Fluid connection for a fuel cell stack

Abstract

The invention relates to a fuel cell stack fluid connection (100), in particular an insulating plate (100) for a fuel cell stack (10), of a fuel cell assembly (1), preferably for a fuel cell vehicle, with an inlet connection (123, 125) comprising a supply path passage recess (133, 135) for a supply path (21, 31) of the fuel cell stack (10), wherein the supply path passage recess (133, 135) opens at an inlet port (113, 115) for a continuation of the supply path (21, 31) in the fuel cell stack (10), wherein the inlet connection (123, 125), in particular in the region of its inlet port (113, 115), has a fluid containment device (140; 141, 142) such that downstream of the inlet port (113, 115) Product water in the supply path (21, 31) by means of the fluid containment device (140;141, 142) is kept away from at least one inlet opening in a bipolar plate (14) of the fuel cell stack (10).;

Description

[0001] The invention relates to a fuel cell stack fluid connection, in particular an insulating plate for a fuel cell stack, and to a fuel cell stack for a fuel cell assembly. Furthermore, the invention relates to a fuel cell assembly or a fuel cell system, preferably for a fuel cell vehicle. State of the art

[0002] In a low-temperature polymer electrolyte fuel cell of a fuel cell system (stationary or mobile), such as a fuel cell vehicle, an electrochemical conversion of two reactants from two operating media into electrical energy and heat takes place. The fuel cell comprises at least one membrane electrode assembly, for example, a membrane electrode assembly (MEA). Typically, the fuel cell is designed with a multiple stack of membrane electrode assemblies and bipolar plates positioned between them (fuel cell stack or stack with multiple individual fuel cells). Task

[0003] Water in an individual cell of a fuel cell stack can impede the supply, particularly of anode operating fluid. This can lead to so-called fuel starvation (lack of (anode) operating fluid) and / or other functional problems, which in turn result in a severely negative potential in the affected individual cell and consequently trigger irreversible damage mechanisms and / or damage (burnout of a membrane in a membrane electrode assembly) in the fuel cell stack. It is an object of the invention to prevent water ingress into an individual cell of a fuel cell stack as far as possible. Disclosure of the invention

[0004] The object of the invention is achieved by means of a fuel cell stack fluid connection, in particular an insulating plate for a fuel cell stack; by means of a fuel cell stack for a fuel cell assembly; and by means of a fuel cell assembly and a fuel cell system, preferably for a fuel cell vehicle. Advantageous further developments, additional features and / or advantages of the invention will become apparent from the dependent claims and the following description.

[0005] The electrochemical process of the fuel cell stack produces product water on the cathode side. While the membranes of the fuel cell stack's membrane electrode assemblies ensure separation of the anode-side and cathode-side fluids, some product water does pass through (crossover). Since the anode fluid is recirculated, liquid product water returns to the fuel cell stack, depending on the efficiency of any anode-side water separator. Flooding of an individual cell is particularly problematic in its anode compartment, but should also be avoided in its cathode compartment.

[0006] During investigations leading to the present invention, it was surprisingly found that, regardless of the orientation of the fuel cell stack (vertical or horizontal), the first upstream cell(s) is / are always affected by flooding with product water. Furthermore, these investigations revealed that the unwanted product water migrates as a film along the inner wall of a relevant inlet connection. This effectively guides the product water, in particular, into the anode-side openings of the first upstream bipolar plate(s).

[0007] The fuel cell stack fluid connection according to the invention, hereinafter referred to only as fluid connection, comprises an inlet connection comprising a supply path passage recess for a supply path of the fuel cell stack, wherein the supply path passage recess opens at an inlet port for a continuation of the supply path in the fuel cell stack, wherein the inlet connection, in particular in the area of ​​its inlet port, has a fluid retention device such that downstream of the inlet port, product water in the supply path can be kept away from at least one inlet opening in a bipolar plate of the fuel cell stack by means of the fluid retention device.

