Fluid-tight electrochemical cell stack

Abstract

The invention relates to an electrochemical cell stack (60) for an electrochemical unit, in particular an electrolysis cell stack (60) or a fuel cell stack (10), having a plurality of individual electrochemical cells which, together with a plurality of bipolar plates, alternate with one another in an actual cell stack (100) of the cell stack (60), wherein at least the actual cell stack (100) is fluid-sealed to the outside in a stack housing (66), and at least during operation of the cell stack (60), a stack housing space directly on the actual cell stack (100) is at least partially filled with a fluid other than air.

Description

[0001] The invention relates to an electrochemical cell stack for an electrochemical assembly. Furthermore, the invention relates to an electrochemical assembly and an electrochemical system. State of the art

[0002] In an electrolyzer of an electrolyzer unit (stationary or mobile), e.g., an electrolyzer system, e.g., a fuel cell vehicle, an electrochemical conversion of water into hydrogen and oxygen takes place using electrical energy, generating heat. - In a low-temperature polymer electrolyte fuel cell of a fuel cell unit (mobile or stationary), e.g., a fuel cell system, e.g., a fuel cell vehicle, an electrochemical conversion of two reactants of two operating media into electrical energy and heat takes place.

[0003] The electrolyzer unit or fuel cell unit can comprise at least one membrane electrode assembly (MEA) with a PEM (proton exchange membrane) or an AEM (anion exchange membrane). The electrolyzer unit or fuel cell unit can be configured with a plurality of membrane electrode units arranged in a stack and bipolar plates arranged between them, forming the so-called electrolysis cell stack or fuel cell stack (cell stack, stack) with a plurality of individual electrolysis cells or individual fuel cells (individual cells). Alternatively, at least one electrode can be arranged apart from and, of course, directly opposite a membrane at a fluid transport layer. Task

[0004] In electrochemical cell stacks of electrolyzer units and / or fuel cell units, leaks, particularly gas leaks, can occur between the cell layers. The leakage of hydrogen is particularly critical, as this can lead to explosive gas mixtures in the environment. It is an object of the invention to provide an improved electrochemical cell stack for an electrolyzer unit and / or a fuel cell unit. Disclosure of the invention

[0005] The object of the invention is achieved by means of an electrochemical cell stack for an electrochemical unit, in particular an electrolysis cell stack or a fuel cell stack; as well as by means of an electrochemical unit, in particular an electrolyzer unit or a fuel cell unit, and an electrochemical system, in particular an electrolyzer system or a fuel cell system. Advantageous developments, additional features, and / or advantages of the invention emerge from the dependent claims and the following description.

[0006] The cell stack according to the invention has a large number of individual electrochemical cells which are clamped together in an actual cell stack of the cell stack, wherein at least the actual cell stack is essentially fluid-sealed to the outside, i.e. with respect to a later installation environment, in a stack housing, and at least during operation of the cell stack, a stack housing space directly on the actual cell stack is at least partially filled with a fluid other than air. - In this case, a large number of bipolar plates and the individual electrochemical cells preferably alternate with one another in the actual cell stack of the cell stack. The cell stack differs from the actual cell stack in that, in addition to the actual cell stack, it also has at least the stack housing.

[0007] The fluid tightness of the cell stack, of course, only applies to the extent that proper operational function of the cell stack is guaranteed. And air, of course, refers to the gas mixture of the Earth's atmosphere with its three main components: nitrogen (approx. 78 vol%), oxygen (approx. 21 vol%), and argon (approx. 1 vol%). A fluid other than air has at least a significantly different composition, in particular a significantly reduced oxygen content (less than approximately 5 vol%), or a completely different composition (see examples below).

