Electrochemical membrane

Abstract

To provide a thin composite membrane having high performance and low ion resistance while exhibiting high resistance to penetration and subsequent short-circuiting.SOLUTION: A) at least two reinforcement layers, each of the at least two reinforcement layers comprising a microporous polymer, and b) an ion-exchange material (IEM) at least partially imbibed within the microporous polymer structure of the at least two reinforcement layers to render the microporous polymer structure occlusive, wherein the composite membrane has an average puncture pressure failure of at least 1034 kPa (150 psi) as measured according to the Specific Average Puncture Pressure Failure Test; And wherein the microporous polymer structure is present in a total content of at least 15% by volume, based on the total volume of the composite membrane.SELECTED DRAWING: FIG. 1A

Description

[Technical Field]

[0001] Field The present disclosure relates to polymer electrolyte membranes, and in particular to composite membranes having at least two reinforcing layers comprising microporous polymer structures and having surprisingly high puncture resistance. [Background technology]

[0002] background Polymer electrolyte membranes (PEMs) are key components in many applications such as fuel cells, electrolyzers, and redox flow batteries.

[0003] In a fuel cell, the polymer electrolyte membrane (PEM) is part of the membrane electrode assembly (MEA). The MEA is the core component of the fuel cell where the electrochemical reactions that generate electricity occur. A typical MEA includes a PEM, two catalyst layers (i.e., an anode and a cathode attached to either side of the PEM), and two gas diffusion layers (GDLs) attached to the two outer surfaces of the catalyst layers. The PEM separates two reactant gas streams. On the anode side of the MEA, fuel, e.g., hydrogen gas, is oxidized to separate electrons and protons. The cell is designed so that the electrons travel through an external circuit while the protons migrate through the PEM. On the cathode side, the electrons and protons react with an oxidant (oxygen or air) to produce water and heat. In this way, the electrochemical potential is maintained, and electrical current can be drawn from the fuel cell to perform useful work.

[0004] Redox flow batteries use two soluble redox couples as electroactive materials to store energy through oxidation and reduction reactions. Typically, redox flow batteries contain two electrolyte reservoirs (cationic and anionic electrolytes) from which the electrolyte is circulated by a pump through an electrochemical cell stack. The cell stack typically contains multiple cells connected in series or parallel, allowing the electrochemical reaction to occur at the inert electrode. Each cell in the stack contains an anode, a cathode, and an ion-exchange membrane separator (e.g., a polymer electrolyte membrane PEM) to prevent cross-mixing of the electrolyte solutions from the two reservoirs while allowing the diffusion of ions across the membrane separator.

[0005] Electrolyzers hydrolyze water to produce hydrogen and oxygen. The reactions that occur in electrolyzers are very similar to those in fuel cells, except that the reactions at the anode and cathode are reversed. In fuel cells, hydrogen gas is consumed at the anode, while in electrolyzers, hydrogen gas is produced at the cathode. Bipolar electrolyzers (or PEM electrolyzers) use the same type of electrolyte separator as PEM fuel cells. The electrolyte separator is a thin, solid, ionically conductive membrane that replaces the thick, porous membrane that separates the aqueous solutions used in alkaline electrolyzers.

[0006] High selectivity (due to high conductance and / or low permeance), high durability, and low cost are all desirable qualities for a PEM. However, as a practical engineering problem, optimizing these properties often involves conflicts, and trade-offs must be accepted. Selectivity can be improved by increasing conductance through a reduction in membrane thickness. Thinner PEMs also reduce cost because ionomers are expensive and less is used. However, thinner membranes increase hydrogen permeation, negating the selectivity gains from increased proton conduction, resulting in thin membranes exhibiting comparable or lower selectivity than thicker membranes. Furthermore, thinner membranes are often weaker and lack sufficient mechanical durability for harsh automotive conditions. Reducing the membrane's physical thickness also increases its susceptibility to damage or puncture by other electrochemical device components, potentially shortening the cell's lifetime.

[0007] PEM penetration can be particularly problematic in redox flow batteries (RFBs), which use electrode layers positioned on either side of the PEM. RFB electrode layers typically contain porous layers (typical pore sizes of 1-200 microns). Porous layers can include felt, paper, or woven materials, among others. RFB electrodes typically contain carbon fibers that can penetrate the PEM when the electrode layers are compressed against the PEM during PEM-electrode assembly. Therefore, access to membranes with higher proton conductance is limited by the requirement for transmembrane resistance.

[0008] Finally, PEM electrochemical devices can fail due to pinholes that initiate and propagate through the polymer electrolyte membrane. Additionally, these devices can also fail if electronic current passes through the PEM, causing a short circuit in the system.

[0009] A state-of-the-art approach to improving the mechanical and puncture resistance of PEMs involves reinforcing the polymer electrolyte membrane with a continuous layer of microporous polymer structure. This layer of microporous polymer structure is fully imbibed with the polymer electrolyte (e.g., ionomer) and therefore fully conductive to ions. However, even reinforced PEMs can be subject to puncture during assembly of the PEM during electrochemical device fabrication.

[0010] Therefore, a need exists for thin composite membranes that exhibit higher resistance to penetration and subsequent shorting by electrochemical device components than state-of-the-art composite membranes, while retaining high performance and low ionic resistance. Summary of the Invention

[0011] Abstract The present inventors have endeavored to solve the above-mentioned problems. Surprisingly, the inventors have discovered that for a given total content of microporous polymer structures and thickness of the composite membrane at 0% RH, distributing the microporous polymer structures among at least two (or more) reinforcing layers further increases the membrane's resistance to puncture by components of an electrochemical device during device fabrication. The inventors have also discovered that increasing the total content of microporous polymer structures (distributed among at least two reinforcing layers) in the composite electrolyte membrane further improves the average burst pressure of the composite electrolyte membrane. These findings are highly advantageous because, compared to state-of-the-art composite electrolyte membranes, the composite membranes described herein exhibit superior resistance to penetration by components of an electrochemical device into which the composite membrane may be incorporated. The inventors have also surprisingly discovered that separating at least two reinforcing layers by a distance d further increases the composite membrane's resistance to penetration by components of an electrochemical device during device fabrication. Thus, the composite membranes described herein have superior resistance to penetration by components of an electrochemical device during device fabrication without compromising membrane performance.

[0012] In one embodiment, a composite membrane for an electrochemical device comprising: a) at least two reinforcing layers, each of the at least two reinforcing layers comprising a microporous polymer structure; and b) an ion exchange material (IEM) at least partially absorbed within the microporous polymer structure of said at least two reinforcing layers, causing said microporous polymer structure to become occlusive; A composite membrane for an electrochemical device is provided, comprising:

[0013] Within the context of this disclosure, the term composite membrane includes polymer electrolyte membranes (PEMs) as well as composite electrolyte membranes.

[0014] The microporous polymer structure is present in the composite membrane in a total content (or amount) of at least about 20 volume percent based on the total volume of the composite membrane. Within the context of the present disclosure, the total content of the microporous polymer structure in the composite membrane is the total content (mass or volume) of the microporous polymer structure present in the composite membrane (distributed among at least two reinforcing layers). Within the context of the present disclosure, the total content of the microporous polymer structure in the composite membrane can also be expressed as the reinforced microporous polymer structure content in the composite membrane.

[0015] The composite membrane may include two reinforcing layers. The composite membrane may include three reinforcing layers. The composite membrane may include four reinforcing layers. The composite membrane may include five reinforcing layers. The composite membrane may include between two and ten reinforcing layers. The composite membrane may include any suitable number of reinforcing layers.

[0016] The composite membrane can have a thickness of at least about 10 μm at 0% relative humidity (RH). The composite membrane can have a thickness of about 10 μm to about 115 μm, or about 10 μm to about 100 μm, or about 10 μm to about 90 μm, or about 10 μm to about 80 μm, or about 10 μm to about 75 μm, or about 10 μm to about 70 μm, or about 10 μm to about 60 μm, or about 10 μm to about 50 μm, or about 10 μm to about 40 μm, or about 10 μm to about 30 μm, or about 1 μm to about 50 μm, or about 10 μm to about 40 μm, or about 10 μm to about 50 μm, or about 10 μm to about 50 μm, or about 10 μm to about 6 ... It can have a thickness of 0 μm to about 20 μm, or about 10 μm to about 15 μm, or about 10 μm to about 12 μm, or about 20 μm to about 60 μm, or about 30 μm to about 60 μm, or about 40 μm to about 60 μm, or about 12 μm to about 30 μm, or about 12 μm to about 20 μm, or about 15 μm to about 30 μm, or about 15 μm to about 20 μm, or about 20 μm to about 30 μm. The composite membrane has a thickness at 0% RH of about 10 μm, or about 11 μm, or about 12 μm, or about 13 μm, or about 14 μm, or about 15 μm, or about 16 μm, or about 17 μm, or about 18 μm, or about 19 μm, or about 20 μm, or about 21 μm, or about 22 μm, or about 23 μm, or about 24 μm, or about 25 μm, or about 30 μm, or about 35 μm, or about 40 μm, or about 45 μm, or about 50 μm, or about 55 μm, or about 60 μm, or about 65 μm, or about 70 μm, or about 75 μm, or about 80 μm, or about 85 μm, Alternatively, it may have a thickness of about 90 μm, or about 95 μm, or about 100 μm, or about 105 μm, or about 110 μm, or about 115 μm.

[0017] Within the context of the present disclosure, the total content of microporous polymer structures in the composite membrane is defined as the total mass per area (g / m) of microporous polymer structures (distributed among the at least two reinforcing layers) in the composite membrane. 2) The composite membrane can contain more than one type of microporous polymer structure. For example, the composite membrane can contain a single type of microporous polymer structure (e.g., ePTFE) present in at least two reinforcement layers. The composite membrane can contain at least two reinforcement layers, each of which can contain a mixture of different types of microporous polymer structures (e.g., a fluorinated polymer and a hydrocarbon polymer). The composite membrane can contain at least two reinforcement layers, a first of which can contain a single type of microporous polymer structure (e.g., ePTFE) and a second of which can contain a single type of microporous polymer structure (e.g., a hydrocarbon polymer) that is different from the microporous polymer structure of the first of the at least two reinforcement layers. The total content of microporous polymer structures in a composite membrane, expressed in mass per area (i.e., the sum of the masses of the microporous polymer structures present in each reinforcement layer of the composite membrane divided by the area of ​​the composite membrane), can be normalized using the following formula:

number

[0018] The matrix skeletal density is the mass of the solid divided by the volume of the solid excluding open and closed cells. Since the matrix skeletal density represents the density of the solid part of the material, the unit is 1 cm of solid. 3 The matrix skeletal density is the number of grams of solid per cubic meter. The matrix skeletal density is typically assessed by helium pycnometry experiments and represents the true solid density of a material in the absence of closed cells. For non-porous solids, the matrix skeletal density is the same as the geometric or envelope density. Within the context of this disclosure, the matrix skeletal density of ePTFE is approximately 2.25 g / cm. 3The matrix skeletal density of the track-etched porous polycarbonate is approximately 1.20 g / cm 3 It can be thought of as:

[0019] In embodiments where the composite membrane comprises two or more types of microporous polymer structures, the normalized total content (mass per area) of the microporous polymer structures within the composite membrane can be calculated by the following formula:

number

[0020] The normalized total content of microporous polymer structures within the composite membrane is at least about 2.4·10 based on the total area of ​​the composite membrane. -6 m (i.e., 2.4 μm), or about 3 μm, or about 3.5 μm, or about 4 μm, or about 4.5 μm, or about 5 μm, or about 5.5 μm, or about 6 μm, or about 6.5 μm, or about 7 μm, or about 8 μm, or about 8.5 μm, or about 9 μm.

[0021] As mentioned above, the total content of the microporous polymer structure in the composite membrane can be expressed as the volume percentage occupied by the microporous polymer structure (distributed among the at least two reinforcing layers) in the composite membrane. The microporous polymer structure can be present in a total content of at least about 15% by volume, or at least about 20% by volume, or at least about 25% by volume, or at least about 30% by volume, or at least about 35% by volume, or at least about 40% by volume, or at least about 45% by volume, or at least about 50% by volume, or at least about 55% by volume, or at least about 60% by volume, or at least about 65% by volume, or at least about 70% by volume, based on the total volume of the composite membrane.

[0022] The microporous polymer structure comprises, based on the total volume of the composite membrane, about 15% by volume to about 70% by volume, or about 20% by volume to about 70% by volume, or about 30% by volume to about 70% by volume, or about 40% by volume to about 70% by volume, or about 50% by volume to about 70% by volume, or about 60% by volume to about 70% by volume, or about 65% by volume to about 70% by volume, or about 15% by volume to about 65% by volume, or about 20% by volume to about 65% by volume, or about The microporous polymer structure may be present in a total content of about 30% to about 65% by volume, about 40% to about 65% by volume, about 50% to about 65% by volume, about 60% to about 65% by volume, about 20% to about 60% by volume, about 20% to about 50% by volume, about 20% to about 40% by volume, about 20% to about 30% by volume, about 40% to about 60% by volume, or about 40% to about 50% by volume. The microporous polymer structure may be present in a total content of about 20% by volume, about 25% by volume, about 30% by volume, about 35% by volume, about 40% by volume, about 45% by volume, about 50% by volume, about 55% by volume, about 60% by volume, or about 65% by volume, based on the total volume of the composite membrane.

[0023] The at least two reinforcing layers may have the same composition, or the at least two reinforcing layers may have different compositions.

[0024] The microporous polymer structure may comprise a fluorinated polymer. The microporous polymer structure may comprise one or more fluorinated polymers selected from the group consisting of polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (EPTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), or mixtures thereof. Preferably, the fluorinated polymer may be perfluorinated expanded polytetrafluoroethylene (ePTFE).

[0025] The microporous polymer structure may comprise a hydrocarbon polymer, which may include polyethylene, polypropylene, polycarbonate, track-etched polycarbonate, polystyrene, or mixtures thereof.

[0026] In embodiments in which the microporous polymer structure comprises ePTFE, the total mass per area of ​​the microporous polymer structure is at least about 5.5 g / m, based on the total area of ​​the composite membrane. 2 , or at least about 6 g / m 2 , or at least about 7 g / m 2 , or at least about 8 g / m 2 , or at least about 9 g / m 2 , or at least about 10 g / m 2 , or at least about 11 g / m 2 , or at least about 12 g / m 2 , or at least about 14 g / m 2 , or at least about 16 g / m 2 It can be.

[0027] In embodiments in which the microporous polymer structure comprises ePTFE, the total mass per area of ​​the microporous polymer structure is about 5.5 g / m, based on the total area of ​​the composite membrane. 2 ~about 80g / m 2 , or about 5.5 g / m 2 ~about 70g / m 2 , or about 5.5 g / m 2 ~about 60g / m 2 , or about 5.5 g / m 2 ~about 60g / m 2 , or about 5.5 g / m 2 ~about 50g / m 2 , or about 5.5 g / m 2 ~about 40g / m 2 , or about 5.5 g / m 2 ~Approx. 35g / m 2 , or about 5.5 g / m 2 ~About 30g / m 2 , or about 5.5 g / m 2 ~about 20g / m 2 , or about 5.5 g / m2 ~about 15g / m 2 It can be.

[0028] When the composite membrane is intended for redox flow battery applications, the total mass per area of ​​the microporous polymer structure is preferably about 5.5 g / m, based on the total mass per area of ​​all microporous layers present in the composite membrane. 2 ~Approx. 35g / m 2 , or about 5.5 g / m 2 ~Approx. 16g / m 2 , or about 5.5 g / m 2 ~Approx. 14g / m 2 , or about 5.5 g / m 2 ~Approx. 12g / m 2 , or about 5.5 g / m 2 ~about 10g / m 2 , or about 9 g / m 2 ~about 20g / m 2 , or about 9 g / m 2 ~about 15g / m 2 , or about 10 g / m 2 ~Approx. 18g / m 2 , or about 8 g / m 2 ~about 15g / m 2 It can be.

[0029] When the composite membrane is intended for electrolyzer applications, the content of the microporous polymer structure may be higher than that for redox flow battery applications. For example, when the composite membrane is intended for electrolyzer applications, the total mass per area of ​​the microporous polymer structure may be about 20 g / m, based on the total mass per area of ​​all microporous layers present in the composite membrane. 2 ~about 80g / m 2 , or about 30 g / m 2 ~about 70g / m 2 , or about 20 g / m 2 ~about 50g / m 2 , or about 30 g / m 2 ~about 60g / m 2 It can be.

[0030] In embodiments in which the microporous polymer structure comprises ePTFE, the total area mass of the microporous polymer structure is about 5.5 g / m, based on the total area mass of all microporous layers present in the composite membrane. 2 , or about 6 g / m 2 , or about 7 g / m 2 , or about 8 g / m 2 , or about 9 g / m 2 , or about 10 g / m 2 , or about 11 g / m 2 , or about 12 g / m 2 , or about 13 g / m 2 , or about 14 g / m 2 , or about 15 g / m 2 , or approximately 16 g / m 2 , or about 17 g / m 2 , or about 18 g / m 2 , or about 19 g / m 2 , or about 20 g / m 2 It can be.

