Patent Description:
Electrochemical cells are commonly used in a stack configuration for a variety of applications such as electricity generation from hydrogen or hydrocarbon fuel, production and compression of hydrogen, production and compression of oxygen or oxygen-enriched air, or production of nitrogen-enriched air. Although stack configurations can vary, a common design involves a series membranes (e.g., proton exchange membranes, also known as polymer electrolyte membranes or "PEM") in planar membrane electrode assemblies ("MEA"), each disposed in a stackable frame, separated by electrically conductive separator plates, also referred to as bi-polar plates. The bi-polar plates serve to connect the stacked MEA's in series, and to separate the fluid on the anode side of each MEA from the fluid on the cathode side of the adjacent MEA in the stack. Fluid flow channels to deliver and receive fluid flow from cells are commonly incorporated in the frames of the stacked components. The stack typically has an end plate at each end of the stack. The stacked components are assembled under a compressive load from bolts extending between the end plates through the stack.

Electrochemical cells and stacks are designed and fabricated in a wide variety of sizes and configurations. This has typically necessitated the custom design and fabrication of a wide variety of components of different sizes, which can lead to increased cost, complexity, and difficulty to maintain quality. Additionally, some components can be difficult or more costly to maintain manufacturing specifications when manufactured in some sizes. Cross-membrane pressure differentials in electrochemical cells can be quite high (e.g., up to <NUM> bar (<NUM> psi) for some applications), which necessitates a considerable degree of precision in order to provide effective, leak-free cell operation. Such precision can be readily achieved for stacks having a relatively small active area per cell, but as the per-cell active area increases, components such as cell frame components, membranes, etc., become increasingly difficult to fabricate to the desired specifications.

From <CIT> there is known a planar electrochemical cell module comprising a planar peripheral frame.

According to some aspects of the invention, there is a method of manufacturing electrochemical cell stacks of different sizes or configurations. According to the method, a first planar frame module having a first planar size and configuration is assembled from a first inventory of parts comprising planar modular parts having mating surfaces along connectable ends thereof. The planar modular parts are connected together, in a co-planar configuration to form the first planar module having the first size and configuration. The first planar module is assembled into the first electrochemical stack comprising a plurality of planar modules to form a first electrochemical stack corresponding to the first planar size and configuration. A second inventory of parts including planar modular parts in common with the first inventory is identified, and a second planar module having a different planar size or configuration than the first planar module is assembled from the second inventory. The second planar module is assembled into a second electrochemical stack comprising a plurality of planar modules to form the second electrochemical stack corresponding to the first planar size and configuration.

According to some aspects of the invention, a planar electrochemical cell module comprises a planar peripheral frame that comprises a plurality of planar modular frame parts connected together at mating surfaces along interconnecting ends of the modular planar peripheral frame parts to extend connected modular planar peripheral frame parts along the plane of the planar peripheral frame.

According to some aspects of the invention, an electrochemical cell stack comprises a planar endplate that comprises a plurality of planar modular endplate parts connected together at mating surfaces along interconnecting ends of the modular planar endplate parts to extend connected modular planar endplate parts along the plane of the planar endplate.

According to some aspects of the invention, a planar electrochemical cell comprises a plurality of planar cell modules comprising components selected from proton exchange membranes, separator plates, electrodes, flow fields, or combinations thereof. The planar cell modules are disposed along a common plane of the electrochemical cell, and are connected at mating surfaces along perimeter ends of the planar cell modules to frame members of a frame comprising a plurality of framed spaces.

According to some aspects of the invention, an electrochemical cell stack comprises a planar electrical bus plate that comprises a plurality of planar modular electrical bus plate parts connected together at mating surfaces along interconnecting ends of the modular planar electrical bus plate parts to extend connected modular planar electrical bus plate parts along the plane of the planar electrical bus plate.

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:.

The detailed description explains representative embodiments, together with advantages and features, by way of example with reference to the drawings.

In some examples of embodiments, the above-described first and second modules can be cell frames, electrical bus plates, end plates, or cell components selected from proton exchange membranes, separator plates, electrodes, flow fields, or combinations thereof. Referring now to <FIG>, an exemplary cell frame module <NUM> is depicted in an exploded view. As shown in <FIG>, six planar modular frame parts <NUM> are assembled together to form the frame module <NUM>. As shown in the magnified view of <FIG>, the modular frame parts <NUM> are connected together at mating surfaces <NUM>, <NUM> that are recessed in a direction perpendicular to the plane of the planar module, with mating surface <NUM> recessed by a dimension <NUM>' and mating surface <NUM> recessed by a dimension <NUM>'. The connection can be facilitated with adhesive or brazing, and/or interlocking features (not shown) along the mating surfaces <NUM>, <NUM>. The planar modular frame parts <NUM> can have openings <NUM> therein such as for transportation of fluids to and from the electrochemical cell, and electrically non-conductive openings <NUM> to accommodate a stack assembly bolt when the frame module is incorporated into a cell stack.