[0008] In embodiments, the stacked housing can essentially only house the actual cell stack. Alternatively, the stacked housing can house the cell stack including at least one end plate. In this case, the stacked housing space can be formed between the actual cell stack and the stacked housing. - Furthermore, in embodiments, no solid can be distributed over the entire surface in the stacked housing space to prevent a chemical reaction. Furthermore, an ambient pressure or an overpressure can prevail in the fluid of the stacked housing space. Furthermore, there can be no negative pressure in the fluid of the stacked housing space compared to the environment.

[0009] The fluid is a liquid and / or a gas. The fluid can be or comprise a product fluid and / or a reactant fluid of the cell stack. Furthermore, the fluid can be or comprise a chemically inert fluid and / or a flame-retardant fluid. Furthermore, the fluid can be or comprise water, potassium hydroxide solution, hydrogen, carbon dioxide, nitrogen, and / or argon. Alternatively or additionally, another inert gas such as helium, etc., or an (inert) gas mixture can also be used.

[0010] Particularly during cell stack operation, the fluid in the stack housing space may be at an overpressure relative to the ambient pressure. The overpressure may, for example, correspond to the maximum pressure that exists on average in the cathode compartments of an electrolysis cell stack. Thus, a cathode side of an electrolysis cell stack can be operated with a fluid overpressure of approximately equal to or greater than approximately 10 bar, 15 bar, 20 bar, 25 bar, 30 bar, 35 bar, 40 bar, 45 bar, or 50 bar, ±2 bar in each case, relative to an anode side.

[0011] The overpressure can be and / or is generated by a reactant fluid and / or a product fluid of the cell stack. In an electrolysis cell stack, for example, the product fluid hydrogen can be used as a pressure supplier. The hydrogen or the pressure from the hydrogen can originate downstream of the electrolysis cell stack, e.g., from a product medium path, e.g., to a hydrogen storage device.

[0012] Furthermore, the overpressure can be generated and / or be generated essentially by means of a leakage fluid of the cell stack. In an electrolysis cell stack, for example, the leakage fluid hydrogen can be used as a pressure supplier. The hydrogen or the pressure can originate directly from the cathode chambers of the electrolysis cell stack. Furthermore, the overpressure can be generated by means of a fluid delivery device that supplies the cell stack with a medium. In an electrolyzer unit, this can be a water delivery device or, in a fuel cell unit, an anode-side or cathode-side delivery device.

[0013] The stack housing of the actual cell stack can comprise at least one end plate, in particular exactly two end plates, of the cell stack. Furthermore, the stack housing can comprise at least or exactly one, two, three, or four side parts, optionally per end plate. In particular, the stack housing can comprise two end plates and exactly two or exactly four side parts. Relevant edges of an end plate and a side part are joined together in a particularly fluid-tight manner. Furthermore, relevant edges of the side part(s) are joined together in a particularly fluid-tight manner.

[0014] A casing of the stack housing extending around the actual cell stack can be designed in such a way that a change in the distance between the end plates of the cell stack is possible, e.g., due to the operation of the cell stack. In this case, the casing can be formed, in particular, by the side part(s).

[0015] The shell of the stacked housing can be spherical, corrugated, or bellows-like, at least in sections, when the stacked housing is not in its extended state. Furthermore, the shell can be substantially rectilinear in the stacking direction when the stacked housing is in its extended state. Furthermore, the shell can comprise two shell sections that can be moved relative to one another in the stacking direction. The shell sections can be configured to move past one another or into one another in the cell stack. Naturally, the shell sections are fluid-sealed relative to one another.

[0016] The two electrical power connections for the entire actual cell stack can be arranged in the stack housing space. Furthermore, electrical measuring connections for the bipolar plates and / or measuring cabling for the cell stack can be arranged in the stack housing space. Furthermore, clamping devices, in particular center sections of clamping devices, for the cell stack can be arranged.

[0017] The unit according to the invention or the system according to the invention comprises an electrochemical cell stack and preferably a control device for controlling and / or regulating the cell stack, wherein the cell stack is designed according to the invention.