[0008] This applies in particular to the installation state of the fluid connection on / in the fuel cell stack. The flow in an upstream (anode and / or cathode) supply path directly at the fuel cell stack is sufficient to deflect, atomize, etc., the product water film by means of the fluid control device and keep it away from the inlet openings of the first upstream bipolar plate(s). The additional fluid control device, provided at an interface to an (anode and / or cathode) inlet of the fuel cell stack, prevents or at least reduces the risk of the first individual cell(s) being flooded with product water.

[0009] A significant advantage of the design solution disclosed here, compared to solutions at the operational control level of the fuel cell stack, lies in the fact that, particularly under transient conditions, the operating parameters of the fuel cell stack often cannot be adjusted in such a way as to prevent liquid product water from entering, especially, at least one upstream first anode chamber. The design solution according to the invention separates this requirement from the operational control requirements. The operating parameters of the fuel cell stack can be optimized with regard to robustness and efficiency. The anode-side product water is no longer a concern, or only a minor one, for operational control.

[0010] The fluid containment device can be designed as a geometric feature of the inlet connection. For this purpose, the supply path opening can have an abrupt change in cross-section at one end and / or in a central section. This means, for example, that the supply path opening has a discontinuity as a fluid containment device. Furthermore, the change in cross-section can be located on the side of the supply path opening that is adjacent to at least one inlet opening of the bipolar plate. If the fluid connection is designed as an insulating plate, this side is naturally adjacent to an end plate opening of the insulating plate. In addition, the change in cross-section can be designed as a reduction or an increase in the cross-section of the supply path opening.

[0011] The fluid deflection device can be provided at / in the supply path opening as a fluid deflection projection at / in the inlet connection, particularly at the inlet port. Furthermore, the fluid deflection device can be provided at / in the supply path opening as a fluid deflection ring in the inlet connection, in the inlet port, or particularly downstream directly at the inlet port. In the latter case, the fluid deflection ring can be designed as a type of fluid-permeable cover for the inlet port.

[0012] The fluid deflection projection can be integrally formed within a wall of the supply path passage recess. Alternatively, the fluid deflection projection can be formed as a separate element, distinct from the wall of the supply path passage recess. This separate fluid deflection projection can be fixed to the wall of the supply path passage recess. This can be achieved, for example, by insertion using a snap-fit ​​connection, a tongue-and-groove connection, etc.; clipping; gluing, etc. The fluid deflection projection can also be cast or molded into a wall of the supply path passage recess as an insert. This can be easily achieved using an injection molding process.

[0013] The fluid deflection ring can be at least partially fluid-permeable in its radial interior area at / in the supply path passage recess, have a radially inner deflection projection, and / or be fully or partially configured as an atomizing grid in its radial interior area. The radially inner deflection projection or the partial atomizing grid of the fluid deflection ring is located on the side of the fluid deflection ring and the supply path passage recess that, in the installed state, is adjacent to the inlet openings of the bipolar plate or, in the case of an insulating plate, to the end plate recess of the insulating plate.

[0014] In this design, the fluid deflection ring is preferably configured as a separate fluid deflection ring from the inlet connection or inlet port. This separate fluid deflection ring is fixed to the respective wall. This can be achieved, for example, by insertion using a snap-fit ​​connection, a tongue-and-groove connection, etc.; clipping; gluing, etc. A cast-in or cast-in fluid deflection ring is, of course, also applicable.

[0015] The fluid deflection device can also be designed as a deflector plate, a deflector lip, and / or a deflector edge at / in the supply path passage opening, particularly downstream directly at the inlet port. The deflector plate, the deflector lip, and / or the deflector edge can be located on the outside of the fluid connection. This can be achieved, for example, by insertion (e.g., with a snap-fit ​​connection, a tongue-and-groove connection, etc.), clipping, or gluing. Furthermore, the fluid deflection device can be designed as a film, particularly a PEN sealing film, glued to the inlet port. In this case, a section of the film, e.g., a modified additional sealing sleeve (sub-gasket, insulating film between bipolar plates), extending over / into the opening of the inlet port, can be designed to resemble a fluid deflection projection, a deflector lip, a deflector edge, etc.

