Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
BIPOLAR PLATE WITH FORCE CONCENTRATOR PATTERN
Document Type and Number:
WIPO Patent Application WO/2017/053278
Kind Code:
A1
Abstract:
Embodiments of present disclosure are directed to a bipolar plate assembly. The bipolar plate assembly has a frame and a base. At least one of the frame and the base has a shape of a force concentrator pattern or has a first surface having a force concentrator pattern, the force concentrator pattern including a raised surface extending partially across the first surface. A surface area of the force concentrator pattern across the length of the frame or base is generally constant, thereby producing a uniform compressive pressure along the length of the frame or base when the bipolar plate assembly is under compression.

Inventors:
VAN BOEYEN, Roger (80 Tadmuck Road, Westford, MA, 01886, US)
Application Number:
US2016/052634
Publication Date:
March 30, 2017
Filing Date:
September 20, 2016
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
NUVERA FUEL CELLS, LLC (129 Concord Road, Building 1Billerica, MA, 01821, US)
International Classes:
H01M8/1004; C25B9/06; C25B9/08; H01M8/0247; H01M8/0273; H01M8/0284; H01M14/00
Domestic Patent References:
WO2013012343A22013-01-24
Foreign References:
US20120107713A12012-05-03
US20130065105A12013-03-14
US20140027272A12014-01-30
Other References:
None
Attorney, Agent or Firm:
CHAPMAN, Ernest, F. et al. (Finnegan, Henderson Farabow, Garrett & Dunner, LLP,901 New York Avenue, N.W, Washington DC, 20001-4413, US)
Download PDF:
Claims:
WHAT IS CLAIMED IS:

1. A bipolar plate assembly, comprising:

a frame and a base, at least one of the frame and the base having a shape of a force concentrator pattern or having a first surface comprising a force concentrator pattern, the force concentrator pattern comprising a raised surface extending partially across the first surface;

wherein a surface area of the force concentrator pattern across the length of the frame or the base is generally constant, thereby producing a uniform compressive pressure along the length of the frame and/or the base when the bipolar plate assembly is under compression.

2. The bipolar plate assembly of claim 1 , wherein the surface area of the force concentrator pattern across the length of the frame or the base ranges from between about 2 cm2/cm to about 10 cm2/cm.

3. The bipolar plate assembly of claim 1 , further comprising at least one seal assembly between the frame and the base.

4. The bipolar plate assembly of claim 3, wherein the seal assembly is an elastomer seal or a polymeric seal.

5. The bipolar plate assembly of claim 3, wherein the compressive pressure on the seal assembly is generally evenly distributed across the seal assembly when the bipolar plate assembly is under compression.

6. The bipolar plate assembly of claim 1 , wherein the frame and the base are two pieces coupled together or are one integrated part.

-

7. The bipolar plate assembly of claim 6, wherein at least one of the frame and the base is laminated with a polymeric material or coated with a polymeric film on a top surface and/or a bottom surface.

8. The bipolar plate assembly of claim 7, wherein the compressive pressure on the polymeric material or the polymeric film is generally evenly distributed across the frame and/or the base when the bipolar plate assembly is under compression.

9. The bipolar plate assembly of claim 2, wherein the bipolar plate assembly is at least one of a plurality of bipolar plate assemblies forming an electrochemical stack.

10. The bipolar plate assembly of claim 2, wherein the compressive pressure ranges from 5,000 psig to 40,000 psig.

11. The bipolar plate assembly of claim 2, wherein the force concentrator pattern has a thickness ranging from 0.025 mm to a thickness of the frame and/or the base.

12. The bipolar plate assembly of claim 2, wherein at least one of the frame and the base has a second surface comprising the force concentrator pattern.

13. A method of assembling a bipolar plate assembly, comprising:

compressing a frame and a base of the bipolar plate assembly, at least one of the frame and the base having a shape of a force concentrator pattern or having a first surface comprising a force concentrator pattern, the force concentrator pattern comprising a raised surface extending partially across the first surface, wherein a surface area of the force concentrator pattern across the length of the frame or the base is generally constant, thereby producing a uniform compressive pressure along the length of the frame and/or the base when the bipolar plate assembly is under compression.

-

14. The method of claim 13, wherein the surface area of the force concentrator pattern across the length of the frame or the base ranges from between about

2 cm2/cm to about 10 cm2/cm.

15. The method of claim 13, wherein the bipolar plate assembly comprises at least one seal assembly between the frame and the base.

16. The method of claim 15, wherein the seal assembly is an elastomer seal or a polymeric seal.

17. The method of claim 15, wherein the compressive pressure on the seal assembly is generally evenly distributed across the seal assembly when the bipolar plate assembly is under compression.

18. The method of claim 15, wherein the compressive pressure on the seal assembly is greater than the yield strength of the material of the seal assembly,

19. The method of claim 13, wherein the frame and the base are two pieces coupled together or are one integrated part;

wherein at least one of the frame and the base is laminated with a polymeric material or coated with a polymeric film on a top surface and/or a bottom surface; and

wherein the compressive pressure on the polymeric material or the polymeric film is generally evenly distributed across the frame and/or the base when the bipolar plate assembly is under compression.

An electrochemical cell comprising;

- a pair of bipolar plate assemblies and a membrane electrode assembly located between the pair of bipolar plate assemblies, wherein at least one of the bipolar plate assembly comprises:

a frame and a base, at least one of the frame and the base having a shape of a force concentrator pattern or having a first surface comprising a force concentrator pattern, the force concentrator pattern comprising a raised surface extending partially across the first surface, wherein a surface area of the force concentrator pattern across the length of the frame or the base is generally constant thereby producing a uniform compressive pressure along the length of the frame and/or base when the bipolar plate assembly is under compression.

-

Description:
BIPOLAR PLATE WITH FORCE CONCENTRATOR PATTERN

[001] This application claims the benefit of U.S. Provisional Application No. 62/221,276, filed September 21, 2015, which is incorporated by reference in its entirety.

[002] The present disclosure is directed towards a bipolar plate, and more particularly, a bipolar plate having a force concentrator pattern.

