., an ionomer thin-film composite membrane). However, one problem associated with conventional ionomer thin-film composite membranes is their reduced ability to maintain structural integrity, particularly when used in flow batteries. For example, it has been found that bubbles or blistering can form in ionomer thin-film composite membranes at weak internal interfaces within the ionomer layers or between multiple coatings of the ionomer, due to conventional multi-pass coating processes used to produce ionomer thin-film composite membranes. Figure 1A-1C A micrograph of a conventional ionomer film composite 100 with bubbles or bubbling 110 in a weak internal interface 120 between multiple coatings 130 of the ionomer is shown.

[0029] A conventional multi-pass coating process for producing ionomer thin-film composites includes a first-pass ionomer coating, which involves contacting a porous substrate, such as expanded polytetrafluoroethylene (ePTFE), with an impregnating agent, such as a perfluorosulfonic acid polymer, to form a first-pass ionomer. The first-pass ionomer is then heated in an oven to dry and thermally anneal the porous substrate containing the impregnating agent. Subsequently, a second-pass ionomer coating is applied to the dried first-pass ionomer, contacting it with the porous substrate to form a second-pass ionomer, which is then dried. Optionally, additional passes of ionomer coatings can be applied, stacked on top of each other, contacting the porous substrate, and then dried and annealed. The resulting structure is characterized by a discontinuous ionomer phase, having an internal interface between each ionomer, for example, between the first-pass and second-pass ionomers. Figure 2A-2B A micrograph of a conventional ionomer thin film composite membrane 200 having a discontinuous ionomer phase 210 is shown, wherein bubbles or bubbles 220 are formed at the internal interfaces 230 between the individual ionomers 240. Protofibrous structures 250 are observed within the bubbles or bubbles 220.

[0030] Unbound by theory, the liquid electrolyte used in flow batteries can be attracted to the ionomer layers or the internal interfaces between the ionomers, potentially leading to an osmotic pressure gradient within the composite membrane during flow battery operation. This osmotic pressure gradient serves as the driving force for drawing water into the internal interfaces during flow battery operation. The hydraulic expansion forces associated with water being drawn into the internal interfaces cause the formation of bubbles or foaming between the ionomers.

[0031] To address these issues, in one embodiment, the invention further relates to composite membranes having a continuous ionomer phase. As used herein, a “continuous ionomer phase” refers to any number of layers or coatings of porous substrate and / or ion exchange material stacked on top of each other, which do not have any internal interfaces within or between the ionomer layers. For example, an integral interface can be formed by drying and thermally annealing the porous substrate and / or ion exchange material prior to the application of subsequent layers or coatings. In some embodiments, as described herein, a single-pass ionomer coating process is performed to produce a single-pass ionomer composite membrane having a continuous ionomer phase. The thickness of the composite membrane produced by single-pass ionomer coating is optionally 7 to 100 micrometers at 0% relative humidity (RH), 17 to 50 micrometers at 0% RH, or 25 to 40 micrometers at 0% RH, and optionally contains 3 g / m³. 2 Up to 80g / m 2 Porous substrate, or 5g / m 2 Up to 50g / m 2 Porous substrates, or 10g / m 2 Up to 30g / m 2 A porous substrate. In an alternative embodiment, as described herein, a multi-pass ionomer coating process is performed, with no drying step between each coating pass, to produce a multi-pass ionomer composite film having a continuous ionomer phase. The thickness of the multi-pass ionomer composite film is optionally 10 to 150 micrometers at 0% RH, 15 to 80 micrometers at 0% RH, or 20 to 60 micrometers at 0% RH, and optionally contains 3 g / m³. 2 Up to 80g / m 2 Porous substrate, or 5g / m 2 Up to 50g / m 2 Porous substrate, or 10g / m 2 Up to 30g / m 2Porous substrate. In some embodiments, as described herein, a specific equivalence of ion exchange material is used in an ionomer coating process to produce a composite membrane having a continuous ionomer phase. The equivalence of the ion exchange material is optionally between 500 and 2000 g / mol equivalents, or between 700 and 1500 g / mol equivalents, or between 700 and 1200 g / mol equivalents, or between 810 and 1100 g / mol equivalents. In some embodiments, as described herein, a single-pass or multi-pass ionomer coating process is performed, and there is no drying step between each coating pass, to produce a composite membrane having a continuous ionomer phase and a predetermined haze. The haze of the composite membrane is optionally between 5% and 95%, or between 10% and 90%, or between 20% and 85%. After undergoing a bubbling test procedure, the haze value of the composite membrane optionally decreases or remains unchanged. Therefore, in one embodiment, the present invention relates to a composite film having a continuous ionomer phase, which does not have an internal interface in the ionomer layer or between multiple coatings of the ionomer, and exhibits desirable high ionic conductivity, low reactive substance cross-passage level, high mechanical strength and low in-plane swelling properties.

[0032] The following are the various definitions used in this disclosure.

[0033] As used herein, the terms "ionomer" and "ion exchange material" refer to cation exchange materials, anion exchange materials, or ion exchange materials that possess both cation and anion exchange capabilities. Mixtures of ion exchange materials may also be used. Ion exchange materials can be perfluorinated or hydrocarbon-based. Suitable ion exchange materials include, for example, perfluorosulfonic acid polymers, perfluorocarboxylic acid polymers, perfluorophosphonic acid polymers, styrene-type ion exchange polymers, fluorostyrene-type ion exchange polymers, polyaryletherketone ion exchange polymers, polysulfone ion exchange polymers, bis(fluoroalkylsulfonyl)imides, (fluoroalkylsulfonyl)(fluorosulfonyl)imides, polyvinyl alcohol, polyethylene oxide, divinylbenzene, metal salts with or without polymers, and mixtures thereof. In an exemplary embodiment, the ion exchange material comprises a perfluorosulfonic acid (PFSA) polymer prepared by copolymerizing tetrafluoroethylene and perfluorosulfonyl vinyl ester and converting it to a proton form. Of course, the suitability of a particular ion exchange material depends to some extent on the intended use of the composite membrane. Examples of suitable perfluorosulfonic acid polymers for fuel cell or flow battery applications include... (EI DuPont de Nemours, Inc., Wilmington, Del., US) (Asahi Glass Co., Ltd., Tokyo, JP) and (Asahi Chemical Co., Ltd., Tokyo, JP) These are commercially available perfluorosulfonic acid copolymers. Other examples of suitable perfluorosulfonic acid polymers for fuel cell applications include perfluorinated sulfonyl polymers or copolymers, such as those described in U.S. Patent No. 5,463,005.

[0034] As used herein, a “continuous ionomer phase” refers to an ionomer without internal interfaces. A continuous ionomer phase may refer to, but is not limited to, a composite film made by a single-pass ionomer coating. A composite film made by a single-pass ionomer coating may comprise one or more layers of material layers (e.g., a coating of an absorbent layer (e.g., an ionomer layer impregnated in a microporous polymer structure)) formed by stacking one layer on top of the other, drying and thermally annealing (e.g., curing), and laminating a microporous polymer layer.

[0035] As used herein, the term "microporous polymer structure" refers to a polymer matrix supporting an ion exchange material, which enhances the structural integrity and durability of the resulting composite membrane. In some exemplary embodiments, the microporous polymer structure comprises expanded polytetrafluoroethylene with a node and fibrillary structure. The microporous structures described herein have pores that are not visible to the naked eye. According to various optional embodiments, the average pore diameter can be from 0.01 to 100 micrometers, for example, from 0.05 to 10 micrometers or from 0.1 to 1 micrometer.

[0036] In some embodiments, the microporous polymer structure is expanded polytetrafluoroethylene with an average pore size of 0.01 to 100 micrometers, such as 0.05 to 10 micrometers or 0.1 to 1 micrometer.

[0037] As used herein, an internal volume of a microporous polymer structure is described as “substantially closed” when it is characterized by low volumetric porosity (less than 10 vol%) and high gas impermeability (Gurley number greater than 10,000 s). Conversely, an internal volume of a microporous polymer structure is described as “non-closed” when it is characterized by large volumetric porosity (greater than 10 vol%) and gas permeability (Gurley number less than 10,000 s).

[0038] In some embodiments, the microporous polymer structure is expanded polytetrafluoroethylene with an average pore size of 0.01 to 100 micrometers, such as 0.05 to 10 micrometers or 0.1 to 1 micrometer, and a void size of less than 10% by volume.

[0039] Suitable microporous polymer structures depend largely on the application using the composite membrane. The microporous polymer structure preferably possesses good mechanical properties, is chemically and thermally stable in the environment where the composite membrane is used, and is resistant to any additives used for impregnation with the ion exchange material. Suitable microporous polymer structures for redox flow battery or fuel cell applications may include porous polymer materials. Porous polymer materials may include fluoropolymers, chlorinated polymers, hydrocarbons, polyamides, polycarbonates, polyacrylates, polysulfones, copolyether esters, polyvinylidene fluoride, polyaryletherketones, polybenzimidazoles, poly(ethylene-co-tetrafluoroethylene), and poly(tetrafluoroethylene-co-hexafluoropropylene). In some embodiments, the microporous polymer structure comprises a perfluorinated porous polymer material. Perfluorinated porous polymer materials may include polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), or mixtures thereof. In some embodiments, the microporous polymer structure comprises a hydrocarbon material. Hydrocarbon materials may include polyethylene, expanded polyethylene, polypropylene, expanded polypropylene, polystyrene, or mixtures thereof. Examples of suitable perfluorinated porous polymer materials for redox flow battery or fuel cell applications include ePTFE prepared according to the teachings of U.S. Patent No. 8,757,395, the entire contents of which are incorporated herein by reference and are available in various forms from WL Gore & Associates, Inc., Elkton, Maryland.