[0031] In embodiments in which the microporous polymer structure comprises a hydrocarbon polymer, the total mass per area of ​​the microporous polymer structure is at least about 3.5 g / m, based on the total area of ​​the composite membrane. 2 , or at least about 4 g / m 2 , or at least about 4.5 g / m 2 , or at least about 5 g / m 2 , or at least about 5.5 g / m 2 , or at least about 6 g / m 2 , or at least about 7 g / m 2 , or at least about 8 g / m 2 It can be.

[0032] The composite membrane may have an average burst pressure of at least about 150 psi, or at least about 160 psi, or at least about 170 psi, or at least about 180 psi, or at least about 190 psi, or at least about 200 psi, as measured by the Average Puncture Pressure Burst Test Average Puncture Pressure Burst Test described below.

[0033] The composite membrane can have an average burst pressure of about 150 psi to about 2000 psi, or about 150 psi to about 1500 psi, or about 150 psi to about 1000 psi, or about 150 psi to about 500 psi, or about 150 psi to about 300 psi, or about 200 psi to about 400 psi, or about 200 psi to about 400 psi, as measured by the Average Puncture Pressure Burst Test described below.

[0034] The composite membrane may have an average burst pressure of about 150 psi, or about 200 psi, or about 250 psi, or about 300 psi, or about 350 psi, or about 400 psi, or about 450 psi, or about 500 psi, as measured by the Average Puncture Pressure Burst Test described below.

[0035] The at least two reinforcing layers may be in direct contact. Alternatively, the at least two reinforcing layers may not be in contact with each other. The at least two reinforcing layers may be separated by a distance d. In embodiments in which the at least two reinforcing layers are in direct contact, the distance d may be about 0 μm. The distance d can be about 0.1 μm to about 20 μm, or about 0.1 μm to about 15 μm, or about 0.1 μm to about 10 μm, or about 10 μm to about 20 μm, or about 10 μm to about 15 μm, or about 15 μm to about 20 μm, or about 2 μm to about 8 μm, or about 2 μm to about 6 μm, or about 2 μm to about 4 μm, or about 4 μm to about 8 μm, or about 6 μm to about 8 μm, or about 3 μm to about 6 μm, or about 0.5 μm to about 10 μm, or about 1 μm to about 10 μm, or about 4 μm to about 6 μm, or about 1 μm to about 5 μm, or about 5 μm to about 10 μm. The distance d can be about 0.1 μm, or about 0.5 μm, or about 1 μm, or about 2 μm, or about 3 μm, or about 4 μm, or about 5 μm, or about 6 μm, or about 7 μm, or about 8 μm, or about 9 μm, or about 10 μm, or about 11 μm, or about 12 μm, or about 13 μm, or about 14 μm, or about 15 μm, or about 16 μm, or about 17 μm, or about 18 μm, or about 19 μm, or about 20 μm.

[0036] The at least two reinforcement layers can be separated by at least one layer of ion exchange material (IEM). Each of the at least one layer of ion exchange material can comprise a single ion exchange material. Each of the at least one layer of ion exchange material can comprise a mixture of two or more ion exchange materials. Each of the at least one layer of ion exchange material can comprise at least one ionomer. The at least one ionomer can comprise a proton-conducting polymer. The proton-conducting polymer can comprise a hydrocarbon ionomer. The proton-conducting polymer can comprise a perfluorinated ionomer. The proton-conducting polymer can comprise a perfluorosulfonic acid. Each of the at least one layer of ion exchange material can be about 1 μm to about 10 μm thick. The ion exchange material can have an equivalent volume of about 240 cc / molar equivalent to about 870 cc / molar equivalent, or about 240 cc / molar equivalent to about 650 cc / molar equivalent, or about 350 cc / molar equivalent to about 475 cc / molar equivalent. The ion exchange material may have a density of about 1.9 g / cc or greater at 0% relative humidity.

[0037] The at least two reinforcement layers can be separated by a layer of ion exchange material (IEM). The layer of ion exchange material can comprise a single ion exchange material. The layer of ion exchange material can comprise a mixture of two or more ion exchange materials.

[0038] The at least two reinforcement layers can be separated by two or more layers of ion exchange material, at least two of the two or more layers of ion exchange material can comprise different ion exchange materials, or at least two of the two or more layers of ion exchange material can comprise the same ion exchange material.

[0039] The at least two reinforcement layers may be separated by a layer of ion exchange material (IEM), the ion exchange material comprising two or more layers of ion exchange material, the layers of ion exchange material disposed between the at least two reinforcement layers being formed from different ion exchange materials.

[0040] Each of the at least two reinforcement layers can have a first surface and a second surface, and at least one or both of the first surface and the second surface of each reinforcement layer can be at least partially impregnated with an ion exchange material.

[0041] In embodiments where the composite membrane comprises two reinforcement layers, the first reinforcement layer can comprise a first surface and a second surface, and the second reinforcement layer can comprise a first surface and a second surface. The first surfaces of the first reinforcement layer and the second reinforcement layer can be at least partially impregnated with an ion exchange material. The second surfaces of the first reinforcement layer and the second reinforcement layer can be at least partially impregnated with an ion exchange material.

[0042] In embodiments in which both the first surface of the first reinforcement layer and the second surface of the second reinforcement layer are at least partially impregnated with ion exchange material, the ion exchange material on the first surface of the first reinforcement layer may be the same as or different from the ion exchange material on the second surface of the second reinforcement layer.

[0043] The microporous polymer structure can be partially imbibed with ion exchange material. The microporous polymer structure can be completely imbibed with ion exchange material. In embodiments where the composite membrane has two reinforcement layers, the microporous polymer structure of the two reinforcement layers can be completely imbibed with ion exchange material. Furthermore, the composite membrane can include two additional layers of ion exchange material on the first and second surfaces of the composite membrane. Furthermore, the first and second reinforcement layers can be separated from each other by another (internal) layer of ion exchange material. In one embodiment, the at least two reinforcement layers can be separated from each other by another (internal) layer of ion exchange material that forms a distance d. The layers of ion exchange material disposed on the first surface of the composite membrane, on the second surface of the composite membrane, and / or between the two reinforcement layers can include the same or different ion exchange materials. For example, the ion exchange material can be an ionomer.

[0044] In embodiments in which the microporous polymer structure of at least one of the reinforcement layers is partially imbibed with ion exchange material, the ion exchange material can leave a non-occluding portion of the microporous polymer structure closest to the first surface, second surface, or both surfaces of the reinforcement layer. The non-occluding portion can be a portion of the microporous polymer structure that does not include any ion exchange material. Alternatively, the non-occluding portion can include a coating of ion exchange material on the interior surface of the microporous polymer structure, but can be a portion of the microporous polymer structure that does not include ion exchange material on the exterior surface of the microporous polymer structure (i.e., the composite membrane does not include a layer of unreinforced ion exchange material, but can include ion exchange material coating the interior fibrils of the microporous polymer structure).

[0045] The total average equivalent volume of the ion exchange material can be about 240 cc / molar equivalent to about 870 cc / molar equivalent. The average equivalent volume of the ion exchange material can be about 240 cc / molar equivalent to about 650 cc / molar equivalent. The average equivalent volume of the ion exchange material can be about 350 cc / molar equivalent to about 475 cc / molar equivalent. The total average equivalent volume of the ion exchange material can include the total volume of the ion exchange material distributed among all ion exchange material layers of the composite membrane.

[0046] The ion exchange material has a concentration of about 400 g / eq to about 2000 g / eq of SO - The ion exchange material can have a total equivalent weight (EW) of about 470 g / eq to about 1275 g / eq of SO3 - The ion exchange material can have a total equivalent weight (EW) of about 700 g / eq to about 1000 g / eq of SO3 - The ion exchange material can have a total equivalent weight (EW) of about 710 g / eq of SO3 - The ion exchange material can have an equivalent weight of about 810 g / eq of SO3 - The ion exchange material can have an equivalent weight of about 910 g / eq of SO3 - It can have an equivalent weight of

[0047] In embodiments in which the composite membrane includes two reinforcing layers disposed in direct contact, the second surface of the first reinforcing layer and the first surface of the second reinforcing layer can be in direct contact.

[0048] In embodiments in which the composite membrane includes two reinforcement layers spaced apart from one another, the second surface of the first reinforcement layer and the first surface of the second reinforcement layer can be separated by a distance d by a layer of ion exchange material (i.e., an inner layer of ion exchange material). The inner layer of ion exchange material can have a thickness d.

[0049] The composite membrane can include a first surface and a second (opposite) surface. The first surface of the composite membrane can include a first ion exchange material. The second surface of the composite membrane can include a second ion exchange material. The composite membrane can include at least one inner layer of ion exchange material between at least two reinforcement layers.

[0050] In embodiments where the composite membrane includes three or more reinforcement layers, all of the reinforcement layers may be in direct contact with each other. Alternatively, some of the reinforcement layers may be in direct contact with each other, while some of the reinforcement layers may be separated from each other (e.g., by a layer of ion exchange material). Alternatively, all of the reinforcement layers may be separated from each other. In embodiments where the reinforcement layers are separated from each other, the reinforcement layers may be separated from each other by an ion exchange material. For example, a composite membrane may include three or more reinforcement layers, each separated from the next by one or more layers of ion exchange material. Additionally, the outer reinforcement layers may be at least partially impregnated with an ion exchange material on their outer surfaces.

[0051] The composite membrane can include at least one ion exchange material on each of its outer surfaces. Additionally, the composite membrane can include at least one internal ion exchange material between at least two reinforcement layers. The at least one ion exchange material can be an unreinforced ion exchange material. Within the context of the present disclosure, an unreinforced ion exchange material can be a layer of ion exchange material that is not substantially embedded within a reinforcement layer. In other words, in a composite membrane having one or more reinforcement layers, an unreinforced ion exchange material is a layer of ion exchange material that is present somewhere within the composite membrane (e.g., on an outer surface or as an internal layer), but that is not substantially embedded (or absorbed) within one or more reinforcement layers.

[0052] The composite membrane can further include a backer layer disposed on the first surface of the composite membrane, the second surface of the composite membrane, or both. Suitable backer layers can include at least one support structure, which can include a woven material, such as a scrim made from woven expanded porous polytetrafluoroethylene fibers, a web made from extruded or oriented polypropylene or polypropylene netting (available from Conwed, Inc., Minneapolis, Minnesota), and a woven polypropylene and polyester material (available from Tetko Inc., Burial Cliff, New York). Suitable nonwoven materials can include, for example, spunbond polypropylene from Reemay Inc., Old Hickory, Tennessee. In other embodiments, the support structure can comprise a web of 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 oxide ("PPO"), polyphenylether ("PPE"), polymethylpentene ("PMP"), polyethylene terephthalate ("PET"), or polycarbonate ("PC"). In some embodiments, the support structure also includes a protective layer that can 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 oxide ("PPO"), polyphenylether ("PPE"), polymethylpentene ("PMP"), polyethylene terephthalate ("PET"), or polycarbonate ("PC").The support structure can optionally include a reflective layer comprising a metal substrate (e.g., an aluminum substrate). The specific metal selected can vary widely, so 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 can optionally include a mixture or alloy of two or more metals, and optionally includes two or more of the above metals. The reflective layer can optionally include a highly reflective polymer multilayer film, such as Vikuiti™ Enhanced Specular Reflector available from 3M. In yet another example, the reflective layer can optionally include a highly reflective non-metallic inorganic dielectric multilayer film, including materials such as magnesium fluoride, calcium fluoride, titanium dioxide, and silicon dioxide.

[0053] In another aspect, there is provided a membrane electrode assembly for an electrochemical device, comprising: at least one electrode; and a composite membrane as described above in contact with said at least one electrode; A membrane electrode assembly is provided, comprising:

[0054] The composite membrane can be attached to at least one electrode. The composite membrane can be glued to at least one electrode. The composite membrane can be attached to at least one electrode. The composite membrane can be pressed against at least one electrode. The composite membrane can be fused to at least one electrode.

[0055] At least one electrode can include fibers. At least one electrode can be a fibrous electrode. At least one electrode can be doped with fibers. At least one electrode can include carbon fibers. At least one electrode can include a porous layer (typical pore size 1-200 microns). The porous layer can include felt, paper, or a woven material, among others.

[0056] The membrane electrode assembly comprises: a first electrode, a second electrode, and a composite membrane as described above sandwiched between said first electrode and said second electrode; The redox flow battery membrane electrode assembly may include:

[0057] The membrane electrode assembly comprises: a first electrode having a first surface and a second surface; a second electrode having a first surface and a second surface; and a composite membrane having a first surface and a second surface as described above; Including, The redox flow battery membrane electrode assembly may be one in which the second surface of the first electrode is in contact with the first surface of the composite membrane, and the first surface of the second electrode is in contact with the second surface of the composite membrane.

[0058] The first electrode may be a first electrode layer, and the second electrode may be a second electrode layer. A redox flow battery membrane electrode assembly may include a first electrode layer attached to a first surface of the composite membrane and a second electrode layer attached to a second surface of the composite membrane. The electrodes may be porous layers having pore sizes of about 1 to about 200 μm. The electrodes may be selected from felt, paper, or woven materials. The electrodes may include doped carbon fibers.

[0059] The membrane electrode assembly comprises: 1. A composite membrane as described above, wherein said composite membrane has a first surface and a second surface. a first layer of an electrocatalyst adhered to a first surface of the composite membrane; and a second layer of electrocatalyst adhered to a second surface of the composite membrane; The fuel cell membrane electrode assembly may include:

[0060] The fuel cell membrane electrode assembly may further include a fluid diffusion layer. The fluid diffusion layer may be a gas diffusion layer and / or a liquid (e.g., water) diffusion layer. The fluid diffusion layer may be disposed on the outer surface of the first layer of electrocatalyst and / or the second layer of electrocatalyst. The fuel cell membrane electrode assembly may include: 1. A composite membrane as described above, wherein said composite membrane has a first surface and a second surface. a first layer of electrocatalyst adhered to a first surface of the composite membrane, and a first fluid diffusion layer disposed on the first layer of electrocatalyst; and a second layer of electrocatalyst adhered to a second surface of the composite membrane, and a second fluid diffusion layer disposed on the second layer of electrocatalyst; may include:

[0061] In the fuel cell membrane electrode assembly, the first fluid diffusion layer can be disposed on the opposite side of the composite membrane. The first layer of electrocatalyst can be disposed between the composite membrane and the first fluid diffusion layer. The second first fluid diffusion layer can be disposed on the opposite side of the composite membrane. The second layer of electrocatalyst can be disposed between the composite membrane and the second fluid diffusion layer. In other words, the first and second fluid diffusion layers can be the outermost layers of the fuel cell membrane electrode assembly and can sandwich the composite membrane and the first and second layers of electrocatalyst.

[0062] In the fuel cell membrane electrode assembly, the first and second electrocatalyst layers can be nanoporous layers having pore sizes of about 100 nm or less. The first and second electrocatalyst layers are adhered to the composite membrane. The first electrocatalyst layer can be an anode, and the second electrocatalyst layer can be a cathode.

[0063] In the fuel cell membrane electrode assembly, the first and second layers of the electrocatalyst are one or more ionomers, a catalyst support such as carbon black, and platinum, Includes:

[0064] The membrane electrode assembly comprises: A composite membrane as described herein having a layer of catalyst laminated onto the composite membrane; and Electrodes, and a gas diffusion layer disposed between the composite membrane and the electrode; The electrolytic cell electrode assembly may include:

[0065] The membrane electrode assembly comprises: 1. A composite membrane as described above, wherein said composite membrane has a first surface and a second surface. a first layer of an electrocatalyst adhered to a first surface of the composite membrane; and The electrolytic cell electrode assembly can include a second layer of electrocatalyst adhered to a second surface of the composite membrane. A fluid (e.g., gas / water) diffusion layer can be disposed on the outer surface of the electrocatalyst.

[0066] In another aspect, there is provided an electrochemical device comprising the composite membrane as described above. The electrochemical device can be a fuel cell, a redox flow battery, or an electrolyzer.

[0067] In another aspect, there is provided a fuel cell comprising a composite membrane or fuel cell membrane electrode assembly as described above.

[0068] In another aspect, there is provided a redox flow battery comprising a composite membrane or redox flow battery membrane electrode assembly as described above.

[0069] In another aspect, there is provided an electrolytic cell comprising a composite membrane or electrolytic cell membrane electrode assembly as described above.

[0070] The present inventors have endeavored to solve the problem of low puncture resistance of state-of-the-art PEMs, as described above. As a result, it has been surprisingly discovered that increasing the content of reinforced microporous polymer structure in the composite membrane (i.e., the total content of microporous polymer structure distributed between at least two reinforcement layers) continuously increases the puncture resistance. Surprisingly, this increase in puncture resistance can be achieved without increasing the thickness of the composite membrane or the amount of ionomer used.

[0071] Furthermore, the inventors have found that for a given total content of reinforced microporous polymer structure, providing the microporous polymer structure in a multi-layer arrangement of reinforced layers (at least two layers) significantly improves the puncture resistance of the composite membrane compared to a polymer electrolyte membrane comprising an equivalent content of microporous polymer structure provided in a single layer.

