WO2004076079A1

WO2004076079A1 - Electrostatic processing of electrochemical device components

Info

Publication number: WO2004076079A1
Application number: PCT/US2004/005243
Authority: WO
Inventors: Gary Wnek; Elliot H. Sanders; Jon A. Regrut; Joshua J. Bennet; Terence Latham; Karen Mcgrady; Douglas W. Bates; David Sopchak
Original assignee: Virginia Commonwealth University
Priority date: 2003-02-21
Filing date: 2004-02-20
Publication date: 2004-09-10

Abstract

An electrochemical device includes electrodes and/or backing layers made from electrosprayed polymer droplets. By using the electroprocessing technique, the various chemical and electrochemical performance parameters of the electrode layer adjacent an electrolyte layer may be modified and perfected.

Description

ELECTROSTATIC PROCESSING OF ELECTROCHEMICAL DEVICE COMPONENTS

This application claims the benefit of the filing of United States Application No. 60/448,819 filed February 21, 2003.

The present invention relates to electrochemical devices that incorporate one or more polymer-based components. Fabrication of the polymer-based component(s) through the use of electrostatic processing may enhance the operation and performance of the component(s) and the overall electrochemical device.

Background of the Invention

A broad range of electrochemical devices including, without limitation, batteries, fuel cells, electrolyzers, electrochemical reactors, electrolytic capacitors, organic solar cells, electrochromic displays, and organic light- emitting displays, have as their main component the fundamental electrode /electrolyte /electrode sandwich construction. These layers, laminated together, provide the electrochemical basis for the operation of the given device. Polymer matrices in the form of films or membranes are frequently used as a solid structure that may serve as an electrode or electrolyte. These polymer matrices may also be simply a structure into which an electrolytic or other conductive material is impregnated to serve the electrochemical needs of the larger device. These polymer matrices are typically attached by way of lamination to other layers of the electrochemical device structure. The quality of the layer interface between one or more layers in the electrochemical device is particularly important for good device performance. For instance, adhesion of the layers and low electrical resistance across the interfaces are desirable and necessary for acceptable performance of the device.

One particular type of electrochemical device that is of significant interest is polymer electrolyte fuel cells (PEFC). As a result of low operating temperatures, high power density, and efficient energy conversion, PEFCs are attractive for applications such as fuel cell powered vehicles, power generation facilities, and as replacements for batteries. The requirements for use for this technology include low cost, high performance, and performance reliability.

A complete PEFC membrane electrode assembly has an arrangement from the center out of an ionomeric membrane, catalyst layer, and hydrophobic/ conductive backing. Gas (fuel) access to the electrodes is important, and this is typically facilitated by the presence of porous gas diffusion layers on top of each of the electrodes. A quality of the electrode /electrolyte interface (e.g., adhesion of components in low electrical resistance across interfaces) is particularly important ψ good fuel cell performance. It is also desirable to be able to control, at will, the composition, porosity, and wettability of materials deposited. Figure 1

illustrates a basic fuel cell construction.

Modern batteries are another type of electrochemical device that incorporates a polymer layer. For instance, in lithium batteries a porous polymer electrolytic membrane is frequently employed. In the current state- of-the-art technology, poly(vinylidene fluoride) or PVDF membranes are made porous by incorporating plasticiser with subsequent removal (the so- called Bellcore technique) - this technique suffers from high cost and is cumbersome, thereby limiting the usefulness of lithium devices with PVDF electrolytes. A process that can reduce this inefficiency is greatly desired. The prerequisites for replacing the current processing technique include increased adhesion integrity between electrolyte and electrode, minimal interface resistance and easier and less costly fabrication. Moreover, there is a need to improve the adhesion between lithium ion- conducting electrolytes and attendant electrodes, and to control the composition and thickness of materials that serve to passivate the electrodes and extend battery life and the number of charge-discharge cycles.