[003] Electrochemical cells, usually classified as fuel cells or electrolysis cells, are devices used for generating current from chemical reactions, or inducing a chemical reaction using a flow of current. A fuel cell converts the chemical energy of a fuel (e.g., hydrogen, natural gas, methanol, gasoline, etc.) and an oxidant (air or oxygen) into electricity and waste products of heat and water. A basic fuel cell comprises a negatively charged anode, a positively charged cathode, and an ion- conducting material called an electrolyte.

[004] Different fuel cell technologies utilize different electrolyte materials. A Proton Exchange Membrane (PEM) fuel cell, for example, utilizes a polymeric ion- conducting membrane as the electrolyte. In a hydrogen PEM fuel cell, hydrogen atoms may electrochemically split into electrons and protons (hydrogen ions) at the anode. The electrons flow through the circuit to the cathode and generate electricity, while the protons diffuse through the electrolyte membrane to the cathode. At the cathode, hydrogen protons may react with electrons and oxygen (supplied to the cathode) to produce water and heat.

[005] An electrolysis cell represents a fuel cell operated in reverse. A basic electrolysis cell may function as a hydrogen generator by decomposing water into hydrogen and oxygen gases when an external electric potential is applied. The basic technology of a hydrogen fuel cell or an electrolysis cell may be applied to electrochemical hydrogen manipulation, such as, electrochemical hydrogen compression, purification, or expansion.

[006] An electrochemical hydrogen compressor (EHC), for example, may be used to selectively transfer hydrogen from one side of a cell to another. An EHC may include a proton exchange membrane sandwiched between a first electrode (i.e., an anode) and a second electrode (i.e., a cathode). A gas containing hydrogen may contact the first electrode and an electric potential difference may be applied between the first and second electrodes. At the first electrode, the hydrogen molecules may be oxidized and the reaction may produce two electrons and two protons. The two protons are electrochemically driven through the membrane to the second electrode of the cell, where they are rejoined by two rerouted electrons and reduced to form a hydrogen molecule. The reactions taking place at the first electrode and second electrode may be expressed as chemical equations, as shown below.

[007] EHCs operating in this manner are sometimes referred to as hydrogen pumps. When the hydrogen accumulated at the second electrode is restricted to a confined space, the electrochemical cell compresses the hydrogen or raises the pressure. The maximum pressure or flow rate an individual cell is capable of producing may be limited based on the cell design. To achieve greater compression or higher pressure, multiple cells may be linked in series to form a multi-stage EHC. In a multi-stage EHC the gas flow path, for example, may be configured so the compressed output gas of the first cell may be the input gas of the second cell.

Alternatively, single-stage cells may be linked in parallel to increase the throughput capacity (i.e., total gas flow rate) of an EHC. In both a single-stage and multi-stage EHC, the cells may be stacked and each cell may include a cathode, an electrolyte membrane, and an anode. Each cathode/membrane/anode assembly constitutes a "membrane electrode assembly", or "MEA," which is typically supported on both sides by bipolar plates.

[008] The bipolar plates may provide mechanical support to the EHCs, and may physically separate individual cells in a stack while electrically connecting them. The bipolar plates may also provide high pressure zones, where the reactant or the fuel, for example, hydrogen, accumulates. In addition, the bipolar plates may also act as current collectors/conductors, and may provide passages for the reactant or the fuel. Typically, bipolar plates are made from metals, for example, stainless steel, titanium, etc., and from non-metallic electrical conductors, for example, graphite.

[009] Hydrogen compressors or hydrogen pumps typically have hydrogen accumulated at the second electrode restricted to the high pressure zone formed by the bipolar plates. In addition, the pressure of the high pressure zone may increase as more and more hydrogen is formed and accumulated. To reduce the potential of hydrogen leaks and improve safety and energy efficiency, the high pressure zone may be sealed by one or more seals between the bipolar plates. A compressive load may be applied to the bipolar plates of an EHC or an EHC stack to compress the seals and create sealing of the high pressure zone. The seals may include ring- shaped seals extending around the circumference of the high pressure zone and/or may include a polymeric film coated or laminated on the surface of one or more of the bipolar plates.

[010] Sufficient and generally even compressive pressure needs to be applied to the seal between the bipolar plates. A minimum compressive pressure applied may be greater than the yield strength of the material of the seal such that the material of the seal may deform and thereby create a sealing surface. In some embodiments, the minimum compressive pressure may be below the yield strength of the material. If the compressive pressure is not generally even or non-uniform across the sealing surface, the minimum compressive pressure may not be applied to some areas on the sealing surface, which may result in leaking of the reactant or the fuel at those areas. Current options to prevent or reduce the potential of leaking due to non-uniform compressive pressure applied to the seal include applying a higher compressive load to the bipolar plates to ensure the minimum compressive pressure is applied across the sealing surface. However, applying a higher compressive load may result in a higher compressive pressure not only on the sealing surface, but also on places of the bipolar plates that have been applied the minimum compressive pressure and may not withstand a higher compressive pressure. Thus a higher compressive load may result in higher requirement for the materials for the bipolar plates and/or other components of the EHC or the EHC stack, including, for example, material compatibility, material strength, cost of material, cost of manufacturing, and ease of manufacturing. Therefore, there exists a need for a bipolar plate assembly that allows for more uniform and/or even distribution of compressive pressure across the sealing surface and/or the bipolar plates.

[011] One aspect of the present disclosure is directed to a bipolar plate assembly. The bipolar plate assembly may include a frame and a base. At least one of the frame and the base may have a shape of a force concentrator pattern or include a first surface. The first surface may include a force concentrator pattern that may include a raised surface extending partially across the first surface. The surface area of the force concentrator pattern across the length of the frame or base may be generally constant, thereby producing a uniform compressive pressure along the length of the frame and/or base when the bipolar plate assembly is under compression.

[012] Another aspect of the present disclosure is directed to a method of compressing a bipolar plate. The method may include compressing a frame and a base of the bipolar plate assembly. At least one of the frame and the base may have a shape of a force concentrator pattern or may include a first surface. The first surface may include a force concentrator pattern that may include a raised surface extending partially across trie first surface. The surface area of the force

concentrator pattern across the length of the frame or base may be generally constant. The method may further include producing a uniform compressive pressure along the length of the frame and/or base when the bipolar plate assembly is under compression.