[0072] Providing a composite membrane that is highly resistant to puncture reduces the likelihood of battery failure due to short circuits that may occur if the composite membrane is pierced during cell assembly. Furthermore, reducing the occurrence of short circuits can extend the life of electrochemical devices fabricated with the composite membrane. Furthermore, given that thinner composite membranes require a lower ionomer content for a comparable reinforcement ratio, providing a composite membrane that is highly resistant to puncture by other electrochemical device components without increasing the thickness of the composite membrane allows the ionic conductivity of the composite membrane to remain high and reduces manufacturing costs. [Brief explanation of the drawings]

[0073] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1A]1A shows a schematic diagram of a cross section of a composite membrane according to one embodiment of the present disclosure. The composite membrane has two reinforcement layers in direct contact with each other. Each of the reinforcement layers comprises a microporous polymer structure. The composite membrane also includes two outer layers of unreinforced ion exchange material. In this particular example, both reinforcement membranes are impregnated with the same ion exchange material (although in other examples, the reinforcement layers can be impregnated with different ion exchange materials).

[0074] [Figure 1B] FIG. 1B shows the composite membrane of FIG. 1A with a backer layer.

[0075] [Figure 2] Figure 2 shows a schematic cross-sectional view of a composite membrane according to another embodiment, which has a similar structure to the composite membrane of Figures 1A and 1B, except that the first reinforcement layer is impregnated with a first ion exchange material and the second reinforcement layer is impregnated with a second (different) ion exchange material.

[0076] [Figure 3A] 3A shows a schematic diagram of a cross section of a composite membrane according to one embodiment of the present disclosure. The composite membrane has two reinforced layers, each comprising a microporous polymer structure. The two reinforced layers are separated by an inner, unreinforced layer of ion exchange material. The composite membrane also includes two outer layers of unreinforced ion exchange material on the outer surfaces of the reinforced layers.

[0077] [Figure 3B] FIG. 3B shows a schematic diagram of a cross section of a redox flow battery membrane-electrode assembly including the composite membrane of FIG. 3A and two electrode layers.

[0078] [Figure 4]Figure 4 shows a schematic cross-sectional view of a composite membrane according to another embodiment of the present disclosure. The structure is similar to that of Figure 3 (having two reinforcement layers impregnated with ion exchange material, separated by an inner layer of unreinforced ion exchange material disposed between the two reinforcement layers). This composite membrane has a single layer of unreinforced ion exchange material on the outer surface of one of the reinforcement layers, but no layer of unreinforced ion exchange material on the opposite side (i.e., the outer surface of the other reinforcement layer).

[0079] [Figure 5] Figure 5 shows a schematic cross-sectional view of a composite membrane according to another embodiment of the present disclosure. The structure is similar to that of the membrane of Figure 1, with two reinforcement layers in direct contact with each other without an intervening layer of unreinforced ion exchange material. In this example, the composite membrane has a single layer of unreinforced ion exchange material on one outer surface but no layer of unreinforced ion exchange material on the opposite side (i.e., one outer surface of the reinforcement layer is coated with a layer of unreinforced ion exchange material, while the outer surface of the other reinforcement layer is not coated with a layer of unreinforced ion exchange material).

[0080] [Figure 6] Figure 6 shows a schematic cross-sectional view of a composite membrane according to another embodiment of the present disclosure. The structure is similar to that of the membrane of Figure 1, with two reinforced layers in direct contact with each other, without an intervening layer of unreinforced ion exchange material, and without an outer layer of unreinforced ion exchange material.

[0081] [Figure 7] 7 shows a schematic diagram of a cross section of a composite membrane according to another embodiment of the present disclosure. In this embodiment, the composite membrane has three reinforcement layers comprising a microporous polymer structure impregnated with ion exchange material. All three reinforcement layers are in direct contact with each other, and the composite membrane has two outer layers of unreinforced ion exchange material disposed on the outer surfaces of both sides of the composite membrane.

[0082] [Figure 8]8 shows a schematic diagram of a cross section of a composite membrane according to another embodiment of the present disclosure. In this embodiment, the composite membrane has three reinforcement layers, each comprising a microporous polymer structure impregnated with an ion exchange material. The reinforcement layers are separated from each other by an inner layer of unreinforced ion exchange material. The composite membrane has two outer layers of unreinforced ion exchange material on the outer surfaces of both sides of the composite membrane.

[0083] [Figure 9] FIG. 9 shows a schematic diagram of a composite membrane similar to that of FIG. 6, having two reinforcing layers in direct contact with each other, one of the reinforcing layers being completely imbibed with ion exchange material and the other reinforcing layer being mostly imbibed with ion exchange material but containing non-imbibed or non-blocked regions of the microporous polymer structure.

[0084] [Figure 10] 10 shows a graph depicting the average burst pressure (psi) of the composite membranes of the examples versus the total ePTFE content (mpa) of the composite membrane. The graph shows four series of data, each series having an equivalent composite membrane thickness.

[0085] [Figure 11-1] FIG. 11-1 shows Table 1 showing the properties of the composite membranes of the examples. [Figure 11-2] FIG. 11-2 shows Table 1 showing the properties of the composite membranes of the examples.

[0086] [Figure 12] FIG. 12 shows Table 2, which shows the properties of the microporous polymer structures used in the composite membranes of the examples.

[0087] [Figure 13] FIG. 13 shows a schematic diagram of a method for making a composite membrane according to an embodiment of the present disclosure having reinforcement layers separated by inner layers of ion exchange material (ionomer). DETAILED DESCRIPTION OF THE INVENTION

[0088] Detailed Description The present application discloses a composite membrane for an electrochemical device having an improved mean burst pressure compared to state-of-the-art composite membranes, which leads to improved resistance to puncture of the composite membrane by other components of the electrochemical device during device assembly. Without wishing to be bound by theory, providing a composite membrane with at least two reinforcement layers, each of which contains a microporous polymer structure, significantly improves the puncture resistance of the composite membrane compared to a composite membrane of similar thickness and content of microporous polymer structure provided in a single reinforcement layer. Furthermore, for a given composite membrane thickness, increasing the total content of microporous polymer structure distributed between two or more reinforcement layers further improves the puncture resistance of the composite membrane. Without wishing to be bound by theory, for any given microporous polymer content and composite membrane thickness, providing a separation between at least two reinforcement layers within the composite membrane can further improve the puncture resistance of the composite membrane.

[0089] In some embodiments, there is provided a composite membrane for an electrochemical device, comprising: a) at least two reinforcing layers, wherein each of the at least two reinforcing layers comprises a microporous polymer structure; and b) an ion exchange material (IEM) at least partially absorbed within the microporous polymer structure of said at least two reinforcing layers, causing said microporous polymer structure to become occlusive; wherein the composite membrane has a thickness of at least about 10 μm at 0% RH.

[0090] The embodiments have been described using volumetric values ​​to provide a meaningful comparison between composite membrane compositions containing ionomers and microporous polymer structures of different densities.

[0091] In order to provide meaningful values ​​for the content of microporous polymer structures within a composite membrane, but to provide these values ​​independent of the intrinsic molecular weight / matrix skeletal density of the microporous polymer structures, embodiments have been described using normalized total mass / area values. This takes into account that some embodiments may include different microporous polymer structures within the reinforcing layer. The content of microporous polymer structures within a composite membrane is also expressed in terms of mass per area, which is an appropriate measurement in embodiments including a single type of microporous polymer structure.

[0092] The microporous polymer structure may be present in a total content of at least about 20% by volume, based on the total volume of the composite membrane. The composite membrane may have a density of at least about 3.10, based on the total area of ​​the composite membrane divided by the matrix skeletal density of the microporous polymer structure. -6 The polymeric polymer may have a total microporous polymeric structure content of at least about 1 μm (ie, at least about 3 μm).

[0093] Various definitions used in this disclosure are provided below.

[0094] As used herein, the terms "ionomer" and "ion exchange material" refer to cation exchange materials, anion exchange materials, or ion exchange materials containing both cation and anion exchange capabilities. Mixtures of ion exchange materials can also be used. The 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-based ion exchange polymers, fluorostyrene-based 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 made by converting tetrafluoroethylene and perfluorosulfonyl vinyl ester to the proton form and copolymerizing them.

[0095] As used herein, the "equivalent weight" (EW) of an ionomer or ion exchange material refers to the weight (in molecular weight) of polymer in the ionomer per sulfonic acid group. Thus, a lower equivalent weight indicates a higher acid content. The equivalent weight of an ionomer refers to the EW when the ionomer is in its proton form at 0% RH and contains negligible impurities. The term "ion exchange capacity" refers to the reciprocal of the equivalent weight (1 / EW).

[0096] As used herein, the "equivalent volume" of an ionomer or ion exchange material refers to the volume of ionomer per sulfonic acid group. The equivalent volume (EV) of an ionomer refers to the EV when the ionomer is pure and in its proton form at 0% RH, with negligible impurities.

[0097] As used herein, the term "microporous polymer structure" refers to a polymer matrix that supports the ion exchange material and adds structural integrity and durability to the resulting composite membrane. In some exemplary embodiments, the microporous polymer structure comprises expanded polytetrafluoroethylene (ePTFE) having a node and fibril structure. In other exemplary embodiments, the microporous polymer structure comprises a track-etched polycarbonate membrane having a smooth, flat surface, high apparent density, and well-defined pore sizes.

[0098] As used herein, the interior volume of a microporous polymeric structure is referred to as occlusive or "substantially occlusive" when the interior volume has a low volume void space of less than 10% by volume, a highly impermeable structure to gases, and a Gurley number greater than 10,000 seconds. Conversely, the interior volume of a microporous polymeric structure is referred to as "unocclusive" when the interior volume has a high volume void space of more than 10% by volume, and a gas permeability greater than 10,000 seconds.

[0099] composite membrane As shown in Figures 1-9, the composite membrane can include multiple, eg, two or more, absorption-enhancing layers.

[0100] 1-4, a composite membrane 100, 200, 300, 400 is provided that includes two reinforcement layers 105a,b, 205a,b, 305a,b, 405a,b, each reinforcement layer including a microporous polymer structure and an ion exchange material (e.g., ionomer) 110, 210a,b, 310, 410 impregnated into the microporous polymer structure of the reinforcement layer 105a,b, 205a,b, 305a,b, 405a,b. That is, the microporous polymer structure of each of the reinforcement layers 105a,b, 205a,b, 305a,b, 405a,b is imbibed with the ion exchange material 110, 210a,b, 310, 410. The ion exchange material 110, 210a,b, 310, 410 can substantially impregnate or occlude the microporous polymer structure of the reinforcement layers 105a,b, 205a,b, 305a,b, 405a,b so as to render the interior volume substantially occlusive (i.e., the interior volume has a structure characterized by a low volume of voids and being highly impermeable to gases). For example, by filling more than 90% of the interior volume of the microporous polymer structure of each of the reinforcement layers 105a,b, 205a,b, 305a,b, 405a,b with the ion exchange material 110, 210a,b, 310, 410, substantial occlusion occurs and the composite membrane is characterized by a Gurley number greater than 10,000 seconds. As shown in Figures 1-4, the ion exchange material 110, 210a,b, 310, 410 is firmly adhered to the inner and outer surfaces of the microporous polymer structure of the reinforcement layers 105a,b, 205a,b, 305a,b, 405a,b, forming the absorption reinforcement layers 104a,b, 204a,b, 304a,b and 404a,b.

[0101] In some embodiments, the ion exchange material 110, 210a, 210b, 310, 410 is provided as one or more additional layers 115a,b, 215a,b, 315a,b, 415a,b on one or more outer surfaces of the absorption enhancement layer 104a,b, 204a,b, 304a,b, 404a,b, in addition to being impregnated into the microporous polymer structure of the two reinforcement layers 105a,b, 205a,b, 305a,b to form the absorption enhancement layer 104a,b, 204a,b, 304a,b, 404a,b. In other embodiments, the ion exchange material 410, 510 is provided on only one of the outer surfaces of the absorption enhancement layer 404b, 504b, but not on the other outer surface of the composite membrane (i.e., not on the outer surface of the opposite absorption enhancement layer 404a, 504a) (FIGS. 4 and 5). In other embodiments, the ion exchange material 610 is simply provided impregnated into the microporous polymer structure 605 within the absorption enhancement layer 604a,b, i.e., does not include an additional layer of unenhanced ion exchange material (FIG. 6). Nevertheless, the composite membranes 100, 200, 300, 400, 500, 600 can be characterized in that the microporous polymer structure 105a,b, 205a,b, 305a,b or 405a,b, 500a,b, 600a,b occupies more than 20% of the total volume of the composite membrane 100, 200, 300, 400, 500, 600, 700, 800, 900, which total volume includes the volume of the absorption-enhancing layer and, if present, the volume of the additional layers 115a,b, 215a,b, 315a,b,c, 415b,c, 515b, 715a,b and 815a,b,c,d of unreinforced ion exchange material.

[0102] 1A and 1B, the first absorption enhancement layer 104a can be formed by imbibing an ion exchange material 110 into the microporous polymer structure of the first reinforcement layer 105a, and the second absorption enhancement layer 104b can be formed by imbibing the same ion exchange material 110 into the microporous polymer structure of the second reinforcement layer 105b. For example, the ion exchange material 110 can be imbibed into the microporous polymer structure of the first reinforcement layer 105a to form the first absorption enhancement layer 104a, and the same ion exchange material can be imbibed into the microporous polymer structure of the second reinforcement layer 105b to form the second absorption enhancement layer 104b. In this embodiment, the reinforcement layers 105a and 105b are in direct contact. In this embodiment, the composite layer has two outer layers 115a and 115b of ion exchange material formed on the outer surfaces 114a and 114b of the absorption enhancement layers 104a and 104b. The layers 115a and 115b of ion exchange material can include the same ion exchange material as the absorption enhancement layers 104a and 104b. Alternatively, the ion exchange material of one or both layers 115a and / or 115b can be different from the ion exchange material of the absorption enhancement layers 104a and 104b. The ion exchange material of both layers 115a and 115b can be the same or different.

[0103] Although shown only in FIG. 1B, in embodiments according to any one of the structures shown in the figures, the composite membrane 100 may be provided on a backer layer 120 (FIG. 1B). The backer layer 120 may include a release film, such as, for example, a cycloolefin copolymer (COC) layer. In some embodiments, the composite membrane 100 can be peeled (or otherwise separated) from the backer layer 120 before being incorporated into a membrane electrode assembly (MEA).

[0104] In the embodiment according to Fig. 2, the composite membrane 200 can have a structure similar to that of the embodiment according to Fig. 1, with the two reinforcement layers 205a, 205b in direct contact with each other. In the embodiment according to Fig. 2, the first absorption enhancement layer 204a can be formed by imbibing a first ion exchange material 210a into the microporous polymer structure of the first reinforcement layer 205a, and the second absorption enhancement layer 204b can be formed by imbibing a second ion exchange material 210b, different from the first ion exchange material 210a, into the microporous polymer structure of the second reinforcement layer 205b. In these embodiments, the first ion exchange material 210a can be imbibed into the microporous polymer structure of the first reinforcement layer 205a to form the first absorption enhancement layer 204a, and the second ion exchange material 210b can be imbibed into the microporous polymer structure of the second reinforcement layer 205a to form the second absorption enhancement layer 204b. In this embodiment, the composite membrane 200 has two outer layers 215a and 215b of (unreinforced) ion exchange material formed on the outer surfaces 214a and 214b of the absorption enhancement layers 204a and 204b. The outer layers 215a and 215b of ion exchange material can comprise the same ion exchange material as at least one of the absorption enhancement layers 204a or 204b. The ion exchange material in both outer layers 215a and 215b of ion exchange material can be the same or different. Alternatively, the ion exchange material in one or both of the outer layers 215a and / or 215b can be different from that of the absorption enhancement layers 204a and 204b. Although not shown, the composite membrane can have a backer or release layer. The backer layer can be peeled off or removed before assembling the composite membrane into an electrochemical device.

[0105] 3A, the composite membrane 300 can include two reinforcement layers 305a and 305b onto which ion exchange material 310 is imbibed to form absorption enhancement layers 304a,b. The composite membrane 300 can include three layers of unreinforced ion exchange material: a first layer 315a formed on the outer surface 314a of the first absorption enhancement layer 304a; a second layer 315b of unreinforced ion exchange material formed on the outer surface 314b of the second absorption enhancement layer 304a; and a third (inner) layer 315b of unreinforced ion exchange material disposed between the absorption enhancement layers 304a and 304b. The ion exchange material of the unreinforced ion exchange material layers 315a,b,c can be the same or different and can be the same or different from the ion exchange material 310 of the absorption enhancement layers 304a and / or 304b.

[0106] FIG. 3B shows a redox flow battery membrane electrode assembly 350 including a composite membrane 300 as shown in FIG. 3A sandwiched between two electrode layers 320a and 320b disposed on the outermost surface of the composite membrane 300. In this particular embodiment, electrode layer 320a is disposed or attached to the outer surface of unreinforced ion exchange material layer 315a, and electrode layer 320b is disposed or attached to the outer surface of unreinforced ion exchange material layer 315b. The electrode layers 320a,b can be porous layers having pore sizes of about 1 to about 200 μm. The electrode layers 320a,b can be selected from felt, paper, or woven materials. The electrode layers 320a,b can include doped carbon fibers.

[0107] Figure 4 shows a schematic cross-sectional view of a composite membrane 400 according to another embodiment of the present disclosure. The structure is similar to that of membrane 300 of Figure 3A (having two reinforcement layers 405a, b impregnated with ion exchange material, thus forming absorption enhancement layers 304a and 304b). The absorption enhancement layers 304a, b are separated by an inner layer 415c of unreinforced ion exchange material disposed between the two absorption enhancement layers 404a, 404b. This composite membrane 400 has a single layer of unreinforced ion exchange material 415b on the outer surface of absorption enhancement layer 404b, but does not have a layer of unreinforced ion exchange material on the opposite side (i.e., on the outer surface of the other absorption enhancement layer 404a).

