WO2019193500A1

WO2019193500A1 - Non-woven electrode integrated with transport protection layer for electrochemical devices

Info

Publication number: WO2019193500A1
Application number: PCT/IB2019/052703
Authority: WO
Inventors: Bharat Raj Acharya; Gregory M. Haugen; Nicole D. Petkovich; Brian T. Weber; Raymond P. Johnston; Onur Sinan YORDEM
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2018-04-03
Filing date: 2019-04-02
Publication date: 2019-10-10
Anticipated expiration: 2020-10-03

Abstract

A membrane electrode assembly having electrodes integrated with transport protection layers. The assembly includes two non-woven porous electrode composites with an ion permeable membrane disposed between them. Each electrode composite includes an electrode integrated with a transport protection layer such that fibers of the electrode penetrate into the transport protection layer.

Description

NON-WOVEN ELECTRODE INTEGRATED WITH TRANSPORT PROTECTION LAYER FOR

ELECTROCHEMICAL DEVICES

BACKGROUND

As the cost of generation of electrical energy using the renewable sources (e.g., solar and wind) continues to decrease, the desire to integrate more of these resources to the main electrical grid is growing. When more renewable resources are integrated into the electrical grid, the inherent fluctuations in the renewable sources tend to de-stabilize the grid. For example, the renewable sources might not be available when the electricity demand is high and they might be generating excess energy when the demand is low. One of the approaches to mitigate this issue is to use energy storage devices to store the excess energy when available and dispatch when the renewable energy is not available. In order for these energy storage devices to be economically viable, the cost of the energy storage has to be low and the energy storage system should be locally deployable. While the energy storage based on pump hydro (where water is pumped to a reservoir when electricity is available and used to run turbine to generate electricity when needed) offers a low cost option, the geographical restrictions limit its wide spread adoption. Among various electrochemical storage devices, the redox flow batteries are particularly suitable for long discharge duration applications (typically longer than 4 hours) such as renewable integration and micro grid because the energy and power can be decoupled in these batteries. However, because of the high cost involved in the components of these batteries, the cost of energy storage is still high for redox flow batteries for their wide spread applications.

Redox flow batteries include membrane electrode assemblies that consist of two porous carbon electrodes on either side of a thin ion permeable membrane. The carbon electrodes are typically composed of graphite fibers with different structures and morphologies (e.g., felt, woven, and non- woven). The graphitic electrodes are believed to provide the active sites where the electrochemical reactions occur during charge and discharge cycles of the battery. An electrode with high active surface area would support high current density and therefore enable high power redox flow battery. The ion permeable membrane provides electrical insulation between two electrodes while allowing protons to exchange between them. A thinner membrane, while lowering the cost of the battery, will also allow more current to flow across the cell and therefore increase the power output from the battery.

Accordingly, there is a desire to make membrane electrode assemblies with thinner membranes and electrodes with higher active surface area both to reduce the overall cost and increase the power output of the redox flow battery. One of the many approaches to reduce the cost of the battery and increase power output of the battery is to reduce the thickness of the ion conducting membrane. While thinner membranes allow passage of higher current densities through them and reduction of cost, they become more venerable to puncturing from the carbon fibers that typically comprise the electrodes leading to electrical shorting between two electrodes. To eliminate the electrical shorting between two electrodes, a highly porous electrically non-conducting polymer non-woven is dispensed between the carbon electrode and the thin membrane. This polymer non-woven, the transport protection layer, provides a spacing between the thin membrane and the electrode and also facilitates flow of electrolytes across the electrode surface enhancing overall performance of the battery. Usually, the transport protection layer is loosely inserted between the electrode and the membrane during the cell assembly or pre-laminated with the electrodes before cell assembly. In either case, both electrodes and TPL need extra steps of handling that increase complexity and cost in manufacturing membrane electrode assemblies.

SUMMARY

A membrane electrode assembly of an embodiment of the invention includes a first non-woven integrated electrode composite, a second non-woven integrated electrode composite, and an ion permeable membrane disposed between the electrode composites. A first transport protection layer that is an integral part of the first integrated electrode composite is in proximity to the first surface of the ion permeable membrane. A second transport protection layer that is an integral part of the second integrated electrode composite is in proximity to the second surface of the ion permeable membrane

An integrated electrode composite of an embodiment of the invention for use with a membrane electrode assembly includes a non-woven porous carbon electrode composite and a transport protection layer. The porous carbon electrode composite is composed of at least one of a carbon fiber based paper, a felt, and a cloth, and the transport protection layer is composed at least one of a mesh structure, a woven structure, and a non-woven structure. The thin transport protection layer is an integral part of the integrated carbon electrode composite such that fibers of the carbon electrode composite are inter-twined with the fibers of the transport protection layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, explain the advantages and principles of the invention. In the drawings,

FIG. 1 is a cross-sectional diagram of a membrane electrode assembly with integrated electrode composites and transport protection layers;

FIG. 2 is a cross-sectional diagram of an integrated electrode composite with integrated with a transport protection layer that forms an integral part of the electrode composite;

FIGS. 3A-3D are SEM images for the Examples;

FIG. 4 is a cross-sectional diagram of a cell used for electrochemical testing for the Examples; and

FIG. 5 is a cross-sectional diagram showing the set-up of the double half-cell for the operation of the catholyte double half-cell test for the Examples. DETAILED DESCRIPTION

Embodiments of this invention include an integrated electrode composite having an electrode or carbon electrode with a transport protection layer (TPL) forming an integral part of the electrode composite for use in a membrane electrode assembly (MEA). The terms“electrode” and“carbon electrode” refer to any commercially available electrodes or carbon electrodes. The term“carbon electrode composite” refers to an electrode having conducting carbon particulates and polymer particulates. The term“integrated electrode composite” refers to a carbon electrode composite made on a TPL.

FIG. 1 is a cross-sectional diagram of an MEA assembly 10 with integrated carbon electrode composites and TPLs. Assembly 10 includes an integrated electrode composite 11 having a TPL 14 integrated or embedded into a carbon electrode composite 12 and another integrated electrode composite 17 having a TPL 18 integrated or embedded into a carbon electrode composite 20. A membrane 16 is located between and separates integrated electrode composites 11 and 17. As further illustrated in FIG. 4, the MEA can include sub-gaskets between the integrated electrode composites and membrane, to prevent electrical shorting due to loose fibers from the edge of the carbon electrode composites and other constituents (such as adhesives, hot melts etc.) to contain the components of the MEA.

Examples of MEAs are disclosed in PCT Patent Applications Publication Nos. WO 2017/160972, WO 2017/ 160961, and WO 2018/029617, all of which are incorporated herein by reference as if fully set forth.

FIG. 2 is a cross-sectional diagram of a carbon electrode composite 22 integrated with a TPL 24 for use in an MEA. In particular fibers in the carbon electrode composite, as represented by lines 26, penetrate into TPL 24. In this manner, the carbon electrode composite is integrated with the TPL by portions of the carbon electrode composite being embedded into the TPL through a substantial or significant degree of penetration of the fibers that constitute the carbon electrode composite into the TPL, as opposed to the TPL being laminated, adhered or bonded to the carbon electrodes without such penetration into it.

The combination of carbon electrode composite 22 and TPL 24 can be implemented as, for example, a wet-laid non-woven integrated electrode composite article comprising an electrically conductive carbon composite that contains (i) electrically conductive graphitic particles, (ii) electrically conductive carbon nanostructures that may or may not be attached to electrically non-conductive glass fibers, and (iii) polymeric binder and a polymeric web. The carbon electrode composite is directly assembled onto the polymeric web so that the article has the porous polymeric web on one side and conductive carbon electrode composite on the other side. The carbon electrode composite side of the article facilitates electrochemical reaction on electrochemical devices such as redox flow batteries and fuel cells. The non-woven web side of the article, when placed against the thin membranes used in these devices, prevents electrical shorting between two electrodes, improves electrolyte flow across the electrodes while providing mechanical support for the carbon composite.

Embodiments of this invention also include a method of making an integrated electrode composite articles with a TPL as an integral part of the electrode composites. The article and the method of making it can provide the advantages of, for example, saving the processing cost associated with integration of a TPL with the final electrode or carbon electrode composite by making them together, which avoids the additional processing of laminating them together, and providing an increased mechanical strength of a TPL to the carbon electrode composite web for subsequent processing. The method described herein also enables fabrication of integrated electrode composite that is sufficiently thick to provide enough surface area required for electrochemical reactions to occur as opposed to a laminate or stack of multiple thin electrode layers. The method can also eliminate the potential risk of mechanically damaging (e.g., cracking or breaking) the electrode or carbon electrode composite during the lamination/integration process in a conventional method where the TPL layer is laminated to a final electrode or carbon electrode composite. The composition of the integrated electrode composite described herein can also enable roll-to-roll manufacturing of membrane electrode assembly for electrochemical devices such as redox flow batteries and fuel cells.

The following are steps of a method, as performed in the order recited, to make the integrated electrode composite articles according to an embodiment of the invention.

Step 1 : Blend together water, carbon particles, and polymer particles by disbursing carbon fibers and polymer fibers in water to form a carbon electrode composite slurry in water.

Step 2: Pour the carbon electrode composite slurry from Step 1 to deposit the wet carbon electrode composite onto a porous TPL supported on a screen below the TPL to form a wet integrated electrode composite article with an uncured blend.

Step 3: Remove excess water from the integrated electrode composite article of Step 2 through an application of vacuum to the integrated electrode composite article with the uncured blend.

Step 4: Dry the integrated electrode composite article of Step 3 by exposing it to thermal energy.

Step 5: Thermally cure the uncured blend through calendering of the integrated electrode composite article of Step 4.

While the steps described above in making the integrated electrode composite are for discrete sheets, these steps can be integrated to a continuous process to make a roll-good by using a roll of TPL. The following are exemplary materials and configurations for the MEA components, in addition to the Examples.

The carbon electrode composite can be porous, to provide greater surface area for the oxidation/reduction reactions to occur. When porous electrodes are used, the electrolytes may penetrate into the body of the electrode, access the additional surface area for reaction and thus increase the rate of energy generation per unit volume of the electrode. The porous electrode is electrically conductive and the porosity facilitates the oxidation/reduction reaction that occur therein by increasing the amount of active surface area for reaction to occur, per unit volume of electrode, and by allowing the anolyte and catholyte to permeate into the porous regions and access this additional surface area.

In one embodiment, the carbon electrode composite comprises an electrically non-conductive, polymer particulate and an electrically conductive carbon particulate. The electrically conductive carbon particulate is at least one of carbon nanotubes and branched carbon nanotubes and the electrically conductive carbon particulate. At least a portion of the electrically non-conductive polymer particulate surface is fused to form a unitary, porous carbon electrode composite material.

In some embodiments, the polymer of the porous carbon electrode composite material may be at least one of a polymer particulate and polymer binder resin. In some embodiments, the polymer may be a polymer particulate. In some embodiments, the polymer may be a polymer binder resin. In some embodiments the polymer does not include a polymer particulate. In some embodiments, the polymer does not include a polymer binder resin.

The term“particulate”, with respect to both an electrically conductive carbon particulate and a polymer particulate is meant to include particles, flakes, fibers, dendrites and the like. Particulate particles generally include particulates that have aspect ratios of length to width and length to thickness both of which are between about 1 and about 5. Particle size may be from between about 0.001 microns to about 100 microns, from between about 0.001 microns to about 50 microns, from between about 0.001 to about 25 microns, from between about 0.001 microns to about 10 microns, from about 0.001 microns to about 1 microns, from between about 0.01 microns and about 100 microns, from between about 0.01 microns to about 50 microns, from between about 0.01 to about 25 microns, from between about 0.01 microns to about 10 microns, from about 0.01 microns to about 1 microns, from between about 0.05 microns to about 100 microns, from between about 0.05 microns to about 50 microns, from between about 0.05 to about 25 microns, from between about 0.05 microns to about 10 microns, from about 0.05 microns to about 1 microns, from between about 0.1 microns and about 100 microns, from between about 0.1 microns to about 50 microns, from between about 0.1 to about 25 microns, from between about 0.1 microns to about 10 microns, or even from between about 0.1 microns to about 1 microns. Particles may be spheroidal in shape.

Particulate flakes generally include particulates that have a length and a width each of which is significantly greater than the thickness of the flake. A flake includes particulates that have aspect ratios of length to thickness and width to thickness each of which is greater than about 5. There is no particular upper limit on the length to thickness and width to thickness aspect ratios of a flake. Both the length to thickness and width to thickness aspect ratios of the flake may be between about 6 and about 1000, between about 6 and about 500, between about 6 and about 100, between about 6 and about 50, between about 6 and about 25, between about 10 and about 500, between 10 and about 150, between 10 and about 100, or even between about 10 and about 50. The length and width of the flake may each be from between about 0.001 microns to about 50 microns, from between about 0.001 to about 25 microns, from between about 0.001 microns to about 10 microns, from about 0.001 microns to about 1 microns, from between about 0.01 microns to about 50 microns, from between about 0.01 to about 25 microns, from between about 0.01 microns to about 10 microns, from about 0.01 microns to about 1 microns, from between about 0.05 microns to about 50 microns, from between about 0.05 to about 25 microns, from between about 0 05 microns to about 10 microns, from about 0.05 microns to about 1 microns, from between about 0 1 microns to about 50 microns, from between about 0.1 to about 25 microns, from between about 0 1 microns to about 10 microns, or even from between about 0.1 microns to about 1 microns. Flakes may be platelet in shape.