The planar modular frame parts can be part of a common inventory of parts used to form a second planar module having a different size and/or configuration than a first planar module. For example, planar modules having a different size and configuration than the module shown in <FIG> are shown in <FIG> and <FIG>. <FIG> shows a planar frame module <NUM>' having twice the size (as characterized by surface area) of the frame of <FIG> assembled from ten of the modular frame parts <NUM> (shown, but not individually numbered). <FIG> shows a planar frame module <NUM>" having the same size (surface area) as that of <FIG>, but with a different configuration assembled from eight of the modular frame parts <NUM> (shown, but not individually numbered).

As mentioned above, the first and second modules assembled from an inventory of parts including a common inventory of planar modular parts can be proton exchange membranes, separator plates, electrodes, flow fields, or combinations thereof. An example of such an embodiment is shown in an exploded view in <FIG> and <FIG>, which depict planar flow fields of different sizes/configurations assembled from a plurality of planar flow field modular parts <NUM> (two planar flow field component parts <NUM> in <FIG> and six planar flow field component parts <NUM> in <FIG>). The flow field component parts <NUM> are connected together along mating surfaces through protective bridge strip elements <NUM>, which help protect sensitive elements such as the proton exchange membrane at the interface between adjacent flow field component parts <NUM>. As shown in <FIG> and <FIG>, the flow field modular parts <NUM> are assembled together with a unitary separator plate <NUM> and a planar frame <NUM> to form a portion of an electrochemical cell. Flow field modular parts <NUM> are also typically disposed on the opposite side of the separator plate <NUM> from the view depicted in <FIG> and <FIG> so as to provide both anode-side and cathode-side flow fields. The planar frame <NUM> can be assembled from planar frame modular parts <NUM> as shown in <FIG> and <FIG> or can be a unitary frame. Electrically non-conductive bolt pass-through elements <NUM> provide openings for stack assembly bolts (not shown).

In some embodiments, a planar frame assembled from planar frame components can include a peripheral frame and an internal frame, as shown by way of example in <FIG> and <FIG>. As shown in <FIG> and <FIG>, planar frame modules <NUM> and <NUM>' are' depicted in an exploded view (<FIG>) and assembled view (<FIG>) is assembled from planar cell frame modular parts <NUM>, <NUM>, and <NUM>. As shown in <FIG> and <FIG>, the assembled frame includes a peripheral frame portion formed by planar cell frame modular parts <NUM> and <NUM>, and an internal frame portion formed by cell frame modular part <NUM> and the inwardly-extending portions <NUM>' of the cell frame modular parts <NUM>.

Of course, the assembly of first and second planar modules from parts inventories including modular parts common to both inventories is not limited to a single type of module. <FIG> and <FIG> illustrate an embodiment where both frame parts and flow fields are assembled from parts inventories including modular parts common to both inventories. As mentioned above, other types of modules can also be assembled from common parts inventories. Internal frames such as shown in <FIG> and <FIG> can provide a sealing surface so that other components such as membranes or separator plates can be assembled from planar modular parts instead of a unitary membrane or separator plate covering the entire surface area of a stack cell footprint. An example of such an embodiment is depicted in <FIG>, which depict cell modules of different sizes/configurations assembled from a plurality of planar modular parts. As shown in <FIG>, membrane modular parts <NUM>, flow field modular parts <NUM>, and separator plate modular parts <NUM> are connected (indirectly, through the planar cell frame modular parts <NUM>, <NUM>) in a co-planar configuration to form a complete planar cell module for inclusion in a cell stack. Electrodes (not shown) can be disposed on opposite sides of the membrane, and can be printed or coated onto the membrane or integrated into the flow field as is known in the art. As with other modules disclosed herein, the module depicted in <FIG> can be assembled in different sizes and/or configurations, for example in the size/configuration of the frame <NUM> from <FIG> (as shown in <FIG>) and/or in the size/configuration of the frame <NUM>' from <FIG>.