[0108] FIG. 5 shows a cross-sectional schematic diagram of a composite membrane 500 according to another embodiment of the present disclosure. The structure is similar to that of the membrane of FIG. 1, with two reinforcement layers 505a, 505b in direct contact with each other without an intervening layer of unreinforced ion exchange material. The two reinforcement layers 505a, 505b are imbibed with ion exchange material 510 to form absorption enhancement layers 504a, 504b. In this example, the composite membrane 500 has a single layer of unreinforced ion exchange material 515b on one side of the composite membrane (disposed on the outer surface 514b of the absorption enhancement layer 504b), but no layer of unreinforced ion exchange material is disposed on the opposite side (i.e., the outer surface 514b of the absorption enhancement layer 504b is coated with a layer of unreinforced ion exchange material 515b, while the outer surface 514a of the other reinforcement layer 504a is not coated with a layer of unreinforced ion exchange material).

[0109] In the embodiment according to Figure 6, the composite membrane 600 can include multiple, e.g., two or more, absorption enhancement layers 604a and 604b (or more, not shown) formed by two (or more) reinforcement layers 605a and 605b comprising microporous polymer structures imbibed with ion exchange materials 610a and 610b, which can be the same or different. In the embodiment according to Figure 6, the absorption enhancement layers can lack outer or inner layers of unreinforced ion exchange material. That is, the composite membrane 600 can lack additional layers of unreinforced ion exchange material.

[0110] In the embodiment according to Figure 7, the composite membrane 700 can include three absorption enhancement layers 704a, 704b, and 704c. In these embodiments, the absorption enhancement layers are in contact with each other (i.e., there is no inner layer of unreinforced ion exchange material between the absorption enhancement layers 704a, 704c, and 704b). Each of the absorption enhancement layers can include a reinforcement layer 705a, b, or c that includes a microporous polymer structure. The microporous polymer structure of all of the reinforcement layers 705a, b, and c can be the same. While the microporous polymer structure of at least one of the reinforcement layers 705a, 705b, or 705c can be different, the microporous polymer structure of some of the reinforcement layers 705a, b, and c can be the same. The microporous polymer structure of reinforcement layers 705a, 705b, and 705c can fully or partially absorb ion exchange material 710a, 710b, and 710c, respectively, to render the microporous polymer structure occlusive and thus form absorption enhancement layers 704a, 705b, and 704c, respectively. The ion exchange material can include one or more ionomers. Each of ion exchange materials 710a, 710b, and 710c can be the same as or different from all or some of the other ion exchange materials in the composite membrane. The composite membrane 700 shown in FIG. 7 has a layer of unreinforced ion exchange material 715a on the outer surface 714a of the first absorption enhancement layer 704a. The composite membrane has another layer 715b of unreinforced ion exchange material on the outer surface 714b of the third absorption enhancement layer 704b (i.e., the outermost absorption enhancement layer opposite reinforcement layer 704a).

[0111] In the embodiment according to FIG. 8, the composite membrane 800 can include three absorption enhancement layers 804a, 804b, and 804c. Each of the absorption enhancement layers can include a reinforcement layer 805a, 805b, or 805c that includes a microporous polymer structure. The microporous polymer structures of all of the reinforcement layers 805a, 805b, and 805c can be the same. While the microporous polymer structure of at least one of the reinforcement layers 805a, 805b, or 805c can be different, some of the microporous polymer structures of the reinforcement layers 805a, 805b, and 805c can be the same. The microporous polymer structures of the reinforcement layers 805a, 805b, and 805c can be fully or partially imbibed with ion exchange materials 810a, 810b, and 810c, respectively, to form the absorption enhancement layers 804a, 804b, and 804c, respectively. The ion exchange materials 810a, 810b, and 810c can include one or more ionomers. Each of the ion exchange materials 810a, 810b, and 810c may be the same as or different from all or some of the other ion exchange materials in the composite membrane. The composite membrane 800 shown in FIG. 8 has a layer 815a of unreinforced ion exchange material on the outer surface 814a of the first absorption enhancement layer 804a. The composite membrane has another layer 815b of unreinforced ion exchange material on the outer surface 814b of the third absorption enhancement layer 804b. Additionally, in these embodiments, there is an inner layer 815c of unreinforced ion exchange material between the absorption enhancement layers 804a and 804c. There is another inner layer 815d of unreinforced ion exchange material between the absorption enhancement layers 804c and 804b. The inner layers 815c and 815d form a distance d between the absorption enhancement layers 804a and 804c and between the absorption enhancement layers 804c and 804b.

[0112] Although not specifically shown, other embodiments of the composite membranes as described herein can include three or more absorption enhancing layers, each comprising a microporous polymer structure and an ion exchange material absorbed or partially absorbed within the microporous polymer material. In some embodiments, the composite membrane can have only one outer layer of unreinforced ion exchange material on one of the outer surfaces of the composite membrane. In some embodiments, the composite membrane can have an outer layer of unreinforced ion exchange material on both outer surfaces of the absorbed layers. In some embodiments, the composite membrane can have one or more inner layers of unreinforced ion exchange material between at least two of the absorption enhancing layers. In some embodiments, the composite membrane can have an inner layer of unreinforced ion exchange material between each of the absorption enhancing layers. In some embodiments, the composite membrane can have an inner layer of unreinforced ion exchange material between each of the absorption enhancing layers and a single outer layer of unreinforced ion exchange material on one of the outer surfaces of the composite membrane. In some embodiments, the composite membrane can have an inner layer of unreinforced ion exchange material between each of the absorption enhancing layers and an outer layer of unreinforced ion exchange material on both outer surfaces of the composite membrane.

[0113] The absorption enhancement layer of the composite membranes 100, 200, 300, 400, 500, 600, 700, 800, and 900 can be constructed with reinforcement layers comprising two (or more) different microporous polymer structures. For example, referring to FIG. 1 , a first absorption enhancement layer 104a can be formed by imbibing an ion exchange material 110 into a first reinforcement layer 105a comprising a first microporous polymer structure, and a second absorption enhancement layer 104b can be formed by imbibing the same ion exchange material 110 into a second reinforcement layer 105b comprising a second microporous polymer structure. In these embodiments, the first reinforcement layer 105a and the second reinforcement layer 105b are different. The principle of using different types of reinforcement layers in a composite membrane structure can be applied to any of the illustrated embodiments. For example, in the embodiment according to Figure 2, the first absorption enhancement layer 204a can be formed by imbibing a first ion exchange material 210a into a first reinforcement layer 205a comprising a first microporous polymer structure, and the second absorption enhancement layer 204b can be formed by imbibing a second ion exchange material 210b into a second reinforcement layer 205b comprising a second microporous polymer structure 205b. In these embodiments, the first reinforcement layer 205a and the second reinforcement layer 205b are different. Thus, in the composite membranes described herein and shown in the figures, the first microporous polymer structure can be the same as or different from the second microporous polymer structure. The first ion exchange material can be the same as or different from the second ion exchange material.

[0114] In additional embodiments, a portion of the microporous polymer structure (e.g., top or bottom region) of the reinforcement layers 105a,b, 205a,b, 305a,b, 405a,b, 505a,b, 605a,b, 705a,b,c, 805a,b,c can include a non-occluding region (not shown) that is free or substantially free of ion exchange material (i.e., an interior volume having a structure characterized by a high volume of voids and high gas permeability). The location of the non-occluding region is not limited to the top region of the microporous polymer structure. As noted above, the non-occluding region can be provided in the top region of the microporous polymer structure of any or all of the reinforcement layers.

[0115] In yet other embodiments, the non-occluded regions may comprise a small amount of ion exchange material present as a thin node and fibril coating on the interior surface of the microporous polymeric structure, however, the amount of ion exchange material may not be large enough to cause the microporous polymeric structure to become occluded, thereby forming a non-occluded region.

[0116] FIG. 9 shows a schematic diagram of a composite membrane 900 similar to that of FIG. 6 , but with two reinforcement layers 905 a, 905 b in direct contact with each other. Each reinforcement layer 905 a, 905 b comprises a microporous polymer structure. Reinforcement layer 905 a has a first surface 911 a and a second surface 912 a. Similarly, reinforcement layer 905 b has a first surface 911 b and a second surface 912 b. Microporous polymer structure 905 b is completely imbibed with ion exchange material 910 b, forming an occlusive absorption enhancing layer 904 b. However, while microporous polymer structure 905 a is mostly imbibed with ion exchange material 910 a, it includes a region 915 a of non-imbibed or non-occluded area of ​​microporous polymer structure 905 a closest to the first surface 911 a of reinforcement layer 905 a. Within the context of the present disclosure, mostly or substantially imbibed can mean that the microporous polymer structure is approximately 90% occluded with ion exchange material. Thus, the reinforcement layer 905a forms a partially imbibed reinforcement layer 904a that is not completely occlusive. In another similar embodiment (not shown), the first reinforcement layer 905a includes a region 915a of non-imbibed or non-occlusive region of the microporous polymer structure 905a closest to the second surface 912b of the reinforcement layer 905b.

[0117] 9, the first reinforcement layer 905a is completely occlusive, while the second reinforcement layer 910b includes a region of non-absorbent or non-occluded area of ​​the microporous polymer structure 905a proximate the first surface 911b or the second surface 912b of the reinforcement layer 910b. In yet another embodiment (not shown), both reinforcement layers 910a and 910b can include a region of non-absorbent or non-occluded area near one of the surfaces 911a, 912a, 911b, or 912b of each reinforcement layer 910a and 910b. The microporous polymer structure of partially imbibed reinforcement layers 904a and / or 904b can be about 90% occluded with ion exchange material.

[0118] In embodiments where there is no inner layer of unreinforced ion exchange material between at least two reinforcing layers (Figures 1A, 1B, 2, 5, 6, 7, and 9), the at least two reinforcing layers may be in direct contact (i.e., the at least two reinforcing layers may be separated by a distance d of about 0 μm).

[0119] In embodiments where the composite membrane includes an inner layer of unreinforced ion exchange material between at least two reinforcement layers (FIGS. 2, 3, and 8), the at least two reinforcement layers may be separated by a distance d. The distance d can be about 1 μm to about 10 μm, or about 2 μm to about 8 μm, or about 4 μm to about 6 μm, or about 1 μm to about 5 μm, or about 5 μm to about 10 μm, or about 6 μm to about 8 μm. The distance d can be about 1 μm, or about 2 μm, or about 3 μm, or about 4 μm, or about 5 μm, or about 6 μm, or about 7 μm, or about 8 μm, or about 9 μm, or about 10 μm. The distance d can be the thickness of the inner layer of unreinforced ion exchange material disposed between two adjacent reinforcement layers.

[0120] Microporous polymer structure The composite membrane can have at least two reinforcement layers comprising a microporous polymer structure. The composite membrane can have more than two reinforcement layers comprising a microporous polymer structure. For example, the composite membrane can have 2, 3, 4, 5, 6, 7, 8, 9, or 10 reinforcement layers, each comprising a microporous polymer structure.

[0121] The appropriate microporous polymer structure will depend largely on the application the composite membrane will be used in. The microporous polymer structure preferably has good mechanical properties, is chemically and thermally stable in the environment in which the composite membrane will be used, and is tolerant of any additives used with the ion exchange material for impregnation.

[0122] As used herein, the term "microporous" refers to a structure having pores. According to various optional embodiments, the pores can have an average pore size of 0.01 to 100 microns, e.g., 0.05 to 20 microns or 0.1 to 1 micron.

[0123] A suitable microporous polymer structure is intended to refer to a layer having a thickness of at least about 0.1 μm, optionally from about 0.5 μm to about 230 μm, or from about 1 μm to about 100 μm, or from about 1 μm to about 50 μm, and having an average pore size of from about 0.05 μm to about 20 μm, for example, from 0.1 μm to 1 μm.

[0124] Suitable microporous polymer structures of the reinforcement layers 105a,b, 205a,b, 305a,b, 405a,b, 505a,b, 605a,b, 705a,b, 805a,b, 905a,b for electrochemical applications can include porous polymer materials such as fluoropolymers, chlorinated polymers, hydrocarbons, polyamides, polycarbonates, polyacrylates, polysulfones, copolyetheresters, polyethylene, polypropylene, polyvinylidene fluoride, polyaryletherketones, polybenzimidazoles, poly(ethylene-co-tetrafluoroethylene), and poly(tetrafluoroethylene-co-hexafluoropropylene). In some embodiments, the microporous polymer structure of the reinforcement layers includes a perfluorinated porous polymer material. The perfluorinated porous polymeric material can include polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), or mixtures thereof.

[0125] In some embodiments, the microporous polymer structure comprises a hydrocarbon material, which may include polyethylene, expanded polyethylene, polypropylene, expanded polypropylene, polystyrene, polycarbonate, track-etched polycarbonate, or mixtures thereof. Examples of perfluorinated porous polymeric materials suitable for use in fuel cell applications include ePTFE made according to the teachings of U.S. Patent No. 8,757,395, which is incorporated herein by reference in its entirety, and is commercially available in various forms from W.L. Gore & Associates, Inc., Elkton, Maryland.

[0126] In embodiments in which the microporous polymer structure comprises ePTFE, the total mass per area of ​​the microporous polymer structure is about 5.5 g / m, based on the combined mass per area of ​​all microporous layers present in the composite membrane. 2 ~about 20g / m 2 For example, in embodiments in which the microporous polymer structure comprises ePTFE, the total area mass of the microporous polymer structure can be about 5.5 g / m, based on the sum of the area masses of all microporous layers present in the composite membrane. 2 , or about 5.8 g / m 2 , or about 6 g / m 2 , or about 7 g / m 2 , or about 8 g / m 2 , or about 9 g / m 2 , or about 10 g / m 2 , or about 11 g / m 2 , or about 12 g / m 2 , or about 13 g / m 2 , or about 14 g / m 2 , about 15g / m 2 , or about 16 g / m 2 , or about 17 g / m 2 , or about 18 g / m 2 , or about 19 g / m 2 , or about 20 g / m 2 It can be.

[0127] ion exchange materials Suitable ion exchange materials can depend on the application in which the composite membrane is used. The ion exchange material preferably has an average equivalent volume of about 240 cc / molar equivalent to about 870 cc / molar equivalent, optionally about 240 cc / molar equivalent to about 650 cc / molar equivalent, optionally about 350 cc / molar equivalent to about 475 cc / molar equivalent, and is chemically and thermally stable in the environment in which the composite membrane is used. Suitable ionomers can include ion exchange materials such as cation exchange materials, anion exchange materials, or ion exchange materials containing both cation and anion exchange capabilities. In some embodiments, the ion exchange material comprises a proton conducting polymer or a cation exchange material. The ion exchange material can be perfluorocarboxylic acid polymers, perfluorophosphonic acid polymers, styrene-based ion exchange polymers, fluorostyrene-based 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. Examples of suitable perfluorosulfonic acid polymers include Nafion® (EI DuPont de Nemours, Inc., Wilmington, Delaware, USA), Flemion® (Asahi Glass Co., Ltd., Tokyo, JP), Aciplex® (Asahi Chemical Industry Co., Ltd., Tokyo, JP), Aquivion® (SolvaySolexis SPA, Italy), and 3M™ (3M Innovative Properties Company, USA), which are commercially available perfluorosulfonic acid copolymers. Other examples of suitable perfluorosulfonic acid polymers include perfluorinated sulfonyl (co)polymers such as those described in US Pat. No. 5,463,005.

[0128] Properties of the composite membrane As described above, a composite membrane includes a microporous polymer structure and an ion exchange material absorbed into the microporous polymer structure, thereby forming two distinct materials that achieve improved puncture resistance of the composite membrane. Without wishing to be bound by theory, the puncture resistance of a composite membrane can be affected by the distribution of the total content of the microporous polymer structure in multiple (i.e., at least two) reinforcement layers compared to the same content of microporous polymer structure provided in a single reinforcement layer within the composite membrane assembly. Furthermore, the puncture resistance of a composite membrane can be affected by the total content of the microporous polymer structure within the composite membrane.

[0129] The composite membrane has a thickness at 0% RH of at least about 10 μm, for example, about 10 μm to about 115 μm, or about 10 μm to about 100 μm, or about 10 μm to about 90 μm, or about 10 μm to about 80 μm, or about 10 μm to about 70 μm, or about 10 μm to about 60 μm, or about 10 μm to about 50 μm, or about 10 μm to about 40 μm, or about 10 μm to about 30 μm, or about 10 μm It can have a thickness of about 20 μm, or about 10 μm to about 15 μm, or about 10 μm to about 12 μm, or about 20 μm to about 60 μm, or about 30 μm to about 60 μm, or about 40 μm to about 60 μm, or about 12 μm to about 30 μm, or about 12 μm to about 20 μm, or about 15 μm to about 30 μm, or about 15 μm to about 20 μm, or about 20 μm to about 30 μm. The composite membrane can have a thickness at 0% RH of about 10 μm, or about 11 μm, or about 12 μm, or about 13 μm, or about 14 μm, or about 15 μm, or about 16 μm, or about 17 μm, or about 18 μm, or about 19 μm, or about 20 μm, or about 21 μm, or about 22 μm, or about 23 μm, or about 24 μm, or about 25 μm, or about 30 μm, or about 35 μm, or about 40 μm, or about 45 μm, or about 50 μm, or about 55 μm, or about 60 μm, or about 65 μm, or about 70 μm, or about 75 μm. The composite membrane can have a thickness at 0% RH of less than about 10 μm.