Summary of the Invention Accordingly, it is an object of the present invention to overcome the foregoing drawbacks and limitations. Electrostatic processing of polymers to manufacture one or more of the electrochemical device components allows for substantial control over the physical make up and performance of the component and, accordingly, the overall device. The scope of electrostatic processing includes electro spraying (generation of either wet or dry droplets) and electro spinning (generation of fibers), as well as a combination of the two in the transition range between electro spraying and electrospinning. Brief Description of the Drawings

Figure 1 is a schematic demonstrating a hydrogen-air polymer electrolyte fuel cell.

Figures 2A and 2B are schematic diagrams demonstrating apparatuses for forming electrospun fibers and electrosprayed droplets respectively.

Figure 3 is a diagram of a two-axis, computer-controlled stage.

Figure 4 is a graph demonstrating ionic conductivity measurements versus water content for electrosprayed nafion and commercial nafion 117.

Figure 5 is a scanning electron micrograph of an electroprocessed electrode on a cast electrolyte at a magnification of 220 times.

Figure 6 is a schematic of an organic light- emitting display.

Detailed Description Electrostatic processing of polymers may be used to manufacture or modify one or more components in an electrochemical device. In other words, the various components of an electrochemical device may be formed from the electrostatic processing of polymer (or polymer based) droplets and/ or fibers. Alternatively, one or more components in electrochemical device may be coated with electrostatically processed polymer (or polymer based) droplets and/ or fibers, and an entire electrochemical device may be coated or packaged using electrostatic processing to, for example, protect the device from exposure to air and/ or moisture. An entire electrochemical device may be manufactured effectively completely from electrostatically processed polymer, or as little as one component of the electrochemical device may be formed or treated by electrostatic processing of a polymer.

A. Electrostatic Processing

Electrostatic processing includes electrospraying (generation of droplets) and electrospinning (generation of fibers). Electrospraying of polymer (or polymer based) solutions, suspensions or melts is typically accomplished by applying a strong electric field (ca. 1-5 kV/cm) to a polymer solution or suspension. By providing a small pressure at one end of a fluid reservoir and a small orifice at the other, a fine jet can be generated when the solution is charged beyond the Rayleigh limit. This thin, unsupported liquid column will break up into small droplets due to a Rayleigh instability. The resulting droplets are charged and, as solvent evaporates, droplet diameter decreases and increasing charge repulsions lead to fragmentation into smaller droplets. The resulting droplet diameters can be quite small, frequently in the sub-micron regime. The charged droplets can be collected and, depending upon the solvent evaporation rate, dry particles or wet droplets can be deposited onto a grounded target. Electrospraying of a solution of Nafion in alcohols is an example of the latter, and leads to the deposition of free-standing films achieved by coalescence of wet droplets. Hence, proton exchange membranes can be directly deposited by this approach. Electrospraying of solutions, suspensions or melts is anticipated to facilitate bonding of the sprayed layer to a film on the target (e.g., catalyst on proton exchange membrane), affording good molecular adhesion at this critical interface. The phrase 'Nafion solution' is used broadly, as such solutions are believed to contain multi-chain aggregates rather than truly dissolved polymer chains . Polymer solutions, if sufficiently concentrated to afford significant intermolecular entanglements that stabilize the jet, can be processed into fine fibers (electrospinning). See Figures 2A and 2B showing equipment and schematic examples of electrospinning and electrospraying respectively. In either case, the droplet or fiber diameters can be quite small, frequently in the sub-micron regime.