[0016] The fluid connection can have a plate-shaped base on which an anode inlet connection with an anode inlet port and / or a cathode inlet connection with a cathode inlet port is formed as an inlet connection. The anode inlet port and an associated anode outlet port, and / or the cathode inlet port and an associated cathode outlet port, can be located in the plate base. The anode outlet port is preferably a region of an anode outlet connection and / or the cathode outlet port is preferably a region of a cathode outlet connection, each within the plate-shaped base.

[0017] When installed in the fuel cell stack, the fluid connection of the fuel cell is connected to its anode inlet port and / or its cathode outlet port via the fuel cell stack. The anode inlet port and / or the cathode inlet port are located in the end section of an anode supply path or cathode supply path upstream of the actual cell stack. The anode outlet port and / or the cathode outlet port are located in the beginning section of an anode exhaust path or a cathode exhaust path downstream of the actual cell stack.

[0018] The plate-shaped base can be equipped with inlet ports for media flowing into the fuel cell stack (anode operating medium, cathode operating medium, and / or cooling medium) and outlet ports for media flowing out of the fuel cell stack (anode exhaust medium, cathode exhaust medium, and / or cooling medium). Preferably, the ports for the fuel cell stack media are located on a side of the plate base opposite the end plate recess. All ports are preferably located on a single, large-area side of the plate base, particularly away from the end plate recess. Each inlet port and each outlet port forms an opening on the inside of the insulation plate for the fuel cell stack mounted upon it.

[0019] The plate-shaped base may preferably have an end plate recess for an end plate of the fuel cell stack, located between ports arranged on only two sides. The fluid connection with the plate-shaped base and the end plate recess may be designed as an insulating plate. The fluid connection may be formed as a single piece or integrally.

[0020] A one-piece (adhesive) design refers to a fluid connection in which its individual parts are bonded together (adhesive bonding, two-component injection molding, etc.) and the insulation plate preferably cannot be separated into individual parts without damaging one of its components. The cohesion of the insulation plate can further be achieved by means of a force-fit and / or form-fit connection (not in the case of an integral design). An integral design refers to an insulation plate in which there is only a single component that can only be separated by destroying it. The component is manufactured from a single original piece and / or a single original mass (plastic melt), which is itself necessarily integral. Internal cohesion is achieved (exclusively) by means of adhesion and / or cohesion.This may also include a (materially (adhesively) one-piece) coating etc.

[0021] The fuel cell stack according to the invention comprises a plurality of membrane electrode devices and a plurality of bipolar plates, which alternate with one another in an actual cell stack of the fuel cell stack, wherein a plurality of individual cells of the fuel cell stack are formed in between, and in a section of a supply path of the fuel cell stack upstream of at least one inlet opening of at least one upstream bipolar plate, a fluid keeping device is provided, by means of which product water in the supply path can be kept away from the at least one inlet opening.

[0022] This applies, of course, to an operating state of the fuel cell stack in which product water in the supply path is kept away from the inlet openings of the upstream bipolar plate(s) by means of the fluid control device. The fluid control device can be designed as a geometric feature of the supply path. This geometric feature can be located in / on the actual cell stack; in / on a fluid connection, in particular an insulating plate for the fuel cell stack; and / or be designed using both the actual cell stack and a fluid connection.

[0023] The fluid containment device may optionally further comprise a protrusion of a sealing sleeve of a membrane electrode assembly on / in the actual fuel cell stack. The actual cell stack of the fuel cell stack for supplying its operating media may, in particular, comprise the insulation plate only on one side. Furthermore, the fluid connection of the fuel cell stack, in particular the insulation plate, may be designed as a fluid connection according to the invention.