[0130] In some embodiments, the microporous polymer structure of the reinforcing layer comprises about 15% to about 70% by volume, or about 20% to about 70% by volume, or about 30% to about 70% by volume, or about 40% to about 70% by volume, or about 50% to about 70% by volume, or about 65% to about 70% by volume, or about 25% to about 60% by volume, or about 20% to about 50% by volume, or about 20% to about 40% by volume, or about 20% to about 30% by volume, or about 40% to about 60% by volume, or about 40% to about 50% by volume (based on the total volume of the composite membrane). The microporous polymer structure of the reinforcing layer may be present in an amount of about 15 volume %, or about 20 volume %, or about 25 volume %, or about 30 volume %, or about 35 volume %, or about 40 volume %, or about 45 volume %, or about 50 volume %, or about 55 volume %, or about 60 volume %, or about 65 volume %, or about 70 volume %, based on the total volume of the composite membrane.

[0131] In some embodiments, the equivalent volume of the ion exchange material 110 is between about 240 cc / molar equivalent and about 870 cc / molar equivalent. The ion exchange material contains between about 400 g / eq and about 2000 g / eq of SO3 - The composite membranes 100, 200, 300, 400, 500, 600, 700, 800, and 900 can have a total equivalent weight (EW) of 1.2 meq / cc or more at 0% relative humidity, e.g., 1.2 meq / cc to 3.5 meq / cc. In various embodiments, the composite membranes have a thickness of about 10 μm to about 115 μm. Specifically, according to embodiments, the composite membranes have a thickness of about 10 μm to about 115 μm, and the composite membranes have an acid content of 1.2 meq / cc to 3.5 meq / cc.

[0132] The volume percent of the microporous polymer structure in the reinforcing layer in the composite refers to the space occupied by the microporous polymer structure without the ionomer. Therefore, the volume percent of the microporous polymer structure in the composite is different from that of the absorbent layer, which contains the ionomer. The volume percent of the microporous polymer structure in the composite is affected by humidity. Therefore, the experiments discussed below regarding volume percent are performed in dry conditions (e.g., 0% relative humidity (RH)).

[0133] In some embodiments, the normalized total content of the microporous polymer structure within the composite membrane is at least about 3·10 based on the total area of ​​the composite membrane. -6 m, or approximately 3.5 10 -6 m, or approximately 4·10 -6 m, or approximately 4.5 10 -6 m, or about 5.10 -6 m, or approximately 5.5-10 -6 m, or approximately 6.10 -6 m, or approximately 6.5-10 -6 m, or approximately 7.10 -6 m, or approximately 8-10 -6 m, or approximately 8.5-10 -6 m, or approximately 9.10 -6 It can be m.

[0134] The equivalent weight of ion exchange materials is also affected by humidity. Therefore, the experiments discussed below regarding equivalent weight are performed under dry conditions (e.g., 0% relative humidity (RH)), an ideal condition in which the presence of moisture does not affect the equivalent volume values ​​and meaningful comparisons between different ionomers can be made.

[0135] As noted above, it is surprising and unexpected that for any given content of microporous polymer structure and thickness of the composite membrane, distributing the content of microporous polymer structure within two or more reinforcing layers dramatically improves the puncture resistance of the composite membrane.

[0136] The composite membrane can have an average burst pressure of at least about 150 psi, as measured by the Average Puncture Pressure Burst Test described below. For example, the composite membrane can have an average burst pressure of at least about 150 psi, or at least about 160 psi, or at least about 170 psi, or at least about 180 psi, or at least about 190 psi, or at least about 200 psi, as measured by the Average Puncture Pressure Burst Test described below.

[0137] The composite membrane can have an average burst pressure of about 150 psi to about 500 psi when measured by the Average Puncture Pressure Burst Test described below, or can have an average burst pressure of about 150 psi to about 450 psi, or about 150 psi to about 400 psi, or about 150 psi to about 350 psi, or about 150 psi to about 300 psi, or about 200 psi to about 400 psi, or about 200 psi to about 350 psi when measured by the Average Puncture Pressure Burst Test described below.

[0138] The composite membrane may have an average burst pressure of about 150 psi, or about 200 psi, or about 250 psi, or about 300 psi, or about 350 psi, or about 400 psi, or about 450 psi, or about 500 psi, as measured by the Average Puncture Pressure Burst Test described below.

[0139] The membranes were prepared according to a sequential coating process as shown in Figure 13. For membranes with an inner layer of ionomer between reinforcing layers, method 1500 (Figure 13) includes the following steps: 1510) providing a backer layer and coating the backer with a first ionomer solution by depositing a liquid layer of the first ionomer solution; 1520) Laminating (depositing) a first reinforcing layer comprising a microporous polymer structure onto the liquid layer of first ionomer solution, so that the first ionomer solution is absorbed or at least partially absorbed into the microporous polymer structure of the first reinforcing layer; 1530) Optionally, allow the laminate to dry; 1540) Coating the imbibed first reinforcing layer with a liquid layer of a second ionomer solution; 1550) Laminating (depositing) a second reinforcing layer comprising a microporous polymer structure on the liquid layer of second ionomer solution, so that the second ionomer solution is absorbed or at least partially absorbed into the microporous polymer structure of the second reinforcing layer; 1560) optionally drying the laminate; 1570) coating the outermost surface of the laminate furthest from the backer with a final liquid layer of the third ionomer solution; and 1580) Allow the laminate to dry.

[0140] Optionally, the manufacturing method includes repeating steps 1560), 1570), and 1580) with additional reinforcing layers and liquid layers of ionomer solution and drying the laminate. For example, in a composite membrane including three reinforcing layers, a third liquid layer of a third ionomer solution can be deposited on the imbibed second reinforcing layer, a third reinforcing layer can be applied on the third layer of ionomer solution, and the laminate can then be dried. In some embodiments, the method includes adding additional ionomer and reinforcing layers and drying the laminate.

[0141] A membrane electrode assembly can be prepared by depositing electrodes (i.e., anode and cathode) onto a composite membrane by any suitable technique known in the art. For example, a solid electrode layer can be pressed against the composite membrane by any suitable technique. Alternatively, a (liquid) electrode ink can be applied to the composite membrane. The composite can be dried, allowing the solvent in the electrode ink to evaporate and form a solid electrode layer. For the avoidance of doubt, the backer must be removed from the composite membrane before applying the cathode or cathode fluid diffusion layer. The ionomers in the ionomer solution used in each of the ionomer layers can be the same or different. The reinforcing layers used in an electrolyte composite membrane can all be the same, or at least one of the reinforcing layers can be different. [Example]

[0142] example Test procedures and measurement protocols used in the examples Bubble Point Bubble point was measured according to the procedure of ASTM F316-86. Isopropyl alcohol was used as the wetting liquid to fill the pores of the specimen. The bubble point is the air pressure required to produce the first continuous stream of bubbles, detectable by the rise of bubbles through a layer of isopropyl alcohol covering a microporous polymer matrix. This measurement allows for an estimation of the maximum pore size.

[0143] Non-contact thickness A sample of the microporous polymer structure was placed on a flat, smooth metal anvil and pulled to remove any wrinkles. The height of the microporous polymer structure on the anvil was measured and recorded using a non-contact Keyence LS-7010M digital micrometer. The height of the anvil without the microporous polymer matrix was then recorded. The thickness of the microporous polymer structure was obtained as the difference between the micrometer readings with and without the microporous structure on the anvil.

[0144] Mass per area Each microporous polymer structure was strained sufficiently to remove wrinkles and then stretched over a 10 cm 2 The pieces were die cut. 10cm 2 The coupons were weighed on a conventional laboratory balance. The mass per area (M / A) was then calculated as the ratio of the measured mass to the known area. This procedure was repeated twice and the average M / A was calculated.

[0145] Apparent density of microporous polymer structures The apparent density of the microporous polymer structure was calculated using the non-contact thickness and mass per area data using the following formula:

number

[0146] Porosity of microporous polymer structures The porosity of the microporous polymer structure was calculated using the apparent density and skeletal density data using the following formula:

number

[0147] Solids concentration of the ion exchange material (IEM) solution The terms "solution" and "dispersion" are used interchangeably herein when referring to ion exchange materials (IEMs). This test procedure is appropriate for solutions in which the IEMs are in their protonated form and other solids are present in negligible amounts. A 2 cubic centimeter volume of IEM solution was drawn into a syringe, and the mass of the syringe containing the solution was measured via a balance in a solids analyzer (obtained from CEM Corporation, USA). The mass of two sheets of glass fiber paper (obtained from CEM Corporation, USA) was also measured and recorded. The IEM solution was then deposited from the syringe onto two layers of glass fiber paper. The glass fiber paper containing the ionomer solution was placed in the solids analyzer and heated to 160°C to remove the solvent liquid. The mass of the glass fiber paper and residual solids was recorded when it no longer changed with increasing temperature and time. The residual IEM was assumed to be water-free (i.e., the ionomer mass corresponding to 0% RH). The mass of the empty syringe was then measured using the same balance as before and recorded. The ionomer solids content in the solution was calculated according to the following formula:

number

[0148] IEM equivalent weight (EW) The following test procedure is appropriate for IEMs containing a single ionomer resin or a mixture of ionomer resins in the protonated form (i.e., containing negligible amounts of other cations) in a solution containing negligible other ionic species, including protonic acids and dissociated salts. If these conditions are not met, the solution must be purified from ionic impurities according to appropriate procedures known to those skilled in the art prior to testing, or the impurities must be characterized and corrected for their effect on the EW test results.

[0149] As used herein, the EW of an IEM refers to the IEM in its proton form at 0% RH with negligible impurities. The IEM can contain a single ionomer or a mixture of ionomers in the proton form. A quantity of IEM solution containing 0.2 grams of solids and having the solids concentration determined above was poured into a plastic cup. The mass of the ionomer solution was measured using a conventional laboratory scale (obtained from Mettler Toledo, LLC, USA). Five ml of deionized water and five ml of 200-proof denatured ethanol (SDA 3C, Sigma Aldrich, USA) were then added to the ionomer solution in the cup. Next, 55 ml of 2N sodium chloride solution in water was added to the IEM solution. The sample was then allowed to equilibrate for 15 minutes under constant stirring. After the equilibration step, the sample was titrated with 1N sodium hydroxide solution. The volume of 1N sodium hydroxide solution required to neutralize the sample solution to a pH value of 7 was recorded. The EW of the IEM (EW) was then calculated. IEM ) was calculated as follows:

number

[0150] When multiple IEMs were combined to form a composite membrane, the average EW of the IEMs in the composite membrane was calculated using the following equation:

number

[0151] Equivalent volume (EV) of ion exchange material As used herein, the equivalent volume of an IEM refers to the EV when the IEM is pure and in its proton form at 0% RH with negligible impurities. The EV is calculated according to the following formula:

number

[0152] The equivalent weight of each IEM was determined according to the procedure described above. The IEM used in these applications was a perfluorosulfonic acid ionomer resin, and the bulk density of the perfluorosulfonic acid ionomer resin was 1.9 g / cc at 0% RH.

[0153] Composite membrane thickness The composite films were equilibrated in the thickness measurement chamber for at least 1 hour before measurement. The composite films remained attached to the substrates on which they were coated. For each sample, the composite film on the coated substrate was placed on a smooth, flat, and level marble slab. A thickness gauge (obtained from Heidenhain Corporation, USA) was contacted with the composite film, and gauge height readings were recorded at six different spots arranged in a grid pattern on the film. The sample was then removed from the substrate, the gauge was contacted with the substrate, and height readings were recorded again at the same six spots. The thickness of the composite film at a specific relative humidity (RH) in the chamber was calculated as the difference between the gauge height readings with and without the composite film present. Local RH was measured using an RH probe (obtained from Fluke Corporation). The thickness at 0% RH was calculated using the following general formula:

number

number

[0154] Microporous polymer matrix (MPM) volume content of composite membranes The volume percent of the microporous polymer matrix in each composite membrane was calculated according to the following formula:

number

[0155] Acid content of composite membrane The acid content of the composite membrane was calculated according to the following formula:

number

[0156] Ball burst testing of composite microporous layers The mechanical strength of the composite membranes prepared according to the present invention was measured by applying a load pressure to the samples. The sample was tautly fixed in a frame with a 45 mm diameter opening. The sample in the frame was placed in a Shimadzu (Japan) universal testing machine AG-I equipped with an environmentally controlled chamber where the temperature and relative humidity in the chamber were 23°C and 80%, respectively. A 6.35 mm diameter steel ball supported by a support was pressed into the suspended membrane at a constant speed of 100 mm / min. The maximum load generated by the system at the time of sample rupture was recorded. This value is called the ball burst strength.

[0157] Average puncture pressure burst test The sample was placed between two porous carbon electrodes (Sigracet 39AA Carbon Paper) and loaded into an Instron Model 5542 with an electrically insulated, gold-plated, cylindrical platen, 14 mm in diameter. The sample and electrode areas were oversized relative to the platen, extending beyond the platen to eliminate edge effects during puncture. The sample area was oversized relative to the electrode area to prevent the electrodes from touching each other and creating an electronic short circuit that would not pass through the sample. The electrical resistance across the membrane was measured using a Keithley 580 Micro-Ohmmeter connected to the upper and lower platens. While applying a compressive mechanical load to the sample, the upper platen was lowered at a rate of 1 mm / min at ambient conditions, and the electrical resistance measured across the sample was continuously recorded until a compressive mechanical load of 444.8 N (100 lbf) was applied. Higher compressive pressures are accessible with alternative instruments or smaller platen active areas. Membrane puncture was defined as the pressure at which the electrical resistance fell below 18,000 ohms, representing physical contact of the electrode or electrode fiber through the sample. Five replicates were tested for each sample, and the average of the five runs was reported as the average puncture pressure. Puncture pressure is electrode material dependent and may be significantly increased or decreased when using different electrode materials.

number

[0158] example The composite membranes of the present disclosure may be better understood with reference to the following non-limiting examples. The composite membranes were tested for their acid content, volume, and puncture resistance, as well as for their properties, testing procedures, and measurement protocols. Table 1 shows the properties of composite membranes according to embodiments of the present invention and comparative examples. Table 2 shows the properties of the microporous polymer structures used in various testing procedures in a series of five examples and comparative examples according to some aspects of the present invention.

[0159] Ion exchange materials prepared according to aspects of the present disclosure for all examples All ion exchange materials used in the following examples are perfluorosulfonic acid (PFSA)-based ionomers with the equivalent weights (EW) specified in Table 1. Prior to fabrication of the composite membranes, all ionomers were in the form of solutions based on a mixture of water and ethanol as the solvent, with a water content of less than 50% in the solvent phase.

[0160] The composite membrane of the present disclosure was produced using a commonly known ion exchange material, a preferred example of which is a solution obtained by dispersing or dissolving a solid PFSA ionomer represented by the following general formula (a:b=1:1 to 9:1, n=0, 1, or 2) in a solvent. [ka]

[0161] In some embodiments, the solvent is selected from the group consisting of water, alcohols such as methanol, ethanol, propanol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, pentanol and its isomers, hexanol and its isomers, hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N,N-dimethylformamide and N,N-diethylformamide, acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, 1,1,2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane, 1,1,1-trichloroethane, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, dichloromethane, and chloroform. In the present disclosure, the solvent is optionally selected from the group consisting of water, methanol, ethanol, and propanol. Water and the above solvents can be used alone or in combination of two or more.

[0162] Series 1 Prior Art Example 1 Prior Art Example 1 was prepared according to the following procedure: 2 A first ePTFE membrane 1 having an area mass of 810 g / mol of SO3, a thickness of 9.6 μm, an apparent density of 0.29 g / cc, and a bubble point of 34.4 psi was used as the microporous polymer structure of the reinforcing layer. - A PSFA solution with a composition of 17.3% water, 71.5% ethanol, and 11.2% solids was applied to the top surface of the backer layer as the first laydown using a drawdown bar to a theoretical wet coating thickness of 3 mils (76.2 μm). While the coating was still wet, the first reinforcing layer of ePTFE membrane 1, previously fixed to a metal frame, was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. For the second laydown, the same IEM solution was applied to the top surface of the first ePTFE membrane 1 using a drawdown bar to a theoretical wet coating thickness of 4 mils (101.6 μm). While the coating was still wet, a second reinforcing layer of ePTFE membrane 1, previously fixed to a metal frame, was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. At the third laydown, EW = 810 g / mol equivalent of SO3 - A PSFA solution with a solution composition of 6.2% water, 89.8% ethanol, and 4.0% solids was coated on top of the second reinforcement layer using a drawdown bar to a theoretical wet coating thickness of 3 mils (76.2 μm). The composite membrane was then dried again at 165°C. The multilayer composite membrane was completely occlusive, with layers of the IEM on both sides and between the two completely occlusive microporous polymer layers. The resulting composite membrane had a thickness of 8.66 microns at 0% RH.