The electrospraying technique may have multiple functions. For example, electrospraying of 'wet' polymer/ solvent droplets can in some instances lead to coalescence into a film on the grounded target. The polymer/ solvent ratio required for a "wet" deposition is highly dependent on the choice of both polymer and solvent. In general, the electrostatic process involves desolvation to a significant extent unless the solvent/ polymer interactions are particularly strong (i.e, a good solvent - A₂, the second virial coefficient is » 0) and/ or the solvent has a high boiling point. Consequently high boiling good solvents will favor Svet' polymer coalescence. The film thickness is controlled by limiting the polymer solution flow- rate and/ or the spraying time, but they can be thin - - in the range of less than one micron to several hundred microns. Film porosity may be similarly controlled through the addition of either low boiling or high boiling 'poor' or theta solvents (where poor solvents have A₂ « 0 and theta solvents have A₂ = 0). In addition, electrospraying with either rapid solvent evaporation and/ or precipitation of particles (in, for example, a coagulating bath) can afford small particles useful as electro-catalysts, catalyst supports, binders for sintering of electrode and/ or electrolyte layers, and the like. Some preferred solvents used in rapid solvent evaporation processes include dichlorome thane, acetone and chloroform. The particles that can be precipitated include polymer beads having diameters from about 20-800 microns or fibers having a width of from about 0.5-60 microns. Examples of coagulating baths to form particles include sodium alginate droplets from a 0.2 M CaCl₂ bath, and poly(ethylene-co-vinyl acetate) fibers from a water bath.

Electro-catalysts formed from the electrospraying technique include Nafion, sulfonated polystyrenes or PVDF, any of which are blended with carbon and/ or platinum/ carbon and/ or other catalyst particles. Also,

electrostatic deposition can be carried out in the presence of uv-vis light to facilitate chemical reactions during, or just after, deposition. An example is the preparation of a photo-crosslinkable polymer electrolyte or electrode binder. It may also be possible to entrap various molecules (e.g., enzymes) or objects (e.g., biological cells) within electrosprayed or electrospun materials that might be of interest in, for example, a bio-fuel cell. A discussion of bio-fuel cells is set forth in the following article which is incorporated herein by reference. Wilkinson, S.'"Gastrobots' - Benefits and Challenges of Microbrial Fuel Cells in Food Powered Robot Applications"

Autonoumous Robots 2000 , 9, 99-111.

Other articles that discuss electrostatic processing in various applications include the following, each of which is incorporated herein by reference as if set forth in its entirety:

E. H. Sanders, et al., "Characterization of Electrosprayed Nafion Films," Journal of Power Sources, in press (2004).

J. D. Stitzel, G. L. Bowlin, K. Mansfield, G. E. Wnek and D. G. Simpson, "Electrospraying and Electrospinning of Polymers for Biomedical Applications. Poly(Lactic-co-Glycolic Acid) and Poly(Ethylene-co-Vinyl Acetate)," Proc. of the 32nd Annual SAMPE Meeting, pp. 205-211, November 2000.

J. D. Stitzel, K. Pawlowski, G. E. Wnek, D. G. Simpson and G. L. Bowlin, "Arterial Smooth Muscle Cell Proliferation on a Novel Biomimicking, Biodegradable Vascular Graft Scaffold," J. Biomaterials Applications, 15, 1- 12 (2001).

E. D. Boland, G. E. Wnek, D. G. Simpson, K. J. Pawlowski and G. L Bowlin, "Tailoring Tissue Engineering Scaffolds by Employing Electrostatic Processing Techniques: A Study of Poly (Glycolic Acid)," J. Macromol. Set, 38: 1231-43 (2001)

J. A. Matthews, G. E. Wnek, D. G. Simpson and G. L. Bowlin, "Electrospinning of Collagen Nanofibers," Biomacromolecules, 3, 232-238 (2002)

E. R. Kenawy, G. L. Bowlin, K. Mansfield, J. Layman, D. G. Simpson, E. Sanders and G. E. Wnek, "Release of Tetracycline Hydrochloride from Electrospun Poly(Ethylene-co-Vinyl Acetate), Poly(l- Lactic Acid), and a Blend," J. Contr. Release, 81(1,2), 57-64 (2002)