[0018] To pressurize the stack housing space, a fluid line can lead from a medium path, in particular a product medium path, into the stack housing space. A valve can be installed in the fluid line, which only opens when a specific pressure in the medium path is reached. To vent the stack housing space, a fluid line can lead away from the stack housing space and preferably lead into a medium path. Such a medium path can be, in particular, an (anode) exhaust gas path or a product medium path. A check valve can be installed in the fluid line, which only opens when a specific pressure in the stack housing space is reached.

[0019] These embodiments can be implemented within the cell stack, whereby the relevant fluid line and, if applicable, a relevant valve can be arranged, for example, within an end plate of the cell stack. Alternatively, of course, neither a fluid line for pressurization can open into the stack housing space, nor can a fluid line lead away from the stack housing space for venting. - A fluid line is, of course, understood to mean an intentionally arranged fluid passage and not a merely arbitrary fluid passage, e.g., due to a leak.

[0020] The unit or system can either have no ventilation or active ventilation of the cell stack or the actual cell stack. Active ventilation can be provided, for example, by a fan or ventilator on the cell stack or in the unit or system. The fan or ventilator can direct an airflow directly and / or indirectly onto the cell stack. If no ventilation of the cell stack is provided, such a fan or ventilator is obviously missing.

[0021] Furthermore, the unit or system may have no ventilation or only passive ventilation of the cell stack or of the actual cell stack. The passive ventilation can be achieved, for example, by arranging the cell stack in the unit or system in such a way that the unit or system enables a fluid, in particular air, to flow passively around the cell stack. In a stationary unit or system, this can be achieved by an exposed position of the cell stack on / in the unit or system. In a fuel cell vehicle, this can be achieved by an air flow generated by the fuel cell vehicle itself and directed past the cell stack. Short description of the characters

[0022] 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: The Fig. 1 shows a simplified block diagram of an embodiment of a fuel cell unit with an electrochemical fuel cell stack for a fuel cell system of a fuel cell vehicle, the Fig. 2 shows a simplified block diagram of an embodiment of an electrolyzer unit with an electrochemical electrolysis cell stack for an electrolyzer system, the Fig. 3 and Fig. 4 shows in perspective views an electrolysis cell stack according to the prior art ( Fig. 3) and an electrolysis cell stack according to the invention ( Fig. 4), the Fig. 5 to 7 each show a schematic, sectional side view of an electrochemical cell stack with an enclosed actual cell stack, and the Fig. 8 to 10 also show, in a schematic, sectional side view, an electrochemical cell stack and a behavior of a stack housing of the cell stack when the cell stack is elongated. Embodiments of the invention

[0023] The invention is based on an electrochemical cell stack 10, 60 of a fuel cell unit 1 (cf. Fig. 1 and 8 to 10) for a mobile or stationary fuel cell system and a stationary or mobile electrolyzer unit 60 (cf. the Fig. 2 and 4 to 10) for an electrolyzer system (see also above). - The drawing only shows those sections of the fuel cell system or electrolyzer system that are necessary for an understanding of the invention. - Although the invention is described and illustrated in detail by preferred embodiments, the invention is not limited to the disclosed embodiments. Other variations can be derived therefrom without departing from the scope of the invention.

[0024] The Fig. 1 and Fig. 2 each show an electrochemical aggregate 1, 51 ( Fig. 1: Fuel cell unit 1, Fig. 2: Electrolyzer unit 51) according to a general embodiment, with at least one, in particular a plurality of, electrochemical cell stack 10, 60 or a stack 10, 60 ( Fig. 1: Fuel cell stack 10, Fig. 2: Electrolysis cell stack 60) bundled electrochemical single cells 11, 61 ( Fig. 1: Single fuel cells 11, Fig. 2: Individual electrolysis cells 61), which are housed in a preferably fluid-tight stacked housing 16, 66.