[0163] Comparative Example 1.1 Comparative Example 1.1 was prepared according to the following procedure: 2 An ePTFE membrane 2 having an area mass of 1000 psi, a thickness of 19.7 μm, an apparent density of 0.29 g / cc, and a bubble point of 34.8 psi was manually strained to remove wrinkles and restrained in a metal frame. - A first laydown of a PSFA solution with a solution composition of 32.2% water, 49.6% ethanol, and 18.2% solids was coated onto the top surface of a polymer substrate (backer material) for the IEM (obtained from Asahi Glass Co., Ltd.). The polymer substrate (obtained from Daicel Value Coating Co., Ltd., Japan) contained a protective layer of PET and cyclic olefin copolymer (COC) and was oriented with the COC side facing up. The IEM (PFSA solution) coating was applied using a Mayer bar with a theoretical wet coating thickness of 3 mil (76.2 μm). While the coating was still wet, an ePTFE membrane 2, previously fixed to a metal frame, was laminated onto the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the microporous polymer structure (ePTFE membrane) was completely absorbed by the IEM. The IEM also formed a layer between the bottom surface of the microporous polymer substrate and the polymer substrate. During the second laydown, a drawdown bar with a theoretical wet coating thickness of 2.5 mils (63.5 μm) was used to coat the same EW of IEM and a solution with a composition of 18.4% water, 73.3% ethanol, and 8.3% solids onto the top surface (opposite the polymer substrate) of ePTFE Membrane 2. The composite membrane was then dried again at 165°C, at which point it became largely transparent, indicating that the microporous polymer structure was completely impregnated. The composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer structure. The resulting composite membrane had a thickness of 8.6 μm at 0% RH.

[0164] Comparative Example 1.2 Comparative Example 1.2 was prepared according to the same procedure as described for Comparative Example 1.1, except that different materials were used: 3.9 g / m 2 An ePTFE membrane 3 having an area mass of 1000 psi, a thickness of 11.7 μm, an apparent density of 0.34 g / cc, and a bubble point of 97.5 psi was used as the microporous polymer structure. EW = 710 g / mol equivalent of SO - For the IEM (obtained from Asahi Glass Co., Ltd.), a PSFA solution with a composition of 26.4% water, 61.6% ethanol, and 12% solids was coated onto the top surface of a polymer substrate (backer substrate) as a first laydown using a drawdown bar to achieve a theoretical wet coating thickness of 4 mil (101.6 μm). While the coating was still wet, an ePTFE membrane 3, previously restrained in a metal frame, was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the microporous polymer structure (ePTFE membrane) was completely absorbed by the IEM. The IEM also formed a layer between the bottom surface of the microporous polymer substrate and the polymer substrate. During the second laydown, a solution of the same IEM, with a composition of 41% water, 53% ethanol, and 6% solids, was coated onto the top surface of ePTFE Membrane 3 (opposite the polymer substrate) using a drawdown bar to a theoretical wet coating thickness of 2 mils (50.8 μm). The composite material was then dried again at 165°C and became largely transparent, indicating complete impregnation of the microporous polymer structure. The composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer substrate. The resulting composite membrane had a thickness of 7.8 μm at 0% RH.

[0165] Series 2 Prior Art Example 2 Prior Art Example 2 was prepared according to the following procedure: First, two microporous polymer structures, 3.1 g / m 2 a first ePTFE membrane 4 having a mass per area of ​​1.0 g / m, a thickness of 13.3 μm, an apparent density of 0.33 g / cc, and a bubble point of 55.5 psi; 2A second ePTFE membrane 6 having an area mass of 1000 psi, a thickness of 15.2 μm, an apparent density of 0.20 g / cc, and a bubble point of 36.6 psi was strained to remove wrinkles and restrained in contact with a metal frame. - A first laydown of a solution of IEM (obtained from Shanghai Gore 3F Fluoromatenals Co., Ltd., China) with a solution composition of 17.3% water, 71.5% ethanol, and 11.2% solids was coated onto the top surface of a polymer substrate (backer layer). The polymer substrate (obtained from Daicel Value Coating Co., Ltd., Japan) contained a protective layer of PET and cyclic olefin copolymer (COC) and was oriented with the COC side facing up. The first laydown was applied using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). While the coating was still wet, both ePTFE membranes 4 and 6, which had previously been fixed to a metal frame, were laminated to the coating. The IEM solution was absorbed into the pores of the microporous polymer structure. The multilayer composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the microporous polymer matrix completely absorbed the IEM. The IEM also formed a layer between the bottom surface of the microporous polymer matrix and the polymer substrate. During the second laydown, EW = 810 g / mol equivalent of SO - A solution of IEM (obtained from Shanghai Gore 3F Fluoromaterials Co., Ltd., China), 4% water, 95.0% ethanol, and 1% solids was coated onto the top surface of the composite (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 0.5 mil (12.7 μm). The multilayer composite was then dried again at 165°C. At this point, it became mostly transparent, indicating complete impregnation of the microporous polymer matrix. The multilayer composite contained a multilayer composite membrane bonded to the substrate. The multilayer composite membrane was completely occlusive, with a layer of IEM on both sides of the contacting microporous polymer structure. The resulting multilayer composite membrane had a thickness of 7.1 microns at 0% RH.

[0166] Comparative Example 2.1 Comparative Example 2.1 was prepared according to the same procedure as described for Comparative Example 1.1, except that different materials were used: 4.5 g / m 2 An ePTFE membrane 5 having an area mass of 1000 psi, a thickness of 23 μm, an apparent density of 0.2 g / cc, and a bubble point of 55.8 psi was used as the microporous polymer structure. EW = 810 g / mol equivalent of SO - For the IEM (obtained from Asahi Glass Co., Ltd.), a PSFA solution with a solution composition of 33% water, 48.8% ethanol, and 18.2% solids was coated onto the top surface of the polymer substrate (backer layer) as a first laydown using a drawdown bar with a theoretical wet coating thickness of 3 mils (76.2 μm). While the coating was still wet, an ePTFE membrane 5, previously restrained in a metal frame, was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the IEM was completely absorbed into the microporous polymer structure (ePTFE membrane 5). The IEM also formed a layer between the bottom surface of the microporous polymer substrate and the polymer substrate. During the second laydown, a solution of the same IEM, with a composition of 35% water, 56.7% ethanol, and 8.3% solids, was coated onto the top surface of Membrane 5 (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 3 mils (76.2 μm). The composite material was then dried again at 165°C and became largely transparent, indicating complete impregnation of the microporous polymer structure. The composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer substrate. The resulting composite membrane had a thickness of 8.8 μm at 0% RH.

[0167] Series 3 Comparative Example 3.1 Comparative Example 3.1 was prepared according to the same procedure as described for Comparative Example 1.1, except that different materials were used. 2An ePTFE membrane 7 having an area mass of 1000 psi, a thickness of 62.2 μm, an apparent density of 0.16 g / cc, and a bubble point of 56.2 psi was used as the microporous polymer structure. EW = 710 g / mol equivalent of SO - For the IEM (obtained from Asahi Glass Co., Ltd.), a PSFA solution with a solution composition of 32% water, 49.8% ethanol, and 18.2% solids was coated onto the top surface of the polymer substrate (backer layer) in a first laydown using a drawdown bar with a theoretical wet coating thickness of 9 mil (228.6 μm). While the coating was still wet, an ePTFE membrane 7, previously fixed to a metal frame, was laminated onto the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven at 165°C with internal air. Upon drying, the IEM was completely absorbed into the microporous polymer structure (ePTFE membrane 7). The IEM also formed a layer between the bottom surface of the microporous polymer substrate and the polymer substrate. During the second laydown, a solution of the same IEM, with a composition of 41% water, 53% ethanol, and 6% solids, was coated onto the top surface of ePTFE Membrane 7 (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 3 mils (76.2 μm). The composite material was then dried again at 165°C, at which point it became largely transparent, indicating complete impregnation of the microporous polymer structure. The composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer substrate. The resulting composite membrane had a thickness of 15.3 μm at 0% RH.

[0168] Example 3.2 Inventive Example 3.2 was prepared according to the following procedure: 2 A first ePTFE membrane 3 having an area mass of 1000 psi, a thickness of 11.7 μm, an apparent density of 0.34 g / cc, and a bubble point of 97.5 psi was used as the microporous polymer structure of the reinforcement layer. EW=710 g / mol equivalent of SO -For the IEM (obtained from Asahi Glass Co., Ltd.), a PSFA solution with a composition of 35% water, 55.1% ethanol, and 9.9% solids was coated as a first laydown on top of the polymer substrate (backer layer) using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). While the coating was still wet, a first ePTFE membrane 3 restrained on a metal frame was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the microporous polymer structure (ePTFE membrane 3) was completely absorbed by the IEM. A second laydown of the same IEM solution was coated on top of the first membrane 3 (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). While the coating was still wet, a second ePTFE membrane (3), previously restrained in a metal frame, was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at 165°C. A third laydown of a PSFA solution with the same IEM EW, 38.0% water, 57.7% ethanol, and 4.3% solids, was coated onto the top surface of the second membrane (3) using a drawdown bar to a theoretical wet coating thickness of 3 mils (76.2 μm). The composite was then dried in a convection oven with internal air at 165°C. The multilayer composite membrane was completely occlusive, with a layer of IEM on either side of and between two completely occlusive microporous polymer layers of membrane (3) with a separation distance d of approximately 2 μm. The resulting composite membrane had a thickness of 14.5 microns at 0% RH.

[0169] Example 3.3 Inventive Example 3.3 was prepared according to the following procedure: 2 An ePTFE membrane 5 having an area mass of 1000 psi, a thickness of 23 μm, an apparent density of 0.20 g / cc, and a bubble point of 55.8 psi was used as the microporous polymer structure for the reinforcement layer. EW = 710 g / mol equivalent of SO3 -A PSFA solution with a solution composition of 33% water, 52.2% ethanol, and 14.8% solids was coated on top of the polymer substrate (backer layer) as a first laydown using a drawdown bar with a theoretical wet coating thickness of 3 mils (76.2 μm). While the coating was still wet, a first ePTFE membrane 5 restrained on a metal frame was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the microporous polymer structure (ePTFE membrane) was completely absorbed by the IEM. A second laydown of the same IEM solution was coated on top of the first membrane 5 composite (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 6 mils (152.4 μm). While the coating was still wet, a second ePTFE membrane 5, previously restrained in a metal frame, was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at 165°C. A third laydown of a PSFA solution with the same IEM and EW, 10.0% water, 89.0% ethanol, and 1.0% solids, was coated on top of the second membrane 5 using a drawdown bar with a theoretical wet coating thickness of 1.5 mils (38.1 μm). The composite was then dried in a convection oven with internal air at 165°C. The multilayer composite membrane was completely occlusive, with a layer of IEM on either side of and between two completely occlusive microporous polymer layers of membrane 5 with a separation distance d of approximately 2 μm. The resulting composite membrane had a thickness of 14.4 μm at 0% RH.

[0170] Series 4 Comparative Example 4.1 Comparative Example 4.1 was prepared according to the same procedure as described for Comparative Example 1.1, except that different materials were used: 10.4 g / m 2An ePTFE membrane 7 having an area mass of 1000 psi, a thickness of 62.2 μm, an apparent density of 0.16 g / cc, and a bubble point of 56.2 psi was used as the microporous polymer structure. EW = 710 g / mol equivalent of SO - For IEM (obtained from Asahi Glass Co., Ltd.), a PSFA solution with a composition of 32% water, 49.8% ethanol, and 18.2% solids was coated on top of the polymer substrate (backer layer) in the first laydown using a drawdown bar with a theoretical wet coating thickness of 9 mils (228.6 μm). The membrane was then dried in a convection oven with internal air at a temperature of 165°C. In the second laydown, the same IEM solution with a composition of 41% water, 53% ethanol, and 6% solids was coated on top of Membrane 7 using a drawdown bar with a theoretical wet coating thickness of 3 mils (76.2 μm). The membrane was again dried in a convection oven with internal air at a temperature of 165°C. The composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer substrate. The resulting composite membrane had a thickness of 15.3 μm at 0% RH.

[0171] Example 4.2 Inventive Example 4.2 was prepared according to the following procedure: 2 Two microporous polymer structures, ePTFE membrane 5 as a reinforcing layer having an area mass of 1000 psi, a thickness of 23 μm, an apparent density of 0.20 g / cc, and a bubble point of 55.8 psi, were strained to remove wrinkles and restrained in overlapping contact with a metal frame. Then, EW=710 g / mol equivalent of SO3 -A first laydown of a solution with a solution composition of 100% IEM (obtained from Asahi Glass Co., Ltd.), 33% water, 52.2% ethanol, and 14.8% solids was coated onto the top surface of a polymer substrate (backer layer). The polymer substrate (obtained from Daicel Value Coating Co., Ltd., Japan) contained a protective layer of PET and cyclic olefin copolymer (COC) and was oriented with the COC side facing up. The coating was applied using a drawdown bar with a theoretical wet coating thickness of 7 mils (177.8 μm). While the coating was still wet, two ePTFE membranes 5, previously restrained in a metal frame, were laminated onto the coating, allowing the IEM solution to be absorbed into the pores. The multilayer composite was then dried in a convection oven at 165°C with internal airflow. Upon drying, the microporous polymer matrix completely absorbed the IEM. The IEM also formed a layer between the bottom surface of the microporous polymer structure and the polymer substrate. During the second laydown, EW = 710 g / mol equivalent of SO3 - A solution with a solution composition of 1.5 mils (obtained from Asahi Glass Co., Ltd.), 33% water, 52.2% ethanol, and 14.8% solids was coated onto the top surface of ePTFE membrane 5 (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 1.5 mils (38.1 μm). The multilayer composite was then dried again at 165°C. At this point, it was largely transparent, indicating that the microporous polymer matrix was completely impregnated. The multilayer composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer matrix that were in contact. The resulting multilayer composite membrane had a thickness of 14.4 μm at 0% RH.

[0172] Example 4.3 Inventive Example 4.3 was prepared according to the same procedure as Inventive Example 3.3 previously described herein.

[0173] Example 4.4 Inventive Example 4.4 was prepared according to the same procedure as described for Inventive Example 3.3, except that different materials were used. 2An ePTFE membrane 5 having an area mass of 1000 psi, a thickness of 23 μm, an apparent density of 0.20 g / cc, and a bubble point of 55.8 psi was used as the microporous polymer structure for the reinforcing layer. EW = 710 g / mol equivalent of SO - For the IEM (obtained from Asahi Glass Co., Ltd.), a PSFA solution with a solution composition of 29.8% water, 56.8% ethanol, and 13.4% solids was coated onto the top surface of a polymer sheet substrate (backer layer) in a first laydown using a drawdown bar with a theoretical wet coating thickness of 4 mils (101.6 μm). While the coating was still wet, a first ePTFE membrane 5, previously fixed to a metal frame, was laminated onto the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the microporous polymer structure completely absorbed the IEM. The IEM also formed a layer between the bottom surface of the microporous polymer structure and the polymer substrate. During the second laydown, the same IEM solution, with a composition of 29.8% water, 56.8% ethanol, and 13.4% solids, was coated onto the top surface of the first ePTFE membrane 5 using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). A second ePTFE membrane 5, pre-restrained on a metal frame, was laminated to the coating, allowing the IEM solution to be absorbed into the pores. The multilayer composite was then dried in an air-filled convection oven at 165°C. During the third laydown, the same IEM solution, with a composition of 35% water, 59% ethanol, and 6% solids, was coated using a drawdown bar with a theoretical wet coating thickness of 2 mils (50.8 μm). The composite was then dried in an air-filled convection oven at 165°C. The multilayer composite membrane was completely occlusive, with a layer of IEM on either side of and between two completely occlusive microporous polymer layers with a separation distance d of approximately 4 μm. The resulting composite membrane had a thickness of 14.4 μm at 0% RH.

[0174] Series 5 Comparative Example 5.1 Comparative Example 5.1 was prepared according to the same procedure as described for Comparative Example 1.1, except that different materials were used. 2 An ePTFE membrane 8 having an area mass of 1000 psi, a thickness of 33.4 μm, an apparent density of 0.53 g / cc, and a bubble point of 23.7 psi was used as the microporous polymer structure. EW = 810 g / mol equivalent of SO - A PSFA solution with a composition of 32.2% water, 49.6% ethanol, and 18.2% solids was coated onto the IEM (obtained from Asahi Glass Co., Ltd.) as the first laydown using a drawdown bar with a theoretical wet coating thickness of 9 mils (228.6 μm). While the coating was still wet, a first ePTFE membrane 8, previously fixed to a metal frame, was laminated onto the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 165°C. For the second laydown, the same IEM solution with a composition of 15.1% water, 18.4% ethanol, and 4.2% solids was coated onto the top surface of the ePTFE membrane 8 using a drawdown bar with a theoretical wet coating thickness of 1.5 mils (38.1 μm). The composite was again dried in a convection oven with internal air at a temperature of 165°C. The composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer substrate. The resulting composite membrane had a thickness of 23.8 μm at 0% RH.