G. L. Bowlin, K. J.. Pawlowski, E. Boland, D. G. Simpson, J. B. Fenn, G. E. Wnek and J. D. Stitzel, "Electrospinning of Polymer Scaffolds for Tissue Engineering," in Tissue Engineering and Biodegradable Equivalents: Scientific and Clinical Applications, K. Lewandrowsky, D. J. Trantolo, J. D. Gresser, M. J. Yaszemski, D. E. Altobelli and D. L. Wise, Editors, Marcel Dekker, Ch. 9, pp. 165-178 (2002)

E.-R. Kenawy, J. M. Layman, J. R. Watkins, G. L. Bowlin, J. A. Matthews, D. G. Simpson and G. E. Wnek, "Electrospinning of Poly(Ethylene-co-Vinyl Alcohol) Fibers," Biomaterials, 24, 907-913 (2003) G. E. Wnek, M. E. Carr, D. G. Simpson and G. L. Bowlin, "Electrospinning of Nanofiber Fibrinogen Structures," Nano Letters, 3, 213-216 (2003)

E. H. Sanders et al., "Two-Phase Electrospinning from a Single Electrified Jet: Microencapsulation of Aqueous Reservoirs in Poly (Ethylene-co-vinyl Acetate) Fibers," Macromolecules, 36, 3803 (2003)

L. Yao et al., "Electrospinning and Stablization of Fully Hydrolyzed Poly (vinyl alcohol) Fibers," Chem. Mater, 15, 1860 (2003)

Electrochemical Devices

The present invention is directed to electrochemical devices having as there basic functional component the electrode/ electrolyte/ electrode sandwich. These devices include batteries, fuel cells, electrolyzers, electrochemical reactors, electrolytic capacitors, organic solar cells, electrochromic displays, and organic light-emitting displays. Of course, other types of electrochemical devices incorporating the electrode /electrolyte /electrode sandwich feature would benefit from the electrostatic processing described herein.

At the center of any electrochemical device, there is the electrolyte layer. The electrolyte layer provides selective conductivity by allowing ions to move across its width. This layer is selective in that it is effectively impermeable to electrons, and it may allow one type of ion (e.g., cation or anion) to pass through more readily than the other. The electrolyte may itself be a polymer . Examples include Nafion fiuorinated ionomer for fuel cells and alkali metal salt-doped polyethers for Li batteries. Alternatively, the polymer may be mixed with or impregnated with an electrolytic solution that allows for the selective movement of ions across its width, such as propylene carbonate-poly (acrylontrile) gels containing various salts.

Electrodes (catalyst layers) are sandwiched onto either side of the electrolyte layer. On one side of the electrolyte there is the anode electrode. In a fuel cell, for example, this electrode is the oxidation side where protons (positive ions) and electrons (negative ions) are separated. Typically, the anode will include a catalyst to facilitate the breakup of molecules and creation of the positively and negatively charged ions. On the other side of the electrolyte layer is the cathode electrode. In chemical terms, this electrode is the reduction side of the electrolyte. The cathode combines the positively charged and negatively charged particles to form molecules. Once again, this chemical combination is typically facilitated through the incorporation of a catalyst. To be efficient, both of the electrodes require high surface areas in their structure. They also require substantial porosity. In some types of electrochemical devices, backing layers (also referred to as gas diffusion layers or current collectors) are laminated onto the outside of the cathode and anode layers. This backing layer is also necessarily conductive and may be porous.

Specific discussions of the present invention in connection with various types of electrochemical devices are examples of the present invention. At least some of the benefits and processing variations available as a result of electrostatic processing are noted herein. B. Fuel Cells

A broad discussion of various types of fuel cells and the present state of the art is found in a government brochure entitled Fuel Cells-Green Power, Sharon Thomas, et al, published by the Los Alamos National Laboratory, publication number LA-UR-99-3231. That brochure is incorporated by reference herein as if set forth in its entirety.

