Specification

State of the Art

Fuel cells and electrolyser cells are examples of electrochemical cells . Fuel cells are energy conversion devices that allow for conversion of electrochemical fuel to electricity . Electrolyser cells are fuels cells running in reverse mode , i . e , using electricity to generate chemicals ; reversible cells are capable of operating in both modes . Such cells may be formed into cell stacks of the same or similar construction . For example , typically, multiple fuel cells are connected in series to form a fuel cell " stack" , wherein the stacked cells are bound together by end plates provided on opposite ends of the fuel cell stack . In such cell stacks , current collection is commonly accomplished by contact elements that are disposed between an end plate and the fuel cell stack and that are electrically connected to active areas of the fuel cells . In order to allow for current collection from the outside of the fuel cell system, the contact elements are usually connected to respective contact bolts that extend through the end plate from the fuel cell side to the outside . These contact bolts are usually connected to the contact elements by screw connections on the fuel cell side. Electrical insulation between the end plate and the contact bolts is commonly achieved by bushings formed from mica.

Description of the invention

The invention relates to an end plate assembly for an electrochemical cell stack, such as, for example, a stack of fuel cells, electrolyser cells or reversible cells. More specifically, the invention relates to an end plate assembly for a planar, metal-supported electrochemical cell stack. Typically, the invention relates to a solid oxide fuel cell (SOFC) stack or a solid oxide electrolyser cell (SOEC) stack.

The end plate assembly comprises an, preferably flatly extending, end plate having a first side and an opposite second side. In a mounted state of the end plate assembly on a (e.g. fuel) cell stack, the first side of the end plate is facing to the cell stack and the second side is facing away from the cell stack, i.e. to the surroundings.

The end plate assembly further comprises at least one contact device for electrically contacting the cell stack from the second side of the end plate. That is to say, the end plate assembly comprises at least one contact device for providing an electrical connection from the second side of the end plate to the (e.g. fuel) cell stack, for example , preferably for collecting current from a fuel cell stack .

The at least one contact device comprises a contact member having a, optionally flatly extending, plate portion and a bolt portion . The contact member may be formed from metal or metal alloy . The plate portion is positioned in the end plate assembly on the side of the first side of the end plate . The plate portion may extend parallel or perpendicular to the end plate . The plate portion is configured for electrically coupling to active areas of the cell stack . In a mounted state , the plate portion may be in direct contact with cell active areas . The bolt portion protrudes , preferably orthogonally, from the plate portion along a bolt axis . The bolt portion is fixedly attached to the plate portion . The bolt portion and the plate portion may be torque-proof coupled around the bolt axis . The bolt portion may have a connecting end connected to the plate portion and a free end . The bolt portion is designed and arranged in the end plate assembly such that it extends through the end plate , in particular through a respective through opening in the end plate , and protrudes from the second side of the end plate with its free end .

The at least one contact device further comprises a fastening member cooperating with the bolt portion to connect the contact member and the end plate . Preferably, the fastening member is positioned in the end plate assembly on the side of the second side of the end plate . In other words , the fastening member is preferably cooperating with the bolt portion at the side of the second side of the end plate .

The end plate assembly further comprises an insulation device for electrically insulating the at least one contact device from the end plate .

The proposed end plate assembly allows for easy mounting and is robust in its function under ( e . g . fuel ) cell operating conditions . As the bolt portion is fixedly attached to the plate portion, the contact member can be handled in one piece and thus easily be connected to the end plate . More speci fically, the proposed design eliminates the need for additional screwing at the cell side , thus reducing the risk of wear debris contaminating the cell active areas or clogging gas supply paths . In an example , the contact member may be inserted through the end plate with its bolt portion via the first side of the end plate and then fastened from the second side of the end plate by means of the fastening member .

The fastening member may be a nut . Then, the bolt portion may comprise a threaded portion on its free end, configured to cooperate with the nut to connect the contact member with the end plate . This allows for a robust and easily adj ustable connection of the contact member and the end plate .

Preferably, the bolt portion and the plate portion are integrally bonded . That is to say, the bolt portion and the plate portion may be bonded such that they cannot be separated in a non-destructive way . Preferably, the bolt portion and the plate portion are welded . In some embodiments , the bolt portion and the plate portion may be monolithic .

The end plate assembly may further comprise an antirotation device . The anti-rotation device may be configured to prevent rotation of the contact member around the bolt axis . The anti-rotation device may be configured to prevent rotation of the bolt portion around the bolt axis . Preferably, the anti-rotation device is configured to support a tightening torque generated by the fastening member during connection of the contact member and the end plate . Providing an anti-rotation device eliminates the need of counter-holding the contact member during fastening of the contact member, in particular during screwing the fastening nut at the threaded portion of the bolt portion . This allows for assembling the components of the end plate assembly solely by access from second side of the end plate , i . e . from the outside of the cell stack .

