Electrochemical cell unit

Abstract

Proposed is an electrochemical cell unit (25) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit (11), the electrochemical cell unit having: a cell stack (3), the cell stack (3) comprising stacked electrochemical cells (24) as a cell stack (3); a current plate (45) for conducting current; an end plate (47); an insulating plate (46) which electrically insulates the end plate (47) from the current plate (45) and the electrochemical cells (24); at least one inlet channel (50), formed in the cell stack (3), for conducting a process fluid into the electrochemical cells (24), the inlet channel (50) being formed by inlet openings (48) in the end plate (47), in the insulating plate (46) and in the current plate (45); and at least one outlet channel (51), formed in the cell stack (3), for conducting a process fluid out of the electrochemical cells (24), the outlet channel (51) being formed by outlet openings (49) in the end plate (47), in the insulating plate (46) and in the current plate (45), wherein the insulating plate (46) has different material properties in a process fluid region (53) delimiting the at least one inlet opening (48) and / or in a process fluid region (53) delimiting the at least one outlet opening (49) than in a plate region (52) of the insulating plate (46) outside said process fluid region / s (53).

Description

[0001] Description

[0002] title

[0003] Electrochemical cell unit

[0004] The present invention relates to an electrochemical cell unit according to the preamble of claim 1 and an electrochemical cell system according to the preamble of claim 15.

[0005] State of the art

[0006] Fuel cell units, as galvanic cells, convert continuously supplied fuel and oxidant into electrical energy and water through redox reactions at an anode and cathode. Fuel cells are used in a wide variety of stationary and mobile applications, for example, in homes without a power grid connection or in motor vehicles, in rail transport, aviation, aerospace, and shipping. In fuel cell units, a large number of fuel cells are arranged in a stack.

[0007] In fuel cell units, a large number of fuel cells are arranged in a fuel cell stack. Within each fuel cell, there is a gas space for the oxidant, i.e., a flow space for the passage of oxidant, such as ambient air with oxygen. The gas space for the oxidant is formed by channels on the bipolar plate and by a gas diffusion layer for a cathode. The channels are thus formed by a corresponding channel structure of a bipolar plate, and the oxidant, namely oxygen, passes through the gas diffusion layer to reach the cathode of the fuel cell. Similarly, a gas space for fuel is formed at an anode. Electrolysis cell units consisting of stacked electrolysis cells, similar to fuel cell units, are used, for example, for the electrolytic production of hydrogen and oxygen from water.Furthermore, fuel cell units are known that can be operated as reversible fuel cell units and thus as electrolysis cell units. In addition, there are electrolysis cell units that are used exclusively for electrolysis. Fuel cell units and electrolysis cell units form electrochemical cell units. Fuel cells and electrolysis cells form electrochemical cells. In the fuel cell stack as a cell stack, channels for fuel, oxidant, and a coolant as the process fluid are formed. In the electrolysis cell stack as a cell stack, channels for electrolyte as the process fluid are formed. In the electrochemical cell units, the cell stack is supplied with electrical energy or electrical energy is dissipated using two current plates. An electrical potential is therefore present between the two current plates.Insulating plates serve to electrically insulate the current plates and the electrochemical cells from the end plates and the environment. To supply the electrochemical cell stack, process fluids must be introduced into and discharged from the electrochemical cell stack through inlet and outlet channels. For this purpose, inlet and outlet openings are provided in the insulating plate. The mechanical, hydraulic, and chemical stresses on the insulating plate are greatest in the area of ​​these inlet and outlet openings. For this reason, damage to the insulating plate can occur in the area of ​​the inlet and outlet openings, causing a fault current to be diverted from the electrically loaded part of the electrochemical cell stack through an end plate into the environment, or even resulting in a short circuit.This leads to damage or reduced efficiency of the electrochemical cell unit.