[013] Another aspect of the present disclosure is directed to an

electrochemical cell. The electrochemical cell may include a pair of bipolar plates and a membrane electrode assembly located between the pair of bipolar plates. At least one of the bipolar plates may have a shape of a force concentrator pattern or may include a first surface. The first surface may include a force concentrator pattern that may include a raised surface extending partially across the first surface. The surface area of the force concentrator pattern across the length of the frame or base may be generally constant. The method may further include producing a uniform compressive pressure along the length of the frame and/or base when the bipolar plate assembly is under compression.

[014] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.

[015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and together with the description, serve to explain the principles of the disclosure.

[016] FIG. 1 is an exploded side view of part of an electrochemical cell, showing various components of an electrochemical cell, according to an exemplary embodiment. [017] FIG. 2 is a perspective view of a base and a frame of a bipolar plate assembly, according to an exemplary embodiment.

[018] FIG. 3 is a perspective view of a base and a frame of a bipolar plate assembly, according to an exemplary embodiment.

[019] FIG. 4 is a top view of a frame of an exemplary bipolar plate assembly.

[020] FIG. 5 is a top view of a frame of an exemplary bipolar plate assembly.

[021] FIG. 6 is a perspective view of a frame of a bipolar plate assembly, according to an exemplary embodiment.

[022] FIG. 7 is a close up view of a frame of a bipolar plate assembly, according to an exemplary embodiment.

[023] FIG. 8 is a perspective view of a base and a frame of a bipolar plate assembly, according to an exemplary embodiment.

[024] FIG. 9 is a top view of a frame of a bipolar plate assembly, according to an exemplary embodiment.

[025] FIG. 10 is a perspective view of a frame of a bipolar plate assembly, according to an exemplary embodiment.

[026] Reference will now be made in detail to the present exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Although described in relation to an electrochemical cell for compressing hydrogen, it is understood that the devices and methods of the present disclosure may be employed with various types of fuel cells and electrochemical cells, including, but not limited to electrolysis cells, hydrogen purifiers, hydrogen expanders, and hydrogen pumps.

[027] FIG. 1 shows an exploded side view illustration of an electrochemical cell 100, according to an exemplary embodiment. Electrochemical cell 100 may include an anode 110, a cathode 120, and a proton exchange membrane (PEM) 130 disposed between anode 110 and cathode 120. Anode 110, cathode 120, and PEM 130 combined may include a membrane electrode assembly (MEA) 140. PEM 130 may include a pure polymer membrane or composite membrane where other material, for example, silica, heteropolyacids, layered metal phosphates,

phosphates, and zirconium phosphates may be embedded in a polymer matrix. PEM 130 may be permeable to protons while not conducting electrons. Anode 110 and cathode 120 may include porous carbon electrodes containing a catalyst layer. The catalyst material, for example, platinum, may increase the reaction of the reactant or the fuel.

[028] Electrochemical cell 100 may further include two bipolar plates 150, 160. Bipolar plates 150, 160 may act as support plates, conductors, provide passages to the respective electrode surfaces for the reactant or the fuel, and provide passages for the removal of the compressed reactant or fuel. Bipolar plates 150, 160 may also include access channels for cooling fluid (i.e., water, glycol, or water glycol mixture). Bipolar plates 150, 160 may separate electrochemical cell 100 from the neighboring cells in an electrochemical stack (not shown). In some embodiments, bipolar plate 150 and/or 160 may function as the bipolar plates for two neighboring cell such that each side of bipolar plate 150 and/or 160 is in contact with a different MEA 140. For example, multiple electrochemical cells 100 may be linked in series to form a multi-stage electrochemical hydrogen compressor (EHC) or stacked in parallel to form a single-stage EHC.

[029] In operation, according to an exemplary embodiment, hydrogen gas may be supplied to anode 110 through bipolar plate 150. An electric potential may be applied between anode 110 and cathode 120, wherein the potential at anode 110 is greater than the potential at cathode 120. The hydrogen at anode 110 may be oxidized causing the hydrogen to split into electrons and protons. The protons are electrochemically transported or "pumped" through PEM 130 while the electrons are rerouted around PEM 130. At cathode 120 on the opposite side of PEM 130 the transported protons and rerouted electrons are reduced to form hydrogen. As more and more hydrogen is formed at cathode 120 the hydrogen may be compressed and pressurized within a high pressure zone created in bipolar plate 160.

[030] In some embodiments, each of bipolar plates 150 and 160 may be formed of two pieces or components. For example, FIG. 2 shows one embodiment of a two-component bipolar plate 160, wherein bipolar plate 160 includes a frame 170 and a base 180. Frame 170 may define a void 190 in fluid communication with a flow structure of base 180 (not shown). In some embodiments, frame 170 and base 180 may be formed as one integrated part or component. Although the following description references bipolar plate 160, such disclosure may be equally applicable to bipolar plate 150.

[031] Frame 170 and base 180 may be generally planar and have a generally rectangular or elongated profile. In some embodiments, frame 170 and base 180 may have another shape, for example, a square, a "race-track" (i.e., a substantially rectangular shape with semi-elliptical lateral sides), circle, oval, elliptical, or other shape. The shape of frame 170 and base 180 may correspond to the other components of electrochemical cell 100 (e.g., cathode, anode, PEM, flow structure, etc.) or electrochemical cell stack.

[032] Frame 170 and base 180 may be configured for coplanar coupling. Frame 170 and base 180 may be releasably coupled or fixed together, or may be one integrated part. One or more attachment mechanisms may be used including, for example, bonding material, welding, brazing, soldering, diffusion bonding, ultrasonic welding, laser welding, stamping, riveting, resistance welding, and/or sintering. In some embodiments, the bonding material may include an adhesive. Suitable adhesives include, for example, glues, epoxies, cyanoacrylates,

thermoplastic sheets (including heat bonded thermoplastic sheets) urethanes, anaerobic, UV-cure, and other polymers. In some embodiments, frame 170 and base 180 may be coupled by friction fit. For example, one or more seals between the components may produce adequate frictional force between the components when compressed to prevent unintended sliding.