[0025] Each individual cell 11, 61 comprises an electrode chamber 12, 62 formed as an anode chamber 12, 62 and an electrode chamber 13, 63 formed as a cathode chamber 13, 63, which are spatially and electrically separated from one another, for example, by a membrane of a membrane electrode unit 15, 65. An electrically conductive fluid transport layer is arranged in the respective electrode chamber 12, 13; 62, 63, which is in fluid communication with a bipolar plate 100 (see below). Alternatively or in addition to a membrane electrode unit 15, 65 with only one electrode, at least one electrode can also be provided away from the membrane at a fluid transport layer.

[0026] A bipolar plate 100 is arranged between two directly adjacent membrane electrode units 15, 15; 65, 65 including a respective anode compartment 12, 62 and a respective cathode compartment 13, 63, which serves, among other things, to supply / discharge media 3 / 4, 5 / 6, 7 / 8; 53 / 54, 56 for an anode compartment 12, 62 of a first individual cell 11, 61 or a cathode compartment 13, 63 of a directly adjacent second individual cell 11, 61 and, moreover, to create an electrically conductive connection between these individual cells 11, 11; 61, 61. - The cathode compartments 13, 63 and, if applicable, their common inflow area or their actual electrodes form a cathode 39, 89 and the anode compartments 12, 62 and, if applicable, their common inflow area or their actual electrodes form an anode 29, 79 of the cell stack 10, 60.

[0027] In principle, the membrane electrode assemblies 15, 65 of the cell stack 10, 60 can comprise PEMs (proton exchange membranes) or AEMs (anion exchange membranes). PEMs are preferred for a fuel cell stack 10, and AEMs or PEMs are preferred for an electrolysis cell stack 60. In addition to the fuel cell unit 1 or the electrolyzer unit 51, the fuel cell system or electrolyzer system comprises peripheral system components, such as a control unit, which can be one of the fuel cell system or electrolyzer system itself, etc.

[0028] The following explanations only concern the electrochemical unit 1 as a fuel cell unit 1, e.g. according to the Fig. 1. - To supply the electrochemical cell stack 10 as 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 and a cathode supply 30.

[0029] The anode supply 20 preferably comprises: a fuel reservoir 23 for the anode operating medium 3 (flowing in); an anode supply path 21 (medium path 21) with a pressure reducer, a shut-off valve and / or a metering valve 27 (for example), as well as a jet pump 24 (jet pump 24, ejector 24); an anode exhaust gas path 22 (medium path 22) for an anode exhaust gas medium 4 (flowing out, usually into the environment 2); a fuel recirculation path 25 with a fluid conveying device 26 located therein; optionally a water separator with preferably a water tank.

[0030] The cathode supply 30 preferably comprises: a cathode supply path 31 (medium path 31) for the cathode operating medium 5 (flowing in, usually from the environment 2), with a fluid conveying device 33; a cathode exhaust gas path 32 (medium path 32) for a cathode exhaust gas medium 6 (flowing out, usually into the environment 2), preferably with a turbine 34, in particular for the fluid conveying device 33; a humidity 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 gas path 32, with a bypass valve 37; optionally a water separator, preferably with a water tank.

[0031] The fuel cell unit 1 further comprises, in particular, a cooling medium supply 40 of a thermal system, through which the fuel cell stack 10 can be integrated into a cooling circuit for temperature control, preferably by means of its bipolar plates 100 (cooling medium paths 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.

[0032] The following explanations only concern the electrochemical unit 51 as electrolyzer unit 51, e.g. according to the Fig. 2. - To supply the electrochemical cell stack 60 as electrolysis cell stack 60 with water 53 as a supply medium 53, the electrolyzer unit 51 has a water supply 70. And to remove the media 54, 56 of the cell stack 60, the electrolyzer unit 51 has a media removal 80.