Particulate dendrites include particulates having a branched structure. The particle size of the dendrites may be the same as those disclosed for the particulate particles, discussed above.

Particulate fibers generally include particulates that have aspect ratios of the length to width and length to thickness both of which are greater about 10 and a width to thickness aspect ratio less than about 5. For a fiber having a cross sectional area that is in the shape of a circle, the width and thickness would be the same and would be equal to the diameter of the circular cross-section. There is no particular upper limit on the length to width and length to thickness aspect ratios of a fiber. Both the length to thickness and length to width aspect ratios of the fiber may be between about 10 and about 1000000, between 10 and about 100000, between 10 and about 1000, between 10 and about 500, between 10 and about 250, between 10 and about 100, between about 10 and about 50, between about 20 and about 1000000, between 20 and about 100000, between 20 and about 1000, between 20 and about 500, between 20 and about 250, between 20 and about 100 or even between about 20 and about 50. The width and thickness of the fiber may each be from between about 0.001 to about 100 microns, from between about 0.001 microns to about 50 microns, from between about 0.001 to about 25 microns, from between about 0.001 microns to about 10 microns, from about 0.001 microns to about 1 microns, from between about 0.01 to about 100 microns, from between about 0.01 microns to about 50 microns, from between about 0.01 to about 25 microns, from between about 0.01 microns to about 10 microns, from about 0.01 microns to about 1 microns, from between about 0.05 to about 100 microns, from between about 0.05 microns to about 50 microns, from between about 0.05 to about 25 microns, from between about 0.05 microns to about 10 microns, from about 0.05 microns to about 1 microns, from between about 0.1 to about 100 microns, from between about 0.1 microns to about 50 microns, from between about 0.1 to about 25 microns, from between about 0.1 microns to about 10 microns, or even from between about 0.1 microns to about 1 microns. In some embodiments the thickness and width of the fiber may be the same.

In some embodiments, the carbon electrode composites of the present disclosure may contain an electrically non-conductive, inorganic particulate. The electrically non-conductive particulates may be particulates, flakes and fibers. Electrically non-conductive, inorganic particulate include, but is not limited to, minerals and clays known in the art. In some embodiments the electrically non-conductive inorganic particulate may be a metal oxide. In some embodiments the electrically non-conductive, inorganic particulate include at least one of alumina, silica, alumina, titania, and zirconia. In some embodiments the non-conducting particulates are at least partially coated with conductive carbon particulates. In these embodiments, the weight fraction of non-conducting particulates coated with conducting particulates to the total weight of electrically conductive carbon particulate may be from about 0.05 to about 1, from about 0.05 to about 0.8, from about 0.05 to about 0.6, from about 0.05 to about 0.5, from about 0.05 to about 0.4, from about 0.1 to about 1, from about 0.1 to about 0.8, from about 0.1 to about 0.6, from about 0.1 to about 0 5, from about 0.1 to about 0.4, from about 0 2 to about 1, from about 0.2 to about 0.8, from about 0.2 to about 0.6, from about 0.2 to about 0.5, or even from about 0.2 to about 0.4.

The electrically conductive carbon particulate, includes but is not limited to, glass like carbon, amorphous carbon, graphene, graphite, e.g. graphitized carbon, carbon dendrites, carbon nanotubes, branched carbon nanotubes, e.g. carbon nanotrees. In some embodiments, the electrically conductive carbon particulate is at least one of carbon particles, carbon flakes, carbon fibers, carbon dendrites, carbon nanotubes and branched carbon nanotubes, e.g. carbon nanotrees. In some embodiments, the electrically conductive carbon particulate is at least one of graphite particles, graphite flakes, graphite fibers and graphite dendrites. In some embodiments, the graphite may be at least one of graphite particles, graphite flakes, and graphite dendrites. In some embodiments, the electrically conductive carbon particulate carbon does not include carbon fibers.

In some embodiments, the electrically conductive particulate is at least one of carbon nanotubes and branched carbon nanotubes. Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Carbon nanotubes may be produced with length-to-diameter ratio of up to 132,000,000: 1, significantly larger than for any other material, including carbon fiber. Carbon nanotubes may have diameters of from about 1 to 5 nanometers, orders of magnitude smaller than carbon and/or graphite fibers, which may have diameters from 5 to about 10 microns. Carbon nanotubes may have a diameter from about 0.3 nanometers to about 100 nanometers, from about 0.3 nanometers to about 50 nanometers, from about 0.3 nanometers to about 20 nanometers, from about 0.3 nanometers to about 10 nanometers, from about 1 nanometer to about 50 nanometers, from about 1 nanometer to about 20 nanometers, or even from about 1 nanometers to about 10 nanometers. Carbon nanotubes may have a length between about 0.25 microns and about 1000 microns, between about 0.5 microns and about 500 microns, or even between about 1 micron and about 100 microns. Branched carbon nanotubes, e.g. nanotrees may have a diameter from about 0.3 nanometers to about 100 nanometers. Branched carbon nanotubes include multiple, carbon nanotube side branches that are covalently bonded with the main carbon nanotube, i.e. the carbon nanotube stem. Branched carbon nanotubes, with their tree-like, dendritic geometry, may have extensively high surface area. Various synthesis methods have been developed to fabricate such complex structured carbon nanotubes with multiple terminals, including but not limited to the template method, carbon nanotube welding method, solid fiber carbonization, as well as the direct current plasma enhanced chemical vapor deposition (CVD) and several other additive-, catalyst-, or flow fluctuation- based CVD methods. In some embodiments, the diameter of the main carbon nanotube and the diameter of the carbon nanotube side branches of branched carbon nanotubes may be from about 0.3 nanometers to about 100 nanometers, from about 0.3 nanometers to about 50 nanometers, from about 0.3 nanometers to about 20 nanometers, from about 0.3 nanometers.

In some embodiments, the electrically conductive particulate is at least one of carbon nanotubes and branched carbon nanotubes In some embodiments, the electrically conductive carbon particulate includes or consists essentially of carbon nanotubes and branched carbon nanotubes and the weight fraction of branched carbon nanotubes, relative to the total weight of carbon nanotubes and branched carbon nanotubes, may be from about 0.1 to about 1, from about 0.1 to about 0.9, from about 0.1 from 0.8, from about 0.2 to about 1, from about 0.2 to about 0.9, from about 0.2 from 0.8, from about 0.3 to about 1, from about 0.3 to about 0.9, from about 0.3 from 0.8, from about 0.4 to about 1, from about 0.4 to about 0.9, from about 0.4 from 0.8, from about 0.5 to about 1, from about 0.5 to about 0.9, or even from about 0.5 from 0.8. The electrically conducive particulate which includes at least one of carbon nanotubes and branched carbon nanotubes and/or which includes carbon nanotubes and branched carbon nanotubes may further comprises graphite particulate. In these embodiments, the weight fraction of graphite particulate to the total weight of electrically conductive carbon particulate may be from about 0.05 to about 1, from about 0.05 to about 0.8, from about 0.05 to about 0.6, from about 0.05 to about 0.5, from about 0.05 to about 0.4, from about 0.1 to about 1, from about 0.1 to about 0.8, from about 0.1 to about 0.6, from about 0.1 to about 0.5, from about 0.1 to about 0.4, from about 0.2 to about 1, from about 0.2 to about 0.8, from about 0.2 to about 0.6, from about 0.2 to about 0.5, or even from about 0.2 to about 0.4.

In some embodiments, the electrically conductive carbon particulate may be surface treated. Surface treatment may enhance the wettability of the electrode to a given anolyte or catholyte or to provide or enhance the electrochemical activity of the electrode relative to the oxidation-reduction reactions associated with the chemical composition of a given anolyte or catholyte. Surface treatments include, but are not limited to, at least one of chemical treatments, thermal treatments and plasma treatments. In some embodiments, the electrically conductive carbon particulate has enhanced electrochemical activity, produced by at least one of chemical treatment, thermal treatment and plasma treatment. The term“enhanced” means that the electrochemical activity of the electrically conductive carbon particulate is increased after treatment relative to the electrochemical activity of the electrically conductive carbon particulate prior to treatment. Enhanced electrochemical activity may include at least one of increased current density, reduced oxygen evolution and reduced hydrogen evolution. The electrochemical activity can be measured by fabricating a porous electrode from the electrically conductive carbon particulate (prior to and after treatment) and comparing the current density generated in an electrochemical cell by the electrode, higher current density indicating enhancement of the electrochemical activity. Cyclic voltammetry can be used to measure activity improvement, i.e. changes in current density. In some embodiments, the electrically conductive particulate is hydrophilic.

In some embodiments, the amount of electrically conductive carbon particulate contained in the electrode, on a weight basis, may be from about 5 to about 99 percent, from about 5 to about 95 percent, from about 5 to about 90 percent, from about 5 to about 80 percent, from about 5 to about 70 percent, from about 10 to about 99 percent, from about 10 to about 95 percent, from about 10 to about 90 percent, from about 10 to about 80 percent, from about 10 to about 70 percent, from about 25 to about 99 percent, 25 to about 95 percent, from about 25 to about 90 percent, from about 25 to about 80 percent, from about 25 to about 70 percent, from about 30 to about 99 percent, from about 30 to about 95 percent, from about 30 to about 90 percent, from about 30 to about 80 percent, from about 30 to about 70 percent, from about 40 to about 99 percent, from about 40 to about 95 percent, from about 40 to about 90 percent, from about 40 to about 80 percent, from about 40 to about 70 percent, from about 50 to about 99 percent, 50 to about 95 percent, from about 50 to about 90 percent, from about 50 to about 80 percent, from about 50 to about 70 percent, from about 60 to about 99 percent, 60 to about 95 percent, from about 60 to about 90 percent, from about 60 to about 80 percent, or even from about 60 to about 70 percent.

The polymer of the carbon electrode composite may be at least one of a polymer particulate and polymer binder resin. In some embodiments of the present disclosure, the polymeric particulate may be at least one of polymer particles, polymer flakes, polymer fibers and polymer dendrites. In some embodiments, the polymer is fused polymer particulate. Fused polymer particulate may be formed from polymer particulates that are brought to a temperature to allow the contact surfaces of adjacent polymer particulates to fuse together. After fusing the individual particulates that formed the fused polymer particulate can still be identified. A fused polymer particulate is porous. Fused polymer particulate is not particulate that has been completely melted to form a solid substrate, i.e. a non-porous substrate. In some embodiments, the polymer particulate may be fused at a temperature that is not less than about 30 degrees centigrade, not less than about 20 degrees centigrade or even not less than about 10 degrees centigrade lower than the lowest glass transition temperature of the polymer particulate. The polymer particulate may have more than one glass transition temperatures, if, for example, it is a block copolymer or a core shell polymer. In some embodiments, the polymer particulate may be fused at a temperature that is below the highest melting temperature of the polymer particulate or, when the polymer particulate is an amorphous polymer, no greater than 50 degrees centigrade, no greater than 30 degrees centigrade or even no greater than 10 degrees centigrade above the highest glass transition temperature of the polymer particulate.

In some embodiments of the present disclosure, the polymer may be a polymer binder resin and the polymer binder resin may be derived from a polymer precursor liquid. A polymer precursor liquid may be at least one of a polymer solution and a reactive polymer precursor liquid, each capable of being at least one of polymerized, cured, dried and fused to form a polymer binder resin. A polymer solution may include at least one polymer dissolved in at least one solvent. A polymer solution may be capable of being at least one of polymerized, cured, dried and fused to form a polymer binder resin. In some embodiments, the polymer solution is dried to form a polymer binder resin. A reactive polymer precursor liquid includes at least one of liquid monomer and liquid oligomer. The monomer may be a single monomer or may be a mixture of at least two different monomers. The oligomer may be a single oligomer or a mixture at least two different oligomers. Mixtures of one or more monomers and one or more oligomers may also be used. The reactive polymer precursor liquid may include at least one, optional, solvent. The reactive polymer precursor liquid may include at least one, optional, polymer, which is soluble in the liquid components of the reactive polymer precursor liquid. The reactive polymer precursor liquid may be capable of being at least one of polymerized, cured, dried and fused to form a polymer binder resin. In some embodiments, the reactive polymer precursor liquid is cured to form a polymer binder resin. In some embodiments, the reactive polymer precursor liquid is polymerized to form a polymer binder resin. In some embodiments, the reactive polymer precursor liquid is cured and polymerized to form a polymer binder resin. The terms“cure”,“curing”,“cured” and the like are used herein to refer to a reactive polymer precursor liquid that is increasing its molecular weight through one or more reactions that include at least one crosslinking reaction. Generally, curing leads to a thermoset material that may be insoluble in solvents. The terms“polymerize”,“polymerizing”,“polymerized and the like, generally refer to a reactive polymer precursor liquid that is increasing its molecular weight through one or more reactions that do not include a crosslinking reaction. Generally, polymerization leads to a thermoplastic material that may be soluble in an appropriate solvent. A reactive polymer precursor liquid that is reacting by at least one crosslinking reaction and at least one polymerization reaction may form either a thermoset or thermoplastic material, depending on the degree of

polymerization achieved and the amounted crosslinking of the final polymer. Monomers and/or oligomers useful in the preparation of a reactive polymer precursor liquid include, but are not limited to, monomers and oligomers conventionally used to form the polymers, e.g. thermosets, thermoplastics and thermoplastic elastomers, described herein (below). Polymers useful in the preparation of a polymer solution include, but are not limited to the thermoplastic and thermoplastic elastomer polymers described herein (below).