[033] In some embodiments, frame 170 and base 180 may be releasably coupled using fasteners, for example, screws, bolts, clips, or other similar mechanisms. In some embodiments, compression rods and nuts may pass through bipolar plates 150 and 160 or along the outside and be used to compress frame 170 and base 180 together as electrochemical cell 100 or a plurality of electrochemical cells 100 are compressed in a stack.

[034] In some embodiments, frame 170 and base 180 may help define a plurality of different pressure zones, for example, a plurality of seals may define one or more different pressure zones. The plurality of different seals and pressure zones, according to one embodiment are shown in FIG. 2. The plurality of seals may include a first seal 240, a second seal 250, and a third seal 260. First seal 250 may be contained entirely within second seal 250, and second seal 250 may be contained entirely within third seal 260. This arrangement of seals (i.e., one within the other) may be classified as a cascade seal configuration. The cascade seal configuration may provide several advantages. For example, the cascade seal configuration may limit the potential of high pressure hydrogen escaping electrochemical cell 100 by providing seal redundancy in the form of multiple layers of sealing protection. Reducing the potential of hydrogen leaks may benefit safety and energy efficiency. In addition, the cascade seal configuration may also allow for self-regulation of pressure by allowing the bleeding of high pressure from high pressure zones to lower pressure zones.

[035] The shape of first seal 240, second seal 250, and third seal 260 may generally correspond to the shape of bipolar plates 150 and 160, as shown in FIG. 2. First seal 240, acting as a high pressure seal, may define a portion of a high pressure zone 200 and be configured to contain a first fluid 212 (e.g., hydrogen) within high pressure zone 200. First seal 240 may delimit the outer boundaries of high pressure zone 200 at least between frame 170 and base 180. High pressure zone 200 may be configured to contain at least one flow structure (not shown), for example, a cathode flow structure and an anode flow structure, extending through void 190 when frame 170 and base 180 are coupled or when frame 170 and base 180 are formed as one integrated piece.

[036] First fluid 212, such as hydrogen, may be formed at cathode 120 and accumulate at high pressure zone 200 and the connection between frame 170 and base 180 may be sealed by first seal 240. Hydrogen within high pressure zone 200 may be compressed and, as a result, may increase in pressure as more and more hydrogen is formed and collected in high pressure zone 200. Hydrogen in high pressure zone 200 may be compressed to a pressure greater than, for example, about 10,000 psig, about 15,000 psig, about 20,000 psig, about 25,000 psig, about 30,000 psig, or about 35,000 psig.

[037] As shown in FIG. 2, first seal 240 may be configured to extend around the exterior of high pressure ports 210. High pressure ports 210 may be configured to supply or discharge first fluid 212 from high pressure zone 200. High pressure ports 210 may be in fluid communication with high pressure ports of adjacent electrochemical cells in a multi-cell electrochemical compressor. High pressure ports 210 may be in fluid communication with the cathode flow structure (not shown), which may be located on top of base 180 extending through void 190.

[038] In some embodiments, second seal 250 may define the outer circumference of an intermediate pressure zone 202. Intermediate pressure zone 202 may be delimited by first seal 240, second seal 250, frame 170, and base 180. As shown in FIG. 2, intermediate pressure zone 202 may extend around the circumference of high pressure zone 200 separated by first seal 240. Intermediate pressure zone 202 may be configured to contain a second fluid 214. The cross- sectional area and volume of intermediate pressure zone 202 may vary based on the geometry of frame 170, base 180, first seal 240, and second seal 250. Intermediate pressure zone 202 may further include and be in fluid communication with one or more intermediate pressure ports 220. Intermediate pressure ports 220 may be configured to discharge second fluid 214 contained within intermediate pressure zone 202. Intermediate pressure ports 220 may be in fluid communication with the anode flow structure (not shown), which may be located on top of the cathode flow structure extending through void 190.

[039] The shape and number of intermediate pressure ports 220 may vary. For example, intermediate pressure ports 220 may be square, rectangle, triangle, polygon, circle, oval, or other shape. The number of intermediate pressure ports 220 may vary from 1 to 25 or more. As shown in FIG. 2, intermediate pressure ports 220 may be evenly distributed along the length of frame 170 and base 180 of bipolar plate 160. In some embodiments, intermediate pressure ports 220 may extend the full circumference of intermediate pressure zone 202.

[040] In some embodiments, second fluid 212 discharged via intermediate pressure ports 220 may be resupplied to electrochemical cell 100. In some embodiments, second fluid 214 discharged via intermediate pressure ports 220 may be collected and recycled. Second fluid 214 in intermediate pressure zone 202 may generally have lower pressure than first fluid 212 in high pressure zone 200.

[041] In some embodiments, third seal 260 may define low pressure zone 204 and be configured to contain a third fluid 216 within low pressure zone 204. Low pressure zone 204 may be delimited by second seal 250, third seal 260, frame 170, and base 180. As shown in FIG. 2, low pressure zone 204 may extend around the circumference of intermediate pressure zone 202, separated by second seal 240. The cross-sectional area and volume of low pressure zone 204 may vary based on the geometry of frame 170, base 180, second seal 240, and third seal 250. Low pressure zone 204 may further include and be in fluid communication with one or more low pressure ports 230. Low pressure ports 230 may be configured to discharge third fluid 216 collected and/or contained within low pressure zone 204.

[042] The shape and number of low pressure ports 230 may vary. For example, low pressure ports 230 may be square, rectangle, triangle, polygon, circle, oval, or other shape. The number of low pressure ports 230 may vary, for example, from 1 to 50 or more. As shown in FIG. 2, low pressure ports 230 may be spaced between second seal 240 and third seal 250 and evenly distributed along the length of bipolar plate 160. In some embodiments, low pressure ports 230 may extend the full circumference of low pressure zone 204.

[043] In some embodiments, third fluid 216 discharged via low pressure ports 230 may be resupplied to electrochemical cell 100. In some embodiments, third fluid 216 discharged via low pressure ports 230 may be collected and recycled. Third fluid 216 in low pressure zone 204 may generally have lower pressure than first fluid 212 in high pressure zone 200 and second fluid 214 in intermediate pressure zone 202.