[0008] DE 10 2022 101106 A1 discloses an electrolysis cell, comprising a cell frame made of insulating plastic, which encloses a cell and is designed to accommodate a membrane electrode assembly (MEA) and diffusion layers adjacent to both sides of the MEA, wherein the cell frame is arranged between two electrically conductive plates which function as bipolar and / or current collector plates, wherein in each case at least one sealing element is provided between the cell frame and the bipolar or current collector plates, wherein the in each case at least one sealing element is formed by a flat gasket, wherein the flat gaskets provided on both sides of the cell frame are integrated into the cell frame by means of a 2K injection molding process.

[0009] Disclosure of the invention

[0010] Advantages of the invention

[0011] An electrochemical cell unit according to the invention for converting electrochemical energy into electrical energy as a fuel cell unit and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit, comprising a cell stack, the cell stack comprising stacked electrochemical cells as a cell stack, a current plate for conducting current, an end plate, an insulating plate electrically insulating the end plate from the current plate and the electrochemical cells, at least one inlet channel formed in the cell stack for conducting a process fluid into the electrochemical cells, and the inlet channel is formed by inlet openings in the end plate, the insulating plate, and the current plate, at least one outlet channel formed in the cell stack for conducting a process fluid from the electrochemical cells, and the outlet channel is formed by outlet openings in the end plate,the insulating plate and the flow plate, wherein the insulating plate has different material properties in a process fluid region delimiting the at least one inlet opening and / or the at least one outlet opening than in a plate region of the insulating plate outside this process fluid region. The insulating plate can thus advantageously be made in the region of the inlet opening and / or outlet opening from a material properties optimally adapted to the mechanical, hydraulic and chemical requirements in the region of the inlet opening and / or the outlet opening, in particular material,This advantageously avoids the risk of conducting faulty current from the electrochemical cells charged with an electrical potential into the end plate and thus into the environment, essentially at low cost. In a further variant, the insulating plate is formed from a different material in a process fluid region delimiting each of the at least one inlet opening and / or the at least one outlet opening than in a plate region of the insulating plate outside this process fluid region.

[0012] In a supplementary variant, the material of the process fluid region of the insulating plate has a greater modulus of elasticity than the plate region of the insulating plate. Preferably, the modulus of elasticity of the insulating plate in the process fluid region is greater than 2 times, 3 times, 5 times, or 10 times the modulus of elasticity in the plate region.

[0013] In an additional embodiment, the process fluid region of the insulating plate is completely continuous in the circumferential direction of the inlet opening and / or outlet opening. Thus, the entire inlet opening and / or outlet opening is advantageously delimited by the process fluid region of the insulating plate.

[0014] Preferably, the components of the electrochemical cells are layered and span fictitious planes.

[0015] In a further embodiment, the process fluid region of the insulating plate is completely continuous in an axial direction perpendicular to the fictitious planes at the at least one inlet opening and / or the at least one outlet opening. In the axial direction and in the flow direction of the process fluid in the inlet channel and / or the outlet channel, the inlet opening and / or the outlet opening are thus completely delimited by the material with different material properties, in particular a different material, of the process fluid region.

[0016] In a further embodiment, the process fluid region of the insulating plate has a substantially constant extension in a radial direction relative to the at least one inlet opening and / or the at least one outlet opening of the insulating plate, in particular with a deviation of less than 30%, 20%, or 10%. The mechanical stresses on the annular process fluid region can thus advantageously be absorbed by the process fluid region substantially uniformly in the circumferential direction.

[0017] In a supplementary variant, the at least one inlet opening and / or the at least one outlet opening is substantially circular in cross-section. The at least one inlet opening and / or the at least one outlet opening optionally has any desired cross-sectional shape, for example rectangular, in particular square, or elliptical.

[0018] In a further embodiment, the process fluid region is ring-shaped.

[0019] The process fluid area is designed as a sleeve. A sleeve with a cylindrical shape is optimally adapted to the geometry of the inlet channel and / or the outlet channel.

[0020] In an additional embodiment, the process fluid region of the insulating plate and the plate region of the insulating plate are separate components or formed as one piece.