In some embodiments of the present disclosure, the electrically conductive carbon particulate may be adhered to the polymer, polymer particulate and/or polymer binder resin. In some embodiments of the present disclosure, the electrically conductive carbon particulate may be adhered to the surface of the polymer particulate. In some embodiments of the present disclosure, the electrically conductive carbon particulate may be adhered to the surface of the fused polymer particulate. The polymer of the carbon electrode composite may be selected to facilitate the transfer of select ion(s) of the electrolytes through the electrode. This may be achieved by allowing the electrolyte to easily wet a given polymer. The material properties, particularly the surface wetting characteristics of the polymer may be selected based on the type of anolyte and catholyte solution, i.e. whether they are aqueous based or non-aqueous based. As disclosed herein, an aqueous based solution is defined as a solution wherein the solvent includes at least 50% water by weight. A non-aqueous base solution is defined as a solution wherein the solvent contains less than 50% water by weight. In some embodiments, the polymer of the electrode may be hydrophilic. This may be particularly beneficial when the electrode is to be used in conjunction with aqueous anolyte and/or catholyte solutions. In some embodiments the polymer may have a surface contact angle with water, catholyte and/or anolyte of less than 90 degrees. In some embodiments, the polymer may have a surface contact with water, catholyte and/or anolyte of between about 85 degrees and about 0 degrees, between about 70 degrees and about 0 degrees, between about 50 degrees and about 0 degrees, between about 30 degrees and about 0 degrees, between about 20 degrees and about 0 degrees, or even between about 10 degrees and about 0 degrees.

Polymer of the carbon electrode composite, which may be a polymer particulate or a polymer binder resin, may include thermoplastic resins (including thermoplastic elastomer), thermoset resins (including glassy and rubbery materials) and combinations thereof. Useful thermoplastic resins include, but are not limited to, homopolymers, copolymers and blends of at least one of polyalkylenes, e.g.

polyethylene, high molecular weight polyethylene, high density polyethylene, ultra-high molecular weight polyethylene, polypropylene, high molecular weight polypropylene; polyacrylates;

polymethacrylates, styrene and styrene based random and block copolymers, e g. styrene-butadiene- styrene; polyesters, e.g. polyethylene terephtahalate; polycarbonates, polyamides, polyamide-amines; polyalkylene glycols, e.g. polyethylene glycol and polypropylene glycol; polyurethanes; polyethers; chlorinated polyvinyl chloride; fluoropolymers including perfluorinated fluoropolymers, e.g.

polytetrafluoroethylene (PTFE) and partially fluorinated fluoropolymer, e.g. . polyvinylidene fluoride, each of which may be semi-crystalline and/or amorphous; polyimides, polyetherimides, polysulphones; polyphenylene oxides; and polyketones. Useful thermoset resins include, but are not limited to, homopolymer, copolymers and/or blends of at least one of epoxy resin, phenolic resin, polyurethanes, urea-formadehyde resin and melamine resin.

In some embodiments, the polymer has a softening temperature, e.g. the glass transition temperature and/or the melting temperature of between about 20 degrees centigrade and about 400 degrees centigrade, between about 20 degrees centigrade and about 350 degrees centigrade, between about 20 degrees centigrade and about 300 degrees centigrade, between about 20 degrees centigrade and about 250 degrees centigrade, between about 20 degrees centigrade and about 200 degrees centigrade, between about 20 degrees centigrade and about 150 degrees centigrade, between about 35 degrees centigrade and about 400 degrees centigrade, between about 35 degrees centigrade and about 350 degrees centigrade, between about 35 degrees centigrade and about 300 degrees centigrade, between about 35 degrees centigrade and about 250 degrees centigrade, between about 35 degrees centigrade and about 200 degrees centigrade, between about 35 degrees centigrade and about 150 degrees centigrade, between about 50 degrees centigrade and about 400 degrees centigrade, between about 50 degrees centigrade and about 350 degrees centigrade, between about 50 degrees centigrade and about 300 degrees centigrade, between about 50 degrees centigrade and about 250 degrees centigrade, between about 50 degrees centigrade and about 200 degrees centigrade, between about 50 degrees centigrade and about 150 degrees centigrade, between about 75 degrees centigrade and about 400 degrees centigrade, between about 75 degrees centigrade and about 350 degrees centigrade, between about 75 degrees centigrade and about 300 degrees centigrade, between about 75 degrees centigrade and about 250 degrees centigrade, between about 75 degrees centigrade and about 200 degrees centigrade, or even between about 75 degrees centigrade and about 150 degrees centigrade.

In some embodiments, the polymer particulate is composed of two or more polymers and has a core-shell structure, i.e. an inner core comprising a first polymer and an outer shell comprising a second polymer. A core-shell structure is sometimes referred to as a core-sheath structure. In some embodiments the polymer of the outer shell, e.g. second polymer, has a softening temperature, e.g. the glass transition temperature and/or the melting temperature that is lower than softening temperature of the first polymer. In some embodiments, the second polymer has a softening temperature, e.g. the glass transition temperature and/or the melting temperature of between about 20 degrees centigrade and about 400 degrees centigrade, between about 20 degrees centigrade and about 350 degrees centigrade, between about 20 degrees centigrade and about 300 degrees centigrade, between about 20 degrees centigrade and about 250 degrees centigrade, between about 20 degrees centigrade and about 200 degrees centigrade, between about 20 degrees centigrade and about 150 degrees centigrade, between about 35 degrees centigrade and about 400 degrees centigrade, between about 35 degrees centigrade and about 350 degrees centigrade, between about 35 degrees centigrade and about 300 degrees centigrade, between about 35 degrees centigrade and about 250 degrees centigrade, between about 35 degrees centigrade and about 200 degrees centigrade, between about 35 degrees centigrade and about 150 degrees centigrade, between about 50 degrees centigrade and about 400 degrees centigrade, between about 50 degrees centigrade and about 350 degrees centigrade, between about 50 degrees centigrade and about 300 degrees centigrade, between about 50 degrees centigrade and about 250 degrees centigrade, between about 50 degrees centigrade and about 200 degrees centigrade, between about 50 degrees centigrade and about 150 degrees centigrade, between about 75 degrees centigrade and about 400 degrees centigrade, between about 75 degrees centigrade and about 350 degrees centigrade, between about 75 degrees centigrade and about 300 degrees centigrade, between about 75 degrees centigrade and about 250 degrees centigrade, between about 75 degrees centigrade and about 200 degrees centigrade, or even between about 75 degrees centigrade and about 150 degrees centigrade. The polymer of the carbon electrode composite may be an ionic polymer or non-ionic polymer. Ionic polymer include polymer wherein a fraction of the repeat units are electrically neutral and a fraction of the repeat units have an ionic functional group, i.e. an ionic repeat unit. In some embodiments, the polymer is an ionic polymer, wherein the ionic polymer has a mole fraction of repeat units having an ionic functional group of between about 0.005 and about 1. In some embodiments, the polymer is a non ionic polymer, wherein the non-ionic polymer has a mole fraction of repeat units having an ionic functional group of from less than about 0.005 to about 0. In some embodiments, the polymer is a non ionic polymer, wherein the non-ionic polymer has no repeat units having an ionic functional group. In some embodiments, the polymer consists essentially of an ionic polymer. In some embodiments, the polymer consists essentially of a non-ionic polymer. Ionic polymer includes, but is not limited to, ion exchange resins, ionomer resins and combinations thereof. Ion exchange resins may be particularly useful.

As broadly defined herein, ionic resin include resin wherein a fraction of the repeat units are electrically neutral and a fraction of the repeat units have an ionic functional group. In some embodiments, the ionic resin has a mole fraction of repeat units with ionic functional groups between about 0.005 and 1. In some embodiments, the ionic resin is a cationic resin, i.e. its ionic functional groups are negatively charged and facilitate the transfer of cations, e.g. protons, optionally, wherein the cationic resin is a proton cationic resin. In some embodiments, the ionic resin is an anionic exchange resin, i.e. its ionic functional groups are positively charged and facilitate the transfer of anions. The ionic functional group of the ionic resin may include, but is not limited, to carboxylate, sulphonate, sulfonamide, quaternary ammonium, thiuronium, guanidinium, imidazolium and pyridinium groups. Combinations of ionic functional groups may be used in an ionic resin.

Ionomer resin include resin wherein a fraction of the repeat units are electrically neutral and a fraction of the repeat units have an ionic functional group. As defined herein, an ionomer resin will be considered to be a resin having a mole fraction of repeat units having ionic functional groups of no greater than about 0.15. In some embodiments, the ionomer resin has a mole fraction of repeat units having ionic functional groups of between about 0.005 and about 0.15, between about 0.01 and about 0.15 or even between about 0.3 and about 0.15. In some embodiments the ionomer resin is insoluble in at least one of the anolyte and catholyte. The ionic functional group of the ionomer resin may include, but is not limited, to carboxylate, sulphonate, sulfonamide, quaternary ammonium, thiuronium, guanidinium, imidazolium and pyridinium groups. Combinations of ionic functional groups may be used in an ionomer resin. Mixtures of ionomer resins may be used. The ionomers resin may be a cationic resin or an anionic resin. Useful ionomer resin include, but are not limited to NAFION, available from DuPont, Wilmington, Delaware; AQUIVION, a perfluorosulfonic acid, available from SOLYAY, Brussels, Belgium; FLEMION and SELEMION, fluoropolomer ion exchange resin, from Asahi Glass, Tokyo, Japan; FUMASEP ion exchange resin, including FKS, FKB, FKL, FKE cation exchange resins and FAB, FAA, FAP and FAD anionic exchange resins, available from Fumatek, Bietigheim-Bissingen, Germany, polybenzimidazols, and ion exchange materials and membranes described in U S. Pat. No. 7,348,088, incorporated herein by reference in its entirety.

Ion exchange resin include resin wherein a fraction of the repeat units are electrically neutral and a fraction of the repeat units have an ionic functional group. As defined herein, an ion exchange resin will be considered to be a resin having a mole fraction of repeat units having ionic functional groups of greater than about 0.15 and less than about 1 00. In some embodiments, the ion exchange resin has a mole fraction of repeat units having ionic functional groups of greater than about 0 15 and less than about 0.90, greater than about 0.15 and less than about 0.80, greater than about 0.15 and less than about 0.70, greater than about 0.30 and less than about 0.90, greater than about 0.30 and less than about 0.80, greater than about 0.30 and less than about 0.70 greater than about 0.45 and less than about 0.90, greater than about 0.45 and less than about 0.80, and even greater than about 0.45 and less than about 0.70. The ion exchange resin may be a cationic exchange resin or may be an anionic exchange resin. The ion exchange resin may, optionally, be a proton ion exchange resin. The type of ion exchange resin may be selected based on the type of ion that needs to be transported between the anolyte and catholyte through the ion permeable membrane. In some embodiments the ion exchange resin is insoluble in at least one of the anolyte and catholyte. The ionic functional group of the ion exchange resin may include, but is not limited, to carboxylate, sulphonate, sulfonamide, quaternary ammonium, thiuronium, guanidinium, imidazolium and pyridinium groups. Combinations of ionic functional groups may be used in an ion exchange resin. Mixtures of ion exchange resins resin may be used. Useful ion exchange resins include, but are not limited to, fluorinated ion exchange resins, e.g. perfluorosulfonic acid copolymer and perfluorosulfonimide copolymer, a sulfonated polysulfone, a polymer or copolymer containing quaternary ammonium groups, a polymer or copolymer containing at least one of guanidinium or thiuronium groups a polymer or copolymer containing imidazolium groups, a polymer or copolymer containing pyridinium groups. The polymer may be a mixture of ionomer resin and ion exchange resin.

In some embodiments, the amount of polymer contained in the carbon electrode composite, on a weight basis, may be from about 1 to about 95 percent, from about 5 to about 95 percent, from about 10 to about 95 percent, from about 20 to about 95 percent, from about 30 to about 95 percent, from about 1 to about 90 percent, from about 5 to about 90 percent, from about 10 to about 90 percent, from about 20 to about 90 percent, from about 30 to about 90 percent, from about 1 to about 75 percent, from about 5 to about 75 percent, from about 10 to about 75 percent, from about 20 to about 75 percent, from about 30 to about 75 percent, from about 1 to about 70 percent, from about 5 to about 70 percent, from about 10 to about 70 percent, from about 20 to about 70 percent, from about 30 to about 70 percent, from about 1 to about 60 percent, from about 5 to about 60, from about 10 to about 60 percent, from about 20 to about 60 percent, from about 30 to about 60 percent, from about 1 to about 50 percent, 5 to about 50 percent, from about 10 to about 50 percent, from about 20 to about 50 percent, from about 30 to about 50 percent, from about 1 to about 40 percent, 5 to about 40 percent, from about 10 to about 40 percent, from about 20 to about 40 percent, or even from about 30 to about 40 percent.