[0040] II. Composite membrane

[0041] Composite films with continuous or discontinuous ionomer phases have a predetermined haze. Haze refers to the wide-angle scattering of light by the composite film, resulting in a loss of optical contrast required to see objects when observed through the composite film. Haze can be measured using a haze meter or transparency meter as described in detail herein. Composite films with continuous ionomer phases do not bubble. Therefore, the haze of composite films with continuous ionomer phases does not change after a bubbling test or after continuous operation in a flow cell. On the other hand, composite films with discontinuous ionomer phases (i.e., composite films without a continuous ionomer phase) do bubble. Therefore, the haze of composite films with discontinuous ionomer phases changes after a bubbling test or after continuous operation in a flow cell. Before the bubbling test, the haze of a composite film with a continuous ionomer phase is similar to that of a composite film without a continuous ionomer phase. However, after the bubbling test, the haze of a composite film with a continuous ionomer phase differs from that of a composite film without a continuous ionomer phase.

[0042] Composite membranes having either a continuous or discontinuous ionomer phase also have a predetermined bubble or bubbling density, which can be measured after continuous use of the membrane in a flow cell for a predetermined time or after exposure to a bubbling test procedure described in detail herein. The area of ​​the bubbles or bubbles is measured as the ratio of the area of ​​the composite membrane to the area of ​​the bubbles or bubbles within the composite membrane.

[0043] In some embodiments, the composite film having a continuous ionomer phase formed by a single-pass ionomer coating has a predetermined bubble or foaming density of less than 0.3%, less than 0.2%, less than 0.1%, or 0% after 10 days of continuous use in a flow battery. In alternative embodiments, the continuous ionomer phase formed by a multi-pass ionomer coating without a drying step between coating passes has a bubble or foaming area of ​​less than 0.3%, less than 0.2%, less than 0.1%, or 0% after 10 days of continuous use in a flow battery. In other embodiments, the composite film having a continuous ionomer phase formed by a single-pass ionomer coating has a bubble or foaming area of ​​less than 0.3%, less than 0.2%, less than 0.1%, or 0% after exposure to a foaming test procedure. In alternative embodiments, the bubble or bubble area of ​​a continuous ionomer phase formed by multi-pass ionomer coating without a drying step between coating passes, after exposure to a foaming test procedure, is less than 0.3%, less than 0.2%, less than 0.1%, or 0%. In some embodiments, the haze change of a composite film having a continuous ionomer phase formed by single-pass ionomer coating after exposure to a foaming test procedure is 0% or less, between 0% and -60%, or between 0% and -45%, or between 0% and -30%, or between 0% and -21%. In alternative embodiments, the haze change of a composite film having a continuous ionomer phase formed by multi-pass ionomer coating without a drying step between coating passes, after exposure to a foaming test procedure, is 0% or less, between 0% and -60%, or between 0% and -45%, or between 0% and -30%, or between 0% and -21%.

[0044] a. Composite membranes with continuous ionomer phases

[0045] As described above, the composite membranes according to various embodiments have a continuous ionomer phase. For example... Figure 3AAs shown, a composite membrane 301 is provided, comprising a microporous substrate 306 and an impregnating agent containing an ion exchange material or ion exchange resin 304, characterized by a continuous ionomer phase 350 (i.e., no interface between ionomer coatings). The porous substrate 306 is a membrane defined by a thickness of less than 0.4 mm (400 micrometers). The ion exchange resin 304 substantially impregnates the porous substrate 306 to substantially close the internal volume. For example, substantial (significant) closure will occur by filling more than 90% of the internal volume of the porous substrate 306 with ion exchange resin 304.

[0046] The composite membrane disclosed herein can be used in a variety of applications. In some embodiments, the composite membrane disclosed herein can be used in polarity-based chemical separation, pervaporation, gas separation, dialysis separation, industrial electrochemistry such as chlor-alkali electrolysis and other electrochemical applications, as a superacid catalyst, or as a medium for enzyme immobilization. In a preferred embodiment, the composite membrane disclosed herein can be used in electrochemical applications to separate liquids contained within an electrochemical device. In a preferred embodiment, the composite membrane disclosed herein can be used in fuel cells. In another preferred embodiment, the composite membrane disclosed herein can be used in water electrolyzers. In yet another preferred embodiment, the composite membrane disclosed herein can be used in flow batteries, such as redox flow batteries.

[0047] The impregnating agent includes ion exchange materials or ion exchange resin 304. Ion exchange materials or ion exchange resin 304 are cation exchange materials, anion exchange materials, or ion exchange materials that simultaneously possess cation and anion exchange capabilities. Mixtures of ion exchange materials can also be used as impregnating agents.

[0048] Optionally, the impregnating agent solution also includes a surfactant. The surfactant can be used with ion exchange materials to ensure the internal volume of the impregnated porous substrate. Surfactants or surface-active agents having both hydrophobic and hydrophilic portions can be used. Preferred surfactants are those with a molecular weight greater than 100 and can be classified as anionic, nonionic, or amphoteric; they can be hydrocarbon- or fluorocarbon-based, including, for example, hydrocarbon-based surfactants. Or based on fluorocarbon surfactants Both are available from EI DuPont de Nemours, Inc. in Wilmington, Delaware, USA.

[0049] In various embodiments, the surfactant is a nonionic material having the following chemical structure: octylphenoxypolyethoxyethanol.

[0050]

[0051] Where x = 10 (average), it is called Triton X-100 and is commercially available from Rohm & Haas in Philadelphia, Pennsylvania.

[0052] If desired, the impregnating agent may further include other components. For example, the impregnating agent may contain an electrocatalyst composition. Suitable catalyst compositions include unsupported and supported catalysts, including noble metals, transition metals, their oxides, their alloys, and mixtures thereof. The presence of an electrocatalyst in the ion exchange layer of a composite membrane may be desirable for reducing reactant cross-linking, such as methanol in direct methanol fuel cell applications. Furthermore, the electrocatalyst can provide more efficient ionomer-electrocatalyst interactions, thereby promoting the oxidation and reduction of reactant gases.

[0053] The impregnating agent may further comprise an electrochemically inert material that promotes water retention in the composite membrane under normal operating conditions. Polymer, non-polymer, or hydrogel materials may be suitable. For example, the impregnating agent may further comprise particulate and / or fibrous silica, as described in U.S. Patent No. 5,523,181, which is incorporated herein by reference, or a silica-containing hydrogel, as described, for example, in Chemistry of Materials, Vol. 7, pp. 2259-2268 (1995). Other suitable such materials will be apparent to those skilled in the art.

[0054] For example, the impregnating agent may further comprise a compatible mixture of nonionic polymers, such as polyaryletherketones or polysulfones. The presence of nonionic polymers in the impregnating agent may be advantageous in certain applications. For instance, nonionic polymers in the impregnating agent can reduce methanol cross-flow in direct methanol fuel cells.

[0055] In embodiments in which a polymer composition is used, the impregnating agent is typically introduced into the porous substrate by means of an impregnation solution containing the impregnating agent in a suitable solvent. The choice of solvent will depend in part on the composition of the impregnating agent and the composition of the porous substrate. Suitable solvents include, for example, water, ethanol, propanol, butanol, methanol, ketones, carbonates, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, and mixtures thereof. As used herein, “solvent” means any suitable solvent or solvent mixture.

[0056] Alternatively, the ion exchange material may comprise one or more monomers or oligomers that can be impregnated into a porous substrate and subsequently polymerized or otherwise chemically linked. Thus, as used herein, an "impregnating agent solution" includes ion exchange monomers, oligomers, polymers, and / or mixtures thereof in a solvent, and the net phase of the ion exchange material monomers and / or oligomers. Note that in cases where the impregnating solution contains other components besides the ion exchange material, these components do not need to be dissolved in the liquid phase. Therefore, the impregnating solution can also be a dispersion.

[0057] In one embodiment, the composite membrane for a redox flow battery may comprise expanded polytetrafluoroethylene with an average pore size of 0.01 to 100 micrometers; and a perfluorosulfonic acid resin with an EW of 810 to 1100 g / (molar acid equivalent), the perfluorosulfonic acid resin being at least partially embedded in the microporous polymer structure and causing at least a portion of the microporous polymer structure to become closed. The perfluorosulfonic acid resin forms a continuous ionomer phase within the composite membrane. After undergoing a foaming test procedure, the composite membrane exhibits a haze change of 0% or less.

[0058] b. Methods for preparing composite membranes

[0059] Figure 3B-3C Exemplary flowcharts of methods 340 and 360 for constructing exemplary composite membranes 300 and 380, respectively, according to various aspects of this disclosure, are shown. These flowcharts illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of this disclosure. In some alternative implementations, it is logically meaningful that the functions indicated in each block may occur in a different order than shown in the figures. For example, depending on the functions, processes, or end products involved, two consecutively shown blocks may actually be performed substantially simultaneously, or sometimes these blocks may be performed in reverse order.