The anti-rotation device may comprise an anti-rotation member having a first anti-rotation portion form- f ittingly interlocking with the plate portion of the contact member and a second anti-rotation portion form- f ittingly interlocking with the end plate .

The insulation device may comprise an insulation plate configured to electrically insulate the plate portion of the contact member from the end plate . Preferably, the insulation plate is positioned between the plate portion and the end plate . The insulation plate may be formed from mica

The insulation device may comprise an insulation bushing configured to electrically insulate the bolt portion from the end plate . Preferably, the insulation bushing is positioned between the bolt portion and the end plate . Preferably, the insulation bushing is formed from an electrically insulating material , preferably from ceramics .

The end plate assembly may further comprise a first spacer washer acting between the plate portion of the contact member and the end plate , preferably supporting the plate portion of the contact member against the end plate . Alternatively or in addition, the end plate assembly may comprise a second spacer washer acting between the fastening member and the end plate , preferably supporting the fastening member against the end plate . Preferably, the first spacer washer and/or the second spacer washer are arranged coaxially to the bolt portion . Preferably, the first spacer washer and/or the second spacer washer are formed from an electrically insulating material , preferably from ceramics .

The first spacer washer may be formed integrally with the insulation bushing . Preferably, the insulation bushing and the first spacer washer are provided by a single piece . This advantageously improves mechanical stability and reduces the amount of components in the end plate assembly, thus facilitating mounting of the end plate assembly .

Preferably, the first spacer washer cooperates with the plate portion of the contact member and the end plate and/or the insulation plate such that rotation of the contact member around the bolt axis is prevented . In this case , the first spacer washer may form the above-described anti-rotation member .

The first spacer washer may comprise a central portion, a first anti-rotation portion, and a second anti-rotation portion . The central portion may be in the form of a ring portion . The first anti-rotation portion may protrude from a first side of the central portion, in particular orthogonally . The second anti-rotation device may protrude from a second side of the central portion, preferably orthogonally . Preferably, the second side is opposite to the first side . Preferably, the first anti-rotation portion is form- f ittingly interlocking with the plate portion of the contact member, in particular when the contact member is connected to the end plate by the fastening member . Preferably, the second anti-rotation portion is form- fittingly interlocking with the end plate and/or the insulation plate , in particular when the contact member is connected to the end plate by the fastening member .

The insulation bushing, the first spacer washer and/or the second spacer washer may be formed from a, preferably electrically insulating, ceramic material . Preferably, the ceramic material comprises an oxide ceramic . This advantageously reduces mechanical and/or thermal degradation of these components under ( e . g . fuel ) cell operating conditions , and thus supports a durable ( screw) connection of the contact member and the end plate . Such a design is particularly advantageous in automotive applications , where large vibrational stresses may be trans ferred to a fuel cell during driving . Preferably, the insulation bushing, the first spacer washer and/or the second spacer washer are formed from alumina (AI2O3 ) , which provides superior electric insulation, temperature resistance up to > 1000 ° C, and high mechanical strength . In addition, alumina is relatively cheap and can be gas-tight .

Preferably, the end plate assembly comprises two contact devices . Then, the end plate assembly may comprise an antirotation device , an insulation device , a first spacer washer, and/or a second spacer washer as discussed above for each contact device . The first contact device may be electrically connected to the positive pole of the cell stack and the second contact device may be electrically connected to the negative pole of the cell stack .

The invention also relates to a fuel or electrolyser cell system comprising an electrochemical cell stack and an end plate assembly as discussed above . The features and advantages explained above in connection with the end plate assembly itsel f are also applicable to the fuel or electrolyser cell system . Preferably, the fuel or electrolyser cell stack comprises a plurality of cells stacked in a predetermined stacking direction . Preferably, the end plate assembly is positioned at one end of the fuel or electrolyser cell stack .

Further embodiments are derivable from the following description and the drawing .

In the drawing, the figures show :

Figure 1 an illustration of an end plate assembly from a cross-sectional view; and

Figure 2a, b an illustration of the first spacer washer from top view (view a ) and from a side view (view b ) .

Figure 1 schematically depicts an embodiment of a fuel cell system 10 comprising a fuel cell stack 12 ( only indicated in Figure 1 ) and an end plate assembly 14 connected to the fuel cell stack 12 . The fuel cell stack 12 preferably comprises multiple fuel cells (not shown) stacked on top of each other along a stacking direction 16 .

The end plate assembly 14 comprises an end plate 18 having a first side 20 and an opposite second side 22 . In the mounted state of the end plate assembly 14 on the fuel cell stack 12 , the first side 20 is facing the fuel cell stack 12 and the second side 22 is facing away from the fuel cell stack, i . e . to the surroundings ( see Fig . 1 ) . The end plate 18 may be formed from metal or metal alloy .