The polymer and electrically conductive particulate are fabricated into a porous integrated electrode composite by mixing the polymer and electrically conductive particulate to form a carbon electrode composite blend, coating the composite blend onto a transport protection layer and providing at least one of a fusing, curing, polymerizing and drying treatment to form an electrode, wherein the integrated electrode composite is porous. The transport protection layer may be supported on a substrate e g . a polymer mesh, a liner or a release liner. The integrated electrode composite may be in the form of a sheet. After drying or during drying, the temperature may be such that the temperature is near, at or above the softening temperature of the polymer, e.g. the glass transition temperature and/or the melting temperature of the polymer, which may aid in the adhering of carbon particulate to the polymer and/or further fuse the polymer.

In one embodiment, polymer particulate and electrically conductive carbon particulate may be mixed together as dry components, forming a dry blend. Milling media, e g. milling beads may, be added to the dry blend to facilitate the mixing process and/or to at least partially embed the electrically conductive carbon particulate into the surface of the polymer particulate. The dry blend may then be coated, using conventional techniques, including but not limited to knife coating and electrostatic coating, on a transport protection layer supported on a substrate, e.g. a liner or release liner. The coating may then be heat treated at temperatures near, at or above the softening temperature of the polymer particulate, e.g. the glass transition temperature and/or the melting temperature of the polymer particulate, to fuse at least a portion of the polymer particulate/carbon particulate dry blend into a unitary, porous material, thereby forming a porous electrode. The integrated electrode may be in the form of a sheet. The thermal treatment may also aid in adhering the electrically conductive carbon particulate to the surface of the polymer particulate. The thermal treatment may also aid in adhering the electrically conductive carbon particulate to the surface of the fibers of the transport protection layer. The thermal treatment may be conducted under pressure, e.g. in a heated press or between heated rolls. The press and or heated rolls may be set to provide a specific desired gap, which will facilitate obtaining a desired thickness of the integrated electrode composite. The dry coating and fusing processes may be combined into a single step using a roll coating technique, wherein the rolls are set at a desired gap, correlated to the desired electrode thickness, and the rolls are also heated to the desired fusing temperature, thus coating and thermal treatment is conducted simultaneously.

In an alternative embodiment, the dry blend or the individual particulates may be added to an appropriate liquid medium, i.e. a solvent, and mixed, using conventional techniques, e.g. blade mixing or other agitation, forming a polymer particulate/carbon particulate dispersion. The dispersion may be coated on a transport protection layer supported on a substrate, e.g. a liner or release liner, using conventional techniques, e.g. knife coating. The coating may then be dried, via heat treatment at elevated temperatures, to remove the liquid medium and to fuse at least a portion of the polymer particulate/carbon particulate blend and transport protection layer into a unitary, porous material, thereby forming a porous integrate electrode composite. The integrated electrode composite may be in the form of a sheet. The thermal treatment may also aid in adhering the electrically conductive carbon particulate to the surface of the polymer particulate. The thermal treatment may also aid in adhering the electrically conductive carbon particulate and polymer particulates to the surface of the transport protection layer. The heat treatment used to dry the dispersion, i.e. evaporate the liquid medium, and to fuse at least a portion of the polymer particulate may be at the same or different temperatures. Vacuum may be used to remove the liquid medium or aid in the removal of the liquid medium In another embodiment, the polymer particulate may be obtained as a dispersion, e.g. the dispersion resulting from a suspension or emulsion polymerization, and the electrically conductive carbon particulate may be added to this dispersion. Mixing, coating, drying and fusing may be conducted as described above.

In yet another alternative embodiment, the dry blend or the individual particulates may be added to an appropriate liquid medium, i.e. polymer precursor liquid, and mixed, using conventional techniques, e g. blade mixing or other agitation, forming a polymer particulate/carbon particulate dispersion. The dispersion may be coated on a transport protection layer supported on a substrate, e.g. a liner or release liner, using conventional techniques, e.g. knife coating. The coating may then be at least one of dried, cured, polymerized and fused, forming a binder resin and transforming at least a portion of the polymer particulate/carbon particulate blend into a unitary, porous material, thereby forming an integrated electrode composite. The integrated electrode composite may be in the form of a sheet. If thermal treatment is used to form the polymer binder resin or a secondary thermal treatment is applied to the polymer binder resin, the temperature may be such that the temperature is near, at or above the softening temperature of the polymer binder resin, e.g. the glass transition temperature and/or the melting temperature of the polymer binder resin, which may aid in the adhering of carbon particulate to the binder resin and/or further fuse the binder resin.

In another embodiment, an electrically conductive carbon particulate may be dispersed in a polymer precursor liquid and mixed using conventional techniques, e.g. blade mixing or other agitation. The resulting dispersion may be coated on a transport protection layer supported on a substrate, e.g. a liner or release liner, using conventional techniques, e.g. knife coating. The polymer precursor liquid coating may then be at least one of dried, cured, polymerized and fused, forming a binder resin and a corresponding unitary integrated electrode composite. The Integrated electrode may be in the form of a sheet. If a thermal treatment is used to form the polymer binder rein or a secondary thermal treatment is applied to the polymer binder resin, the temperature may be such that the temperature is near, at or above the softening temperature of the polymer binder resin, e.g. the glass transition temperature and/or the melting temperature of the polymer binder resin, which may aid in the adhering of carbon particulate to the binder resin and/or further fuse the binder resin. In some embodiments, the polymer precursor liquid is a polymer solution, e.g. at least one polymer dissolved in at least one solvent, and the electrically, conductive carbon particulate is dispersed in the polymer solution. The resulting dispersion may be coated on a transport protection layer supported on a substrate, e.g. a liner or release liner, using conventional techniques, e.g. knife coating. The dispersion coating may be dried, forming a polymer binder resin and a corresponding, unitary, porous integrated electrode composite. The porous integrated electrode composite may be in the form of a sheet. After drying or during drying, the temperature may be such that the temperature is near, at or above the softening temperature of the polymer binder resin, e.g. the glass transition temperature and/or the melting temperature of the polymer binder resin, which may aid in the adhering of carbon particulate to the binder resin and/or further fuse the binder resin.

The solvent used in the polymer solution is not particularly limited, except that the polymer that will form the polymer binder resin must be soluble in it. The solvent may be selected based on the chemical structure of the polymer and the solubility of the polymer in the solvent. The optional solvent used in the reactive polymer precursor liquid is not particularly limited, except that the at least one of a liquid monomer and a liquid oligomer is soluble in the solvent. Useful solvents include, but are not limited to, water, alcohols (e.g. methanol, ethanol and propanol), acetone, ethyl acetate, alkyl solvents (e.g. pentane, hexane, cyclohexane, heptane and octane), methyl ethyl ketone, ethyl ethyl ketone, dimethyl ether, petroleum ether, toluene, benzene, xylenes, dimethylformamide, dimethyl sulfoxide, chloroform, carbon tetrachloride, chlorobenzene and mixtures thereof.

In some embodiments, the polymer precursor liquid is a reactive polymer precursor liquid, e.g. at least one of a liquid monomer and a liquid oligomer, and the electrically conductive carbon particulate is dispersed in the reactive polymer precursor solution. The reactive polymer precursor may optionally include at least one solvent and may optionally include at least one polymer that soluble in the liquid components of the reactive polymer precursor liquid. The resulting dispersion may be coated on a substrate, e.g. a liner or release liner, using conventional techniques, e.g. knife coating. The reactive polymer precursor liquid coating may then be at least one of dried, cured, polymerized and fused, forming a polymer binder resin and a corresponding integrated electrode composite. The integrated electrode composite may be in the form of a sheet. If a thermal treatment is used to form the polymer binder rein or a secondary thermal treatment is applied to the polymer binder resin, the temperature may be such that the temperature is near, at or above the softening temperature of the polymer binder resin, e.g. the glass transition temperature and/or the melting temperature of the polymer binder resin, which may aid in the adhering of carbon particulate to the binder resin and/or further fuse the binder resin.

When the polymer precursor liquid is a reactive polymer precursor liquid, the reactive polymer precursor liquid may include appropriate additives to aid in the curing and/or polymerization of the reactive polymer precursor liquid. Additives include, but are not limited to catalysts, initiators, curatives, inhibitors, chain transfer agents and the like. Curing and/or polymerization may be conducted by at least one of thermal and radiation. Radiation may include actinic radiation, including UV and visible radiation. Upon curing, the reactive polymer precursor liquid may form a B-stage polymer binder resin, i.e. capable of a second step cure. If B-stageable polymer binder resins are desired, the first cure may be a thermal cure, and the second cure may be a radiation cure, both curing steps may be thermal cure, for example, at two different cure temperatures, both cures may be radiation cure, at two different wavelengths, or the first cure may be a radiation cure and the second cure a thermal cure.

The TPLs of the present disclosure can include at least one of a polymer and a ceramic. The polymer of the TPL is not particularly limited. However, in order to ensure long term stability of the polymer in the anolyte and/or catholyte liquids it may be exposed to during use, the polymer of the TPL can be selected to have good chemical resistance to the anolyte and/or catholyte, including the associated solvent, oxidizing/reducing active species, salts and/or other additives included therein. In some embodiments, the polymer of the TPL can include at least one of a thermoplastic and thermoset. In some embodiments, the polymer of the TPL can include a thermoplastic. In some embodiments, the polymer of the TPL can include a thermoset. In some embodiments, the polymer of the TPL may consist essentially of a thermoplastic. In some embodiments, the polymer of the TPL may consist essentially of a thermoset. Thermoplastics can include thermoplastic elastomers. A thermoset may include a B-stage thermoset, e.g. a B-stage thermoset after final cure. In some embodiments, the polymer of the TPL can include at least one of a thermoplastic and a B-stage thermoset. In some embodiments, the polymer of the TPL may consist essentially of a B-stage thermoset, e.g. a B-stage thermoset after final cure. In some embodiments, polymer of the TPL includes, but is not limited to, at least one of epoxy resin, phenolic resin, ionic polymer, polyurethane, urea-formadehyde resin, melamine resin, polyesters, e.g. polyethylene terephthalate, polyethylene naphthalate, polyamide, polyether, polycarbonate, polyimide, polysulphone, polyphenylene oxide, polyacrylates, polymethacylates, polyolefin, e.g. polyethylene and polypropylene, styrene and styrene based random and block copolymers, e.g. styrene -butadiene-styrene, polyvinyl chloride, and fluorinated polymer, e.g. polyvinylidene fluoride and polytetrafluoroethylene. In some embodiments, the polymer of the TPL can be at least one of polyurethane, polyester, polyamide, polyether, polycarbonate, polyimide, polysulphone, polyphenylene oxide, polyacrylate, polymethacylate, polyolefin, styrene and styrene based random and block copolymers, polyvinyl chloride, and fluorinated polymer. The polymer of the TPL can be a polymer blend or polymer composite. In some embodiments, the polymer blend and/or composite can include at least two polymers selected from the polymers of the present disclosure.

In some embodiments, the TPL, comprising polymer, can include inorganic material, e.g. and inorganic woven structure and/or inorganic non-woven structure which includes inorganic fiber, for example glass fiber. In these embodiments, the inorganic woven structure and inorganic non-woven structure can include a polymer coating. In some embodiments, the TPL includes from about 5 percent to about 100 percent, from about 10 percent to about 100 percent, from about 20 percent to about 100 percent, from about 30 percent to about 100 percent, from about 40 to about 100 percent, from about 50 to about 100 percent, from about 60 to about 100 percent, from about 70 percent to 100 percent or even from about 80 to about 100 percent by weight polymer. In some embodiments, it may be desirable for the TPL to include from at least about 70 percent to 100 percent by weight polymer, due to at least one of lower cost, lower weight and ease of processing.

In some embodiments, the polymer of the TPL has a softening temperature from about 50 degrees centigrade to about 400 degrees centigrade, from about 50 degrees centigrade to about 350 degrees centigrade, from about 50 degrees centigrade to about 300 degrees centigrade or even from about 50 degrees centigrade to about 250 degrees centigrade. In some embodiments, the TPL is non-tacky at 25 degrees centigrade, 30 degrees centigrade, 40 degrees centigrade, or even 50 degrees centigrade. In some embodiments, the polymer of the TPL contains from about 0 percent to about 15 percent by weight, from about 0 percent to about 10 percent by weight, from about 0 percent to about 5 percent by weight, from about 0 percent to about 3 percent by weight, from about 0 percent to about 1 percent by weight or even substantially 0 percent by weight pressure sensitive adhesive in the form of a polymer blend. Low modulus and/or highly viscoelastic materials, such as a pressure sensitive adhesive, may flow during use, due to the compression forces within an electrochemical cell or liquid flow battery, and may make it difficult to obtain the desired separation between cell or battery components. In some embodiments, the electrode assembly and/or MEA is substantially free of a pressure sensitive adhesive and/or a pressure sensitive adhesive layer. In some embodiments the modulus, e.g. Young’s modulus, of the polymer of the TPL can be from about 0.010 GPa to about 10 GPa, from about 0.1 GPa to about 10 GPa, from about 0.5 GPa to about 10 GPa, from about 0.010 GPa to about 5 GPa, from about 0.1 GPa to about 5 GPa or even from about 0.5 GPa to about 5 GPa.

The polymer of the TPL can be ionic polymer. Ionic polymer includes, but is not limited to, ion exchange resin, ionomer resin and combinations thereof. Ion exchange resins may be particularly useful. The ionic polymer of TPL can include polymer wherein a fraction of the repeat units are electrically neutral and a fraction of the repeat units have an ionic functional group, i.e. an ionic repeat unit. In some embodiments, the ionic polymer has a mole fraction of repeat units having an ionic functional group of between about 0.005 and about 1.