[0060] refer to Figure 3B An exemplary flowchart of method 340 illustrates a method for forming a composite material 300 having a fully absorbent microporous polymer structure 307, an additional layer 305 of ion exchange material, and an uncoated, non-blocking layer 309. Method 340 includes providing a support structure, such as a backing 302.

[0061] Suitable support structures may include woven materials, such as loosely woven fabrics made of expanded porous polytetrafluoroethylene fibers; nets made of extruded or oriented polypropylene or polypropylene mesh materials, available from Conwed, Inc., Minneapolis, Minnesota; and woven materials of polypropylene and polyester from Tetko Inc., Briarcliff Manor, NY. Suitable nonwoven materials may include, for example, spunbond polypropylene from Reemay Inc., Old Hickory, Tennessee. In other aspects, the support structure may include a mesh of materials such as polyethylene (“PE”), polystyrene (“PS”), cyclic olefin copolymer (“COC”), cyclic olefin polymer (“COP”), fluorinated ethylene propylene (“FEP”), perfluoroalkoxyalkane (“PFA”), ethylene tetrafluoroethylene (“ETFE”), polyvinylidene fluoride (“PVDF”), polyetherimide (“PEI”), polysulfone (“PSU”), polyethersulfone (“PES”), polyphenylene ether (“PPO”), polyphenylene ether (“PPE”), polymethylpentene (“PMP”), polyethylene terephthalate (“PET”), or polycarbonate (“PC”). In some aspects, the support structure also includes a protective layer, which may include polyethylene (PE), polystyrene (“PS”), cyclic olefin copolymer (“COC”), cyclic olefin polymer (“COP”), fluorinated ethylene propylene (“FEP”), perfluoroalkoxyalkane (“PFA”), ethylene tetrafluoroethylene (“ETFE”), polyvinylidene fluoride (“PVDF”), polyetherimide (“PEI”), polysulfone (“PSU”), polyethersulfone (“PES”), polyphenylene ether (“PPO”), polyphenylene ether (“PPE”), polymethylpentene (“PMP”), polyethylene terephthalate (“PET”), or polycarbonate (“PC”).

[0062] In other aspects, the support structure may include a support structure that optionally includes a reflective layer comprising a metallic substrate (e.g., an aluminum substrate). The specific metal selected can be chosen from a wide range, as long as it is reflective. A non-limiting list of exemplary metals includes: aluminum, beryllium, cerium, chromium, copper, germanium, gold, hafnium, manganese, molybdenum, nickel, platinum, rhodium, silver, tantalum, titanium, tungsten, zinc, or alloys such as Inconel or bronze. The reflective layer optionally comprises two or more metals, optionally mixtures or alloys of two or more metals listed above. The reflective layer may optionally comprise a high-reflectivity polymer multilayer film, such as Vikuiti, available from 3M. TMEnhanced specular reflectivity. In yet another example, the reflective layer may optionally comprise a highly reflective nonmetallic inorganic dielectric multilayer film made of materials such as magnesium fluoride, calcium fluoride, titanium dioxide, or silicon dioxide.

[0063] In step 342, a first ion exchange material is applied as a thickness-controlled layer to the support structure using a single-pass or multi-pass ionomer coating technique, including forward roll coating, reverse roll coating, gravure coating, blade coating, kiss coating, slot die coating, slide die coating, and dip coating, brush coating, painting, and spray coating. The first ion exchange material can be prepared by dissolving it in a solvent. The first ion exchange material may comprise an ion exchange material and a solvent, as well as optional other components, such as surfactants. In some embodiments, the ion exchange material is a cation exchange material, an anion exchange material, or an ion exchange material with both cation and anion exchange capabilities. The choice of solvent may depend in part on the composition of the ionomer and the composition of the porous substrate.

[0064] In step 344, the untreated microporous polymer structure is laminated onto at least a portion of the first ion exchange material using any conventional technique, such as hot roller lamination, ultrasonic lamination, adhesive lamination, contact lamination, or forced hot air lamination, as long as the technique does not compromise the integrity of the untreated microporous polymer structure. In some embodiments, the untreated microporous polymer structure comprises ePTFE having a microporous polymer structure. The microporous polymer structure is characterized by having a uniform structure and composition throughout its thickness. In other aspects, the structure and composition of the microporous polymer structure can vary throughout its thickness. The prepared or obtained microporous polymer structure can have a thickness of less than 400 micrometers at 0% relative humidity, for example, a thickness from 1 micrometer to 400 micrometers. At 0% relative humidity, the mass per unit area of ​​the untreated microporous polymer structure can be greater than 0.05 g / m². 2 For example, 0.3g / m 2 Up to 80g / m 2 .

[0065] For example, a carrier support, such as a backing, can be continuously supplied from the unwinding station to the coating station via alignment and tension rollers. Ion exchange material can be applied as a thickness-controlled layer to the surface of the carrier support (backing) using a suitable coating method, such as a doctor blade. An untreated microporous polymer structure can be continuously supplied from the unwinding station to the alignment rollers, contacting the coated carrier support and impregnating it with the ion exchange material. Alternatively, the carrier support can be removed, and the ion exchange material layer can be applied directly to the untreated microporous polymer structure.

[0066] In step 346, the treated microporous polymer structure is placed in an oven for drying, heat annealing, and to complete the construction of the composite membrane. The oven temperature can be above 60°C, for example, from 60°C to 220°C, or from 150°C to 200°C. Drying and heat annealing the treated microporous polymer structure in the oven allows the ion exchange material to adhere firmly to the inner membrane surface, and optionally the outer membrane surface, such as the fibrils and / or nodes of the microporous polymer structure. The resulting dried and annealed composite membrane 300 can have a thickness greater than 17 micrometers at 0% relative humidity, for example, from 17 micrometers to 100 micrometers. At 0% relative humidity, the mass of the composite membrane can be greater than 30 g / m³. 2 For example, 30g / m 2 Up to 200g / m 2 .

[0067] Now for reference Figure 3C An exemplary flowchart of method 360 illustrates a method for forming a composite material 380 having a fully absorbent microporous polymer structure 307, an additional layer 305 of ion exchange material, and a partially coated non-blocking layer 319. Similar to method 340, method 360 includes providing a support structure (e.g., a backing) 302, such as a woven material.

[0068] In step 362, similar to step 342 of method 340, the first ion exchange material is applied as a thickness-controlled layer onto the support structure (backing). Since step 362 is identical to step 342 of method 340 described above, a description of step 362 is omitted here.

[0069] In step 364, the untreated microporous polymer structure is laminated onto the first portion of the first ion exchange material using any conventional technique, such as hot roller lamination, ultrasonic lamination, adhesive lamination, contact lamination, or forced hot air lamination, as long as the technique does not compromise the integrity of the untreated microporous polymer structure. In some embodiments, the untreated microporous polymer structure comprises ePTFE having a microporous polymer structure. The microporous polymer structure is characterized by having a uniform structure and composition throughout its thickness. In other aspects, the structure and composition of the microporous polymer structure may vary throughout its thickness.

[0070] After lamination, the top portion of the microporous polymer structure can be coated, for example, with an ionomer coating using a contact roller 310.

[0071] Step 366 is similar to step 346 of method 340. Therefore, the description of step 366 is omitted here. The dried and annealed microporous polymer structure prepared or obtained can have a thickness greater than 17 micrometers, for example, from 17 micrometers to 100 micrometers, at 0% relative humidity. At 0% relative humidity, the mass of the composite membrane can be greater than 30 g / m³.2 For example, 30g / m 2 Up to 200g / m 2 .

[0072] refer to Figure 3D An exemplary flowchart of method 320 illustrates a method for forming a composite material 321 having a fully absorbent microporous polymer structure 307 and two additional ion exchange material layers 305. Similar to methods 340 and 360, method 320 includes providing a support structure (e.g., a backing) 302, such as a woven material.

[0073] In step 322, similar to step 342 of method 340, the first ion exchange material is applied as a thickness-controlled layer onto the support structure (backing). Since step 322 is identical to step 342 of method 340 described above, a description of step 322 is omitted here.

[0074] In step 324, the untreated microporous polymer structure is laminated onto the first portion of the first ion exchange material using any conventional technique, such as hot roller lamination, ultrasonic lamination, adhesive lamination, contact lamination, or forced hot air lamination, as long as the technique does not compromise the integrity of the untreated microporous polymer structure. In some embodiments, the untreated microporous polymer structure comprises ePTFE having a microporous polymer structure. The microporous polymer structure is characterized by having a uniform structure and composition throughout its thickness. In other aspects, the structure and composition of the microporous polymer structure may vary throughout its thickness.

[0075] Following lamination, in step 326, a second ion exchange material 327 is applied as a thickness-controlled layer to the top side of the microporous polymer structure using ionomer coating techniques, including forward roll coating, reverse roll coating, gravure coating, blade coating, kiss coating, slot die coating, slide die coating, as well as dip coating, brush coating, painting, and spray coating. The second ion exchange material can be prepared by dissolving the ion exchange material in a solvent. The second ion exchange material may comprise an ion exchange material and a solvent, as well as optional other components, such as surfactants. In some embodiments, the ion exchange material is a cation exchange material, an anion exchange material, or an ion exchange material with both cation and anion exchange capabilities. The choice of solvent may depend in part on the composition of the ionomer and the composition of the porous substrate.