[044] According to exemplary embodiments, first seal 240, second seal 250, and third seal 260 may be part of an assembly of sealing components capable of sealing different pressure zones (e.g., high pressure zone 200, intermediate pressure zone 202, and low pressure zone 204) of bipolar plate 160, and

withstanding pressures in excess of about 15,000 psig, about 20,000 psig, about 25,000 psig, about 30,000 psig, about 35,000 psig, about 40,000 psig, or greater than about 40,000 psig for long periods of time (e.g., greater than 10 years) and withstand many pressure cycles (e.g., greater than 1,000 cycles). For example, first seal 240 may be capable of sealing high pressure zone 200 having a pressure ranging from about 25,000 psig to about 40,000 psig, second seal 250 may be capable of sealing intermediate pressure zone 202 having a pressure ranging from about 0 psig to about 3,000 psig, and third seal 260 may be capable of sealing low pressure zone 204 having a pressure ranging from about 0 psig to about 20 psig.

[045] In some embodiments, bipolar plates 150 and 160 may be configured such that just two pressure zones are formed. For example, bipolar plates 150 and 160 may be configured such that just first seal 240 and third seal 260 form high pressure zone 200 and low pressure zone 204, thereby eliminating second seal 250 and intermediate pressure zone 202. In some embodiments, it is also contemplated that bipolar plates 150 and 160 may be configured such that more than three pressure zones are formed. For example, a fourth pressure zone may be formed by adding a fourth seal.

[046] Traditionally, elastomer seals (e.g., O-rings) are used for first seal 240, second seal 250, and/or third seal 260, for sealing high pressure zone 200, intermediate pressure zone 202, and/or low pressure zone 204 created between

- frame 170 and base 180 and for sealing high pressure ports 210. Elastomers are often a reliability issue in a high pressure system. In addition to making the electrochemical cell less robust and tolerant, elastomeric seals need to be either die cut, hand placed, over-molded, or deposited using an x-y table and then cured. Further, elastomer seals may require either frame 170 or base 180 to have glands or grooves on the surface. Although elastomer seals can be bonded into the grooves, they may slip out of place during fabrication, assembly, and/or during operation. Due to the unreliability and complication of the fabrication process caused by elastomer seals, in some embodiments, polymeric seals may be advantageously used for sealing at least one of the pressure zones formed between frame 170 and base 180.

[047] Polymeric seals can be applied to frame 170 and/or base 180 by a variety of techniques, for example, laminating, spray coating, or dip coating. Utilizing polymeric seals may allow the complexity of bipolar plates 150, 160 to be reduced. For example, glands or grooves on the surfaces of frame 170 and/or base 180 may be eliminated. Eliminating the glands or grooves may allow frame 170 and/or base 180 to be thinner, reduce the amount of machining and/or fabrication required, and increase the area of a sealing surface between frame 170 and base 180, which may reduce the compressive pressure that frame 170 and/or base 180 need to withstand. For another example, using polymeric seals may allow frame 170 and base 180 to be formed as one integrated piece, which may further reduce the thickness of bipolar plates 150, 160. In addition, laminated or spray coated polymeric seals may be tightly bonded to frame 170 and/or base 180 and thus may be firmly held in place. Polymeric seals may allow lower cost of fabrication due to less machining of the bipolar plates 150 and 160, lower application cost and reduced material of the bipolar plates 150 and 160.

[048] As shown in FIG. 3, a polymeric seal 175, for example, may be laminated or coated on one or both surfaces or frame 170 and/or base 180. When a compressive load is applied to frame 170 and base 180, polymeric seal 175 may deform and seal high pressure zone 200, intermediate pressure zone 202, and/or low pressure zone 204. Polymeric seal 175 may be configured, for example, to aid in containing first fluid 212 within high pressure zone 200, containing second fluid 214 within intermediate pressure zone 202, an/or containing third fluid 216 within low pressure zone 204. In some embodiments, polymeric seal 175 may cover part or all of the surface area of frame 170 and/or base 180. Polymeric seal 175 may have a

- sealing surface extending across a compressed area between frame 170 and base 180, and may extend around the circumferences of high pressure zone 200, intermediate pressure zone 202, and/or low pressure zone 204.

[049] In some embodiments, polymeric seal 175 may be used in place of first seal 240, second seal 250, and/or third seal 260. For example, as shown in FIG. 4, polymeric seal 175 may be used together with first seal 240 sealing high pressure zone 200 and polymeric seal 175 sealing the intermediate pressure zone 202 and low pressure zone 204. In some embodiments, one or more channels may form between intermediate pressure ports 220 and high pressure zone 200, allowing intermediate pressure ports 220 to be in fluid communication with first seal 240, high pressure zone 200, and/or the anode flow structure (not shown). Polymeric seal 175 may also include one or more channels 178 to allow intermediate pressure ports 220 to be in fluid communication with high pressure zone 200.

[050] In some embodiments, polymeric seal 175 may be capable of sealing different pressure zones and withstand pressures in excess of about 15,000 psig, about 20,000 psig, about 25,000 psig, about 30,000 psig, about 35,000 psig, or about 40,000 psig, for long periods of time (e.g., greater than 10 years) and withstand many pressure cycles (e.g., greater than 1,000 cycles). For example, polymeric seal 175 may be capable of sealing high pressure zone 200 having a pressure ranging from about 25,000 psig to about 40,000 psig, sealing intermediate pressure zone 202 having a pressure ranging from about 0 psig to about 3,000 psig, and/or sealing low pressure zone 204 having a pressure ranging from about 0 psig to about 20 psigg. This allows the reactant or the fuel, such as hydrogen, formed at cathode 120 to be highly compressed in, for example, high pressure zone 200.