Ionic polymer can include conventional thermoplastics and thermosets that have been modified by conventional techniques to include at least one of type of ionic functional group, e.g. anionic and/or cationic. Useful thermoplastic resins that may be modified include, but are not limited to, at least one of polyethylene, e.g. high molecular weight polyethylene, high density polyethylene, ultra-high molecular weight polyethylene, polypropylene, e.g. high molecular weight polypropylene, polystyrene, poly(meth)acrylates, e.g. polyacrylates based on acrylic acid that may have the acid functional group exchanged for, for example, an alkali metal, chlorinated polyvinyl chloride, , fluoropolymer, e.g.

perfluorinated fluoropolymer and partially fluorinated fluoropolymer (for example polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) each of which may be semi crystalline and/or amorphous, polyetherimides and polyketones. Useful thermoset resins include, but are not limited to, at least one of epoxy resin, phenolic resin, polyurethanes, urea-formadehyde resin and melamine resin. Ionic polymer includes, but are not limited to, ion exchange resins, ionomer resins and combinations thereof. Ion exchange resins may be particularly useful.

As defined herein, ionic polymer include polymer wherein a fraction of the repeat units are electrically neutral and a fraction of the repeat units have an ionic functional group. In some embodiments, the ionic polymer has a mole fraction of repeat units with ionic functional groups between about 0.005 and 1. In some embodiments, the ionic polymer is a cationic resin, i.e. its ionic functional groups are negatively charged and facilitate the transfer of cations, e.g. protons, optionally, wherein the cationic resin is a proton cationic resin. In some embodiments, the ionic polymer is an anionic exchange resin, i.e. its ionic functional groups are positively charged and facilitate the transfer of anions. The ionic functional group of the ionic polymer can include, but is not limited, to carboxylate, sulphonate, sulfonamide, quaternary ammonium, thiuronium, guanidinium, imidazolium and pyridinium groups. Combinations of ionic functional groups may be used in an ionic polymer.

The polymer of the TPL can include a hydrophilic polymer, e g. ionic polymer previously disclosed herein having a mole fraction of repeat units having ionic functional groups of between about 0.03 and about 1, between about 0.05 and about 1, between about 0.10 and 1, between about 0.03 and about 0.8, between about 0.05 and 0.80 or even between about 0.1 and 0.80. In some embodiments, the TPL comprises from about 5 percent to about 100 percent by weight, from about 10 percent to 100 percent by weight, from about 25 percent to about 100 percent by weight, from about 5 percent to about 80 percent by weight, from about 10 percent to 80 percent by weight, from about 25 percent to about 80 percent by weight, from about 5 percent to about 60 percent by weight, from about 10 percent to 60 percent by weight or even from about 25 percent to about 60 percent by weight of a hydrophilic polymer. In some embodiments, the hydrophilic polymer may be included in the polymer as a polymer blend or may be included as a polymer coating. In some embodiments the TPL includes a hydrophilic polymer coating. Hydrophilic polymers know in the art may be used, including but not limited to, polyacrylic acids, polymethacylic acids, polyvinyl alcohols, polyvinyl acetate, polyethylene glycol, polypropylene glycol, polyethylene oxide, polypropylene oxide, polyacrylamides, maleic anhydride polymers, cellulosic polymers, polyelectrolytes and polymers with amine groups in their main chain or side chains, e.g. nylon 6, 6, nylon 7, 7, and nylon 12, polysulfone, epoxies, polyester, and polycarbonate.

In some embodiments, the TPL includes a hydrophilic coating. The hydrophilic coating can be an organic material or inorganic material. The hydrophilic coating can include at least one of a high molecular weight molecular species (number average molecular weight greater than 10000 g/mol,), an oligomeric molecular species (number average molecular weight greater than 1000 g/mol and no greater than 10000 g/mol), a low molecular weight molecular species (number average molecular weight no greater than 1000 g/mol and no less than 20 g/mol) and combinations thereof. The hydrophilic coatings may include molecular species comprising one or more polar functional groups, e.g. acid, hydroxyl, ester, ether and/or amine. In some embodiments, the hydrophilic polymer and/or hydrophilic coating of the TPL can have a surface contact angle with water, catholyte and/or anolyte of between about 90 and 0 degrees, between about 85 degrees and about 0 degrees, between about 70 degrees and about 0 degrees, between about 50 degrees and about 0 degrees, between about 30 degrees and about 0 degrees, between about 20 degrees and about 0 degrees, or even between about 10 degrees and about 0 degrees. The contact angle may be measured by known techniques in the art, including receding contact angle measurement and advancing contact angle measurements. In some embodiments, the hydrophilic polymer and/or hydrophilic coating of the TPL can have a receding contact angle with water, catholyte and/or anolyte of between about 90 and 0 degrees, between about 85 degrees and about 0 degrees, between about 70 degrees and about 0 degrees, between about 50 degrees and about 0 degrees, between about 30 degrees and about 0 degrees, between about 20 degrees and about 0 degrees, or even between about 10 degrees and about 0 degrees. In some embodiments, the hydrophilic polymer and/or hydrophilic coating of the TPL can have an advancing contact angle with water, catholyte and/or anolyte of between about 90 and 0 degrees, between about 85 degrees and about 0 degrees, between about 70 degrees and about 0 degrees, between about 50 degrees and about 0 degrees, between about 30 degrees and about 0 degrees, between about 20 degrees and about 0 degrees, or even between about 10 degrees and about 0 degrees. In some embodiments, the TPL can have an advancing contact angle and/or receding contact angle with water, catholyte and/or anolyte of between about 90 and 0 degrees, between about 85 degrees and about 0 degrees, between about 70 degrees and about 0 degrees, between about 50 degrees and about 0 degrees, between about 30 degrees and about 0 degrees, between about 20 degrees and about 0 degrees, or even between about 10 degrees and about 0 degrees. Use of hydrophilic polymers and/or coatings for the TPL may improve liquid transport, e.g. anolyte and/or catholyte flow, through the layer and improve electrochemical cell and/or liquid flow battery performance.

The thickness, T, of the TPL is not particularly limited. In some embodiments, the thickness of the TPL, e.g. the thickness of at least one of a plurality of discrete structures, a mesh structure, a woven structure and a non-woven structure, is from about 0.05 micron to about 3000 microns, from about 0.05 micron to about 2000 microns, from about 0.05 micron to about 1000 microns, about 0.05 micron to about 500 microns, from about 1 micron to about 3000 microns, from about 1 micron to about 2000 microns, from about 1 micron to about 1000 microns, about 1 micron to about 500 microns, from about 10 microns to about 3000 microns, from about 10 microns to about 2000 microns, from about 10 microns to about 1000 microns, about 10 microns to about 500 microns, from about 50 microns to about 3000 microns, from about 50 microns to about 2000 microns, from about 50 microns to about 1000 microns, or even from about 50 microns to about 500 microns. In some embodiments, to maximize the resistance to shorting of a cell or battery (associated with, for example, carbon fiber penetration of the ion permeable membrane), it may be desirable to have a thicker TPL. In these embodiments, the thickness of the TPL can be on the higher end of the ranges of thickness described above. For example, the thickness of the TPL can be from about 25 microns to about 3000 microns, from about 25 microns to about 2000 microns, from about 25 microns to about 1000 microns, from about 25 microns to about 500 microns, from about 50 microns to about 3000 microns, from about 50 microns to about 2000 microns, from about 50 microns to about 1000 microns, from about 50 microns to about 500 microns, from about 75 microns to about 3000 microns, from about 75 microns to about 2000 microns, from about 75 microns to about 1000 microns, from about 75 microns to about 500 microns, from about 100 microns to about 3000 microns, from about 100 microns to about 2000 microns, from about 100 microns to about 1000 microns, or even from about 100 microns to about 500 microns.

In some embodiments, to enhance cell resistance and/or short resistance, the thickness of the porous protection layer can be between about 25 microns and about 500 microns, between about 50 microns and about 500 microns, between about 75 microns and about 500 microns, between about 100 microns and about 500 microns, between about 25 microns and about 400 microns, between about 50 microns and about 400 microns, between about 75 microns and about 400 microns, between about 100 microns and about 400 microns, between about 25 microns and about 300 microns, between about 50 microns and about 300 microns, between about 75 microns and about 300 microns, or even between about 100 microns and about 300 microns.

In some embodiments, in order to improve the cell resistance (lower the cell resistance), it may be desirable to have a thinner TPL. In these embodiments, the thickness of the TPL can be on the lower end of the ranges of thickness described above. For example, the thickness of the TPL can be between about 25 microns and about 500 microns, between about 50 microns and about 500 microns, between about 75 microns and about 500 microns, between about 100 microns and about 500 microns, between about 25 microns and about 400 microns, between about 50 microns and about 400 microns, between about 75 microns and about 400 microns, between about 100 microns and about 400 microns, between about 25 microns and about 300 microns, between about 50 microns and about 300 microns, between about 75 microns and about 300 microns, or even between about 100 microns and about 300 microns.

In some embodiments, the TPL can include a mesh structure. Mesh structure include a continuous sheet or layer having a plurality of open regions, e.g. a plurality of through-holes. A mesh structure can include, for example, a polymer film with a plurality of through-holes. The mesh structure of the present disclosure does not include conventional woven and non-woven structures, i.e. woven and non-woven substrates. The shape of the plurality of open regions of the mesh structure is not particularly limited and includes, but is not limited to, circular, elliptical, irregular polygons and regular polygons, e.g. triangle, quadrilateral (square, rectangle, rhombus and trapezoid), pentagon, hexagon and octagon. Combinations of shapes may be used. In some embodiments, the plurality of open regions of the mesh structure can have a length and/or width of from about 10 microns to about 10 mm, 50 microns to about 10 mm, 100 microns to about 10 mm, from about 200 microns to about 10 mm, from about 500 microns to about 10 mm, from about 1000 microns to about 10 mm, 10 microns to about 8 mm, 50 microns to about 8 mm, from about 100 microns to about 8 mm, from about 200 microns to about 8 mm, from about 500 microns to about 8 mm, from about 1000 microns to about 8 mm, 10 microns to about 6 mm, 50 microns to about 6 mm, from about 100 microns to about 6 mm, from about 200 microns to about 6 mm, from about 500 microns to about 6 mm, from about 1000 microns to about 6 mm or even from about 10 microns to about 1000 microns. The depth of the plurality of open regions may correspond to the thickness, T, of the TPL, as previously described. The dimensions, i.e. length, width and/or depth of each open region may be substantially the same or may be different. The plurality of open regions of the mesh structure may be random or may be in a pattern. Patterns include, but are not limited to, square arrays, hexagonal arrays and the like. Combination of patterns can be used.

Mesh structures can be fabricated by known techniques in the art. For example, a polymer fdm can be fabricated by an extmsion process and a plurality of open regions can be formed in the polymer fdm via techniques known in the art, including, but not limited to, die cutting, laser cutting, water jet cutting, needle punching, etching and the like. A mesh structure can also be formed by an extrusion process where a first set of strands of polymer, substantially parallel to one another, for example, are extruded in one direction on a porous electrode and a second set of polymer strands, substantially parallel to one another, yet off-set by an angle, theta, relative to the first set of strands, is extruded on the porous electrode, thereby forming a mesh structure. Theta may be from about 5 degrees to about 90 degrees, from about 15 degrees to about 90 degrees, from about 30 degrees to about 90 degrees or even from about 45 degrees to about 90 degrees.

In some embodiments, the TPL can include a woven structure, i.e. a woven substrate having a plurality of open regions. Conventional woven structures known in the art can be used, e.g. woven cloths and woven fabrics. In some embodiments, the plurality of open regions of the woven structure can have a length and/or width of from about 10 microns to about 10 mm, from about 50 microns to about 10 mm, from about 100 microns to about 10 mm, from about 200 microns to about 10 mm, from about 500 microns to about 10 mm, from about 1000 microns to about 10 mm, from about 10 microns to about 8 mm, from about 50 microns to about 8 mm, from about 100 microns to about 8 mm, from about 200 microns to about 8 mm, from about 500 microns to about 8 mm, from about 1000 microns to about 8 mm, from about 10 microns to about 6 mm, from about 50 microns to about 6 mm, from about 100 microns to about 6 mm, from about 200 microns to about 6 mm, from about 500 microns to about 6 mm, or even from about 1000 microns to about 6 mm. The depth of the plurality of open regions can correspond to the thickness, T, of the TPL, as previously described. In some embodiments, the TPL can include a non-woven structure, i.e. a non-woven substrate having open regions, the open regions may be substantially interconnected. Conventional non-woven structures known in the art can be used, e g. non-woven paper, non-woven felt and non-woven web.

The woven and non-woven structures of the TPL of the present disclosure can be non-conductive structures. The woven and non-woven structures of the TPL, generally, include fiber. In some embodiments, the TPLs include a woven non-conductive structure and is free of a non-woven non- conductive structure. In some embodiments, the TPLs include a non-woven non-conductive structure and is free of a woven non-conductive structure. The woven and non-woven non-conductive structure of the TPL include polymer and, optionally can include an inorganic. The woven and non-woven structures can include a non-conductive polymer material and, optionally, a non-conductive inorganic material. The woven and non-woven non-conductive substrate may comprise fiber, e g. a plurality of fibers. The woven and non-woven structures can be fabricated from polymer fiber, e.g. non-conductive polymer fiber and, optionally inorganic fiber, e.g. non-conductive inorganic fiber. In some embodiments, the woven and non-woven structures can include polymer fiber and exclude inorganic fiber.