[0024] The above statements regarding the fluid connection (geometric design, cross-sectional changes, fluid deflection projection, fluid deflection ring, deflection plate, deflection lip, deflection edge, foil, etc.) are of course also applicable here analogously, even outside the fluid connection described above. The fuel cell stack has no dead cell directly at an anode-side and / or cathode-side end plate, or directly at both end plates. Furthermore, it is preferred that the fuel cell stack has no dead cell. Brief description of the characters

[0025] The invention is explained in more detail below using exemplary embodiments with reference to the attached schematic and not-to-scale drawing. In the invention, a feature can be configured positively, i.e., present, or negatively, i.e., absent. In this specification, a negative feature is not explicitly explained as a feature unless it is important for the invention to be absent. This means that the invention actually made, and not one constructed by the prior art, consists in omitting this feature. The absence of a feature (negative feature) in an exemplary embodiment indicates that the feature may be optional (to a person skilled in the art). - In the merely exemplary figures (Fig.) of the drawing show: The Fig. 1 shows a highly simplified block diagram of an embodiment of a fuel cell unit for a fuel cell system of a fuel cell vehicle, the Fig. 2 a lateral perspective view of a fluid connection designed as an insulating plate for a fuel cell stack, wherein arrows indicate positions of fluid containment device(s) of the fluid connection according to the invention, and the Fig. 3 to 6 three embodiments of a fluid containment device according to the invention at / in an anode inlet port (preferred) and / or at / in a cathode inlet port. Embodiments of the invention

[0026] The invention relates to a fuel cell stack fluid connection 100, hereinafter referred to only as fluid connection 100, in particular designed as an insulating plate 100 - cf. the Fig. 2 to 6 with the embodiments according to the invention one ( Fig. 3), two ( Fig. 4) and three ( Fig. 5 and Fig. 6) - for a fuel cell stack 10 of a fuel cell assembly 1, in particular for a low-temperature polymer electrolyte fuel cell system of a fuel cell vehicle, i.e., a motor vehicle comprising a fuel cell or a fuel cell system, explained in more detail. Only those sections of the fuel cell system necessary for understanding the invention are shown in the drawing.

[0027] Although the invention is described and illustrated in detail by preferred embodiments, the invention is not limited to the disclosed embodiments. Other variations may be derived therefrom without departing from the scope of the invention. In particular, the invention can also be applied to another mobile or stationary fuel cell unit 1 or fuel cell system.

[0028] The Fig. 1 shows a schematic diagram of a fuel cell assembly 1 according to one embodiment, comprising at least one, in particular a plurality of, electrochemical individual fuel cells 11 (individual cells 11) bundled into a fuel cell stack 10, which are housed in a preferably fluid-tight stack housing 16. Each individual cell 11 comprises an electrode chamber 12 configured as an anode chamber 12 and an electrode chamber 13 configured as a cathode chamber 13, which are spatially and electrically separated from one another by a membrane of a membrane electrode device 15.

[0029] A membrane electrode assembly 15 comprises a membrane, two electrodes, and preferably two transport layers, with at least one electrode being provided on the membrane and / or at least one electrode being provided on a transport layer opposite the membrane. Of course, both electrodes can also be provided on the membrane (membrane electrode assembly) or on the transport layers. The membrane or the membrane electrode assembly is preferably arranged in a sealing sleeve ((sub-)gasket), against which a bipolar plate 14 can be sealingly brought into contact. The respective transport layer is arranged in the fuel cell stack 10 in a respective anode compartment 12 or cathode compartment 13.

[0030] A bipolar plate 14 is arranged between each two directly adjacent membrane electrode devices 15, 15, including a respective anode chamber 12 and a respective cathode chamber 13. The bipolar plate 14 serves, among other things, to guide operating media 3, 5 into an anode chamber 12 of a first individual cell 11 and a cathode chamber 13 of a directly adjacent second individual cell 11, as well as to discharge the exhaust gas media 4, 6 generated therein. Furthermore, the bipolar plate 14 establishes an electrically conductive connection between these two individual cells 11, 11 and imparts mechanical stability to the fuel cell stack 10.