[0021] In a further embodiment, a distance is formed between the process fluid region of the insulating plate and the plate region of the insulating plate, in particular in the radial direction. This distance, in particular in the radial direction, is preferably at least 1%, 3%, 5%, or 10% of the radial extent, in particular the maximum radial extent, of the process fluid region without prestressing the electrochemical cell stack.

[0022] Preferably, the plate area of ​​the insulating plate is made of plastic.

[0023] In a further variant, the process fluid region of the insulating plate is formed at least partially, in particular completely, from ceramic.

[0024] An electrochemical cell system according to the invention for converting electrochemical energy into electrical energy as a fuel cell system and / or for converting electrical energy into electrochemical energy as an electrolysis cell system, comprising an electrochemical cell unit as a fuel cell unit and / or an electrolysis cell unit, at least one supply system for at least one process fluid, wherein the electrochemical cell unit is designed as an electrochemical cell unit described in this patent application

[0025] In a further embodiment, the material of the process fluid region of the insulating plate has a greater hardness, in particular a greater Shore hardness, than the plate region of the insulating plate. Preferably, the hardness, in particular Shore hardness, of the insulating plate in the process fluid region is greater than 2 times, 3 times, 5 times, or 10 times the hardness, in particular Shore hardness, in the plate region.

[0026] In an additional embodiment, the insulating plate has a lower permeation coefficient at each process fluid region than at the plate region. In particular, the permeation coefficient of the process fluid region is less than 70%, 50%, 30%, or 10% of the permeation coefficient of the plate region. The high permeation coefficient at the process fluid region advantageously substantially prevents radial diffusion of the process fluid into the insulating plate.

[0027] Preferably, the insulating plate on the respective process fluid region and / or the plate region is formed from a plastic with a modulus of elasticity less than 50, 20, 10, 5, 3 or 2 GPa and / or greater than 10, 20, 5, 3 or 2 GPa.

[0028] Preferably, the insulating plate is formed on the respective process fluid region and / or the plate region from a plastic, in particular as FKM and / or EPDM and / or silicone.

[0029] In another variant, the inlet openings are aligned to form one inlet channel each.

[0030] In a further variant, the discharge openings are aligned to form a discharge channel each. In an additional embodiment, inlet openings and / or outlet openings are formed in the electrochemical cells, so that at least one inlet channel and / or at least one discharge channel is formed in the cell stack, preferably for conducting the at least one process fluid through the channels in the electrochemical cells.

[0031] Preferably, the inlet openings and / or outlet openings are arranged in alignment to form at least one inlet channel and / or at least one outlet channel.

[0032] In a further embodiment, the fuel cell system comprises a fuel supply system with a pressure vessel for fuel as a process fluid and an oxidant supply system with a gas conveying device for oxidant as a process fluid and / or at least one discharge opening for discharging at least one process fluid into the environment.

[0033] In a further embodiment, the electrolysis cell system comprises an electrolyte supply system with a storage container for electrolyte and a pump for electrolyte and preferably a separator for hydrogen and / or a separator for oxygen.

[0034] In a supplementary variant, the current plate lies directly on an electrochemical cell.

[0035] In a supplementary variant, the fuel cell system comprises a fuel cell unit, a cooling system, an oxidant supply system and a fuel supply system.

[0036] In a further embodiment, the electrochemical cells each comprise an ion exchange membrane, in particular a proton exchange membrane and / or an anion exchange membrane, an anode, a cathode, preferably at least one gas diffusion layer and / or at least one separator plate, in particular a bipolar plate. In electrolysis cells, in contrast to fuel cells, no bipolar plates are required, but rather bipolar plates as separator plates made of only one plate, because there is no channel for coolant in electrolysis cells. In fuel cells, the bipolar plate made of

[0037] 2 plates at least one channel for coolant is formed between the 2 plates.

[0038] Preferably, the fuel is hydrogen, hydrogen-rich gas, reformate gas or natural gas.