In some embodiments, the fibers of the woven and non-woven structures can have aspect ratios of the length to width and length to thickness both of which are greater about 10 and a width to thickness aspect ratio less than about 5. For a fiber having a cross sectional area that is in the shape of a circle, the width and thickness would be the same and would be equal to the diameter of the circular cross-section. There is no particular upper limit on the length to width and length to thickness aspect ratios of a fiber. Both the length to thickness and length to width aspect ratios of the fiber may be between about 10 and about 1000000, between 10 and about 100000, between 10 and about 1000, between 10 and about 500, between 10 and about 250, between 10 and about 100, between about 10 and about 50, between about 20 and about 1000000, between 20 and about 100000, between 20 and about 1000, between 20 and about 500, between 20 and about 250, between 20 and about 100 or even between about 20 and about 50. The width and thickness of the fiber may each be from between about 0.001 to about 500 microns, from between about 0.001 to about 250 microns, from between about 0.001 to about 100 microns, from between about 0.001 microns to about 50 microns, from between about 0.001 to about 25 microns, from between about 0.001 microns to about 10 microns, from about 0.001 microns to about 1 microns, from between about from between about 0.01 to about 500 microns, from between about 0.01 to about 250 microns, 0.01 to about 100 microns, from between about 0.01 microns to about 50 microns, from between about 0.01 to about 25 microns, from between about 0.01 microns to about 10 microns, from about 0.01 microns to about 1 microns, from between about 0.05 to about 500 microns, from between about 0.05 to about 250 microns, from between about 0.05 to about 100 microns, from between about 0.05 microns to about 50 microns, from between about 0.05 to about 25 microns, from between about 0.05 microns to about 10 microns, from about 0.05 microns to about 1 microns, from between about 0.1 to about 100 microns, from between about 0.1 to about 500 microns, from between about 0.1 to about 250 microns, from between about 0.1 microns to about 50 microns, from between about 0.1 to about 25 microns, from between about 0.1 microns to about 10 microns, or even from between about 0.1 microns to about 1 microns. In some embodiments the thickness and width of the fiber may be the same. In some embodiments, smaller microfibers can be woven or bonded together to form macro-fibers having significantly larger dimension, e.g. width and/or thickness, than the individual fibers they are composed of.

The fibers can be fabricated into a woven and non-woven structure using conventional techniques. A non-woven structure can be fabricated by a melt blown fiber process, spunbond process, a carding process and the like. In some embodiments, the length to thickness and length to width aspect ratios of the fiber may be greater than 1000000, greater than about 10000000 greater than about

100000000 or even greater than about 1000000000. In some embodiments, the length to thickness and length to width aspect ratios of the fiber may be between about 10 to about 1000000000; between about 10 and about 100000000 between about 10 and about 10000000, between about 20 to about 1000000000; between about 20 and about 100000000 between about 20 and about 10000000, between about 50 to about 1000000000; between about 50 and about 100000000 or even between about 50 and about 10000000.

The at least one of a woven and non-woven structure can include conventional woven and non- woven paper, felt, mats and cloth (fabrics) known in the art. The woven and non-woven structure may include polymer fiber and, optionally, ceramic fiber. The number of types, polymer fiber types and ceramic fiber types, used to form the at least one of a woven and non-woven non-conductive substrate, is not particularly limited. The polymer fiber can include at least one polymer, e.g. polymer composition or one polymer type. The polymer fiber can include at least two polymers, i.e. two polymer compositions or two polymer types. The polymer fiber can be a core-sheath polymer fiber composed of at least two different polymer types. For example, the polymer fiber can include one set of fibers composed of polyethylene and another set of fibers composed of polypropylene. If at least two polymers are used, the first polymer fiber can have a lower glass transition temperature and or melting temperature than the second polymer fiber. The first polymer fiber may be used for fusing the polymer fiber of the at least one of a woven and non-woven structure together, to improve, for example, the mechanical properties of the woven and non-woven structure. The optional ceramic fiber can include at least one ceramic, e.g. one ceramic composition or one ceramic type. The optional ceramic fiber can include at least two ceramics, i.e. two ceramic compositions or two ceramic types. The woven and non-woven structures can include at least one polymer fiber, e.g. one polymer composition or polymer type, and at least one ceramic fiber, e.g. one ceramic composition or one ceramic type. For example, the at least one of a woven and non-woven non-structure can include polyethylene fiber and glass fiber.

The basis weight of the at least one of a woven and non-woven structure is not particularly limited. In some embodiments, the basis weight of the at least one of a woven and non-woven structure, measured in gram per square meter (gsm) of material, may be between about 4 gsm and about 60 gsm, between about 4 gsm and about 50 gsm, between about 4 gsm and about 40 gsm, between about 4 gsm and about 32 gsm, between about 6 gsm and about 60 gsm, between about 6 gsm and about 50 gsm, between about 6 gsm and about 40 gsm, between about 6 gsm and about 32 gsm, between about 8 gsm and about 60 gsm, between about 8 gsm and about 50 gsm, between about 8 gsm and about 40 gsm or even between about 8 gsm and about 32 gsm.

In some embodiments, the woven and non-woven structure can include small amounts of one or more conductive material, so long as the conductive material does not alter the at least one of a woven and non-woven non-conductive substrate to be conductive. In some embodiments, the at least one of a woven and non-woven non-conductive structure is substantially free of conductive material. In this case, “substantially free of conductive material” means that the at least one of a woven and non-woven non- conductive substrate includes less than about 25% by wt., less than about 20% by wt., less than about 15% by wt., less than about 10% by wt., less than about 5% by wt., less than about 3% by wt., less than about 2%, by wt., less than about 1% by wt., less than about 0.5% by wt., less than about 0.25% by wt., less than about 0.1% by wt., or even 0.0% by wt. conductive material.

The polymer fiber of the at least one of a woven and non-woven structure is not particularly limited. In some embodiments, the polymer fiber of the at least one of a woven and non-woven structure is non-conductive. In some embodiments, the polymer fiber of the woven and non-woven structure can include least one of a thermoplastic and thermoset. Thermoplastics can include thermoplastic elastomers. A thermoset can include a B-stage polymer. In some embodiments, polymer fiber of the woven and non- woven structure includes, but is not limited to, at least one of epoxy resin, phenolic resin, polyurethane, urea-formadehyde resin, melamine resin, polyester, e.g. polyethylene terephthalate, polyethylene naphthalate, polyamide, polyether, polycarbonate, polyimide, polysulphone, polyphenylene oxide, polyacrylates, polymethacylates, polyolefin, e.g. polyethylene and polypropylene, styrene and styrene based random and block copolymers, e.g. styrene-butadiene-styrene, polyvinyl chloride, and fluorinated polymers, e.g. polyvinylidene fluoride and polytetrafluoroethylene. In some embodiments, the polymer fiber comprises at least one of polyurethane, polyester, polyamide, polyether, polycarbonate, polyimides, polysulphone, polyphenylene oxide, polyacrylates, polymethacylates, polyolefin, styrene and styrene based random and block copolymers, polyvinyl chloride, and fluorinated polymer.

The optional ceramic fiber of the woven and non-woven structure is not particularly limited. The ceramic of the ceramic fiber can include, but is not limited to, metal oxides, for example silicon oxide, e.g. glass and doped glass, and aluminum oxide.

If a ceramic fiber is used as the woven and/or non-woven structure, the ceramic fiber can include, but is not limited to at least one of metal oxides, for example silicon oxide, e.g. glass and doped glass, and aluminum oxide. The TPL can be a multi-layer structure. In some embodiments, the TPL comprises at least one layer. In some embodiments, the TPL comprises two or more layers. The layers of the TPL may be the same composition and/or structure or may include two or more different compositions and/or two or more different structures.

The substrates of the present disclosure are not particularly limited and may include conventional liners and release liners, e.g. polymer fdms that may or may not have a low surface energy coating. The polymer of the substrate may be at least one of a thermoplastic polymer and a thermoset polymer.

Thermoplastic polymers, include polyalkylenes; e g. polyethylene and polypropylene; polyurethane; polyamide; polycarbonates; polysulfones; polystrenes; polyester, e g. polyethylene terephthalate and polybutylene terephthalate; polybutadiene; polyisoprene; polyalkylene oxides, e.g. polyethylene oxide; ethylene vinyl acetate; cellulose acetate; ethyl cellulose and block copolymers of any of the proceeding polymers. Thermoset polymers include, but are not limited to, polyimide, polyurethanes, polyesters, epoxy resins, phenol-formaldehyde resins, urea formaldehyde resins and rubber. In some embodiments, the substrate is a dielectric polymer, substrate. The polymer of the substrate may be a polymer blend.

The substrate may include holes or pores.

The integrated composite electrodes of the present disclosure may be washed using conventional techniques to remove loose carbon particulate. The washing technique may include and appropriate solvent, e.g. water, and/or surfactant to aid in the removal of loose carbon particulate. The integrated electrode composites of the present disclosure may be made by a continuous roll to roll process, the integrated electrode composite sheet being wound to form a roll good.

In some embodiments, the integrated electrode composite may be hydrophilic. This may be particularly beneficial when the porous integrated electrode is to be used in conjunction with aqueous anolyte and/or catholyte solutions. Uptake of a liquid, e.g. water, catholyte and/or anolyte, into the pores of a liquid flow battery electrode may be considered a key property for optimal operation of a liquid flow battery. In some embodiments, 100 percent of the pores of the electrode may be filled by the liquid, creating the maximum interface between the liquid and the electrode surface. In other embodiments, between about 30 percent and about 100 percent, between about 50 percent and about 100 percent, between about 70 percent and about 100 percent or even between about 80 percent and 100 percent of the pores of the electrode may be filled by the liquid. In some embodiments the porous electrode may have a surface contact angle with water, catholyte and/or anolyte of less than 90 degrees. In some embodiments, the microporous protection layer may have a surface contact with water, catholyte and/or anolyte of between about 85 degrees and about 0 degrees, between about 70 degrees and about 0 degrees, between about 50 degrees and about 0 degrees, between about 30 degrees and about 0 degrees, between about 20 degrees and about 0 degrees, or even between about 10 degrees and about 0 degrees.

In some embodiments, the integrated electrode composite may be surface treated to enhance the wettability of the electrode to a given anolyte or catholyte or to provide or enhance the electrochemical activity of the electrode relative to the oxidation-reduction reactions associated with the chemical composition of a given anolyte or catholyte. Surface treatments include, but are not limited to, at least one of chemical treatments, thermal treatments and plasma treatments.

Surfactants may be used in the electrode dispersion/coating solutions, for example, to improve wetting and/or aid in dispersing of the electrically conductive carbon particulate. Surfactants may include cationic, anionic and nonionic surfactants. Surfactants useful in the electrode dispersion/coating solutions include, but are not limited to TRITON X-100, available from Dow Chemical Company, Midland, Michigan; DISPERSBYK 190, available from BYK Chemie GMBH, Wesel, Germany; amines, e g. olyelamine and dodecylamine; amines with more than 8 carbons in the backbone, e g 3-(N, N- dimethyldodecylammonio) propanesulfonate (SB12); SMA 1000, available from Cray Valley USA, LLC, Exton, Pennsylvania; 1,2-propanediol, triethanolamine, dimethylaminoethanol; quaternary amine and surfactants disclosed in U.S. Pat. Publ. No. 20130011764, which is incorporated herein by reference in its entirety. If one or more surfactants are used in the dispersions/coating solutions, the surfactant may be removed from the electrode by a thermal process, wherein the surfactant either volatilizes at the temperature of the thermal treatment or decomposes and the resulting compounds volatilize at the temperature of the thermal treatment. In some embodiments, the electrode is substantially free of surfactant. By“substantially free” it is meant that the electrodes contain, by weight, from 0 percent to 0.5 percent, from 0 percent to 0.1 percent, from 0 percent to 0.05 percent or even from 0 percent to 0.01 percent surfactant. In some embodiments, the electrode layer contains no surfactant. The surfactant may be removed from the electrode by washing or rinsing with a solvent of the surfactant. Solvents include, but are not limited to water, alcohols (e.g. methanol, ethanol and propanol), acetone, ethyl acetate, alkyl solvents (e.g. pentane, hexane, cyclohexane, heptane and octane), methyl ethyl ketone, ethyl ethyl ketone, dimethyl ether, petroleum ether, toluene, benzene, xylenes, dimethylformamide, dimethyl sulfoxide, chloroform, carbon tetrachloride, chlorobenzene and mixtures thereof.

The thickness of the integrated electrode composite may be from about 10 microns to about 5000 microns, from about 10 microns to about 1000 microns, from about 10 microns to about 500 microns, from about 10 microns to about 250 microns, from about 10 microns to about 100 microns, from about 25 microns to about 5000 microns, from about 25 microns to about 1000 microns, from about 25 microns to about 500 microns, from about 25 microns to about 250 microns, or even from about 25 microns to about 100 microns. The porosity of the porous electrodes, on a volume basis, may be from about 5 percent to about 95 percent, from about 5 percent to about 90 percent, from about 5 percent to about 80 percent, from about 5 percent to about 70 percent, from about 10 percent to about 95 percent, from about 10 percent to 90 percent, from about 10 percent to about 80 percent, from about 10 percent to about 70 percent, from about 10 percent to about 70 percent, from about 20 percent to about 95 percent, from about 20 percent to about 90 percent, from about 20 percent to about 80 percent, from about 20 percent to about 70 percent, from about 20 percent to about 70 percent, from about 30 percent to about 95 percent, from about 30 percent to about 90 percent, from about 30 percent to about 80 percent, or even from about 30 percent to about 70 percent.