[0076] Step 328 is similar to step 346 of method 340. Therefore, the description of step 328 is omitted here. The prepared or obtained dried and annealed composite film can have a thickness greater than 17 micrometers, for example, from 17 micrometers to 100 micrometers, at 0% relative humidity. At 0% relative humidity, the mass of the composite film can be greater than 30 g / m³. 2 For example, 30g / m2 Up to 200g / m 2 .

[0077] Methods 340, 360, and 320 may include optional steps of immersing the composite membrane and boiling the composite membrane. For example, in embodiments using surfactants, the composite membrane is further treated to remove the surfactant. This can be accomplished by immersing or submerging the composite membrane in a solution such as water, isopropanol, hydrogen peroxide, methanol, and / or glycerol. During this step, the surfactant initially mixed with the ion exchange material in the solution is removed. This immersion or submersion causes slight swelling of the composite membrane, but the ion exchange material remains within the internal volume of the porous substrate.

[0078] In an optional boiling step, the composite membrane is treated by boiling in a suitable swelling agent (preferably water), causing it to swell slightly in the x, y, and z directions. The swollen composite membrane exhibits higher and stronger ion transport rates. Unlike membranes composed solely of ion exchange materials, the swollen composite membrane retains its mechanical integrity and dimensional stability while maintaining the desired ion transport characteristics. A correlation exists between the amount of swelling agent within the composite membrane and its transport performance. The swollen composite membrane transports chemicals faster than the unswollen composite membrane.

[0079] like Figure 3B-3D As shown, composite membranes 300, 380, and 321 comprise a microporous polymer structure 306 and an ion-exchange material (e.g., an ionomer) 304 impregnated within the microporous polymer structure 306. That is, the microporous polymer structure 306 absorbs the ion-exchange material 304. The ion-exchange material 304 can substantially impregnate the microporous polymer structure 306 such that the internal volume is substantially closed (i.e., the internal volume has a structure characterized by small volumetric voids, which are highly impermeable to gases). For example, by filling more than 90% of the internal volume of the microporous polymer structure 306 with the ion-exchange material 304, a significant amount of closure will occur, and the membrane will be characterized by a Grignard number greater than 10,000 s. The ion-exchange material 304 is firmly adhered to the inner and outer surfaces of the microporous polymer structure 306, for example, to the fibrils and / or nodes of the microporous polymer structure 306 that form the absorbent layer 307.

[0080] In some embodiments, the ion exchange material 304, in addition to being impregnated in the microporous polymer structure 307 in the absorber layer 307, is also provided as one or more additional layers 305 (e.g., also referred to as "butter coating (BC)") on one or more outer surfaces of the absorber layer 307.

[0081] like Figure 3BAs shown in the composite membrane 300, a portion of the microporous polymer structure 306 (e.g., the top or bottom surface region) may include a non-occluded layer 309 (i.e., a structure with a large volumetric porosity and high gas permeability) that contains no or substantially no ion exchange material 304. The location of the non-occluded layer 309 is not limited to the top surface region of the microporous polymer structure 306. As described above, the non-occluded layer 309 may be disposed on the bottom surface region of the microporous polymer structure 306.

[0082] like Figure 3C As shown in the composite membrane 300, the non-blocking layer 319 may include a small amount of ion exchange material 304 present on the inner surface of the microporous polymer structure 306, which serves as a thin node and fibrillary coating. However, the amount of ion exchange material 304 may be insufficient to block the microporous polymer structure 306, thereby forming the non-blocking layer 319.

[0083] In some embodiments, composite membranes 300, 380, and 321 may be disposed on a support layer 302. The support layer 302 may include a backing, a release film, such as a cyclic olefin copolymer (COC) layer. In some embodiments, composite membranes 300, 380, and 321 may be released from the support layer 302 (or otherwise disconnected) before being incorporated into a membrane electrode assembly (MEA).

[0084] Figure 3B-3D Exemplary composite membranes 300, 380, and 321 comprising a single type of ion exchange material 304 are shown. However, this application is not limited to composite membranes having a single type of ion exchange material 304 or a single absorber layer 307.

[0085] Figure 3E-3F Micrographs of composite membranes with porous substrates according to various embodiments are shown, the porous substrates being characterized by nodes interconnected by fibrils and a continuous ionomer phase. Figure 3E-3F As shown, the composite membrane prepared according to aspects of the present invention has a uniform thickness, no internal interfaces within the ionomer layer or between multiple ionomer coatings, and no discontinuities or pores on its surface. The internal volume of the composite membrane is substantially closed, making it impermeable to nonpolar gases and the bulk liquid flow.

[0086] c. Preparation and application of impregnating agent solutions

[0087] Referring again to steps 342, 362, and 322, further details regarding the preparation of the impregnating agent solution and its application on the support structure are described below.

[0088] Impregnating agent solutions are prepared by dissolving ion exchange materials in a solvent. The impregnating agent solution contains the ion exchange material in the solvent, along with optional other components, such as surfactants. The ion exchange material can be a cation exchange material, an anion exchange material, or an ion exchange material with both cation and anion exchange capabilities. The choice of solvent will depend in part on the composition of the impregnating agent and the composition of the porous substrate.

[0089] A single-pass ionomer coating technique can be used to apply an impregnating agent solution as a thickness-controlled layer to an untreated porous substrate. This coating technique includes forward roll coating, reverse roll coating, gravure coating, doctor blade coating, kiss coating, as well as dip coating, brush coating, painting, and spray coating, provided the liquid solution can penetrate the pores and internal volume of the untreated porous substrate. Excess solution can be removed from the surface of the treated porous substrate. For example, a carrier support can be continuously supplied from the roll unwinding station to the coating station via alignment and tension rollers. The impregnating agent solution can be applied as a thickness-controlled layer to the surface of the carrier support using a suitable coating means, such as a doctor blade. The untreated porous substrate can be continuously supplied from the roll unwinding station to the alignment roller, contacting the coated carrier support and impregnating it with the impregnating agent solution. Alternatively, the carrier support can be removed, and the ionomer solution layer can be applied directly to the untreated porous substrate.

[0090] The resulting treated porous substrate or composite film, prepared by single-pass ionomer coating, has a thickness of 7 to 100 micrometers, 17 to 50 micrometers, or 25 to 40 micrometers, and optionally contains 3 g / m³. 2 Up to 80g / m 2 Porous substrate, or 5g / m 2 Up to 50g / m 2 Porous substrate, or 10g / m 2 Up to 30g / m 2 Porous substrate. It should be understood that single-pass ionomer coating produces a composite film with a continuous ionomer phase that does not have internal interfaces in a single ionomer coating.

[0091] In some embodiments, an impregnating agent solution is applied as multiple additional layers (i.e., multi-pass ionomers) of controlled thickness to a treated porous substrate using similar coating techniques, such as forward roll coating, reverse roll coating, gravure coating, blade coating, kiss coating, and dip coating, brush coating, painting, and spray coating. For example, the treated porous substrate can be continuously fed to an alignment roller and re-contacted one or more times (multi-pass) with a coated carrier support and impregnated with the impregnating agent solution. Alternatively, the carrier support can be removed, and the impregnating agent solution layers can be applied directly to the treated porous substrate multiple times. This process can be repeated any number of times (e.g., twice) without including a drying step between each coating pass, thereby forming a treated porous substrate with multiple layers. The resulting multi-pass composite film has a thickness of 10 to 150 micrometers at 0% RH, 15 to 80 micrometers at 0% RH, or 20 to 60 micrometers at 0% RH, and optionally contains 3 g / m³. 2 Up to 80g / m 2 Porous substrate, or 5g / m 2 Up to 50g / m 2 Porous substrate, or 10g / m 2 Up to 30g / m 2 Porous substrate. It should be understood that multi-pass ionomer coating produces one or more layers of treated porous substrate having a continuous ionomer phase that does not have internal interfaces within the ionomer layer or between multiple coatings of the ionomer.

[0092] In an alternative embodiment, another untreated porous substrate can be contacted with the coated and treated porous substrate, and the untreated porous substrate can be impregnated with an impregnating agent solution to produce a treated porous substrate with multiple layers (i.e., a multi-pass ionomer composite film). This process can be repeated any number of times (e.g., twice) without including a drying step between each coating pass, thereby forming a treated porous substrate with multiple layers. The resulting multi-pass composite film has a thickness of 10 to 150 micrometers at 0% RH, 15 to 80 micrometers at 0% RH, or 20 to 60 micrometers at 0% RH, and optionally contains 3 g / m³. 2 Up to 80g / m 2 Porous substrate, or 5g / m 2 Up to 50g / m 2 Porous substrate, or 10g / m 2 Up to 30g / m 2 Porous substrate. It should be understood that multi-pass ionomer coating produces a composite film having one or more layers of treated porous substrate, the treated porous substrate having a continuous ionomer phase that does not have internal interfaces within the ionomer layer or between multiple coatings of the ionomer.