[0031] The cathode chambers 13 and, if applicable, their common inflow area or their electrodes form a cathode 39 of the fuel cell stack 10. And the anode chambers 12 and, if applicable, their common inflow area or their electrodes form an anode 29 of the fuel cell stack 10. - To supply the fuel cell stack 10 with its actual operating media 3 (anode operating medium, actual fuel), 5 (cathode operating medium, usually air), the fuel cell unit 1 has an anode supply 20 (operating medium supply 20) and a cathode supply 30 (operating medium supply 30).

[0032] The anode supply 20 comprises, in particular: a fuel reservoir 23 for the anode operating medium 3 (flowing in); an anode supply path 21 with a pressure reducer, a shut-off valve and / or a metering valve 27 (for example) and a jet pump 24 (jet pump 24, ejector 24); an anode exhaust gas path 22 for an anode exhaust gas medium 4 (flowing out, usually into the environment 2); preferably a fuel recirculation path 25 with a fluid conveying device 26 located therein, e.g., a hydrogen recirculation blower 26; optionally, a water separator and optionally, a water tank.

[0033] The cathode supply 30 comprises in particular: a cathode supply path 31 for the cathode operating medium 5 (flowing in, usually from the environment 2), preferably with a fluid conveying device 33; a cathode exhaust path 32 for a cathode exhaust medium 6 (flowing out, usually into the environment 2), preferably with a turbine 34, in particular for the fluid conveying device 33; preferably a moisture exchanger 36, in particular a gas-to-gas humidifier 36; optionally a cathode-side stack bypass 35 (wastegate 35) between the cathode supply path 31 and the cathode exhaust path 32, with a bypass valve 37; optionally a water separator and optionally a water tank.

[0034] The fuel cell unit 1 further comprises, in particular, a cooling medium supply 40 of a thermal system, in particular of the fuel cell vehicle, through which the fuel cell stack 10 can be integrated into a cooling circuit for temperature control, preferably by means of its bipolar plates 14 (cooling medium path 43). The cooling medium supply 40 comprises a cooling medium inlet path 41 and a cooling medium outlet path 42. The cooling medium 7 (inflowing) and 8 (outflowing) circulating in the cooling medium supply 40 are preferably conveyed by means of at least one cooling medium conveying device 44.

[0035] In addition to the fuel cell unit 1, the fuel cell system comprises peripheral system components, such as a control unit, which may be one of the fuel cell vehicle itself.

[0036] During the operation of a fuel cell stack 10 according to the state of the art, under certain operating conditions, the upstream first individual cell 11 may become flooded with product water in its anode compartment 12 and / or in the cathode compartment 13, which usually follows directly downstream (a reversal in a fuel cell stack 10 is of course possible). This is particularly critical on the anode side due to the risk of fuel starvation and / or other functional problems. However, this should also be avoided on the cathode side to ensure the functionality of the active surface of the lowest individual cell 11.

[0037] To avoid this, in the prior art, one or two dummy cells (not shown in the drawing) are used upstream of an active cell stack in the fuel cell stack 10 with regard to the operating media. These dummy cells are electrochemically inactive. Anode gas and, separately, cathode gas are routed via these dummy cells as a 'gas short circuit' from the dummy cell inlets to the dummy cell outlets. - Due to the arrangement away from the active cell stack, product water, which may be present on the inside of a port wall of an inlet connection (123, 125; cf. the Fig. 2) and an inlet port (113, 115; cf. the Fig. 2) an insulation panel (100, see the Fig. 2) of the fuel cell stack 10, by means of which the blind cells are directed to the blind cell outlets. - The problem is that the construction of the fuel cell stack 10 using these blind cells is very complex, as inactive membrane electrode devices and special bipolar plates must also be installed.