In the embodiment depicted in Fig . 1 , the end plate assembly 14 comprises two contact devices 24- 1 , 24-2 for electrically contacting the fuel cell stack 12 from the side 26 of the second side 22 of the end plate 18 . Exemplarily, the contact device 24- 1 shown on the left of Fig . 1 serves to contact the positive pole of the fuel cell stack 12 , whereas the contact device 24-2 shown on the right of Fig . 1 serves to contact the negative pole of the fuel cell stack 12 .

In the following, the structure of the left contact device 24- 1 will be described exemplarily for both contact devices 24- 1 , 24-2 . Unless otherwise noted, the right contact device 24-2 is built identically .

The contact device 24- 1 comprises a contact member 28 having a plate portion 30 and a bolt portion 32 protruding from the plate portion 30 along a bolt axis 34 . The plate portion 30 is positioned on the side 36 of the first side 20 of the end plate 18 . In the embodiment shown, the plate portion 30 is flatly extending parallel to the end plate 18 . The plate portion 30 is in electrical contact with the fuel cell stack 12 . In Fig . 1 , the plate portion 30 of the left contact device 24- 1 may be connected to the positive pole of the fuel cell stack 12 and the plate portion 30 of the right contact device 24-2 may be coupled to the negative pole of the fuel cell stack 12 .

The bolt portion 32 of the contact member 28 is fixedly attached to the plate portion 30 . Preferably, plate portion 30 and bolt portion 32 are connected by welding . In the assembled state , the bolt portion 32 extends through an opening 38 in the end plate 18 and protrudes from the second side 22 of the end plate 18 with a free end 40 ( see Fig . 1 ) .

The contact device 24- 1 , 24-2 further comprises a fastening member 42 , cooperating with the bolt portion 32 to connect the contact member 28 and the end plate 18 . In the embodiment shown, the fastening member 42 is provided by a nut 44 that is screwed on a threaded portion 46 on the free end 40 of the bolt portion 32 . The nut 44 may be formed from an electrically conductive material and thus serve as an electrical connection .

The end plate assembly 14 further comprises a first spacer washer 48 supporting the plate portion 30 of the contact member 28 against the first side 20 of the end plate 18 . In addition, the end plate assembly 14 comprises a second spacer washer 50 supporting the fastening member 42 against the second side 22 of the end plate 18 . The first spacer washer 48 and the second spacer washer 50 are arranged coaxially to the bolt portion 32 .

The end plate assembly 14 further comprises an insulation device 52 for electrically insulating the contact devices 24- 1 , 24-2 from the end plate 18 . In the embodiment shown, the insulation device 52 comprises an insulation plate 54 positioned between the plate portions 30 of the contact devices 24- 1 , 24-2 and the end plate 18 . The insulation plate 54 is formed from an electrically insulating material , e . g . from mica . The insulation device 52 further comprises an insulation bushing 56 for each bolt portion 32 . Each insulation bushing 56 is arranged coaxially to the respective bolt portion 32 and extends through the opening 38 of the end plate 18 together with the bolt portion 32 . As shown in Fig . 1 , the insulation bushings 56 act as a spacer between the respective bolt portions 32 and the end plate 18 as well as between the bolt portions 32 and the first and second spacer washers 48 , 50 . In embodiments not shown, the insulation bushing 56 and the first spacer washer 48 that is assigned to the same contact device 24- 1 , 24-2 may be formed integrally .

Preferably, the insulation bushings 56 , the first spacer washers 48 and the second spacer washers 50 are formed from a ceramic material , in particular from an oxide ceramic, preferably from alumina .

In the embodiment depicted in Fig . 1 , the first spacer washer 48 of the respective contact device 24- 1 , 24-2 acts as an anti-rotation member 58 preventing rotation of the contact member 28 around the bolt axis 34 . For that purpose , the first spacer washer 48 comprises a central ring portion 60 supporting the plate portion 30 against the end plate 18 as discussed above . The first spacer washer 48 further comprises a first protrusion 62 protruding from a first side 64 of the central portion 60 and a second protrusion 66 protruding from an opposite second side 68 of the central portion 60

( see Fig . 2 ) . In the assembled state , the first protrusion 62 is form- fittingly interlocking with a respective recess 70 in the plate portion 30 of the contact member 28 , thus forming a first anti-rotation portion 72 . The second protrusion 66 is form- f ittingly interlocking with a respective recess 74 in the end plate 18 , thus forming a second anti-rotation portion 76 . Hence , the first spacer washer 48 together with the recess 70 and/or the recess 74 forms an anti-rotation device 78 .