[0093] The treated porous substrate can be placed in an oven for drying and heat annealing. The oven temperature can be in the range of 60° to 220°C, but is preferably between 150° to 200°C. Drying and heat annealing the treated porous substrate in the oven will cause the ion exchange material to adhere firmly to the inner membrane surface, as well as optionally the outer membrane surface, such as the fibrils and / or nodes of the porous substrate.

[0094] In embodiments using surfactants, the treated porous substrate is further processed to remove the surfactant. This can be accomplished by immersing or submerging the treated porous substrate in a solution such as water, isopropanol, hydrogen peroxide, methanol, and / or glycerol. During this step, the surfactant initially mixed with the ion exchange material in the solution is removed. This immersion or submersion causes slight swelling of the treated porous substrate, but the ion exchange material remains within the internal volume of the porous substrate.

[0095] The pre-treated porous substrate is treated by boiling in a suitable swelling agent (preferably water), causing the membrane to swell slightly in the x, y, and z directions. The swollen pre-treated porous substrate exhibits higher and stronger ion transport rates. Unlike membranes composed solely of ion exchange materials, the swollen pre-treated porous substrate retains its mechanical integrity and dimensional stability while maintaining the desired ion transport characteristics. There is a correlation between the amount of swelling agent within the pre-treated porous substrate and its transport performance. The swollen pre-treated porous substrate transports chemicals faster than the unswollen pre-treated porous substrate.

[0096] d. Properties of composite membranes

[0097] According to aspects of the invention, a composite film having a continuous ionomer phase has a predetermined clarity. Haze refers to the optical clarity of an object visible when viewed through the composite film, and can be measured using a haze meter or a transparency meter. In some embodiments, the haze of a composite film having a continuous ionomer phase formed by a single-pass ionomer coating is 5% to 95%, or 10% to 90%, or 20% to 85%. In alternative embodiments, the haze of a continuous ionomer phase formed by a multi-pass ionomer coating without a drying step between coating passes is 5% to 95%, or 10% to 90%, or 20% to 85%.

[0098] III. Flow battery

[0099] As described above, the composite film manufactured according to aspects of the present invention (see, for example, [reference needed]) can be used. Figures 3A-3F This can be incorporated into flow batteries (e.g., redox flow batteries). Figure 4As shown, a flow battery 400 is provided according to an aspect of the invention. The flow battery 400 is a fully rechargeable energy storage device comprising: a reservoir 410 containing a cathode electrolyte or positive electrolyte fluid 420, and a second reservoir 430 containing an anode electrolyte or negative electrolyte fluid 440. The cathode electrolyte 420 may be an electrolyte containing specific redox ions that are in an oxidized state and will be reduced during the discharge of the flow battery 400, or in a reduced state and will be oxidized during the charging of the flow battery 400, or may be a mixture of these oxidized ions and ions to be oxidized. The anode electrolyte 440 may be an electrolyte containing redox ions that are in a reduced state and will be oxidized during the discharge of the flow battery 400, or in an oxidized state and will be reduced during the charging of the flow battery 400, or may be a mixture of these reduced ions and ions to be reduced.

[0100] Cathode electrolyte 420 is circulated through exchange region 460 via pump 450, which includes a composite membrane 465 located between positive electrode 470 and negative electrode 480. Anode electrolyte 440 is also circulated through exchange region 460 via pump 490. Composite membrane 465 is manufactured according to aspects of the invention (see, for example...). Figures 3A-3D ).

[0101] In some embodiments, the amounts of cathode electrolyte 420 and anolyte 440 supplied to exchange region 460 can vary depending on the pumping operation of pumps 450 and 490, and therefore, the amount of power generated by the electrolyte reaction in exchange region 460 can vary. Cathode electrolyte 420 and anolyte 440 circulate in their respective spaces, thereby promoting reduction / oxidation chemical processes on both sides of composite membrane 465, resulting in a potential. The battery voltage can be chemically determined by the Nernst equation and ranges from 0.5 to 5.0 volts or from 0.8 to 1.7 volts.

[0102] IV. Test program

[0103] A. Testing of ion exchange materials

[0104] (a) Solid concentration of ion exchange material (IEM) solution

[0105] In this document, the terms "solution" and "dispersion" are used interchangeably when referring to IEM. This test procedure applies to solutions in which the IEM is in proton form and the amount of other solids is negligible. A 2 cubic centimeter volume of IEM solution is drawn into a syringe, and the mass of the syringe containing the solution is measured using a balance in a solids analyzer (purchased from CEM Corporation, USA). The mass of two sheets of glass fiber paper (obtained from CEM Corporation, USA) is also measured and recorded. The IEM solution is then deposited from the syringe onto the two layers of glass fiber paper. The glass fiber paper containing the ion exchange material is placed in the solids analyzer and heated to 160°C to remove the solvent liquid. Once the mass of the glass fiber paper and residual solids stops changing with increasing temperature and time, this mass is recorded. It is assumed that the residual IEM is anhydrous (i.e., the mass of the ionomer corresponding to 0% RH). The mass of the empty syringe is then measured and recorded using the same balance as before. The ionomer solids in the solution are calculated according to the following formula:

[0106]

[0107] (b) Equivalent of ion exchange materials (IEM)

[0108] The following test procedure applies to IEMs composed of a single ionomer resin or a mixture of ionomer resins in proton form (i.e., containing negligible amounts of other cations) and in solution containing negligible amounts of other ionic substances, including protic acids and dissociated salts. If these conditions are not met, the solution must be purified to remove ionic impurities before testing, according to suitable methods known to those skilled in the art, or the impurities must be characterized and their influence on the EW test results must be corrected.

[0109] As used herein, the EW of an IEM refers to the state where the IEM is in its proton form at 0% RH and impurities are negligible. An IEM can contain a single ionomer or a mixture of ionomers in proton form. A certain amount of IEM solution containing 0.2 g of solids with the solid concentration determined as described above is poured into a plastic cup. The mass of the ion exchange material is measured using a standard laboratory balance (from Mettler Toledo, LLC, USA). Then, 5 ml of deionized water and 5 ml of 200°C (proof) denatured ethanol (SDA 3C, Sigma Aldrich) are added to the ion exchange material in the cup. Then, 55 ml of 2N sodium chloride aqueous solution is added to the IEM solution. The sample is then equilibrated for 15 minutes with continuous stirring. After equilibration, the sample is titrated with 1N sodium hydroxide solution. The volume of 1N sodium hydroxide solution required to neutralize the sample solution to pH 7 is recorded. The EW of an IEM (EW) IEM The calculation is as follows:

[0110]

[0111] When combining multiple IEMs to form a composite membrane, the average EW of the IEMs in the composite membrane can be calculated using the following formula:

[0112]

[0113] The mass fraction of each IEM is relative to the total amount of all IEMs. This formula applies to both composite membranes containing ionomer mixtures and composite membranes containing ionomer layers.

[0114] B. Testing of porous membranes

[0115] (a) Bubble point of porous membranes

[0116] Bubble point is measured according to the procedure in ASTM F316-86 (1986). Isopropanol is used as the wetting fluid to fill the pores of the test specimen. The bubble point is the air pressure required to generate the first continuous stream of bubbles, which can be detected by their ascent through the isopropanol layer covering the microporous polymer matrix. This measurement provides an estimate of the maximum pore size.

[0117] (b) Grie number of porous membranes

[0118] According to ASTM D-726-58 (1971), airflow barrier properties are measured using a Gurley densometer. The procedure involves clamping the sample between the permeable plates of the Gurley densometer. A freely sliding inner cylinder of known weight is then released. The Gurley number is defined as the time (in seconds) taken for the released inner cylinder to displace a given volume of air in the densometer through the sample material.

[0119] (c) Non-contact thickness of porous membranes

[0120] The microporous polymer structure sample was placed on a flat, smooth metal anvil and taut to remove wrinkles. The height of the microporous polymer structure on the anvil was measured and recorded using a non-contact Keyence LS-7010M digital micrometer. Next, the height of the anvil without a microporous polymer matrix was recorded. The thickness of the microporous polymer structure was considered as the difference between the micrometer readings on the anvil with and without a microporous structure.

[0121] (d) Mass per unit area of ​​porous membrane

[0122] Each microporous polymer structure was stretched enough to eliminate wrinkles, and then cut into 10cm pieces using a die. 2 The block. Weigh 10cm under standard laboratory conditions. 2 The block is then calculated. The mass per unit area (M / A) is then calculated as the ratio of the measured mass to the known area. This process is repeated twice, and the average of the M / A values ​​is calculated.