The integrated electrode composite may be composed of a single carbon electrode composite layer or multiple layers. When the integrated electrode composite includes multiple layers, there is no particular limit as to the number of layers that may be used. However, as there is a general desire to keep the thickness of electrode and membrane assembly as thin as possible, the integrated electrode composite may include from about 2 to about 20 layers, from about 2 to about 10 layers, from about 2 to about 8 layers, from about 2 to about 5 layers, from about 3 to about 20 layers, from about 3 to about 10 layers, from about 3 to about 8 layers, or even from about 3 to about 5. In some embodiments, when the integrated electrode composite includes multiple layers, the carbon electrode composite material of each layer may be the same, i.e. the composition of the carbon electrode composite material of each layer is the same. In some embodiments, when the integrated electrode composite includes multiple layers, the electrode material of at least one, up to including all of the layers, may be different, i.e. the composition of the electrode material of at least one, up to and including all layers, differs from the composition of the electrode material of another layer. The membranes, e.g. ion permeable membranes, of the present disclosure may be obtained as free standing films from commercial suppliers or can be fabricated by coating a solution of the appropriate membrane resin, e.g. ion exchange membrane resin, in an appropriate solvent, and then heating to remove the solvent. The membrane can be formed from a coating solution by coating the solution on a release liner and then drying the membrane coating solution coating to remove the solvent.

Any suitable method of coating can be used to coat the membrane coating solution on a release liner. Typical methods include both hand and machine methods, including hand brushing, notch bar coating, fluid bearing die coating, wire-wound rod coating, fluid bearing coating, slot-fed knife coating, and three-roll coating. Most typically three-roll coating is used. Coating may be achieved in one pass or in multiple passes. Coating in multiple passes can be useful to increase coating weight without corresponding increases in cracking of the ion permeable membrane.

The amount of solvent, on a weight basis, in the membrane coating solution may be from about 5 to about 95 percent, from about 10 to about 95 percent, from about 20 to about 95 percent, from about 30 to about 95 percent, from about 40 to about 95 percent, from about 50 to about 95 percent, from about 60 to about 95 percent, from about 5 to about 90 percent, from about 10 to about 90 percent, from about 20 percent to about 90 percent, from about 30 to about 90 percent, from about 40 to about 90 percent, from about 50 to about 90 percent, from about 60 to about 90 percent, from about 5 to about 80 percent, from about 10 to about 80 percent from about 20 percent to about 80 percent, from about 30 to about 80 percent, from about 40 to about 80 percent, from about 50 to about 80 percent, from about 60 to about 80 percent, from about 5 percent to about 70 percent, from about 10 percent to about 70 percent, from about 20 percent to about 70 percent, from about 30 to about 70 percent, from about 40 to about 70 percent, or even from about 50 to about 70 percent..

The amount of membrane resin, e.g. ion exchange resin and ionomer resin, on a weight basis, in the membrane coating solution may be from about 5 to about 95 percent, from about 5 to about 90 percent, from about 5 to about 80 percent, from about 5 to about 70 percent, from about 5 to about 60 percent, from about 5 to about 50 percent, from about 5 to about 40 percent, from about 10 to about 95 percent, from about 10 to about 90 percent, from about 10 to about 80 percent, from about 10 to about 70 percent, from about 10 to about 60 percent, from about 10 to about 50 percent, from about 10 to about 40 percent, from about 20 to about 95 percent, from about 20 to about 90 percent, from about 20 to about 80 percent, from about 20 to about 70 percent, from about 20 to about 60 percent, from about 20 to about 50 percent, from about 20 to about 40 percent, from about 30 to about 95 percent, from about 30 to about 90 percent, from about 30 to about 80 percent, from about 30 to about 70 percent, from about 30 to about 60 percent, or even from about 30 to about 50 percent.

The thickness of the ion permeable membrane can be from about 5 microns to about 250 microns, from about 5 microns to about 200 microns, from about 5 microns to about 150 microns, from about 5 microns to about 100 microns, from about 10 microns to about 250 microns, from about 10 microns to about 200 microns, from about 10 microns to about 150 microns, from about 5 microns to about 10 microns, from about 15 microns to about 250 microns, from about 15 microns to about 200 microns, from about 15 microns to about 150 microns, or even from about 15 microns to about 100 microns.

The ion permeable membrane can have the same width as that of the MEA, but that is not a requirement. In some embodiments, the width of the ion permeable membrane can be less than the width of at least one of the membrane electrode assembly and the TPL. In some embodiments, the width of the ion permeable membrane can be greater than the width of at least one of the membrane electrode assembly and the TPL.

The gaskets can be prepared from materials typically used as gasket material in the field of liquid flow batteries. Although the material used for the gasket is not particularly limited, generally, the material of the gasket has good chemical resistance to the anolyte and/or catholyte used in the liquid flow batteries. The gasket can include at least one polymer. In some embodiments the gasket can include, but is not limited to, at least one of polyester, e.g. polyethylene terephthalate, polyamide, polycarbonate, polyimide, polysulphone, polyphenylene oxide, polyethylene naphthalate, polyacrylates,

polymethacylates, polyolefin, e.g. polyethylene and polypropylene, styrene and styrene based random and block copolymers, e.g. styrene-butadiene-styrene, polyvinyl chloride, and fluorinated polymer, e.g. polyvinylidene fluoride and polytetrafluoroethylene.

The following are exemplary configurations for the integrated electrode composite according to embodiments of the invention. Thickness. The integrated electrode composite can have a thickness in the range from 100 microns to 1000 microns, and preferably from 300 microns to 500 microns after

consolidation/calendering. The carbon electrode composite in the integrated electrode composite can have a thickness in the range from 100 microns to 1000 microns, and preferably from 300 microns to 500 microns. The thickness of TPL can be in the range from 50 microns to 500 microns, and preferably from 100 microns to 300 microns.

Composition. The integrated electrode composite can have a carbon particulate in the range from 50 wt% to 98 wt%, and preferably from 85 wt% to 95 wt%.

Type. The integrated electrode composite can include: (1) carbon particulate graphite fibers, graphite particles, carbon nanotubes, carbon nano-structures and a mixture thereof, and preferably long graphitic fibers mixed with short graphitic fibers and/or carbon nanotubes or nano structures; or (2) carbon nanostructures attached to other fibers such as electrically conductive fibers or electrically non conducting fibers, and preferably carbon nanostructures attached to non-conducting glass fibers from 10 wt% to 50 wt%, and preferably 20 wt% to 30 wt%, with respect to total solid content, or (3) carbon nanotubes used in conjunction with other inorganic fibers, preferably glass or alumina fibers.

Porosity: The porous integrated electrode composite can have a porosity ranging from 20% to 95%, and preferably from 60% to 80%.

Openness of the TPL. The carbon electrode composite surface in contact with the TPL can cover 2% to 50% of the surface of the carbon electrode composite, and preferably 2% to 20% of the surface area of the carbon electrode composite is covered.

Mass of TPL: The mass per unit area of the TPL can be from 2 grams per square meter (gsm) to 100 gsm, and preferably from 5 gsm to 30 gsm.

EXAMPLES

Materials

Chopped graphite fibers (received as CN-90C-6Z Lot # 22040C220832 from Nippon Graphite Fiber Corporation) were heat treated in an oven in static air at 575°C for 12 hours. Spool of carbon nanostructures (CNS) grown on glass fibers (received as PCT 00056 from Applied Nanostructured Solutions LLC, Baltimore, MA) were chopped to 0 5” size and heat treated in an oven in static air at 300°C for 4 hours. Fibrillated binding fibers (received as Fybrel E620F from MiniFibers Inc, Johnson City, TN) were used as received.

A polypropylene non-woven web was used as a TPL. The non-woven web was formed using a Drilled Orifice Die Meltblown fibers were created by a molten polymer entering the die, the flow being distributed across the width of the die in the die cavity and the polymer exiting the die through a series of onfices as filaments. A heated air stream passed through air manifolds and an air knife assembly adjacent to the series of polymer orifices that carried out the filaments coming from the die exit (tip). This heated air stream was adjusted for both temperature and velocity to attenuate (draw) the polymer filaments down to the desired fiber diameter. The meltbiown fibers were conveyed in tins turbulent air stream towards a moving belt where they collect to form a web.

A roll of approximately 20 inch (50.8 cm) wide non-woven web was collected under the conditions as follows: The MF-650X polypropylene polymer (manufactured by LyondellBasell, Rotterdam, Netherlands, and commercially available through Nexeo Solutions, The Woodlands, Texas) was extruded through a 20 inch (50.8 cm) wide drilled orifice die (DOD) at 49 lb/hr (22 22 kg/hr) The polymer melt temperature was 435.2 degree F (224 degree C). The die-to-collector distance was 7.5 inches (19.05 cm). Samples of the web were collected on a stainless steel moving belt at 129 ft/min (39.3 m/min), the meltbiown web was separated from the belt and evaluated for effective fiber diameter (EFD) according to the method set forth in Davies, C. N., "The Separation of Airborne Dust and Particles," Institution of Mechanical Engineers, London Proceedings IB, 1952. The air temperature and velocity were adjusted to achieve an effective fiber diameter of 30 micrometers. The basis weight of the web was calculated by die cuting 5.25 inch (13.33 cm) diameter discs and taking their weight in gram. The basis weight of the non-woven web was calculated by dividing the mass of the disc by its area and calculated to be 20 grams per square meter (gsm).

Deionized (DI) water running in the laboratory was used without further purification.

Example 1

A TPL cut in approximately 50cm x 50cm was carefully (without forming wrinkles) laid on the 31.1 cm x 33 cm plastic mesh screen of a Paper Maker (received as a custom built Paper Maker from South East Non-woven, SC) The lid of the Paper Maker was closed and the water tank was filled with 24.74L DI water. The air bubbles trapped on the screen, in between TPL and screen and on the TPL were removed by shaking them off using an aluminum plunger. A four liter laboratory blender (received as Heavy Duty Blender from Waring Commercial) was filled with 3.5L DI water. 0.56g of E620F was added to water in the blender and the mixture was blended for 120s on the“High” setting. On this blend, 7.34g of CN90C-6z and 3.39g of CNS material was added and the slurry was blended for 15s on the“Low” setting. This slurry was then poured into the tank of the Paper Maker. The slurry was briefly agitated for 10s and water was drained for 10s. The solids were collected in the form of a wet sheet on the TPL supported by the plastic screen. The screen was carefully removed from the bottom of the Paper Maker tank and excess water was removed by running the screen over a vacuum line slot on a smooth table. Finally, the wet sheet with TPL was transferred on a plastic screen, and it was dried for more than 30 mins at 85 °C.

Dry carbon electrode composite comprising graphite fibers, CNS material, and polymer fibers supported on TPL were consolidated by briefly exposing them to heat to soften polymer fibers.

Consolidation was achieved by passing the felt between heated nip rolls, maintained at a fixed gap, of a calendering machine. The diameters of the bottom and top stainless steel rolls were 13” and 8”, respectively. Both rotating rolls were heated at 135°C and had a 20 mil gap between them. The carbon electrode composite were placed between two 3 mil thick Kapton films and manually hand fed through the gap between the nip rolls at a rate of 3 ft/min. The consolidation process provides enough heat to soften the polymer fibers without melting them to cover the graphite fibers that can lead to an increase the resistance.

After calendering, each side of the integrated electrode composite sheet was plasma treated following the protocol as disclosed in Kim, K. J , Kim, Y.-T, Kim, J.-H & Park, M.-S. The effects of modification on carbon felt electrodes for use in vanadium redox flow batteries. Mater. Chem. Phys. 131, 547-553 (2011).

Comparative Example

Comparative example was prepared as the Example 1 except (i) the carbon electrode composite sheet was made on the plastic screen mesh of the Paper Maker without TPL and (ii) the gap between two nips of the calendering machine was set at 16mil. Therefore, in the Comparative Example, the carbon electrode composite did not have TPL integrated on it.

Testing

Scanning Electron Microscope (SEM) Imaging

The scanning electron microscopic images of the sample from Example and Comparative Example prepared as described above were acquired using a Table Top Microscope (received as Model TM3030 from Hitachi High Technologies Corporation). The digital images of both sides of the samples were collected at different magnifications. FIGS. 3A and 3B depict the SEM images of the top surface and bottom surface, respectively, of the Counter Example without the TPL integrated on the carbon electrode composite. FIGS. 3C and 3D depict the SEM images of the top surface and the bottom surface, respectively, of the Example where the TPL was integrated onto the carbon electrode composite. The arrows in FIG. 3D indicate the locations where fibers from the carbon electrode composite are entangled with the TPL.