[0038] The Fig. Figures 2 to 6 show solutions according to the invention, which are preferably implemented exclusively by means of the insulating plate 100 (fluid connection 100, see below). The insulating plate 100 serves to supply and dispose of the fuel cell stack 10 with / from its media 3, 4, 5; 6, 7, 8. The insulating plate 100 is essentially divided into two sections: the plate-shaped base 101 and the end plate recess 102 within the plate-shaped base 101. When the insulating plate 100 is installed, an upstream (operating media) end plate of the fuel cell stack 10 is accommodated in the end plate recess 102.

[0039] Apart from the end plate recess 102, the plate-shaped base 101 comprises (see the Fig. 2) On the one hand, an anode inlet port 123 for an anode operating medium supply, a cathode outlet port 126 for a cathode exhaust medium return, and a cooling medium outlet port 128 for a cooling medium return. On the other hand, the plate-shaped base 101 includes an anode outlet port 124 for an anode exhaust medium return, a cathode inlet port 125 for a cathode operating medium supply, and a cooling medium inlet port 127 for a cooling medium supply. A different distribution of the fluid ports 123, 126, 128; 124, 125, 127 is of course possible depending on the requirements of the fuel cell stack 10.

[0040] Here, all fluid connections 123, 126, 128; 124, 125, 127 project from a large surface area of ​​the insulation plate 100 in the region of its plate-shaped base 101, with the plate-shaped base 101 opening on the opposite large surface area of ​​the insulation plate 100 with its respective fluid connection 123, 126, 128; 124, 125, 127 facing the fuel cell stack 10. That is, the respective fluid connection 123, 126, 128; 124, 125, 127 has openings there. Specifically, these are an anode inlet port 113 for the anode operating medium 3, a cathode outlet port for the cathode exhaust medium 6, a cooling medium outlet port for the outflowing cooling medium 8, an anode outlet port for the anode exhaust medium 4, a cathode inlet port 115 for the cathode operating medium 5, and a cooling medium inlet port for the inflowing cooling medium 7.

[0041] To prevent flooding of at least one upstream (operating media) individual cell 11, i.e., its anode compartment 12 and / or its cathode compartment 13, with product water, the supply path 21, 31 at / in the fuel cell stack 10 upstream of at least one inlet opening to the anode compartment 12 and / or cathode compartment 13 of at least one upstream bipolar plate 14, includes a fluid containment device 140; 141, 142 by means of which product water in the supply path 21, 31 is kept away from the at least one inlet opening. In particular, the insulating plate 100 or the fluid connection 100 (see below) of the fuel cell stack 10, or the fluid containment device 140; 141, 142 on the actual fuel cell stack of the fuel cell stack 10, can include the fluid containment device 140; 141, 142.

[0042] The fluid containment device 140; 141, 142 on / in the fuel cell stack 10, on / in the insulation plate 100, or on / in the fluid connection 100 can be designed as a geometric feature of the section of the supply path 21, 31 there (see above). In particular, the fluid containment device 140; 141, 142 can be designed as an abrupt change in cross-section (see above) of the supply path 21, 31, a fluid deflection projection 141 (see above and the Fig. 3, Fig. 4), a fluid deflection ring 142 (see above, the Fig. 5, Fig. 6), a atomizing grid 142 (see above, the Fig. 6), a deflecting plate, a deflecting lip, a deflecting edge, a foil or an area thereof and / or an overhang of a sealing sleeve of a membrane electrode device 15 etc. may be formed.