[0123] (e) Apparent density of porous membranes

[0124] The apparent density of the microporous polymer structure is calculated using the following formula, based on non-contact thickness and mass per unit area data:

[0125]

[0126] C. Testing of composite membranes

[0127] (a) Thickness of composite membrane

[0128] Before measurement, equilibrate the composite film in the thickness measurement chamber for at least 1 hour. The composite film remains adhered to the substrate it coats. For each sample, place the composite film on its coated substrate on a smooth, flat, level marble slab. Bring a thickness gauge (obtained from Heidenhain Corporation, USA) into contact with the composite film and record the height readings at six different points on the film arranged in a grid pattern. Then, remove the sample from the substrate, bring the gauge into contact with the substrate, and record the height readings again at the same six points. Calculate the average thickness of the composite film at a given relative humidity (RH) in the chamber as the difference between the gauge height readings with and without the composite film on the coated substrate. Measure the local RH in the chamber using an RH probe (obtained from Fluke Corporation). Calculate the thickness at 0% RH using the following general formula:

[0129]

[0130] The density of the porous layer represents the skeleton density (ePTFE is 2.25 g / cm³). 3 The density of the ionomer represents the density of the ionomer at 0% RH (PFSA ionomer is 1.96 g / cm³). 3 The density of water is taken as 0.997 g / cm³. 3 The molecular weight of water is taken as 18.015 g / mol, and the parameter λ corresponds to the water absorption rate of the ion exchange material at a specified RH, calculated based on the number of moles of water per mole of acid groups. For PFSA ionomers, the λ value in the gas phase at any RH range of 0% to 100% is calculated using the following formula:

[0131] λ = 80.239 × RH 6 -38.717×RH 5 -164.451×RH 4 +208.509×RH 3 -91.052×RH 2 +21.740×RH 1 +0.084

[0132] (b) Mass per unit area of ​​composite membrane

[0133] The following test procedure can be used to determine the unit area mass of the composite film prepared according to aspects of this disclosure. A section including the substrate and a known area of ​​10 cm² will be cut from the sheet. 2Composite membrane samples were prepared. After cutting, the composite membrane samples on the coated substrate were weighed on a standard laboratory balance, and the weight and the RH value around the laboratory balance were recorded during the measurement. The local indoor RH was measured using an RH probe (obtained from Fluke Corporation). The sample was then removed from the substrate, and the substrate was weighed using the same laboratory balance, and the weight of the substrate was recorded. The weight of the composite membrane at a given indoor RH was calculated as the difference between the balance weight readings with and without the composite membrane on the coated substrate.

[0134] Then, calculate the mass per unit area of ​​the composite membrane when RH is 0% using the following formula:

[0135] M / A 0％RH下复合膜 =M / A 室RH％下复合膜 -density 水 **(Thickness at room temperature RH - Thickness at 0% RH) = [g / m] 2 ]

[0136]

[0137] (c) Haze of composite membrane

[0138] The following haze testing procedure was applied to a sample of an ion exchange membrane having a continuous ionomer phase prepared according to aspects of the present invention (see, for example, Figures 3A-3F A haze test was performed on the composite film that had been dried under environmental conditions (e.g., 20°C to 22°C, relative humidity 30-70%) for at least 24 hours prior to testing. Figure 5A and 5B As shown, the haze testing procedure includes using a haze meter or transparency meter 500 to determine the wide-angle scattering of light by the ion exchange membrane, resulting in the loss of optical contrast required to see an object when observed through the ion exchange membrane. In the haze meter or transparency meter 500 implemented according to an aspect of the invention, a sample 505 (e.g., an ion exchange membrane having a continuous ionomer phase) is placed between a light source 510 and an integrating sphere 515 lined with a diffuse reflective material and equipped with a photodetector 520, a movable diffuse reflective surface 525, and a trap 530 for low-angle scattering and direct transmission of light.

[0139] First, such as Figure 5A As shown, the total transmittance of sample 505 was measured with the trap 530 for low-angle scattered and directly transmitted light enclosed by a diffuse reflective surface. The enclosure of the trap 530 for low-angle scattered and directly transmitted light resulted in the detection of all light passing through sample 505. Total transmittance is defined as the ratio of light transmitted through the sample to the incident light on the sample. Then, as... Figure 5BAs shown, the haze of sample 505 was measured with the trap 530 for low-angle scattered and directly transmitted light open. The openness of the trap 530 for low-angle scattered and directly transmitted light resulted in the detection of only the diffuse component of the light passing through sample 505. Haze is defined as the ratio of diffuse transmittance to the total transmittance of light passing through the sample.

[0140] In some embodiments, the haze of the composite film having a continuous ionomer phase formed by a single-pass ionomer coating is 5% to 95%, or 10% to 90%, or 20% to 85%. In alternative embodiments, the haze of the continuous ionomer phase formed by a multi-pass ionomer coating without a drying step between coating passes is 5% to 95%, or 10% to 90%, or 20% to 85%.

[0141] (d) Bubbling of composite membranes

[0142] The following foaming test procedure was applied to the composite membrane sample prepared according to aspects of the present invention (see, for example, Figures 3A-3D The bubbling test procedure involves subjecting each composite membrane sample to the following stress cycle: immersion for 3 minutes in a beaker containing a 6 mol / L aqueous solution of sulfuric acid at 80°C, followed by immersion for 1 minute in a beaker containing deionized water under ambient conditions (e.g., between 20°C and 22°C, with a relative humidity of 30-70%). This stress cycle is repeated six times. After the stress cycle, each composite membrane sample is dried under ambient conditions (e.g., between 20°C and 22°C, with a relative humidity of 30-70%), and the bubble or bubbling density is counted. The bubble or bubbling area can be calculated in various ways, including manual observation and measurement and / or automated techniques, such as the use of imaging software. ImageJ, developed by the National Institutes of Health (NIH) in the United States, is an example of publicly available imaging processing software that can be used to calculate the number and area of ​​bubbles.

[0143] Figures 6A-6B Low-resolution 3x3cm images prior to the foaming test are shown. 2 and high resolution 1x1 and high resolution 1x1cm after the foaming test. 2 Below, the composite membrane 600 prepared according to aspects of the present invention (see, for example) Figures 3A-3D ) and conventional ion exchange membrane 602. For example Figure 6A As shown, neither the composite membrane 600 nor the conventional ion exchange membrane 602 exhibited foaming before the foaming test performed according to the above foaming test procedure. Figure 6B As shown, the composite membrane 600 did not exhibit bubbling (i.e., 0 bubbles / cm). 2Therefore, this membrane has 0% foaming area, while the conventional ion exchange membrane 602 exhibits foaming (i.e., 95 bubbles / cm²). 2 Each bubble has a radius of 200 μm, and the bubble-forming area of ​​the membrane is 13.5%.

[0144] In some embodiments, the composite film having a continuous ionomer phase formed by a single-pass ionomer coating exhibits less than 0.3%, less than 0.2%, less than 0.1%, or 0% bubble or foam area after exposure to a foaming test procedure. In alternative embodiments, the composite film having a continuous ionomer phase formed by a multi-pass ionomer coating without a drying step between coating passes exhibits less than 0.3%, less than 0.2%, less than 0.1%, or 0% bubble or foam area after exposure to a foaming test procedure. Figures 7A-7C Samples 700, 710, and 720 of composite films prepared according to aspects of the present invention are shown, having a bubble or foaming density of less than 0.1%. In some embodiments, composite films having a continuous ionomer phase formed by a single-pass ionomer coating exhibit a haze change of 0% or less after exposure to a foaming test procedure, between 0% and -60%, or between 0% and -45%, or between 0% and -30%, or between 0% and -21%. In alternative embodiments, composite films having a continuous ionomer phase formed by a multi-pass ionomer coating without a drying step between coating passes exhibit a haze change of 0% or less after exposure to a foaming test, between 0% and -60%, or between 0% and -45%, or between 0% and -30%, or between 0% and -21%.

[0145] V. Example

[0146] Without limiting the scope of the invention, the apparatus and manufacturing method of the invention can be better understood by referring to the following examples. All ePTFE samples provided in the following examples were prepared in accordance with the teachings of U.S. Patent No. 3,593,566. Table 1 lists the physical properties of porous expanded polytetrafluoroethylene (ePTFE).

[0147] Table 1: Physical properties of porous ePTFE used in the examples

[0148] # <![CDATA[g / m 2 ]]> micrometer <![CDATA[g / cm 3 ]]> Second kPa 1 30.6 137.1 0.22 26.3 300 2 26 57.7 0.46 9.3 127 3 18 26 0.7 12.1 130 4 10.8 30 0.36 9.8 296 5 5.8 12.5 0.46 6.6 222

[0149] 1. Comparative Example - Conventional multi-stage ionomers manufactured by drying between each step.

[0150] Example 1.1

[0151] A 26.7-micron-thick composite membrane was prepared using standard laboratory techniques. This membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 920 g / (mol acid equivalent), reinforced with two layers of expanded porous ePTFE membrane #5. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (product FSS2, supplied by Asahi Glass Company) with an EW of 920 g / mol equivalent was coated onto a moving carrier substrate using a slit die, followed by lamination with ePTFE membrane #5 moving in the same direction. The carrier substrate was a polymer sheet (obtained from Daicel Valuecoating Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at this temperature for 1 minute to produce a solid coated structure comprising a carrier substrate bonded to the polymer layers reinforced with expanded porous polytetrafluoroethylene.

[0152] Then, using a slit die, another portion of the same perfluorosulfonic acid resin aqueous-ethanol-based solution was applied to the coated structure, and laminated with another ePTFE membrane #5 moving in the same direction. The laminate was dried again at 160°C and annealed at that temperature for 1 minute. Finally, using a slit die, another portion of the same perfluorosulfonic acid resin aqueous-ethanol-based solution was applied to the coated structure, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane comprises a carrier substrate to which an ion-exchange polymer layer is attached, followed by a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, then another ion-exchange polymer layer, followed by another microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, and then another ion-exchange polymer layer on top, with a total thickness of 26.7 μm at 0% RH and a mass / area of ​​54.0 g / m². 2 The composite film is largely transparent, with a haze value of 5%.