[0033] The water supply 70 preferably comprises: a water reservoir 73 for the water 53 (flowing in), a supply path 71 (medium path 71) and a water conveying device 76 on / in the supply path 71. - The media removal 80 has at least one disposal path 81 (medium path 81) for (cooling) water 54 or (cooling) water with oxygen 54 back into the water reservoir 73, optionally with a gas separator for oxygen, and / or in another direction (shown in dashed lines), e.g. into the environment 2.

[0034] A product medium 56 of the electrolyzer unit 51, i.e., the produced hydrogen 56, is transported away through a product medium path 82 of the medium removal 80. A water separator 83 with a valve 84 can be inserted in the product medium path 82 to separate water in the product medium path 82. The water separated in the water separator 83 can be conveyed back into the water reservoir 73 or in another direction, e.g., into the environment 2, possibly by gravity. The produced hydrogen 56 can be stored, for example, in a hydrogen storage device 90, wherein the product medium path 82 can flow directly into the hydrogen storage device 90. Another method of transporting the hydrogen 56 is, of course, possible.

[0035] Depending on the embodiment of the electrolyzer unit 51, a media guide in the cell stack 60 can be designed differently. In this case, it is possible to provide a temperature control that differs from an electrochemical function of the cell stack 60, in particular water cooling, or to implement the temperature control together with the electrochemical function of the cell stack 60.

[0036] In particular, it is possible, in membrane electrode assemblies 65 with AEMs, to set up a supply of water 53, possibly exclusively on the anode side (dotted arrow at the anode 79). In this case, the water 53 can flow directly into the 'anode' 79. Furthermore, it is possible, in membrane electrode assemblies 65 with PEMs, to set up a supply of water 53, possibly exclusively on the cathode side 89 (dotted arrow at the cathode 89). In this case, the water 53 can flow directly into the 'cathode' 89.

[0037] The Fig. 3 shows an electrolysis cell stack 60 according to the prior art, wherein an actual cell stack 100 of the cell stack 60 is accessible from the outside, apart from the clamping means shown that clamp the cell stack 60 together. In the actual cell stack 100 of the cell stack 60, a plurality of individual electrochemical cells 51 and a plurality of bipolar plates essentially alternate with one another. The bipolar plates 67 of the cell stack 60 are visible on the outside, or their bipolar plates 67 are partially accessible from the outside.

[0038] According to the invention, the actual cell stack 100 (cf. the Fig. 4, which shows an electrolysis cell stack 60) or the cell stack 10, 60 (not shown) in a stack housing 16, 66 (see above) are fluid-sealed to the outside. The stack housing 16, 66 is at least partially filled with a fluid 202, i.e., a gas 202 and / or a liquid 202, which is different from air (see above). The fluid 202 is present in the stack housing 16, 66 at least during operation of the electrochemical unit 1, 51, but can of course also be present in the stack housing 16, 66 outside of operation of the unit 1, 51.

[0039] The fluid 202 is enclosed in a stack housing space 200 (side part(s) 120, see above) that preferably extends substantially completely around the actual cell stack 100 or the cell stack 10, 60. The stack housing space 200 is formed, among other things, between an outer side of the actual cell stack 100 or the cell stack 10, 60 and an inner side of the stack housing 16, 66. If the actual cell stack 100 is fluid-sealed to the outside, the stack housing space 200 is further delimited by the end plates 110 of the actual cell stack 100 ( Fig. 4 to 10). If the cell stack 10, 60 is fluid-sealed to the outside, the end plates 110 of the cell stack 10, 60 are preferably also located at least partially within the stack housing 16, 66 (not shown).

[0040] The Fig. 5 shows an embodiment wherein the stack housing space 200 between the stack housing 66 and the actual cell stack 100 is filled with water 202 and / or another liquid 202. Furthermore, the stack housing space 200 is in fluid communication with a hydrogen outlet of the cell stack 66, e.g., at / in an end plate 110, or the product medium path 82 (fluid line 112), whereby the stack housing space 200 is pressurized with produced hydrogen 56 (pressurization of the stack housing space 202). This results in a reduction in hydrogen leakage to the outside, since the pressure drop between the cathode side of the actual cell stack 100 and the outside of the cell stack 60 is essentially zero (no leakage due to a differential pressure).