[0043] The fluid containment device 140; 141, 142 is arranged in the supply path 21, 31 at / in the fuel cell stack 10 such that product water in the supply path 21, 31 can be kept away from at least one inlet opening of an anode compartment 12 and / or a cathode compartment 13 of at least one upstream (operating media) first bipolar plate 14 of the fuel cell stack 10 by means of the fluid containment device 140; 141, 142. In particular, the fluid containment device 140; 141, 142 can be arranged at / in a supply path through-hole 133, 135 of an inlet connection 123, 125 (see Figure 1). Fig. 4), 125 and / or at / in an inlet port 113, 115 (see Fig. 3 to 6) of this inlet connection 123, 125. In particular, the fluid containment device 140; 141, 142 is located on the anode side.

[0044] It is of course possible not to implement the fluid connection 100 as a complete insulation plate 100. In particular, it is possible to implement a fluid connection for the fuel cell stack 10 or a fluid connection for the actual fuel cell stack by at least one of, or any combination of, the connections: 123, 124, 125, 126, 127, 128. In particular, such a fluid connection 100 naturally has the anode inlet connection 123 and / or the cathode inlet connection 125, whereby at least one further connection (123,) 124, (125,) 126, 127, 128 may optionally be provided.

[0045] Regarding the formation and / or position of the fluid-repellent device 140, 141 as a fluid deflection projection 141 (see the Fig. 3 and Fig. 4) See above. And regarding the design and / or position of the fluid containment device 140, 142 as a fluid deflection ring 142 (see the Fig. 5 and Fig. 6) See also above.