The state of the art with respect to fuel cell construction is to start with a sheet of carbon paper backing which offers conductivity without reactivity, impregnate it with a hydrophobic polymer, such as poly(tetrafluoroethylene) or PTFE with or without carbon; add a layer of Pt/C loaded ionomer solution onto this backing (by coating or lamination); then thermally bond the composite backing layer to either side of a commercially prepared film of ionomeric material, such as Nafion.

Each of the components of the PEFC (the electrolyte, electrodes and backing layers) can be created through the use of electrostatic processing (electrospinning and electrospraying) methods. Creation of the PEFC components using electrostatic processing methods allows control of material deposition, and can therefore be used to reduce material costs, particularly in the case of the catalyst layer, where the cost of the platinum is a significant barrier to fuel cell cost competitiveness as compared to other technologies.

It has also been demonstrated that adhesion between the component layers as a result of electrostatic processing is excellent. Previous designs have been subject to delamination of the component layers, resulting in failure. Electrostatic methods therefore could lead to better performance ■

reliability.

Additional advantages can be realized by progressively varying the construction of tailored layers of materials with designed properties. As an example, consider the membrane-electrode assemblies (MEA) with gas diffusion layers shown, for example, in Fig. 1. The polymer electrolyte membrane may be deposited by electrospraying a solution of Nafion (a perfluorinated polymer with sulfonic acid groups that is the prototypical proton conducting membrane; it is soluble in lower alcohols.)

A catalyst or electrode layer (typically including platinum supported on carbon black) can be electrosprayed with some Nafion in solution to provide protons for the oxygen reduction reaction, to act as a binder for the particles and to impart ionic conductivity in the catalyst (or electrode) layer. It may be deposited on an electroprocessed electrolyte membrane prepared as noted above, or on a free-standing electrolyte substrate obtained elsewhere. It may be desirable to grade the concentration of the catalyst within the electrode, with, more Pt proximate the Nafion membrane (electrolyte) interface. In other words, the concentration of catalyst (e.g., Pt on carbon black) will increase in the electrode (catalyst) layer in relation to its thickness when closer to the electrolyte layer. Stated conversely, in the context of the thickness of the electrode (catalyst layer), the concentration of catalyst decreases as the distance from the electrolyte layer interface increases. This may be done by changing the composition of the fluid in the electrospray jet during the electroprocessing and/or by using another jet or jets having different compositions that may be used during at least a portion of the electroprocessing. It may also be desirable to alter the porosity of the electrode layer in a direction perpendicular to the electrode area, and this could be accomplished by changing the polymer composition to favor electrospinning of fibers. In other words, the degree of porosity of the electrode (catalyst) layer may increase in the thickness of the layer as the distance from the electrolyte layer interface increases. It may be further desirable to alter or grade the wettability of the layer, becoming progressively more hydrophobic as one moves away from the electrolyte membrane, perhaps by co-depositing Teflon particles. (This could mitigate water pooling at the cathode /electrolyte interface that could block oxygen access.) This could be accomplished by, for example, progressively adding some Teflon powder to the mixture as the layer builds during electroprocessing.

The gas diffusion layer (backing layer) may be formed directly onto the catalyst layer by electro-processing. Control of porosity and hydrophobicity can be achieved by tailoring the solution composition as described above. It is also possible to electrostatically deposit selected materials using melts rather than solutions. Mixtures/ suspensions of solutions and melts may also be used.

It is expected that control of the processes could lead to better performing and more cost efficient PEFCs. Experiment 1

A solution of 5% wt. Nafion (Sigma) was electrosprayed from a syringe using a blunted needle and an applied voltage of 20kV. The solution was deposited onto a Teflon coated rotating mandrel which remained grounded at all times. A film with an average cross section of approximately 60 microns was removed from the mandrel.