[0041] The Fig. 6 shows an embodiment wherein the stack housing space 200 between the stack housing 66 and the actual cell stack 100 is / is filled with hydrogen 202 (= 56) produced from a leak in the actual cell stack 100. This results in a reduction in hydrogen leakage to the outside, since a pressure drop between the cathode side of the actual cell stack 100 and the outside of the cell stack 60 is essentially zero (no leakage due to a differential pressure).

[0042] Pressurization of the stack housing space 200 can occur through hydrogen leakage from the actual cell stack 100. - Furthermore, a fluid line 112 (dashed line) for pressurizing (see valve above) and / or venting (see check valve above) the stack housing space 202 can be provided between the stack housing space 200 and a hydrogen outlet of the cell stack 66, e.g., on / in an end plate 110, or the product medium path 82.

[0043] The Fig. 7 shows an embodiment wherein the stack housing space 200 between the stack housing 66 and the actual cell stack 100 is / is filled with nitrogen 202 and / or another suitable gas 202. Pressurization of the stack housing space 200 can occur through hydrogen leakage from the actual cell stack 100. This results in a reduction in hydrogen leakage to the outside, since the pressure drop between the cathode side of the actual cell stack 100 and the outside of the cell stack 60 is essentially zero.

[0044] In the embodiments of the Fig. 5 to 7 and, of course, others, no separate ventilation of the actual cell stack 100 or the electrolysis cell stack 60 is required. There are no strict requirements regarding the leakage of hydrogen 56 to the outside. Protection of the environment of the cell stack 60 is ensured in the event of an accident. - This, of course, applies analogously to a fuel cell stack 10.

[0045] Furthermore, it is preferred that the stack housing 16, 66 follows a change in the distance of the end plates 110 of the cell stack 10, 60, e.g., an elongation / shortening of the actual cell stack 100 during operation of the fuel cell unit 1 or the electrolyzer unit 51. For this purpose, a jacket 120; 120, 120; ... of the stack housing 16, 66, which runs around the actual cell stack 100, is designed such that it follows the change in the distance of the end plates 110. This is shown in the Fig. 8 to 10 are shown as examples.

[0046] For this purpose, the casing 120; 120, 120; ... or its side parts 120 can be crowned at least in sections ( Fig. 8), corrugated spring-like (not shown), bellows-like ( Fig. 9) etc. If the stacking housing 16, 66 elongates, the casing 120; 120, 120; ... or its side parts 120 stretches in the stacking direction, whereby the casing 120; 120, 120; ... or its side parts 120 straighten.

[0047] Furthermore, the side parts 120 can be formed in two parts, wherein a section of a side part 120 can be moved past each other relative to another section of the same side part 120 ( Fig.10) or is configured to be movable into one another (not shown). Here, the two sections of the same side part 120 are, of course, fluid-sealed from one another. This naturally applies analogously to the casing 120; 120, 120; .... A dividing plane of a respective side part 120 or the casing 120; 120, 120; ... is located between the two end plates 110.