Claims

[1] Fuel cell stack fluid connection (100), in particular insulation plate (100) for a fuel cell stack (10) of a fuel cell unit (1), preferably for a fuel cell vehicle, with an inlet connection (123, 125) comprising a supply path through-hole (133, 135) for a supply path (21, 31) of the fuel cell stack (10), wherein the supply path through-hole (133, 135) opens at an inlet port (113, 115) for a continuation of the supply path (21, 31) in the fuel cell stack (10), characterized by , that the inlet connection (123, 125), in particular in the region of its inlet port (113, 115), has a fluid-retaining device (140; 141, 142) such that downstream of the inlet port (113, 115), product water in the supply path (21, 31) can be kept away from at least one inlet opening in a bipolar plate (14) of the fuel cell stack (10) by means of the fluid-retaining device (140; 141, 142). [2] Fuel cell stack fluid connection (100) according to the preceding claim, characterized by that the fluid-retaining device (140; 141, 142) is designed as a geometric configuration of the inlet connection (123, 125), wherein preferably: • the supply path through-hole (133, 135) has an abrupt change in cross-section at one end and / or in a central section, • the cross-sectional change is arranged on that side on / in the supply path through-hole (133, 135) which is adjacent to the at least one inlet opening of the bipolar plate (14), and / or • the change in cross-section is designed as a reduction in cross-section or an enlargement in cross-section of the supply path through-recess (133, 135). [3] Fuel cell stack fluid connection (100) according to one of the preceding claims, characterized by that the fluid-retaining device (140; 141, 142) is arranged on / in the supply path through-recess (133, 135) as a fluid deflection projection (140, 141) is provided on / in the inlet connection (123, 125), in particular on the inlet port (113, 115), or as a fluid deflection ring (140, 142) is provided in the inlet connection (123, 125), in the inlet port (113, 115) or in particular downstream directly at the inlet port (113, 115). [4] Fuel cell stack fluid connection (100) according to one of the preceding claims, characterized by , that: • the fluid deflection projection (140, 141) is integrally formed in a wall of the supply path through-recess (133, 135), • the fluid deflection projection (140, 141) is designed as a fluid deflection projection (140, 141) external to a wall of the supply path through-hole (133, 135), • the fluid deflection projection (140, 141) outside the wall is fixed to the wall of the supply path through-hole (133, 135), and / or • the fluid deflection projection (140, 141) is cast or molded as an insert onto / into a wall of the supply path passage recess (133, 135). [5] Fuel cell stack fluid connection (100) according to one of the preceding claims, characterized by that the fluid deflection ring (140, 142) on / in the supply path passage recess (133, 135): • is at least partially fluid-permeable in its radial inner region, • has a radially inner deflection projection, and / or • is formed completely or partially as an atomization grid in its radial inner region. [6] Fuel cell stack fluid connection (100) according to one of the preceding claims, characterized by , that • the fluid-retaining device (140) is designed as a deflection plate, a deflection lip or a deflection edge (140) on / in the supply path passage recess (133, 135), in particular downstream directly at the inlet port (113, 115), • the deflection plate (140), the deflection lip (140) or the deflection edge (140) is arranged on an outer side of the fuel cell stack fluid connection (100), and / or • the fluid-retaining device (140) is designed as a film, in particular a PEN sealing film, glued to the inlet port (113, 115). [7] Fuel cell stack fluid connection (100) according to one of the preceding claims, characterized by , that: • the fuel cell stack fluid connection (100) has a plate-shaped base (101) on which an anode inlet connection (123) with an anode inlet port (113) and / or a cathode inlet connection (125) with a cathode inlet port (115) is formed as an inlet connection (123, 125), • the anode inlet port (113) and the anode outlet port (114) associated therewith, as well as the cathode inlet port (115) and the cathode outlet port (116) associated therewith, are arranged in the plate base (101), and / or • inlet connections (123, 125, 127) for inflowing media (3, 5, 7) of the fuel cell stack (10) and outlet connections (124, 126, 128) for outflowing media (4, 6, 8) of the fuel cell stack (10) are formed on the plate-shaped base (101). [8] Fuel cell stack fluid connection (100) according to one of the preceding claims, characterized by , that: • in the plate-shaped base (101), an end plate recess (102) for an end plate of the fuel cell stack (10) is preferably provided between ports (113, 115) arranged therein only on two sides, • the fuel cell stack fluid connection (100) with the plate-shaped base (101) and the end plate recess (102) is designed as an insulation plate (100), and / or • the fuel cell stack fluid connection (100) is formed in one piece or integrally. [9] Fuel cell stack (10) for a fuel cell unit (1), preferably for a fuel cell vehicle, with a plurality of membrane electrode devices (15) and a plurality of bipolar plates (14), which (14, 15) alternate with one another in an actual cell stack of the fuel cell stack (10), wherein a plurality of individual cells (11) of the fuel cell stack (10) are formed therebetween, characterized by , that in a section of a supply path (21, 31) of the fuel cell stack (10) upstream of at least one inlet opening of at least one upstream bipolar plate (14), a fluid-retaining device (140; 141, 142) is arranged, by means of which fluid-retaining device product water in the supply path (21, 31) can be kept away from the at least one inlet opening. [10] Fuel cell stack (10) according to the preceding claim, characterized bythat the fluid-retaining device (140; 141, 142) is formed in the section of the supply path (21, 31) as a geometric configuration of the supply path (21, 31), and the geometric configuration: • is set up in / on the actual cell stack, • is arranged in / on a fuel cell stack fluid connection (100), in particular an insulation plate (100) for the fuel cell stack (10), or • is formed both by means of the actual cell stack and a fuel cell stack fluid connection (100). [11] Fuel cell stack (10) according to the preceding claim, characterized by , that: • the fluid-retaining device (140) comprises a projection of a sealing sleeve of a membrane electrode device (15) on / in the actual fuel cell stack (10), • the actual cell stack of the fuel cell stack (10) for supplying its operating media comprises, in particular, only one side of the insulation plate (100), and / or • the fuel cell stack fluid connection (100) of the fuel cell stack (10), in particular the insulation plate (100), is designed as a fuel cell stack fluid connection (100) according to one of the preceding claims. [12] Fuel cell unit (1) or fuel cell system preferably for a fuel cell vehicle, characterized by that the fuel cell unit (1) or the fuel cell system comprises a fuel cell stack (10) according to one of the preceding claims, and / or has a fuel cell stack fluid connection (100) according to one of the preceding claims.

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