A solution of 2.5% wt. Nafion solution was prepared and 20% loaded Pt/C particles were added to the solution. The composite solution was then sonicated for 30 minutes to disperse the particles. The resulting solution was then electrosprayed onto a flat piece of Nafion 117 (Dupont) film from a syringe and using a blunted needle, 20kV applied voltage, and a tip to target distance of 5 cm. Both sides of the film were coated with a 5cm square area.

A custom two-axis computer controlled stage was developed to position the target during electrospraying. The stage had a total working area of 250 cm by 250 cm, and the motor controllers were designed to use HPGL for simple programming input. See Figure 3 showing a diagram of the stage

apparatus.

Results Ionic conductivity measurements were made on the electrosprayed Nafion films and commercial Nafion 117. The properties of the sprayed film were nearly equivalent to those obtained form commercially availably Nafion 117 film. See Figure 4. Conductance measurements suggested an optimal loading range that provided good conductivity in the catalyst/ electrode layer. Too high of loading resulted in material that did not have desirable mechanical stability.

Samples of the MEA with electrosprayed catalyst layer were freeze fractured after submerging in liquid nitrogen. Scanning electron micrographs showed excellent adhesion between the Nafion 117 film and the catalyst layer, with no discernable line of demarcation between the two layers. In addition, the micrographs revealed a complex geometry of the catalyst layer in which the effective surface of the catalyst layer is increased. Handling of the MEAs shows excellent mechanical stability, with no apparent delaminating of the catalyst layer.

C. Batteries

Another preferred embodiment of the current invention involves the electroprocessing of poly(vinylidene fluoride) or PVDF, which by controlling the solution properties (either by wt % PVDF or solvent composition - ratio of acetone /methylethyl ketone (MEK) to dimethylformamide (DMF)) can be selectively spun or sprayed to yield non-woven fibrous mats or porous sprayed films.

Experiment II

In a typical experiment, a solution of 10 wt % PVDF (M_w ~ 180 kDa) in acetone/ dmf solvent mixtures (0/ 100, 25/75, 50/50, 75/25 and 100/0 solvent wt %s, respectively) were electroprocessed by applying an electric potential of between 10-25 kV over a distance of 10-25 cm. The choice of solvent ratio has a large impact on the type of material produced - again, in the case of PVDF, high boiling good solvents such as dmf favor vet' drops and low boiling theta solvents such as acetone favor fiber formation. In this example, the electroprocessed polymer solutions went from Vet' films (0/ 100 acetone/ dmf) to a mixture of drops with small fibers (50/50 acetone/ dmf) to a non-woven fibrous mat (100/0 acetone /dmf). Alternative methods for inducing this change from drops to fibers can be achieved by varying the wt % of PVDF (lower wt %s favor drops/films and higher wt %s favor fibers/mats). For instance in dmf solutions, below ~20 wt % PVDF, the drops/ films are formed and fiberrous mats are generated above 25 wt %. In addition, these threshhold values should be affected by the size of the polymer (larger M_w will tend to spin fibers at lower wt %s since chain entanglements should increase) . The range of solutions and their concommittant impact on the polymer morphology allows one to envision conditions that optimize the porosity of the sprayed films by controlling the good-to-theta solvent ratio, the wt % of PVDF and the size of PVDF. The SEM image (Figure 5) indicates pores on the scale of 1 micron. This pore size and frequency should be alterable by judicious solvent and PVDF concentrations. The selection of PVDF for these illustrative purposes is by intention as this material is commonly used in batteries as binder and 'gel-electrolyte'.