[0153] To determine properties, such as the sensitivity of the composite membrane to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test as described above, the haze of the sample of composite membrane 1.5 with the discontinuous ionomer phase increased by 320%, reaching a value of 21.0%. The bubble or foaming area of ​​the sample of composite membrane with the discontinuous ionomer phase prepared as described above was approximately 13.5%, expressed as the ratio of the area of ​​the ionomer to the area of ​​the bubble or foam within the ionomer. Figure 6BPhotographs of 3cm × 3cm and 1cm × 1cm areas of the composite membrane 602 representing Example 1.1 are shown before and after a foaming test, wherein the membrane after the foaming test has bubbles or bubbles 604 in the weak internal interfaces of the ionomer layer or between multiple ionomer coatings.

[0154] Example 1.2

[0155] A 44.2-micron-thick composite membrane was prepared using standard laboratory techniques. This membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 810 g / (mol acid equivalent), reinforced with a layer of expanded porous ePTFE membrane #2. First, an aqueous-ethanol-based solution of the ion-exchange perfluorosulfonic acid resin (from Shanghai Gore 3F Fluoromaterials Co.,LTD., China) with an EW of 810 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down rod, followed by lamination with ePTFE membrane #2. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at this temperature for 1 minute. Then, another portion of the same perfluorosulfonic acid resin aqueous-ethanol-based solution was applied to the coated structure using a pull-down rod, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane comprises a carrier substrate to which an ion-exchange polymer layer is attached, followed by a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, and another ion-exchange polymer layer on top, with a total thickness of 44.2 μm and a mass / area of ​​90.5 g / m² at 0% RH. 2 The composite film is largely transparent, with a haze value of 4.6%.

[0156] To determine properties, such as the sensitivity of the composite membrane to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the membrane exhibited bubbles or bubbling in the ionomer layer or at the weak internal interfaces between multiple ionomer coatings. After the foaming test as described above, the haze of the sample of composite membrane 1.2 with a discontinuous ionomer phase increased by 35%, reaching a value of 6.3%. The bubble or bubbling area of ​​the sample of composite membrane 1.2 with a discontinuous ionomer phase prepared as described above was approximately 1.3%, calculated as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or bubbling within the ionomer.

[0157] Example 1.3

[0158] A 27.9-micron-thick composite membrane was prepared using standard laboratory techniques. This membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 1100 g / (mol acid equivalent), reinforced with a layer of expanded porous ePTFE membrane #2. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (D2021, from IonPower Inc., USA) with an EW of 1100 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down rod, and then laminated with ePTFE membrane #2. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at that temperature for 1 minute. Next, another aqueous-ethanol-based solution of the same perfluorosulfonic acid resin was applied to the coated structure using a pull-down rod, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane comprises a carrier substrate to which an ion-exchange polymer layer is attached, followed by a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, and another ion-exchange polymer layer on top. At 0% RH, the total thickness is 27.9 μm, and the mass / area ratio is 58.4 g / m². 2 The composite film is largely transparent, with a haze value of 16.8%.

[0159] To determine properties, such as the sensitivity of the composite membrane to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the membrane exhibited bubbles or bubbling in the ionomer layer or at the weak internal interfaces between multiple ionomer coatings. After the foaming test as described above, the haze of the sample of composite membrane 1.3 with a discontinuous ionomer phase increased by 34%, reaching a value of 22.6%. The bubble or bubbling area of ​​the sample of composite membrane 1.3 with a discontinuous ionomer phase prepared as described above was approximately 0.5%, calculated as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or bubbling within the ionomer.

[0160] Example 1.4

[0161] A 22.7-micron-thick composite membrane was prepared using standard laboratory techniques. This membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 900 g / (mol acid equivalent), reinforced with a layer of expanded porous ePTFE membrane #3. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (from Shanghai Gore 3F Fluorine Materials Co., Ltd., China) with an EW of 900 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down rod, followed by lamination with ePTFE membrane #3. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at that temperature for 1 minute. Next, another aqueous-ethanol-based solution of the same perfluorosulfonic acid resin was applied to the coated structure using a pull-down rod, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane comprises a carrier substrate to which an ion-exchange polymer layer is attached, followed by a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, and another ion-exchange polymer layer on top. At 0% RH, the total thickness is 22.7 μm, and the mass / area ratio is 47.1 g / m². 2 The composite film is largely transparent, with a haze value of 19.4%.

[0162] To determine properties, such as the sensitivity of the composite membrane to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the membrane exhibited bubbles or bubbling in the ionomer layer or at the weak internal interfaces between multiple ionomer coatings. After the foaming test as described above, the haze of the sample of composite membrane 1.4 with a discontinuous ionomer phase increased by 45%, reaching a value of 28%. The bubble or bubbling area of ​​the sample of composite membrane 1.4 with a discontinuous ionomer phase prepared as described above was approximately 0.3%, calculated as the ratio of the area of ​​the ionomer to the area of ​​the bubbles or bubbling within the ionomer.

[0163] Example 1.5

[0164] A 17.9-micron-thick composite membrane was prepared using standard laboratory techniques. This membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 900 g / (mol acid equivalent), reinforced with a layer of expanded porous ePTFE membrane #4. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (from Shanghai Gore 3F Fluorine Materials Co., Ltd., China) with an EW of 900 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down bar, and then laminated with ePTFE membrane #4. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at that temperature for 1 minute. Next, another aqueous-ethanol-based solution of the same perfluorosulfonic acid resin was applied to the coated structure using a pull-down bar, dried again at 160°C, and annealed at that temperature for 1 minute. The resulting composite membrane comprises a carrier substrate to which an ion-exchange polymer layer is attached, followed by a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, and another ion-exchange polymer layer on top. At 0% RH, the total thickness is 17.9 μm, and the mass / area ratio is 36.7 g / m². 2 The composite film is largely transparent, with a haze value of 5.7%.

[0165] To determine properties, such as the sensitivity of the composite membrane to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the membrane exhibited bubbles or bubbling in the ionomer layer or at the weak internal interfaces between multiple ionomer coatings. After the foaming test as described above, the haze of the sample of composite membrane 1.5 with a discontinuous ionomer phase increased by 31%, reaching a value of 7.5%. The bubble or bubbling area of ​​the sample of composite membrane 1.5 with a discontinuous ionomer phase prepared as described above was approximately 6.3%, calculated as the ratio of the area of ​​the ionomer to the area of ​​bubbles or bubbling within the ionomer.

[0166] The results of comparative examples 1.1-1.5 are summarized in Table 2.

[0167] Table 2: Summary of data from Comparative Examples 1.1-1.5

[0168]

[0169]

[0170] 2. Embodiments of the Invention - According to some aspects of the present invention, a continuous ionomer is manufactured by single-pass ionomer coating. Phase composite membrane

[0171] Example 2.1

[0172] A 21.6-micron-thick composite membrane was prepared using standard laboratory techniques. This membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 820 g / (mol acid equivalent), and was reinforced with an expanded porous polytetrafluoroethylene membrane #3. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (product IW100-800, from Asahi Glass Company) with an EW of 820 g / mol equivalent was coated onto a moving carrier substrate using a slit die, followed by lamination with an ePTFE membrane #3 moving in the same direction. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a protective layer of PET and a cyclic olefin copolymer (COC), oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at that temperature for 1 minute to produce a solid coated structure. This structure includes a carrier substrate to which an ion-exchange polymer layer is attached, followed by a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded. At 0% RH, the total thickness is 21.6 μm, and the mass / area ratio is 44.9 g / m². 2 .from Figure 3E-3F It can be seen that the resulting composite membrane is characterized by having ion exchange material embedded within the microporous polymer structure, leaving a non-blocked portion in the microporous polymer structure closest to the first surface, and forming a layer on the second surface of the microporous polymer structure. The haze value of the resulting composite membrane is 65%.

[0173] To determine properties, such as the sensitivity of the composite membrane to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test as described above, the haze of the sample of composite membrane 1.5 with a discontinuous ionomer phase decreased by -6.2%, reaching a value of 61.0%. The bubble or foaming area of ​​the sample of composite membrane 2.1 with a continuous ionomer phase prepared as described above was approximately 0%, expressed as the ratio of the area of ​​the ionomer to the area of ​​the bubble or foam within the ionomer. Figure 6A Photographs of 3cm×3cm and 1cm×1cm areas of the composite membrane 600 before and after a bubbling test are shown. No bubbles or bubbling are present in the membrane after the bubbling test.

[0174] Example 2.2

[0175] A 44.6-micron-thick composite membrane was prepared using conventional laboratory techniques. This membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 810 g / (mol acid equivalent), reinforced with a layer of expanded porous ePTFE membrane #1. First, an aqueous-ethanol-based solution of the perfluorosulfonic acid resin (from Shanghai Gore 3F Fluorine Materials Co., Ltd., China) with an EW of 810 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down bar, followed by lamination with ePTFE membrane #1. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. Subsequently, the laminate was dried in an oven at 160°C and annealed at this temperature for 1 minute to produce a solid coated structure comprising the carrier substrate bonded to the polymer layer reinforced with expanded porous polytetrafluoroethylene. The resulting composite membrane comprises a carrier substrate to which an ion-exchange polymer layer is attached, followed by a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded. At 0% RH, the total thickness is 44.6 μm, and the mass / area ratio is 91.8 g / m². 2 The resulting composite membrane is characterized by having ion exchange material embedded within a microporous polymer structure, leaving a non-blocked portion in the microporous polymer structure closest to the first surface and forming a layer on the second surface of the microporous polymer structure. The haze value of the composite membrane is 24.4%.