Tensile Measurement

The improvement in the mechanical strength of the integrated electrode composite was accessed by performing tensile measurement using an Instron instrument (received as Model 5943 from Instron Corporation, Norwood, MA) equipped with a lkN load cell. A dog -bone-shaped sample measuring 12.0cm in length, 2.45cm in width was die cut from the integrated electrode composite. The narrow section of the sample at the center measured 2.45cm in length and 1.5875cm in width. Sample was mounted between two jaws of the Instron instmment that were 5 08cm apart. With the bottom jaw fixed, the sample was stretched by moving the top jaw while applying a constant force of INewton per second on the sample until the sample broke and applied load reached a threshold of 0. IN. The force required to break the sample was recorded as the Maximum Load. The test was repeated with two samples from each example and the average and standard deviation of the mean was calculated. Table 1 below shows the measured Average Maximum Load for both examples.

Short Resistance Test

Electronic short resistance was measured using a fuel cell test stand and a potentiostat. The test fixture used was a 50 cm² active area quad serpentine cell (received from Fuel Cell Technologies, Albuquerque, New Mexico). The fuel cell test stand consists of two mass flow controllers (received from MKS Instruments, Andover, MA) for nitrogen flow control, two HPLC pumps (received from Scientific Systems Inc State College, PA) for humidification control, temperature controller (received from Love Controls, Michigan City, Indiana). The cell under test is assembled in a specific order between two graphite blocks with machined flow fields. For Comparative Example without TPL (i.e. carbon electrode composite) the sequence of cell assembly was: gasket, carbon electrode composite, 20 gsm TPL, subgasket, membrane, subgasket, 20 gsm TPL, gasket, carbon electrode composite. For Comparative Example with TPL, i.e., when a loose TPL layer was used to minimize electronic shorting, the sequence of cell assembly was: gasket, carbon electrode composite, 20 gsm TPL, subgasket, membrane, subgasket, 20 gsm TPL, gasket, carbon electrode composite. For the Example with integrated electrode composite (i.e ., where the carbon electrode composite was formed on TPL, the sequence of cell assembly was: gasket, integrated electrode composite, subgasket, membrane, subgasket, gasket, integrated electrode composite. For the samples with integrated TPL (i.e., Example) the integrated electrode composite was placed between the membrane and the flow field so that the surface that had TPL was in contact with the membrane. Once the stack is built, the cell bolts are tightened in a star pattern to a fixed torque of 110 in.lbs with a torque wrench. The subgaskets are 25 micrometer thick polyethylene naphthalate (PEN) die cut for alignment pins and the 50 cm² active area. The gaskets are a polytetrafluoroethylene (PTFE) glass fiber composite die cut for a 57 cm² opening. The thickness of the gasket is chosen so that its thickness combined with the subgasket thickness provides the desired final thickness of the carbon electrode composite. The membrane used was a 25 micrometer thick 825ew, cast, unsupported PFSA membrane (received from 3M Company, St Paul, MN). The cell was connected to the test stand and the following conditions were set - 1000 seem N₂ per side, 0.4 cc/min water per side and the cell set-point temperature was set at 50 °C. A potentiostat (received as Solaritron 1470 Multistat from Leicester, England) was used to apply a voltage across the electrode and measure the current. The test sequence used was follows: first the cell was maintained at an open circuit voltage (OCV) for 15 minutes, then two loops of a potentiodynamic scan from 0 to 0.25 volts at 5 mV/s followed by five cyclic voltammagrams of 0.25-0.5 volts at 5 mV/s then an OCV step of five minutes were executed. The slope of the plot of voltage (in Volts) vs. current (in amperes) for the cyclic voltammagrams gives the electronic resistance (in W) which was then multiplied by the cell area (in cm²) to give the electronic resistance in W*ah². Samples that have high electronic resistances typically show a hysteresis with sweep direction. With the limited voltage swing and increasing hysteresis, the upper bound of test accuracy was limited at 50 k W*ah²

The results presented below in Table 2 show that the when carbon electrode composite are tested without TPL the electronic resistance is low that is an indication of electronic short across the membrane. When a loose TPL is inserted between the membrane and the carbon electrode composite the electronic resistance is high (i.e., TPL minimizes the electronic shorting). The data also shows that the integrated electrode composite is as efficient in minimizing short resistance as the loose laid TPL inserted between the membrane and carbon electrode composite.

Catholyte Double Half-cell Test

In-house machined flow cells with serpentine channels were used for double half-cell testing. A diagram of the flow cell is shown in FIG. 4 and includes working electrode 32 having a gasket 38, a counter electrode 42 having a gasket 48, and a membrane 52 separating the electrode. The unloaded cell contains several other parts. First, there are two graphite/polymer composite bipolar plates 36 and 46 that contain machined flow channels that allow entry and exit of electrolyte through two machined through holes in the bipolar end plates. Second, there are two gold-plated copper current collectors 34 and 44 that are placed in contact with the bipolar plates 36 and 46. The end plates allow for attachment of the leads of the potentiostat 60 (see FIG. 5) to apply desired potential. Third, a polymeric, electrically-insulating separator 40 and 50 is placed on the outer surface of the current collector. Finally, there are two aluminum end plates 30 and 31 with eight aligned machined holes in each.

Different composite electrode samples were evaluated using a Catholyte Double Half-cell Test following standard test protocol (see e.g., Darling, R. M.; Perry, M. L. J Electrochem Soc. 2014. 161, A1381). In this test, a steel die was used to hand cut electrodes 6.75 cm² in area. These composite electrodes were weighed, their thicknesses were measured, and they were loaded into a flow cell. To assemble the cell, a composite electrode was placed over the serpentine flow field (750 pm wide lands and channels) inscribed into graphite/polymer bipolar plate. One electrode was placed on top of the flow field. A 15 mil Teflon gasket with a 6.75 cm² opening aligned to the composite electrode was then placed around the electrode. For sample from Comparative Example, a 20 gsm TPL (6.75 cm² in area) was placed directly over the carbon electrode composite. A 1 mil Kapton gasket with a smaller 5 cm² opening was then placed over the stacked materials. A supported 3M perfluorosulfonic acid (PFSA) membrane with an equivalent weight of 825 and a thickness of 25 micrometers was used as a separator for the two sides. In reverse order, the same configuration of gaskets, TPLs and carbon electrode composite were stacked on the other side. This cell is symmetric about the membrane separator (see Figure 4 for the final configuration). The cell was then compressed by tightening eight bolts that were threaded into the aluminum endplates using a torque of 110 in-lb. For the test with sample from Example with integrated electrode composite, the 6.75 cm² sample piece was placed over the bipolar plates such that the TPL side of the integrated electrode composite was facing to the membrane while the carbon composite surface was facing toward the channels on the bipolar plates.

A 50% state of charge (SOC) electrolyte catholyte solution was made for this test by flowing a 50:50 mix of vanadium (III) and vanadium (IV) sulfate in sulfuric acid (received from Riverside Specialty Chemical with a vanadium concentration of 1.5 M and a sulfuric acid contraction of 2.6 M) through a carbon paper-loaded flow cell with a 50 micrometers PFSA membrane. The electrolyte was charged to 1.41 V in this separate charging cell. The solution from the working side of the cell, the catholyte, was recovered after charging.

During half-cell test, the 50% SOC catholyte was placed in a glass reservoir and fed into each side of the flow cell using a dual-headed corrosion resistant diaphragm pump (received as NFB 25, KNF Neuberger Inc., Trenton, NJ). The fluid was pumped into the top of each side of the cell and then out at the bottom, using a pump 62 as illustrated in FIG. 5. The two outlet streams recombined in the reservoir, maintaining the state of charge at 50% SOC. Electrolyte flow on both sides of the cell was maintained at roughly 22 mL per minute for the duration of the test.

For the half-cell test, the flow cell was connected to a four-channel Arbin battery tester (received as Model BT-2000 from Arbin Instruments, College Station, TX). The assembled cell was discharged at 50 mV, 100 mV, 150 mV, 200 mV, 250 mV, and 300 mV for 5 minutes each. The cell was then kept at open-circuit voltage for 10 minutes and discharged at 200 mV for 30 minutes, and this process was repeated two more times. This procedure constitutes one cycle of the test. Eighteen cycles were performed and then the cell was charged (polarity reversed for the electrodes) using the same procedure as above for two cycles. A final discharge cycle was performed after the charging cycles. In total, 21 cycles were performed. Upon the completion of the half-cell testing protocols, a potentiostat (received as Model SP-300 BioLogic from Science Instruments, France) with an integrated frequency response analyzer was connected to the test cell. An impedance spectrum was taken while the electrolyte continued to flow through the cell. The spectra were taken in the frequency range from 50 mHz to 20 kHz using a 10 mV signal amplitude. Measurements were taken at open circuit voltage. The high frequency resistance (HFR), which is taken as the X-axis intercept for the impedance spectra taken from the cells provides the sum of all the ohmic resistances in the cell, and varies largely due to the electrode alone, since all other components of the cell are fixed from test to test.

The results of the catholyte double half-cell and the HFR measurements are shown in Table 3 below. These results show that the total cell resistance in catholyte double half cell of the carbon electrode composite tested with lose laid 20gsm TPL (Comparative Example) is similar to that of the integrated electrode composite when the composite electrode is made on 20gsm TPL (Example). The data also shows that the HFR of both the Comparative Example and Example are similar.

The experimental results presented above show (i) integrating TPL during the manufacturing of the electrode composite improves mechanical strength (ii) the integrated TPL prevents electrical shorting to the same extent as the lose laid TPL with same morphology (iii) the catholyte double half-cell performance of integrated electrode composite (i.e. with integrated TPL) is very similar to that of carbon electrode composite when tested with lose laid TPL over it. Carbon electrode composite article with integrated TPL can provide for additional mechanical support to the composite electrode while enabling a low cost streamlined manufacturing path by eliminating the need for laminating the TPL during the manufacturing of MEAs.

Claims

The invention claimed is:

1. A membrane electrode assembly, comprising:

a first non-woven porous integrated electrode composite having a first carbon electrode composite;

a second non-woven porous integrated electrode composite having a second carbon electrode composite;

an ion permeable membrane disposed between the first and second integrated electrode composites;

a first transport protection layer integrated with the first carbon electrode composite; and a second transport protection layer integrated with the second carbon electrode composite.

2. The membrane electrode assembly of claim 1, wherein the first and second transport protection layers each comprises at least one of a mesh structure, a woven structure, and a non-woven structure.

3. The membrane electrode assembly of claim 1, wherein the first and second carbon electrodes each comprises at least one of a carbon fiber based paper, a felt, and a cloth.

4. The membrane electrode assembly of claim 1, wherein the first and second carbon electrodes each comprise a carbon electrode composite on a polymeric web.

5. The membrane electrode assembly of claim 4, wherein the carbon electrode composite comprises electrically conductive graphite particles and electrically conductive carbon nanostructures attached to electrically non-conductive glass fibers.

6. An electrochemical cell comprising a membrane electrode assembly according to claim 1.

7. The membrane electrode assembly of claim 1, wherein the first integrated electrode composite has a thickness in a range from 100 microns to 1000 microns.

8. The membrane electrode assembly of claim 1, wherein the first carbon electrode composite has a thickness in a range from 100 microns to 1000 microns.

9. The membrane electrode assembly of claim 1, wherein the first transport protection layer has a thickness in a range from 50 microns to 500 microns.

10. The membrane electrode assembly of claim 1, wherein the first integrated electrode composite has a carbon particulate in a range from 50 wt% to 98 wt%.

11. The membrane electrode assembly of claim 10, wherein the carbon particulate comprises carbon particulate graphite fibers, graphite particles, carbon nanotubes, carbon nano-structures and mixture thereof

12. The membrane electrode assembly of claim 10, wherein the first integrated electrode composite comprises carbon nanostructures attached to other fibers.

13. The membrane electrode assembly of claim 10, wherein the first integrated electrode composite comprises carbon nanotubes with glass or alumina fibers.

14. The membrane electrode assembly of claim 1, wherein the integrated electrode composite has a porosity in a range from 20% to 95%.

15. The membrane electrode assembly of claim 1, wherein a surface of the carbon electrode composite in contact with the transport protection layer covers between 2% and 50% of a surface of the carbon electrode composite.

16. The membrane electrode assembly of claim 1, wherein a mass per unit area of the transport protection layer is between 2 grams per square meter and 100 grams per square meter.

17. An integrated electrode composite for use with a membrane electrode assembly, comprising: a non-woven porous electrode composed of at least one of a carbon fiber based paper, a felt, and a cloth; and

a transport protection layer composed at least one of a mesh structure, a woven structure, and a non-woven structure,

wherein the porous electrode is integrated with the transport protection layer such that fibers of the carbon electrode composite penetrate into the transport protection layer.

18. The integrated electrode composite of claim 17, wherein the porous electrode comprises a carbon composite on a polymeric web.

19. The integrated electrode composite of claim 18, wherein the carbon composite comprises electrically conductive graphite particles and electrically conductive carbon nanostructures attached to electrically non-conductive glass fibers.

20. A method of making an integrated electrode composite for use with a membrane electrode assembly, comprising steps of:

blending together water, carbon particles, and polymer particles by disbursing carbon fibers and polymer fibers in water to form a carbon electrode composite slurry in water;

depositing the carbon electrode composite slurry onto a porous transport protection layer supported onto a screen below the transport protection layer to form a wet integrated electrode composite article with an uncured blend;

removing water from the wet integrated electrode composite article through an application of vacuum to the wet integrated electrode composite article with the uncured blend;

drying the wet integrated electrode composite article by exposing the wet integrated electrode composite article to thermal energy; and

thermally curing the uncured blend through calendering of the integrated electrode composite article.