Another type of electrochemical cell stack module that can be assembled in different sizes/configurations as described herein is an intermediate module as described in more detail in <CIT>. These intermediate modules can (i) include a cavity disposed internally within the intermediate module that is in fluid communication with a fluid source at a pressure higher than the operating pressure of the electrochemical cell stack on either side of the intermediate module, and/or (ii) can provide an electrically non-conductive channel along a fluid communication path between electrochemical cells having a different operating voltage for electrically conductive process liquids in fluid communication with a plurality of electrochemical cells in the stack. The intermediate modules can include plates that provide a mount for anchors against lateral stress resulting from stack operating pressures. The anchors are disposed along a perimeter portion of at least one plate, with the anchors extending from plate in a direction perpendicular to the plane of the stacked planar modules. The anchors include a surface portion that provides structural support along the external perimeter surface of the stacked planar modules against stress in a direction parallel to the plane of the stacked planar module.

An example of an embodiment is shown in an exploded view in <FIG>, with intermediate module endplates <NUM> and <NUM> having an intermediate module inner plate disposed between the intermediate module endplates <NUM>, <NUM>. Anchors <NUM> provide reinforcement against lateral stress from pressurized fluids during operation. The intermediate module inner plate is assembled from intermediate module inner plate planar modular parts <NUM> having optional cooling fluid flow channels <NUM> disposed therein. The intermediate module inner plate can be assembled with different numbers and/or configurations of the inner plate planar modular parts <NUM> in similar fashion as described above.

The various modules described herein can be assembled together in an electrochemical cell stack. An example of such an embodiment is shown in a partially-exploded view in <FIG>. As shown in <FIG>, the stack includes membranes <NUM>, cathode-side cell assemblies <NUM>, and anode-side cell assemblies <NUM>. As shown in the upper exploded view portion of <FIG>, the cathode-side and anode-side cell assemblies include a separator plate <NUM> and modular flow field parts <NUM> in a planar frame <NUM> made from modular frame parts <NUM>. As further shown in <FIG>, the stack also includes intermediate modules assembled from intermediate module inner plate planar modular parts <NUM>, intermediate module endplates <NUM>, <NUM>, and anchors <NUM>. Bolts or tie-rods <NUM> and nuts <NUM> apply a compressive load to the stack.

With continued reference to <FIG>, additional modules are seen to be assembled from planar modular parts are connected in co-planar fashion along mating surfaces. Electrical bus plates <NUM> are assembled from planar electrical bus plate module parts <NUM>, which are butted against one another in electrically-conductive contact. Insulator plates <NUM> are assembled from planar insulator plate module parts <NUM> to electrically insulate endplates <NUM> from the electrical bus plates <NUM>. Endplates <NUM> are assembled from planar endplate module parts <NUM>. In some embodiments, the endplate module parts <NUM> are connected at overlapping mating surfaces <NUM> that are recessed in a direction perpendicular to the plane of the planar endplate.

As mentioned above, the electrochemical cell stacks typically include polymer electrolyte membranes having an anode and a cathode disposed on opposite sides thereof. An anode-side flow field structure and a cathode-side flow field structure are typically disposed on either side of the membrane. These flow field structures are typically disposed distal from the membrane, with the MEA and flow field structures each mounted in a frame assembly as described above to provide space for fluid flow in contact with the MEA. The flow field structures can be electrically conductive (e.g., a steel mesh) to provide an electrical connection through a conductive separator plate from a cathode of one cell to the anode of an adjacent cell so that the cells of the stack are electrically connected in series. Proton exchange membranes can comprise electrolytes that are solids under the operating conditions of the electrochemical cell. Useful materials from which the membranes can be fabricated include proton conducting ionomers and ion exchange resins. Ion-exchange resins useful as proton conducting materials include hydrocarbon- and fluorocarbon-type resins. Fluorocarbon-type resins typically exhibit excellent resistance to oxidation by halogen, strong acids, and bases. One family of fluorocarbon-type resins having sulfonic acid group functionality is NAFION® resins (commercially available from E. du Pont de Nemours and Company, Wilmington, Del.

Claim 1:
A method of manufacturing electrochemical cell stacks of different sizes or configurations, comprising:
assembling a first planar frame module (<NUM>) having a first planar size and configuration from a first inventory of parts comprising planar modular parts (<NUM>) having mating surfaces (<NUM>, <NUM>) along connectable ends thereof, including connecting the planar modular parts (<NUM>) together in a co-planar configuration to form the first planar frame module (<NUM>) having the first size and configuration;
assembling the first planar frame module (<NUM>) in a first electrochemical stack comprising a plurality of planar modules to form the electrochemical stack corresponding to said first planar size and configuration;
identifying a second inventory of parts including planar modular parts in common with the first inventory, and assembling from the second inventory a second planar frame module having a different planar size or configuration than the first planar frame module; and
assembling the second planar frame module in a second electrochemical stack comprising a plurality of planar modules to form the second electrochemical stack corresponding to said second planar size or configuration.