[0175] Example 5.2 Inventive Example 5.2 was prepared following the same procedure as described for Inventive Example 4.2, except that different materials were used. 2 a first ePTFE membrane 5 having a mass per area of ​​10.4 g / m, a thickness of 23 μm, an apparent density of 0.20 g / cc, and a bubble point of 55.8 psi; 2 A second ePTFE membrane 7 having an area mass of 1000 psi, a thickness of 62.2 μm, an apparent density of 0.16 g / cc, and a bubble point of 56.2 psi was used as the microporous polymer structure for the two reinforcing layers. EW = 810 g / mol equivalent of SO3 -A PSFA solution with a solution composition of 32.2% water, 49.6% ethanol, and 18.2% solids was coated onto the IEM (obtained from Asahi Glass Co., Ltd.) as the first laydown using a drawdown bar with a theoretical wet coating thickness of 9 mils (228.6 μm). While the coating was still wet, the first ePTFE membrane 5 and the second ePTFE membrane 7, which had previously been fixed to a metal frame, were laminated onto the coating, allowing the IEM solution to be absorbed into the pores of both ePTFE membranes. The composite was then dried in a convection oven with internal air at a temperature of 165°C. For the second laydown, the same IEM solution with a composition of 18.4% water, 73.3% ethanol, and 8.3% solids was coated onto the top surfaces of the two ePTFE membranes 5 and 7 using a drawdown bar with a theoretical wet coating thickness of 4 mils (101.6 μm). The composite material was dried again in a convection oven with internal air at 165°C. The multilayer composite membrane was completely occlusive, with a layer of IEM on each side, and two completely occlusive microporous polymer layers in contact with each other. The thickness of the resulting composite membrane at 0% RH was 24.1 µm.

[0176] Example 5.3 Inventive Example 5.3 was prepared according to the following procedure: 2 Three microporous polymer structures were prepared: an ePTFE membrane 5 having an area mass of 1000 μm, a thickness of 23 μm, an apparent density of 0.20 g / cc, and a bubble point of 55.8 psi; and the ePTFE was strained to remove wrinkles and restrained in contact with a metal frame. Then, a solution of SO3 with an EW of 810 g / mol equivalent was added. -A first laydown of a solution of IEM (obtained from Asahi Glass Co., Ltd.), 32.2% water, 49.6% ethanol, and 18.2% solids, was coated onto the top surface of a polymer substrate (backer layer). The substrate (obtained from Daicel Value Coating Co., Ltd., Japan) contained a protective layer of PET and cyclic olefin copolymer (COC) and was oriented with the COC side facing up. The coating was applied using a drawdown bar with a theoretical wet coating thickness of 9 mils (228.6 μm). While the coating was still wet, three ePTFE membranes (5) previously fixed to a metal frame were laminated onto the coating, allowing the IEM solution to be absorbed into the pores. The multilayer composite was then dried in a convection oven with internal air at a temperature of 165°C. Upon drying, the microporous polymer matrix was completely absorbed with the IEM. The IEM also formed a layer between the bottom surface of the microporous polymer matrix and the polymer substrate. During the second laydown, EW = 710 g / mol equivalent of SO3 - A solution of IEM (obtained from Asahi Glass Co., Ltd.), 18.4% water, 73.3% ethanol, and 8.3% solids was coated onto the top surface of the composite (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 2 mils (50.8 μm). The multilayer composite was then dried again at 165°C, at which point it became largely transparent, indicating complete impregnation of the microporous polymer matrix. The multilayer composite membrane was completely occlusive, with a layer of IEM on both sides of the contacting microporous polymer matrix. The resulting multilayer composite membrane had a thickness of 24.2 μm at 0% RH.

[0177] Example 5.4 Inventive Example 5.4 was prepared following the same procedure as described for Inventive Example 4.2, except that different materials were used: 9.9 g / m 2 A first ePTFE membrane 9 having an area mass of 1000 psi, a thickness of 23 μm, an apparent density of 0.43 g / cc, and a bubble point of 130 psi, and a second ePTFE membrane 9 of the same material were used as the microporous polymer structure. EW=810 g / mol equivalent of SO3 -For the IEM (obtained from Asahi Glass Co., Ltd.), a PSFA solution with a solution composition of 26.0% water, 55.0% ethanol, and 19% solids was coated onto the top surface of the polymer substrate (backer layer) as the first laydown using a drawdown bar with a theoretical wet coating thickness of 9 mils (228.6 μm). While the coating was still wet, a first ePTFE membrane 9 and a second ePTFE membrane 9, previously restrained in a metal frame, were laminated onto the coating, allowing the IEM solution to be absorbed into the pores of both ePTFE membranes. The composite was then dried in a convection oven with internal air at a temperature of 165°C. For the second laydown, the same IEM solution with a composition of 18.4% water, 73.3% ethanol, and 8.3% solids was coated onto the top surface of the composite using a drawdown bar with a theoretical wet coating thickness of 2 mils (50.8 μm). The multilayer composite material was then dried in an air-filled convection oven at 165°C. The resulting multilayer composite membrane was completely occlusive, with a layer of IEM on each side and two completely occlusive microporous polymer layers in contact with each other. The thickness of the resulting composite membrane at 0% RH was 24.0 µm.

[0178] Series 6 Comparative Example 6.1 Comparative Example 6.1 was prepared according to the same procedure as described for Comparative Example 1.1, except that different materials were used. 2 An ePTFE membrane 10 having an area mass of 1100 g / mol equivalent of SO3, a thickness of 137 μm, an apparent density of 0.22 g / cc, and a bubble point of 43.5 psi was used as the microporous polymer structure. -For the first laydown, a PSFA solution with a solution composition of 38% water, 41.8% ethanol, and 20.2% solids (IEM, obtained from EI du Pont de Nemours and Company) was coated onto the polymer substrate (backer layer) using a drawdown bar with a theoretical wet coating thickness of 10 mils (254 μm). While the coating was still wet, an ePTFE membrane 10, previously fixed to a metal frame, was laminated onto the coating, allowing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at 165°C. For the second laydown, the same IEM solution with a composition of 26% water, 64.2% ethanol, and 9.8% solids was coated onto the top surface of the composite using a drawdown bar with a theoretical wet coating thickness of 3 mils (76.2 μm). The composite was then dried in a convection oven with internal air at 165°C. The resulting composite membrane was completely occlusive, with a layer of IEM on both sides of the microporous polymer substrate, and had a thickness of 38.8 μm at 0% RH.

[0179] Example 6.2 Inventive Example 6.2 was prepared according to the following procedure: 2 An ePTFE membrane 7 having an area mass of 1000 g / mol, a thickness of 62.2 μm, an apparent density of 0.16 g / cc, and a bubble point of 56.2 psi was used as the microporous polymer structure for the reinforcing layer. EW = 1100 g / mol equivalent of SO -A PSFA solution with a solution composition of 24.4% water, 56.6% ethanol, and 19.0% solids was coated on top of a polymer substrate (backer layer) to form an IEM (obtained from EI du Pont de Nemours and Company). The polymer substrate (obtained from Daicel Value Coating Co., Ltd., Japan) contained a protective layer of PET and cyclic olefin copolymer (COC) and was oriented with the COC side facing up. Coating was performed using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). While the coating was still wet, a first ePTFE membrane 7 restrained on a metal frame was laminated to the coating, and the IEM solution was absorbed into the pores. The composite was then dried in a convection oven with internal air at a temperature of 125°C. Upon drying, the IEM was completely absorbed into the microporous polymer structure (ePTFE membrane 7). A second laydown of the same IEM solution was coated onto the top surface of the composite (opposite the polymer substrate) using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). While the coating was still wet, a second ePTFE membrane 7, previously restrained in a metal frame, was laminated onto the coating, causing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at 125°C. A third laydown of the same IEM solution was coated onto the top surface of the composite using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). While the coating was still wet, a third ePTFE membrane 7, previously restrained in a metal frame, was laminated onto the coating, causing the IEM solution to be absorbed into the pores. The composite was then dried in a convection oven with internal air at 125°C. A fourth laydown of PSFA solution with the same IEM and EW, 20.0% water, 76.0% ethanol, and 4.0% solids was coated onto the top surface of the composite using a drawdown bar with a theoretical wet coating thickness of 5 mils (127 μm). The multilayer composite was then dried in an air-filled convection oven at a temperature of 165°C.The multilayer composite membrane was completely occlusive, with a layer of IEM on each side and between each of three completely occlusive microporous polymer layers with a separation distance d of approximately 1 μm. The thickness of the resulting composite membrane at 0% RH was 38.6 μm.

[0180] Properties of the example composite membranes are listed in Table 1 (Figure 11). Properties of the microporous polymer structure used in the composite membranes are listed in Table 2 (Figure 12). The improvement in puncture resistance is illustrated in Figure 10, which shows a graph comparing the average burst pressure of comparable composite membranes with that of the composite membranes of the present invention, plotted against the normalized microporous polymer structure content (μm) for each composite membrane. Referring to Figure 10, each data point correlates the average burst pressure data (psi) against the normalized microporous polymer structure content for each set of examples, discussed in more detail below.

[0181] Discussion of results Series 1 (plotted as 8 μm A in FIG. 10 ) includes Prior Art Example 1, which corresponds to Example 11.2 of WO 2018 / 232254 and is incorporated herein in its entirety. Series 1 also includes two Comparative Examples. The composite membranes have a similar thickness of about 8 μm at 0% RH. Prior Art Example 1 has two reinforcing layers comprising ePTFE as a microporous polymer structure disposed in contact with each other, while Comparative Examples 1.1 and 1.2 have a single reinforcing ePTFE layer. The ePTFE content (expressed as the mass per area of ​​the ePTFE in the composite membrane) is comparable in Prior Art Example 1 and Comparative Example 1.1 (as shown in Table 1, the total mass per area of ​​ePTFE in the composite membrane is about 6 g / m). 2 As shown in Table 1, the normalized total content of the microporous polymer structure is about 2.5 μm. Comparative Example 1.2 has a low content of ePTFE in a single reinforcing layer (3.9 g / m 2 or normalized total ePTFE content 1.7 μm). All three examples provide low average burst pressures, well below 150 psi. Therefore, these composite membranes are susceptible to puncture by components of electrochemical devices, such as redox flow batteries, during device assembly.

[0182] Series 2 (plotted as 8 μm B in FIG. 10) includes Prior Art Example 2 (corresponding to Example 7.3 in WO 2018 / 232254) which has two ePTFE reinforcement layers separated by an inner layer of unreinforced ion exchange material. This series also includes Comparative Example 2.1 which has a single ePTFE reinforcement layer. In this series, the composite membranes also have a thickness of about 8 μm at 0% RH. The total ePTFE content is 4.5 g / m² compared to Comparative Example 2.1 (4.5 g / m²). 2 or 2 μm normalized total ePTFE content) than Prior Art Example 2 (6.1 g / m 2 or 2.7 μm normalized total ePTFE content). Both composite membranes present offer low average burst pressures below 150 psi. Therefore, these composite membranes are susceptible to puncture by components of electrochemical devices such as redox flow batteries during device assembly.

[0183] Series 3 (plotted as 15 μm in FIG. 10) includes one comparative example 3.1 with a single ePTFE reinforcing layer and two inventive examples with two ePTFE reinforcing layers. The membranes have a thickness of approximately 15 μm at 0% RH. Comparative example 3.1 is thicker than inventive example 3.2 (7.8 g / m). 2 or 3.6 μm normalized total ePTFE content) and 3.3 (9 g / m 2 or 4 μm normalized total ePTFE content) 2 or 4.6 μm normalized total ePTFE content), Comparative Example 1 has an unacceptable average burst pressure of less than 150 psi, while both inventive examples have significantly improved average burst pressures of greater than 150 psi.

[0184] Series 4 (plotted as 15 μm B in FIG. 10) includes three inventive examples with two ePTFE reinforcing layers. In FIG. 10, this series is also plotted against Comparative Example 4.1 (the same sample as Comparative Example 3.1) because all composite membranes have a similar thickness of approximately 15 μm at 0% RH. These three inventive samples were prepared in a similar manner and contained the same content of ePTFE (9 g / m) distributed across the two reinforcing layers.2 or 4 μm normalized total ePTFE content). 2 All three inventive examples have a higher total ePTFE content (10.4 g / m), as does inventive example 3.2 from series 3, which has 2 ), but had similar average burst pressures above 150 psi, unlike Comparative Examples 3.1 / 4.1, which had unacceptable average burst pressures below 150 psi despite the use of reinforced layers. It can be seen that in this series, separation between the reinforcing layers does not result in a significant difference in average burst pressure.

[0185] Series 5 (plotted as 25 μm in Figure 10) is 18 g / m 2 The composite membranes had one comparative example 5.1 with a single reinforcing ePTFE layer with a total ePTFE content of 13.5 g / m² (normalized total ePTFE content of 8 μm), inventive examples 5.1 and 5.3 with two reinforcing ePTFE layers in direct contact, and inventive example 5.2 with three reinforcing ePTFE layers in direct contact. All of these composite membranes had equivalent thicknesses of about 25 μm and a mass of about 13.5 g / m². 2 ~about 20g / m 2 The thicker membranes had a total ePTFE content of 100 μm (normalized total ePTFE content between 6 and 8.8 μm). As shown in FIG. 10, these thicker membranes had improved mean burst pressures compared to the inventive examples of Series 3 and 4. While not wishing to be bound by theory, the increased total ePTFE content in the membrane may improve the mean burst pressure. Furthermore, Comparative Example 5.2, which had three ePTFE layers, had significantly improved mean burst pressures compared to Examples 5.1 and 5.3, in which an equivalent total ePTFE content was distributed across two reinforcing layers rather than three. All inventive examples in this series showed superior mean burst pressures compared to Comparative Example 5.1, in which the total ePTFE content was distributed across a single reinforcing layer (and had an equivalent total content as Inventive Example 5.4).

[0186] Finally, series 6 (plotted as 41 μm in Figure 10) is approximately 29.5 g / m 2One comparative example 6.1 has a single reinforced ePTFE layer with a total mass of ePTFE per area of ​​the composite membrane of about 31.2 g / m 2 The composite membranes had Inventive Example 6.2 and Inventive Example 6.3, which had a total mass of ePTFE per area of ​​composite membrane of about 13 μm. The membranes had equivalent thicknesses of about 40 μm at 0% RH and similar density-normalized total ePTFE contents of about 13 μm. Each sample exhibited average burst pressures well above 150 psi due to their higher thickness and ePTFE content. However, Inventive Sample 6.2 showed a significant improvement over Comparative Example 6.1, as none of the five 6.2 samples tested failed when tested up to 419 psi, and is reported as a maximum observable average burst pressure of >419 psi.

[0187] Surprisingly, these data show that for a given content of microporous polymer structure in a composite membrane, distributing the microporous polymer structure across at least two reinforcement layers significantly improves the average burst pressure compared to distributing the same content of microporous polymer structure across a single reinforcement layer. However, this observation only occurs for membranes with a minimum thickness of approximately 10 μm at 0% RH. As shown in Series 1 and 2, composite membranes with a thickness of approximately 8 μm at 0% RH had unacceptable average burst pressures, regardless of the number of reinforcement layers. Furthermore, as shown in Series 5 and 6, increasing the number of reinforcement layers containing microporous polymer structure (e.g., from 0 to 2 or from 2 to 3) for a comparable total content of microporous polymer structure significantly improves the average burst pressure. Finally, for similar composite membrane structures (in terms of the number of reinforcement layers containing microporous polymer structure), increasing the total content of microporous polymer structure in the composite membrane improves the average burst pressure. Composite membranes according to the present disclosure are therefore highly desirable because they have excellent resistance to puncture by elements of electrochemical devices during device fabrication without compromising membrane performance.