[051] The dimensions of polymeric seal 175 including the shape, thickness, and width may vary, and may be based on the dimensions of electrochemical cell 100 and bipolar plate 160. The thickness of polymer seal 175 may range, for example, from about 0.01 mm to about 0.025 mm, from about 0.025 mm to about 0.05 mm, from about 0.05 mm to about 0.1 mm, from about 0.1 mm to about 0.2 mm, from about 0.2 mm to about 0.3 mm, from about 0.025 mm to about 0.1 mm, from about 0.025 mm to about 0.2 mm, from about 0.025 mm to about 0.254 mm, from about 0.025 mm to about 0.3 mm, from about 0.05 mm to about 0.1 mm, from about 0.05 mm to about 0.2 mm, from about 0.05 mm to about 0.3 mm, from about 0.1 mm to about 0.2 mm, or from about 0.1 mm to about 0.3 mm. In some

- embodiments, polymeric seal 175 may be a separate thin polymeric film sandwiched between frame 170 and base 180. In some embodiments, polymeric seal 175 may be coated or laminated on either frame 170 or base 180 or on both frame 170 and base 180. In some embodiments, polymeric seal 175 may be applied to the surface of frame 170 that face base 180 and/or the surface of base 180 that face frame 170. In some embodiments, polymeric seal 175 may be applied to the surface of frame 170 facing a base 180 of an adjacent cell and/or may be applied to the surface of base 180 facing a frame 170 an adjacent cell. In some embodiments, polymeric seal 175 may be applied to both surfaces of frame 170 and/or base 180. In some embodiments, frame 170 may be formed by the material of polymeric seal 175 such that the range of the thickness of polymeric seal 175 is substantially the same as that of frame 170.

[052] In some embodiments, first seal 230, second seal 240, and/or third seal 250 may be made of or be replaced by polymeric seal 175, as described herein. In some embodiments, polymeric seal 175 may be used together with first seal 240, second seal 250, and/or third seal 260. In some embodiments, polymeric seal 175, first seal 240, second seal 250, and/or third seal 260 may be made of a polymeric sealing material including, but not limited to, Teflon™, Torion ® , polyether ether ketone (PEEK), polyethyleneimine (PEI), polyethylene terephthalate (PET), polycarbonate (PC), polyimide, and polysulfone. The polymer materials may be acid resistant and may not leach materials that are harmful to the operation of

electrochemical cell 100. In some embodiments, frame 170 and/or base 180 may be coated with an adhesive configured to aid in sealing. The adhesive may be, for example, a pressure or heat activated adhesive

[053] When bipolar plate 160 is assembled, frame 170 and base 180 (not shown in FIG. 4) may be joined and compressive pressure may be applied to frame 170, base 180, and polymeric seal 175 applied to frame 170 and/or base 180. In some embodiments, a minimum compressive pressure applied may be greater than the yield strength of the material of polymeric seal 175 such that the material of polymeric seal 175 may deform and thereby create a sealing surface. In some embodiments, a minimum compressive pressure applied may not need to be greater than the yield strength of the material of polymeric seal 175 when the surface of frame 170 and/or base 180 that polymeric seal 175 is applied to are substantially polished and a sealing surface may be created. The sealing surface may be formed at a compressed area of frame 170 and/or base 180. Although the following description references frame 170, such disclosure may be equally applicable to base 180.

[054] As shown in FIG. 4, for example, the compressed area of frame 170 may extend across a top surface of frame 170. In some embodiments, frame 170 may have an elongated shape with a first end 171, a second end 172, and an elongated body 173 extending therebetween. In some embodiments, as shown in FIG. 4, first end 171 and second end 172 of frame 170 may have wider areas compared to elongated body 173, the compressed area along elongated body 173 of frame 170 may be narrower or smaller than the compressed area at first end 171 and second end 172 of frame 170. When a compressive load is applied to the compressed area of frame 170, the compressed area at first end 171 and second end 172 of frame 170 may undergo a smaller compressive pressure due to the difference in contact area than the compressed area along elongated body 173 of frame 170. Such a situation may result in non-uniform compressive pressure across the compressed area of frame 170 and the sealing surface of polymeric seal 175. This may cause leaking of fluid at some places along the sealing surface, such as the places near first end 171 and second end 172 where the compressive pressure may be less and in some situation may not meet the minimum compressive pressure.

[055] FIG. 5 shows an example when non-uniform compressive pressure is applied to the compressed area of frame 170 and the sealing surface of polymeric seal 175. The magnitude of the compressive pressure is shown in density of diagonal lines. As shown in FIG. 5, the compressive pressure applied at second end 172 of frame 170 is smaller than that applied to elongated body 173 of frame 170. In this example, if a minimum compressive pressure is applied to the compressed area along elongated body 173 of frame 170, a compressive pressure smaller than the minimum compressive pressure may then be applied to the compressed area at second end 172 of frame 170, posing potential risks, for example, of fluid leaking from high pressure zone 200 to intermediate pressure zone 202, leaking from intermediate pressure zone 202 to low pressure zone 204 or to the external of the bipolar plate, and/or leaking from low pressure zone 204 to the external of the bipolar plate. Alternatively, if a compressive pressure applied to the compressed area at second end 172 of frame 170 is equal to or sufficiently higher than a minimum compressive pressure, then the compressive pressure applied to the compressed area along elongated body 173 of frame 170 may substantially exceed the maximum compressive pressure that the material of frame 170 can withstand, which may necessitate higher design requirement and/or overdesign of frame 170 to

accommodate the excessive compressive pressure.

[056] To increase the uniformity of compressive pressure applied to the compressed area of frame 170 and/or base 180 and the sealing surface of polymeric seal 175, frame 170 and/or base 180 may define a force concentrator pattern 300. As shown in FIG. 6, force concentrator pattern 300 may be a surface raised from a top and/or a bottom surface of frame 170 and/or base 180. For example, force concentrator pattern 300 may be generated by chemically etching or machining the top surface of frame 170. In some embodiments, force concentrator pattern 300 may be generated by machining frame 170 and/or base 180 to remove materials of frame 170 and/or base 180 such that the surface profile of frame 170 and/or base 180 may be substantially the same as force concentrator pattern 300. For example, some materials of frame 170 near first end 171 and second end 172 may be removed or etched away to generate force concentrator pattern 300. Although the following description references to force concentrator pattern 300 as a raised surface, such disclosure may be equally applicable to force concentrator pattern 300 as substantially same as the profile of frame 170 and/or base 180.