[0176] To determine properties, such as the composite membrane's sensitivity to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the composite membrane showed no bubbles or bubbling. Following the foaming test as described above, the haze of the sample of composite membrane 2.2 with a continuous ionomer phase decreased by -11.3%, reaching a value of 21.6%. The bubble or bubbling area of ​​the sample of composite membrane 2.2 with a continuous ionomer phase prepared as described above was approximately 0%, expressed as the ratio of the area of ​​the ionomer to the area of ​​bubbles or bubbling within the ionomer.

[0177] Example 2.3

[0178] A 28.1-micron thick composite membrane was prepared using standard laboratory techniques. The membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 1100 g / (mol acid equivalent), reinforced with a layer of expanded porous ePTFE membrane #1. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (D2021, from IonPower Inc., USA) with an EW of 1100 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down bar, followed by lamination with ePTFE membrane #1. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at this temperature for 1 minute. The resulting composite membrane, comprising the carrier substrate connected to a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, had a total thickness of 28.1 microns and a mass / area of ​​59.5 g / m² at 0% RH. 2 The resulting composite membrane is characterized by having ion exchange material embedded within a microporous polymer structure, leaving a non-blocked portion in the microporous polymer structure closest to the first surface, and having no layer on the second surface of the microporous polymer structure. The haze value of the composite membrane is 27.8%.

[0179] To determine properties, such as the sensitivity of the composite membrane to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the composite membrane showed no bubbles or bubbling. Following the foaming test as described above, the haze of the sample of composite membrane 2.3 with a continuous ionomer phase decreased by -5.9%, reaching a value of 26.2%. The bubble or bubbling area of ​​the sample of composite membrane 2.3 with a continuous ionomer phase prepared as described above was approximately 0%, expressed as the ratio of the area of ​​the ionomer to the area of ​​bubbles or bubbling within the ionomer.

[0180] Example 2.4

[0181] A 23.2-micrometer-thick composite membrane was prepared using conventional laboratory techniques. The membrane consisted of a perfluorosulfonic acid resin ion-exchange polymer with an EW of 900 g / (mol acid equivalent) and was reinforced with a layer of expanded porous ePTFE membrane #2. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (from Shanghai Gore 3F Fluorine Materials Co., Ltd., China) with an EW of 900 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down bar, followed by lamination with ePTFE membrane #2. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at this temperature for 1 minute. The resulting composite membrane, comprising the carrier substrate connected to a microporous polytetrafluoroethylene membrane layer in which the ion-exchange polymer is embedded, had a total thickness of 23.2 micrometers and a mass / area of ​​49.2 g / m² at 0% RH. 2 The resulting composite membrane is characterized by having ion exchange material embedded within a microporous polymer structure, leaving a non-blocked portion in the microporous polymer structure closest to the first surface, and having no layer on the second surface of the microporous polymer structure. The haze value of the composite membrane is 35.2%.

[0182] To determine properties such as the composite membrane's sensitivity to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the composite membrane showed no bubbles or bubbling. Following the foaming test as described above, the haze of the sample of composite membrane 2.4 with a continuous ionomer phase decreased by -20.7%, reaching a value of 27.9%. The bubble or bubbling area of ​​the sample of composite membrane 2.4 with a continuous ionomer phase prepared as described above was approximately 0%, expressed as the ratio of the area of ​​the ionomer to the area of ​​bubbles or bubbling within the ionomer.

[0183] Example 2.5

[0184] A 18.4-micron thick composite membrane was prepared using standard laboratory techniques. The membrane consisted of an ion-exchange polymer, perfluorosulfonic acid resin, with an EW of 900 g / (mol acid equivalent), reinforced with a layer of expanded porous ePTFE membrane #3. First, an aqueous-ethanol-based solution of perfluorosulfonic acid resin (from Shanghai Gore 3F Fluorine Materials Co., Ltd., China) with an EW of 900 g / mol equivalent was coated onto a carrier substrate constrained within a frame using a pull-down bar, followed by lamination with ePTFE membrane #3. The carrier substrate was a polymer sheet (obtained from Daicel Investment Co., Ltd., Japan) containing a PET and cyclic olefin copolymer (COC) protective layer, oriented with the COC side on top. The laminate was then dried in an oven at 160°C and annealed at this temperature for 1 minute. The resulting composite membrane, comprising the carrier substrate bonded to the polymer layer reinforced with expanded porous polytetrafluoroethylene, had a total thickness of 18.4 microns and a mass / area of ​​38.6 g / m² at 0% RH. 2 The resulting composite membrane is characterized by having ion exchange material embedded within a microporous polymer structure, leaving a non-blocked portion in the microporous polymer structure closest to the first surface, and having a layer on the second surface of the microporous polymer structure. The haze value of the composite membrane is 77.3%.

[0185] To determine properties such as the composite membrane's sensitivity to foaming in a fully liquid environment with variable ionic strength, a foaming test procedure was performed as described above. After the foaming test, the composite membrane showed no bubbles or bubbling. Following the foaming test as described above, the haze of the sample of composite membrane 2.5 with a continuous ionomer phase decreased by -8.7%, reaching a value of 60.5%. The bubble or bubbling area of ​​the sample of composite membrane 2.5 with a continuous ionomer phase prepared as described above was approximately 0%, expressed as the ratio of the area of ​​the ionomer to the area of ​​bubbles or bubbling within the ionomer.

[0186] The data from embodiments 2.1-2.5 of this invention are summarized in Table 3.

[0187] Table 3: Summary of data from Examples 2.1-2.5 of the present invention

[0188]

[0189] While the invention has been described in detail, modifications within the spirit and scope of the invention will be apparent to those skilled in the art. It should be understood that aspects and features of the invention and its embodiments as described above and / or in the appended claims can be combined or interchanged in whole or in part. In the foregoing description of various embodiments, those embodiments referred to in another embodiment can be suitably combined with other embodiments as will be understood by those skilled in the art. Furthermore, those skilled in the art should understand that the foregoing description is merely exemplary and is not intended to limit the invention.

Claims

1. A method for forming a composite membrane, the method comprising: (a) Provide a support layer, (b) In one step, an ion-exchange material is applied to the support layer. (c) Obtaining a microporous polymer structure comprising at least one microporous polymer layer, (d) Laminating at least one microporous polymer layer onto an ion exchange material to form an impregnated microporous polymer structure having a continuous ionomer phase. (e) Applying an ion-exchange material to the top surface of the impregnated microporous polymer structure according to step (d) of the method. (f) The impregnated microporous polymer structure obtained in step (e) is dried to form a composite film with a continuous ionomer phase, and (g) Heat anneal the composite film; There is no drying step between the application of the ion exchange material in step (b) and the application of the ion exchange material in step (e).

2. The method as described in claim 1, characterized in that, There is no internal interface between the application of ion exchange materials, microporous polymer structures, or any combination thereof.

3. The method as described in claim 1, characterized in that, The drying and thermal annealing of the composite film are carried out at a temperature of 160-220°C.

4. The method as described in claim 1, characterized in that, The composite membrane comprises: Microporous polymer structure; and An ion exchange material, which is at least partially embedded within a microporous polymer structure and closes at least a portion of the microporous polymer structure. In this process, the ion exchange material forms a continuous ionomer phase within the composite membrane. The composite membrane comprises multiple ion exchange material layers, which are provided on top of each other without any internal interfaces between the layers. Among them, the haze change of the composite membrane after the foaming test procedure is 0% or lower; The foaming test procedure includes: In the first step, the composite membrane is immersed in a 6 mol / L sulfuric acid aqueous solution at 80°C for 3 minutes. In the second step, the composite membrane is removed from the sulfuric acid aqueous solution. In the third step, the composite membrane is immersed in deionized water for 1 minute under ambient conditions. In the fourth step, the composite membrane is removed from the deionized water. Repeat the cycle from step one to step four at least twice. In the fifth step, the composite membrane is dried under environmental conditions, and In step six, the bubbles or bubbling formed on the composite membrane are counted.

5. The method as described in claim 4, characterized in that, Prior to the bubbling test procedure, the haze value of the composite membrane was between 5% and 95%.

6. The method as described in claim 4, characterized in that, After undergoing the foaming test procedure, the composite film with a continuous ionomer phase has bubbles or a foaming area of ​​less than 0.3%.

7. The method as described in claim 1, characterized in that, The microporous polymer structure contains expanded polytetrafluoroethylene.

8. The method as described in claim 1, characterized in that, Microporous polymer structures contain hydrocarbon polyolefins.

9. The method as described in claim 8, characterized in that, Hydrocarbon polyolefins include polyethylene, polypropylene, or polystyrene.

10. The method as described in claim 1, characterized in that, The ion exchange material contains at least one ionomer.

11. The method as described in claim 10, characterized in that, The at least one ionomer comprises a proton-conducting polymer.

12. The method as described in claim 11, characterized in that, The proton-conducting polymer contains perfluorosulfonic acid.

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