Claims

[1] Electrochemical cell stack (10, 60) for an electrochemical unit (1, 51), in particular electrolysis cell stack (60) or fuel cell stack (10), with a plurality of electrochemical individual cells (11, 51) which are clamped together in an actual cell stack (100) of the cell stack (10, 60), characterized by , that at least the actual cell stack (100) is fluid-sealed to the outside in a stack housing (16, 66), and at least during operation of the cell stack (10, 60) a stack housing space (200) directly on the actual cell stack (100) is at least partially filled with a fluid (202) other than air. [2] Electrochemical cell stack (10, 60) according to the preceding claim, characterized by , that: • the stack housing (16, 66) essentially only houses the actual cell stack (100), or • the stack housing (16, 66) encloses the cell stack (10, 60) including at least one end plate (110), and / or • the stack housing space (200) is formed between the actual cell stack (100) and the stack housing (16, 66). [3] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized by , that: • there is no solid material distributed over the entire surface in the stack housing space (200) to prevent a chemical reaction, • an ambient pressure or an overpressure prevails in the fluid (202) of the stack housing space (200), and / or • there is no negative pressure in the fluid (202) of the stack housing space (200) compared to an environment (2). [4] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized by that the fluid (202) as a liquid (202) and / or gas (202): • a product fluid (202) and / or a reactant fluid (202) of the cell stack (10, 60), • a chemically inert fluid (202) and / or a flame retardant fluid (202), and / or • Water (202), potassium hydroxide solution (202), hydrogen (202), carbon dioxide (202), nitrogen (202) and / or argon (202). [5] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized by that, in particular during operation of the cell stack (10, 60), the fluid (202) in the stack housing space (200) has an overpressure relative to the environment (2), wherein: • the overpressure can be generated and / or is generated by means of a reactant fluid (202) and / or a product fluid (202) of the cell stack (10, 60), • the overpressure can be generated and / or is generated essentially by means of a leakage fluid of the cell stack (10, 60), and / or • the overpressure can be generated by means of a fluid conveying device (33, 76) which supplies the cell stack (10, 60) with a medium (3, 5; 53). [6] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized by that the stack housing (16, 66) of the actual cell stack (100): • comprises at least one end plate (110), in particular exactly two end plates (110), of the cell stack (10, 60), • comprises at least or exactly one, two, three or four side parts (120), if necessary per end plate (110), • mutually relevant edges of an end plate (110) and a side part (120) are joined together in a fluid-tight manner, and / or • the edges of the side part(s) (120) that concern each other are joined together in a fluid-tight manner. [7] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized bythat a jacket (120; 120, 120; ...) of the stack housing (16, 66) running around the actual cell stack (100) is designed in such a way that a change in the distance between the end plates (120) of the cell stack (10, 60) is possible. [8] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized by that the shell of the stacking housing (16, 66): • in a non-elongated state of the stack housing (16, 66) is at least partially crowned, corrugated spring-like or bellows-like, • in an elongated state of the stacking housing (16, 66) is formed substantially rectilinearly in the stacking direction, and / or • comprises two shell sections that can be moved relative to one another in the stacking direction. [9] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized by that in the stacking housing space (200): • the electrical power connections for the entire actual cell stack (100) are set up, • electrical measuring connections of the bipolar plates (17, 67) and / or a measuring cabling of the cell stack (10, 60) is set up, and / or • clamping means, in particular central sections of clamping means, of the cell stack (10, 60) are arranged. [10] Electrochemical unit (1, 51), in particular electrolyzer unit or fuel cell unit, or electrochemical system, in particular electrolyzer system or fuel cell system, with an electrochemical cell stack (10, 60) and a control device for controlling and / or regulating the cell stack (10, 60), characterized by , that the cell stack (10, 60) is designed according to one of the preceding claims. [11] Electrochemical aggregate (1, 51) or electrochemical system according to the preceding claim, characterized by , that: • for pressurizing the stack housing space (202), a fluid line (112) opens into the stack housing space (202) from a medium path (31, 82), in particular a product medium path (82), and / or • for venting the stack housing space (202), a fluid line (112) leads away from the stack housing space (202) and preferably opens into a medium path (22, 82), or • neither a fluid line for pressurization opens into the stack housing space (202) nor a fluid line leads away from the stack housing space (202) for ventilation. [12] Electrochemical unit (1, 51) or electrochemical system according to one of the preceding claims, characterized by that in the unit (1, 51) or system no or active ventilation of the cell stack (10, 60) or of the actual cell stack (100) is provided, and / or no or passive ventilation of the cell stack (10, 60) or of the actual cell stack (100) is provided.

Images