[056] As shown in FIG. 7, for example, force concentrator pattern 300 may be described as a raised surface 300' above the top surface of frame 170. In such embodiments, polymeric seal 175 may be laminated or coated on force concentrator pattern 300. In such embodiments, force concentrator pattern 300 may be formed by polymeric seal 175. In some embodiments, force concentrator pattern 300 may have a thickness, for example, from about 0.01 mm to about 0.025 mm, from about 0.025 mm to about 0.05 mm, from about 0.05 mm to about 0.1 mm, from about 0.1 mm to about 0.2 mm, from about 0.2 mm to about 0.3 mm, from about 0.025 mm to about 0.1 mm, from about 0.025 mm to about 0.2 mm, from about 0.025 mm to about 0.254 mm, from about 0.025 mm to about 0.3 mm, from about 0.05 mm to about 0.1 mm, from about 0.05 mm to about 0.2 mm, from about 0.05 mm to about 0.3 mm, from about 0.1 mm to about 0.2 mm, or from about 0.1 mm to about 0.3 mm. In some embodiments, force concentrator pattern 300 may be on either frame 170 or base 180 or on both frame 170 and base 180. In some embodiments, force concentrator pattern 300 may be on the surface of frame 170 that face base 180 and/or the surface of base 180 that face frame 170. In some embodiments, force concentrator pattern 300 may be on the surface of frame 170 facing a base 180 of an adjacent cell and/or may be applied to the surface of base 180 facing a frame 170 an adjacent cell. In some embodiments, force concentrator pattern 300 may be on both surfaces of frame 170 and/or base 180. In some embodiments, the thickness of force concentrator pattern 300 may be substantially the same as that of frame 170 and/or base 180.

[058] As shown in FIG. 6 and FIG. 7, in some embodiments, force

concentrator pattern 300 may extend across elongated body 173 of frame 170 and partially across first end 171 and/or second end 172 of frame 170. Force

concentrator pattern 300 may be designed such that the compressed area across frame 170, for example, across the length of frame 170, may be approximately or generally constant or uniform. In some embodiments, force concentrator pattern 300 may extend from high pressure zone 200 to the outer edge of frame 170. In some embodiments, force concentrator pattern 300 may be narrower than a width of elongated body 173 of frame 170. For example, force concentrator pattern 300 may or may not extend from the inner edge of frame 170 to the outer edge of frame 170. In some embodiments, the compressed area of frame 170, the surface area of force concentrator pattern 300, and the surface area of the sealing surface of polymeric seal 175 may be substantially the same. The design of force concentrator pattern 300 may allow the compressive pressure across the compressed area of frame 170 and the sealing surface of polymeric seal 175, to be generally uniform or constant. In some embodiments, decreasing the surface area of force concentrator pattern 300, for example, in first end 171 and/or second end 172, may increase the uniformity or evenness of the compressive pressure across the compressed area of frame 170 and the sealing surface of polymeric seal 175.

[059] FIG. 8 shows an exemplary embodiment of bipolar plate 160 whose frame 170 has a force concentration pattern 300. When a compressive load is being applied to frame 170 and/or base 180, the compressive pressure applied may be generally uniformly distributed across force concentrator pattern 300 of frame 170, the compressed area of frame 170, and/or the sealing surface of polymeric seal 175. The compressed area along the length of frame 170 may range from about 2 cm 2 /cm to about 4 cm 2 /cm, from about 2 cm 2 /cm to about 6 cm 2 /cm, from about 2 cm 2 /cm to

- about 8 cm 2 /cm, from about 2 cm 2 /cm to about 10 cm 2 /cm, from about 4 cm 2 /cm to about 6 cm 2 /cm, from about 4 cm 2 /cm to about 8 cm 2 /cm, from about 4 cm 2 /cm to about 10 cm 2 /cm, from about 5 cm 2 /cm to about 7 cm 2 /cm, from about 6 cm 2 /cm to about 8 cm 2 /cm, from about 6 cm 2 /cm to about 10 cm 2 /cm. In some embodiments, a repeating distance between intermediate ports 220 and/or low pressure ports 230 may range from about 1 cm to about 3 cm. In some embodiments, the length of frame 170 and/or base 180 may range from about 15 cm to about 30 cm, from about 15 cm to about 50 cm, from about 15 cm to about 80 cm, from about 15 cm to about 100 cm, from about 30 cm to about 50 cm, from about 30 cm to about 80 cm, from about 30 cm to about 100 cm, from about 50 cm to about 80 cm, from about 50 cm to about 100 cm, or from about 80 cm to about 100 cm. In some embodiments, the width of frame 170 and/or base 180 may range from about 5 cm to about 10 cm, from about 10 cm to about 20 cm, from about 20 cm to about 30 cm, from about 5 cm to about 20 cm, from about 5 cm to about 30 cm, from about 10 cm to about 30 cm, or from about 20 cm to about 30 cm.

[060] In some embodiments, the compressed area of frame 170, the surface area of force concentrator pattern 300, and/or the surface area of the sealing surface of polymeric material 175 may range from about 50 cm 2 to about 100 cm 2 , from about 100 cm 2 to about 200 cm 2 , from about 200 cm 2 to about 300 cm 2 , from about 300 cm 2 to about 400 cm 2 , from about 400 cm 2 to about 500 cm 2 , from about 500 cm 2 to about 600 cm 2 , from about 600 cm 2 to about 700 cm 2 , from about 700 cm 2 to about 800 cm 2 , from about 800 cm 2 to about 900 cm 2 , from about 900 cm 2 to about 1000 cm 2 , from about 1000 cm 2 to about 1100 cm 2 , from about 1100 cm 2 to about 1200 cm 2 , from about 1200 cm 2 to about 1300 cm 2 , from about 1300 cm 2 to about 1400 cm 2 , or from about 1400 cm 2 to about 1500 cm 2 . In some embodiments, the generally uniform compressive pressure distributed along the compressed area of frame 170 and/or the sealing surface of polymeric seal 175 may range from about 5,000 psig to about 10,000 psig, from about 5,000 psig to about 20,000 psig, from about 5,000 psig to about 30,000 psig, from about 5,000 psig to about 40,000 psig, from about 10,000 psig to about 40,000 psig, from about 10,000 psig to about 30,000 psig, from about 10,000 psig to about 20,000 psig, from about 20,000 psig to about 30,000 psig, from about 20,000 psig to about 40,000 psig, or from about 30,000 psig to about 40,000 psig. [061] FIG. 9 illustrates an example when generally uniform compressive pressure is distributed across the compressed area of frame 170 and the sealing surface of polymeric seal 175, when utilizing force concentrator pattern 300 as described herein. The magnitude of the compressive pressure is shown in density of diagonal lines. The uniform density of the diagonal lines in FIG. 9 indicates that the magnitude of compressive pressure across the compressed area of frame 170 is generally uniform. As shown in FIG. 9, force concentrator pattern 300 reduces the compressed area at first end 171 of frame 170, and thus allows the compressed area extending across first end 171 and elongated body 173 of frame 170 to be approximately constant, resulting in generally uniform or even distribution of the compressive pressure cross the compressed area of frame 170 and the sealing surface of polymeric seal 175. In some embodiments, for example, given a compressive load of about 1 ,000,000 pounds, the area of force concentrator pattern 300 and the compressive area of frame 170 may be about 50 in 2 , and thus the compressive pressure may be about 20,000 psig across frame 170. This