[0188] While the present invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those skilled in the art. It will be understood that aspects of the invention, parts of various embodiments, and various features recited above and / or in the appended claims can be combined or interchanged in whole or in part. In the above description of various embodiments, embodiments that refer to separate embodiments can be appropriately combined with other embodiments, as will be understood by those skilled in the art. Furthermore, those skilled in the art will understand that the above description is merely exemplary and is not intended to limit the invention. (Aspect) (Aspect 1) a) at least two reinforcing layers, each of the at least two reinforcing layers comprising a microporous polymer structure; and b) an ion exchange material (IEM) at least partially absorbed within the microporous polymer structure of the at least two reinforcing layers, causing the microporous polymer structure to become occlusive; 1. A composite membrane for an electrochemical device comprising: the composite film has a thickness of at least about 10 μm at 0% RH; and A composite membrane for an electrochemical device, wherein the microporous polymer structure is present in a total content of at least about 15 volume percent based on the total volume of the composite membrane. (Aspect 2) 2. The composite membrane of embodiment 1, wherein the at least two reinforcement layers have the same composition or the at least two reinforcement layers have different compositions. (Aspect 3) 3. The composite membrane of any one of claims 1 to 2, wherein the microporous polymer structure comprises at least one fluorinated polymer, and optionally the fluorinated polymer is polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (EPTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), or a mixture thereof. (Aspect 4) the fluorinated polymer is perfluorinated expanded polytetrafluoroethylene (ePTFE), and optionally The composite membrane has a mass per area of ​​at least about 5.5 g m based on the total mass per area of ​​all reinforcing layers present in the composite membrane. -2 or having a total content of microporous polymer structures of The composite membrane has a mass per area of ​​about 5.5 g m based on the total mass per area of ​​all reinforcing layers present in the composite membrane. -2 ~Approx. 80g m -2 4. The composite membrane of embodiment 3, having a total microporous polymer structure content of at least one of: (Aspect 5) 10. The composite membrane of any one of the preceding aspects, wherein the microporous polymer structure comprises a hydrocarbon polymer; and optionally the hydrocarbon polymer comprises polyethylene, polypropylene, polycarbonate, polystyrene, or a mixture thereof. (Aspect 6) the at least two reinforcing layers are in direct contact, or 10. The composite membrane of any one of the preceding aspects, wherein the composite membrane comprises at least one inner layer of ion exchange material between the at least two reinforcement layers. (Aspect 7) 10. The composite membrane of any one of the preceding embodiments, wherein the at least two reinforcement layers are separated by a distance d. (Aspect 8) The distance d is about 0.1 μm to about 20 μm at 0% RH, 8. The composite membrane of embodiment 7, wherein the distance d is at least one of about 0.5 μm to about 5 μm at 0% RH. (Aspect 9) the ion exchange material comprises a plurality of layers of ion exchange material, and the layers of ion exchange material are formed from the same ion exchange material; or 20. The composite membrane of any one of the preceding embodiments, wherein the ion exchange material comprises multiple layers of ion exchange material, and a first layer of the ion exchange material is formed from a different ion exchange material than the ion exchange material of a second layer of ion exchange material. (Aspect 10) The microporous polymer structure may be fully imbibed with the ion exchange material or the microporous polymer structure of each of the at least two reinforcement layers has a first surface and a second surface, and the ion exchange material forms a layer on at least one of the first surface or the second surface of each of the at least two reinforcement layers; 10. The composite membrane of any one of the preceding embodiments, wherein the composite membrane is at least one of: (Aspect 11) the microporous polymer structure of each of the at least two reinforcing layers having a first surface and a second surface; and 10. The composite membrane of any one of claims 1 to 9, wherein the microporous polymer structure is mostly imbibed with the ion exchange material but includes regions of non-imbibed or non-occluded regions of the microporous polymer structure proximate a first surface of at least one of the at least two reinforcement layers, or proximate a second surface of at least one of the at least two reinforcement layers, or both, and optionally the non-occluded portions comprise a coating of ion exchange material on the inner surface of the microporous polymer structure. (Aspect 12) 12. The composite membrane of embodiment 11, wherein the microporous polymer structure of the at least two reinforcement layers is about 90% blocked with ion exchange material. (Aspect 13) 10. The composite membrane of any one of the preceding embodiments, wherein the average equivalent volume of the ion exchange material is from about 240 cc / molar equivalent to about 870 cc / molar equivalent, and optionally, the average equivalent volume of the ion exchange material is from about 350 cc / molar equivalent to about 475 cc / molar equivalent, or from about 240 cc / molar equivalent to about 650 cc / molar equivalent. (Aspect 14) The ion exchange material comprises at least one ionomer, and optionally the at least one ionomer comprises a proton conducting polymer, and further optionally, the proton conducting polymer comprises a hydrocarbon ionomer, a perfluorinated ionomer, or a perfluorosulfonic acid; the at least one ionomer has a density of about 1.9 g / cc or greater at 0% relative humidity; 10. The composite membrane of any one of the preceding embodiments, wherein the composite membrane is at least one of: (Aspect 15) the composite membrane has a thickness at 0% RH of about 10 μm to about 115 μm, or about 10 μm to about 90 μm, or about 10 μm to about 40 μm, or about 10 μm to about 30 μm, or about 10 μm to about 20 μm; the composite film has a thickness of about 15 μm at 0% RH; the composite film has a thickness of about 25 μm at 0% RH; 10. The composite membrane of any one of the preceding embodiments, wherein (Aspect 16) 10. The composite membrane of any one of the preceding embodiments, wherein the composite membrane has an average burst pressure of about 150 psi to about 500 psi when measured according to the Average Puncture Pressure Burst Test Average Puncture Pressure Burst Test described herein. (Aspect 17) 10. The composite membrane of any one of the preceding embodiments, further comprising at least one backer layer removably attached to one or more outer surfaces of the composite membrane. (Aspect 18) at least one electrode; and 18. The composite membrane of any one of embodiments 1 to 17, in contact with the at least one electrode. 1. A membrane electrode assembly for an electrochemical device comprising: (Aspect 19) the composite membrane is attached to the at least one electrode; the at least one electrode comprises a porous layer; the at least one electrode comprises carbon fibers, optionally the carbon fibers having a diameter of about 5 to about 30 μm; 20. The membrane electrode assembly of embodiment 18, wherein the membrane electrode assembly is at least one of: (Aspect 20) The membrane electrode assembly comprises: a first electrode having a first surface and a second surface; a second electrode having a first surface and a second surface; and A composite membrane having a first surface and a second surface according to any one of embodiments 1 to 17. 1. A redox flow battery membrane electrode assembly comprising: the second surface of the first electrode contacts the first surface of the composite membrane, and the first surface of the second electrode contacts the second surface of the composite membrane; Depending on the situation, the redox flow battery membrane electrode assembly includes a first electrode layer attached to a first surface of the composite membrane and a second electrode layer attached to a second surface of the composite membrane; the first electrode layer and / or the second electrode layer is a porous layer having a pore size of about 1 to about 200 μm, 20. The membrane electrode assembly of any one of embodiments 18 or 19, wherein the membrane electrode assembly is at least one of: (Aspect 21) 21. The membrane electrode assembly of any one of aspects 18 to 20, wherein the at least one electrode is selected from felt, paper, or woven materials. (Aspect 22) the first electrode and / or the second electrode is a carbon / platinum electrode containing an ionomer, or the electrode comprises an alloy containing an ionomer; the first electrode and / or the second electrode comprise doped carbon fibers; 22. The membrane electrode assembly according to embodiment 20 or 21, wherein the membrane electrode assembly is at least one of: (Aspect 23) The membrane electrode assembly comprises: 18. The composite membrane of any one of claims 1 to 17, wherein the composite membrane has a first surface and a second surface. a first layer of an electrocatalyst adhered to the first surface of the composite membrane; and a second layer of electrocatalyst adhered to the second surface of the composite membrane; 1. A fuel cell membrane electrode assembly comprising: Depending on the situation, the first layer and the second layer of the electrocatalyst are nanoporous layers having a pore size of about 100 nm or less; The first layer and the second layer of the electrocatalyst are one or more ionomers, a catalyst support such as carbon black, and platinum, Contains or 20. The membrane electrode assembly of embodiment 18 or 19, wherein the membrane electrode assembly is at least one of: (Aspect 24) The membrane electrode assembly comprises: 18. The composite membrane of any one of Aspects 1 to 17, wherein the composite membrane has a first surface and a second surface. a first layer of an electrocatalyst adhered to the first surface of the composite membrane; and a second layer of electrocatalyst adhered to the second surface of the composite membrane; 20. The membrane electrode assembly of embodiment 18 or 19, which is an electrolyzer electrode assembly comprising: (Aspect 25) 25. The membrane electrode assembly of any one of embodiments 23 or 24, wherein a layer of platinum or ruthenium catalyst is adhered to the composite membrane. (Aspect 26) 27. A fuel cell comprising the composite membrane of any one of embodiments 1 to 17, or the membrane electrode assembly of embodiment 18 or 19 or 23 or 25. (Aspect 27) A redox flow battery comprising the composite membrane according to any one of embodiments 1 to 17 or the membrane electrode assembly according to embodiments 18 to 22. (Aspect 28) 26. An electrolytic cell comprising the composite membrane according to any one of embodiments 1 to 17, or the membrane electrode assembly according to embodiment 18, 19, 24, or 25.

Claims

1. a) at least two reinforcing layers, each of the at least two reinforcing layers comprising a microporous polymer structure; and b) an ion exchange material (IEM) at least partially absorbed within the microporous polymer structure of the at least two reinforcing layers, causing the microporous polymer structure to become occlusive; 1. A composite membrane for an electrochemical device comprising: the composite membrane has an average burst pressure of at least 1034 kPa (150 psi) when measured according to the Average Puncture Pressure Burst Test described herein; and The normalized total content of the microporous polymer structure in the composite membrane is at least 3.5 μm based on the total area of ​​the composite membrane, and the normalized total content of the microporous polymer structure in the composite membrane is calculated by the following formula: [Equation 1] where mps1 is microporous polymer structure 1, mps2 is microporous polymer structure 2, mpsN is microporous polymer structure N (if N different types of microporous polymer structures are present in the composite membrane), and M ｍｐｓ１ represents the mass (g) of the microporous polymer structure 1, and M ｍｐｓ２ represents the mass (g) of the microporous polymer structure 2, and M ｍｐｓＮ represents the mass (g) of the microporous polymer structure N, and A composite membrane is the total area of ​​the composite membrane (m ２ ) represents the matrix skeletal density ｍｐｓ1 is the matrix skeleton density (g / cm) of the microporous polymer structure 1 ３ ) represents the matrix skeletal density ｍｐｓ２ is the matrix skeleton density (g / cm) of the microporous polymer structure 2 ３ ) represents the matrix skeletal density ｍｐｓＮ is the matrix skeleton density (g / cm) of the microporous polymer structure N ３ ) a composite membrane for electrochemical devices.

2. 10. The composite membrane of claim 1, wherein the composition of the at least two reinforcement layers is the same, or the composition of the at least two reinforcement layers is different, or the ion exchange material comprises a single ionomer or a mixture of ionomers.

3. 3. The composite membrane of claim 1 or 2, wherein the microporous polymer structure comprises at least one fluorinated polymer, or the microporous polymer structure comprises at least one fluorinated polymer and the fluorinated polymer is polytetrafluoroethylene (PTFE), poly(ethylene-co-tetrafluoroethylene) (EPTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), expanded polyvinylidene fluoride (ePVDF), expanded poly(ethylene-co-tetrafluoroethylene) (eEPTFE), or a mixture thereof.

4. the fluorinated polymer is perfluorinated expanded polytetrafluoroethylene (ePTFE), or the fluorinated polymer is perfluorinated expanded polytetrafluoroethylene (ePTFE) and The composite membrane has a mass per area of ​​at least 8 g m based on the total mass per area of ​​all reinforcing layers present in the composite membrane. －２ or having a total content of microporous polymer structures of The composite membrane has a mass per area of ​​9 g m based on the total mass per area of ​​all reinforcing layers present in the composite membrane. －２ ~20g・m －２ 4. The composite membrane of claim 3, having a total microporous polymer structure content of at least one of:

5. 3. The composite membrane of claim 1 or 2, wherein the microporous polymer structure comprises a hydrocarbon polymer, or the microporous polymer structure comprises a hydrocarbon polymer and the hydrocarbon polymer comprises polyethylene, polypropylene, polycarbonate, polystyrene, or a mixture thereof.

6. the at least two reinforcing layers are in direct contact, or the composite membrane comprises at least one inner layer of ion exchange material between the at least two reinforcement layers; or the composite membrane comprises at least one inner layer of ion exchange material between the at least two reinforcement layers, and the at least one inner layer of ion exchange material comprises a single ion exchange material or a mixture of more than one ion exchange material; 3. The composite membrane according to claim 1, wherein the composite membrane is any one of the following:

7. 3. The composite membrane of claim 1, wherein the at least two reinforcement layers are separated by two or more layers of ion exchange material, and wherein at least two of the two or more layers of ion exchange material comprise different ion exchange materials, or at least two of the two or more layers of ion exchange material comprise the same ion exchange material.

8. the at least two reinforcement layers are separated by a distance d; or the at least two reinforcing layers are separated by a distance d that is between 0.1 μm and 20 μm at 0% RH; 3. The composite membrane of claim 1 or 2, wherein the at least two reinforcement layers are separated by a distance d that is between 0.5 μm and 5 μm at 0% RH.

9. the ion exchange material comprises a plurality of layers of ion exchange material, and the layers of ion exchange material are formed from the same ion exchange material; or 3. The composite membrane of claim 1, wherein the ion exchange material comprises multiple layers of ion exchange material, and a first layer of the ion exchange material is formed from an ion exchange material that is different from the ion exchange material of a second layer of ion exchange material.

10. The microporous polymer structure may be fully imbibed with the ion exchange material or the microporous polymer structure of each of the at least two reinforcement layers has a first surface and a second surface, and the ion exchange material forms a layer on at least one of the first surface or the second surface of each of the at least two reinforcement layers; 3. The composite membrane according to claim 1, wherein the composite membrane is at least one of:

11. the microporous polymer structure of each of the at least two reinforcing layers having a first surface and a second surface; and 3. The composite membrane of claim 1, wherein the microporous polymer structure is mostly imbibed with the ion exchange material but includes regions of non-imbibed or non-blocked regions of the microporous polymer structure proximate to a first surface of at least one of the at least two reinforcement layers, or proximate to a second surface of at least one of the at least two reinforcement layers, or both.

12. 12. The composite membrane of claim 11, wherein the microporous polymer structure of said at least two reinforcement layers is 90% blocked with ion exchange material.

13. 3. The composite membrane of claim 1, wherein the average equivalent volume of the ion exchange material is from 240 cc / mole equivalent to 870 cc / mole equivalent, or the average equivalent volume of the ion exchange material is from 350 cc / mole equivalent to 475 cc / mole equivalent, or the average equivalent volume of the ion exchange material is from 240 cc / mole equivalent to 650 cc / mole equivalent.

14. The ion exchange material comprises at least one ionomer, or the ion exchange material comprises at least one ionomer and the at least one ionomer comprises a proton conducting polymer; the at least one ionomer has a density of 1.9 g / cc or greater at 0% relative humidity; 3. The composite membrane according to claim 1, wherein the composite membrane is at least one of:

15. the composite membrane has a thickness at 0% RH of at least 10 μm, or from 10 μm to 115 μm, or from 10 μm to 90 μm, or from 10 μm to 40 μm, or from 10 μm to 30 μm, or from 10 μm to 20 μm; The composite film has a thickness of 15 μm at 0% RH, or The composite film has a thickness of 25 μm at 0% RH, or 3. The composite membrane according to claim 1, wherein the composite membrane is any one of the following:

16. 3. The composite membrane of claim 1 or 2, wherein the composite membrane has an average burst pressure of from 1034 kPa (150 psi) to 3447 kPa (500 psi) when measured according to the Average Puncture Pressure Burst Test described herein.

17. 3. The composite membrane of claim 1 or 2, further comprising at least one backer layer removably attached to one or more outer surfaces of the composite membrane.

18. at least one electrode; and 3. The composite membrane of claim 1 or 2, in contact with the at least one electrode.

1. A membrane electrode assembly for an electrochemical device comprising:

19. the composite membrane is attached to the at least one electrode; the at least one electrode comprises a porous layer; the at least one electrode comprises carbon fiber; 20. The membrane electrode assembly of claim 18, wherein the membrane electrode assembly is at least one of:

20. The membrane electrode assembly comprises: a first electrode having a first surface and a second surface; a second electrode having a first surface and a second surface; and A composite membrane having a first surface and a second surface according to any one of claims 1 or 2.

1. A redox flow battery membrane electrode assembly comprising:

20. The membrane electrode assembly of claim 18, wherein the second surface of the first electrode is in contact with the first surface of the composite membrane, and the first surface of the second electrode is in contact with the second surface of the composite membrane.

21. the redox flow battery membrane electrode assembly includes a first electrode layer attached to a first surface of the composite membrane and a second electrode layer attached to a second surface of the composite membrane; the first electrode layer and / or the second electrode layer is a porous layer having a pore size of 1 to 200 μm; 21. The membrane electrode assembly of claim 20, wherein the membrane electrode assembly is at least one of:

22. 20. The membrane electrode assembly according to claim 18 or 19, wherein the at least one electrode is selected from felt, paper, or woven materials.

23. the first electrode and / or the second electrode is a carbon / platinum electrode containing an ionomer, or the electrode comprises an alloy containing an ionomer; the first electrode and / or the second electrode comprise doped carbon fibers; 22. The membrane electrode assembly according to claim 20 or 21, wherein the membrane electrode assembly is at least one of:

24. The membrane electrode assembly comprises:

3. The composite membrane of claim 1 or 2, wherein the composite membrane has a first surface and a second surface. a first layer of an electrocatalyst adhered to the first surface of the composite membrane; and a second layer of electrocatalyst adhered to the second surface of the composite membrane; 20. The membrane electrode assembly of claim 18 or 19, which is a fuel cell membrane electrode assembly comprising:

25. the first layer and the second layer of the electrode catalyst are nanoporous layers having a pore size of 100 nm or less; The first layer and the second layer of the electrocatalyst are one or more ionomers, A catalyst support, and platinum, Contains or 25. The membrane electrode assembly of claim 24, wherein the membrane electrode assembly is at least one of:

26. The membrane electrode assembly comprises:

3. The composite membrane of claim 1 or 2, wherein the composite membrane has a first surface and a second surface. a first layer of an electrocatalyst adhered to the first surface of the composite membrane; and a second layer of electrocatalyst adhered to the second surface of the composite membrane; 20. The membrane electrode assembly of claim 18 or 19, which is an electrolytic cell electrode assembly comprising:

27. 27. The membrane electrode assembly of claim 24 or 26, wherein a layer of platinum or ruthenium catalyst is adhered to the composite membrane.

28. 28. A fuel cell comprising a composite membrane according to claim 1 or 2, or a membrane electrode assembly according to claim 18 or 19 or 24 or 27.

29. 20. A redox flow battery comprising the composite membrane of claim 1 or 2, or the membrane electrode assembly of claim 18 or 19.

30. 20. An electrolytic cell comprising a composite membrane according to claim 1 or 2, or a membrane electrode assembly according to claim 18 or 19.

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