As an example, consider an electrode/ electrolyte/ electrode sandwich with application to Li battery technology. The electrolyte membrane must transport Li ions and be inert toward electrochemical reactions at the electrodes. A common electrolyte is the so-called 'gel' system, wherein a porous polymer matrix is infiltrated with a low viscosity electrolyte (e.g., propylene carbonate) and a salt (e.g., LiPF₆). The anode is either Li metal or, more commonly today, Li-doped carbon. The cathode is frequently a transition metal oxide such as vanadium oxide or a mixed oxide. Electrostatic deposition of each of these layers is feasible. For example, Li- doped carbon and transition metal oxide particles, with an electrolyte binder, can be deposited on a porous polymer support (such as poly(vinylidene fluoride) from which plasticizer has been extracted to create pores) . After the sandwich is prepared, infiltration of the porous membrane with liquid electrolyte can be achieved. An advantage of electrostatic deposition over more conventional lamination is that high temperatures needed for lamination, which sometimes can degrade thermally sensitive materials, can be avoided. Electrospinning may be a useful means to prepare the porous electrolyte support. Also, electrostatic deposition can be carried in the presence of uv-vis light to facilitate chemical reactions during, or just after, deposition. An example is the preparation of a photo-crosslinkable polymer electrolyte or electrode binder, such as an acrylic-modified polyether containing salts to impart ionic conductivity.

D. Organic Light Emitting Displays

Electrostatic deposition can also be applied to the fabrication of flexible, organic light-emitting displays. A schematic is shown in Fig. 6. Conventional devices actually have more layers than the three shown to assist in carrier generation and transport at the electrodes. Flexible devices are being prepared using tin-doped indium oxide on plastic as the anode, with component layers deposited by spin coating. Electrospraying of each layer is conceivable, with an advantage being uniform deposition and good adhesion to the underlying layer. A similar structure 'in reverse' can be used as a photovoltaic device-, wherein absorbed light is used to generate electricity. Here, materials with bipolar (n and p) transport capability can assist in the dissociation of excitons (bound electron-hole pairs). Multi- component organic materials may meet these needs by providing multiple absorption pathways and high interfacial areas between electron and hole transport regions that can provide a mechanism for exciton dissociation. Such multi-component materials containing, for example, various sustituted poly(phenylene vinylene) materials, poly(fluorenes) and the like, may be deposited electrostatically.

While the invention has been described with reference to specific embodiments thereof, it will understood that numerous variations, modifications and additional embodiments are possible, and accordingly, all

such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A method of forming an electrochemical device comprising the steps of: providing an electrolyte layer substrate; electrospraying a first polymer electrode layer onto at least one side of the electrolyte layer.

2. A method as described in claim 1, further comprising the step of electrospraying a second polymer electrode layer onto the side of the electrolyte layer opposite the first polymer electrode layer.

3. A method as described in claim 1, wherein the first polymer electrode layer comprises a catalyst comprising platinum.

4. A method as described in claim 1 , wherein the first polymer electrode layer comprises a perfluorinated polymer with sulfonic acid groups.

5. A method as described in claim 1, wherein the first polymer electrode layer is a cathode layer.

6. A method as described in claim 1, wherein the first polymer electrode layer is an anode layer.

7. A method as described in claim 1, further comprising the step of electrospinning a first, polymer backing layer onto the opposite side of the first polymer electrode layer from the electrolyte layer.

8. A method as described in claim 1, wherein the first polymer electrode layer comprises a catalyst, and wherein the concentration of catalyst in the first polymer electrode layer decreases as the distance from the electrolyte layer interface increases.

9. A method as described in claim 1, wherein the porosity of the first polymer electrode layer increases as the distance from the electrolyte layer interface increases.

10. An electrochemical device comprising an electrode layer of electrosprayed polymer droplets.

11. An electrochemical device as described in claim 10, wherein the electrode layer is a cathode.

12. An electrochemical device as described in claim 10, wherein the electrode layer is an anode.

13. An electrochemical device as described in claim 10, wherein the electrode layer comprises a catalyst comprising platinum.

14. An electrochemical device as described in claim 10, wherein the electrode layer comprises a perfluorinated polymer with sulfonic acid groups.

15. An electrochemical device comprising an electrolyte layer between two electrode layers, wherein each of the electrode layers comprises electrosprayed polymer droplets.

16. The product of the process described in claim 1.

17. The product of the process described in claim 2.