substantially uniform or even distribution of compressive pressure may reduce or prevent the potential of fluid leaking from high pressure zone 200. In some embodiments, the variability of compressive pressure cross the compressed area of frame 170 and/or the sealing surface of polymeric seal 175 may not be greater than about 2%, about 5%, about 8%, about 10%, about 15%, or about 20%.

[062] In some embodiments, force concentrator pattern 300 may not be continuous across frame 170. For example, force concentrator patter 300 may include separated portions at the corners of frame 170. For example, as shown in FIG. 10, corner portions 310 may be similarly raised surfaces added to frame 170 as a part of force concentrator pattern 300. Corner portions 310 may be generated by chemically etching or machining frame 170 in the same manner as force

concentrator pattern 300. Comer portions 310 may have the same thickness as that of force concentrator pattern 300. In some embodiments, the surface area of force concentrator pattern 300 may be reduced by adding comer portions 310 to frame 170. In some embodiments, corner portions 310 and force concentrator pattern 300 together allow the compressed area of frame 170 and the sealing surface 175 to be approximately constant, and thus the compressive pressure to be generally uniformly or evenly distributed across frame 170.

- [063] In some embodiments, force concentrator pattern 300 may be formed in polymeric seal 175. For example, polymeric seal 175 may have a larger thickness across force concentrator pattern 300 and a smaller thickness across other areas. In some embodiments, force concentrator pattern 300 may be an integral part of frame 170 and/or base 180. In some embodiments, force concentrator pattern 300 may be on a selected surface or both surfaces of frame 170 and/or based 180. In some embodiments, each EHC cell in an EHC stack may have force concentrator pattern 300.

[064] In some embodiments, the use of force concentrator pattern 300 may reduce the requirement for the amount of compressive load applied to frame 170 and base 180. The reduced requirement for the compressive load may allow reduced requirement for the materials of frame 170 and base 180, which may allow for a wide selection of materials to be used for frame 170 and base 180. In some

embodiments, frame 170 and base 180 may be formed of the same materials or different materials. Frame 170 and base 180 may be formed of a metal, such as, stainless steel, titanium, aluminum, nickel, iron, etc., or a metal alloy, such as, nickel chrome alloy, nickel-tin alloy, Inconel, Monel, Hastelloy, or a combination there of. In some embodiment, frame 170 may also be formed of polymers, composites, ceramics, or any material capable of handling the compressive load, force, and/or pressure applied to the EHC cell or EHC stack upon assembly.

[065] In some embodiments, frame 170 and base 180 may include a clad material, for example, aluminum clad with stainless steel on one or more regions. Cladding may provide the advantages of both metals, for example, in the case of a bipolar plate fabricated from stainless steel-clad aluminum, the stainless steel protects the aluminum core from corrosion during cell operation, while providing the superior material properties of aluminum, such as, high strength-to-weight ratio, high thermal and electrical conductivity, etc. In some embodiments, frame 170 may include anodized, sealed, and primed aluminum. In some embodiments, frame 170 may include chromated and spray coated aluminum.

[066] In some embodiments, frame 170 may be formed of a composite, such as, carbon fiber, graphite, glass-reinforce polymer, and thermoplastic composites. In some embodiments, frame 170 may be formed of a metal that is coated to prevent both corrosion and electrical conduction. According to various embodiments, frame 170 may be generally non-conductive, reducing the likelihood of shorting between

- the electrochemical cells. Base 180 may be formed of one or more materials that provide electrical conductivity as well as corrosion resistance during cell operation. For example, base 180 may be configured to be electrically conductive in the region where the active cell components sit (e.g., flow structure, MEA, etc.).

[067] Factors and properties to be considered in selecting the material and geometry for a component (e.g., polymeric seal 175, first seal 230, second seal 240, third seal 250, frame 170, and base 180) may include at least the design of force concentrator pattern 300, compressive load requirements, material compatibility, sealing pressure requirement, cost of material, cost of manufacturing, and ease of manufacturing. The variety of materials made suitable by force concentration pattern 300 described herein may allow for the selection of less expensive materials and less costly manufacturing. For example, lower cost commodity plastics, some of which have been listed herein, may be used for the polymeric seals (e.g., polymeric seal 175, first seal 230, second seal 240, and third seal 250). In addition, multi- component bipolar plates could be expensive to manufacture due to the intricate details on the plates requiring the use of expensive conventional milling. Utilizing the polymeric seal 175 and force concentrator pattern 300 as described herein may reduce the cost and complexity of the manufacture of bipolar plates 150 and 160. For example, frame 170 and base 180 may be manufactured together with force concentrator pattern 300, which may reduce the thickness of bipolar plates 150 and 160, manufacturing cost, and manufacturing complexity by allowing the use of polymeric seal 175 and generally uniform distribution of compressive pressure along the sealing surface of polymeric seal 175.

[068] It is understood that the features described herein may be used to seal other components of the electrochemical cell and/or may be used in cells that do not employ the cascade seal configuration.

[069] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the present disclosure herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present disclosure being indicated by the following claims.