[0039] Advantageously, the electrochemical cells and / or components of the electrochemical cells are essentially flat and / or disc-shaped.

[0040] In another variant, the electrochemical cell unit comprises a housing and / or a connection plate. The stack is enclosed by the housing and / or the connection plate.

[0041] Preferably, at least one inlet opening and / or at least one outlet opening is formed in the connection plate.

[0042] In a complementary variant, the oxidizing agent is air with oxygen or pure oxygen.

[0043] Preferably, the fuel cell unit is a PEM fuel cell unit with PEM fuel cells or an SOFC fuel cell unit with SOFC fuel cells or an alkaline fuel cell (AFC).

[0044] Short description of the drawings

[0045] In the following, exemplary embodiments of the invention are described in more detail with reference to the accompanying drawings. They show:

[0046] Fig. 1 is a highly simplified representation of a fuel cell system,

[0047] Fig. 2 a highly simplified representation of an electrolysis cell system and

[0048] Fig. 3 shows a cross-section of the cell stack in the region of an inlet opening or outlet opening. In Fig. 1, a fuel cell unit 1 is shown as a fuel cell stack 3, i.e. as a fuel cell stack 3, or generally cell stack 12. The fuel cell unit 1 comprises the fuel cell stack 3, a housing 13 and a connection plate 15. The housing 13 delimits an interior space 14. The connection plate 15 also functions as a housing 13 and is fixed to the remaining housing 13 by fixing elements 16, in particular screws 17. In the fuel cell stack 3, fuel cells 4 are stacked as PEM fuel cells 5 and arranged in alignment. Due to the large number of stacked fuel cells 4, approximately 300 to 400, not all of them are shown in Fig. 1 for the sake of simplicity. The principle of fuel cells 4 is that electrical energy orelectrical current is generated. Hydrogen H2 is fed to an anode (not shown) as a gaseous fuel as recirculation fuel and the anode forms the negative pole. A gaseous oxidant, namely air with oxygen, is fed to a cathode (not shown), i.e. the oxygen in the air provides the necessary gaseous oxidant. Reduction (electron absorption) takes place at the cathode. Oxidation as electron release takes place at the anode. The fuel cells 4 also comprise an ion exchange membrane as a proton exchange membrane (Proton Exchange Membrane, PEM), which is arranged between the anode and the cathode. The electrodes as the anode and cathode (not shown) are arranged on the two sides of the PEM, each facing gas spaces as channels of the fuel cells 4.A unit consisting of the PEM, anode, and cathode is referred to as a membrane electrode assembly (MEA) (not shown). A gas diffusion layer (GDL) is deposited on the anode and cathode. A bipolar plate (not shown) is deposited on the GDL. The electrically conductive bipolar plate serves as a current collector, for water drainage, and for conducting the reaction gases. The fuel cells 4 and the components of the fuel cells 4 are layered and span fictitious planes 41.

[0049] In the fuel cell unit 1, the fuel cells 4 are arranged between two clamping elements 18 as clamping plates 19. An upper clamping plate 20 rests indirectly on the uppermost fuel cell 4 and a lower clamping plate 21 rests indirectly on the lowermost fuel cell 4. The clamping elements 18 apply a compressive force to the fuel cells 4, i.e. the upper clamping plate 20 rests with a compressive force on the uppermost fuel cell 4 and the lower clamping plate 21 rests with a compressive force on the lowermost fuel cell 4. The fuel cell stack 3 is thus clamped in order to ensure the tightness for the fuel, the oxidizing agent and the coolant, in particular due to elastic seals, and also to keep the electrical contact resistance within the fuel cell stack 3 as low as possible.To clamp the fuel cells 4 with the clamping elements 18, four connecting devices 22 are designed as bolts 23 on the fuel cell unit 1, which are subjected to tensile stress. The four bolts 23 are firmly connected to the clamping plates 19.

[0050] An inlet opening 48 for introducing recirculation fuel into the recirculation fuel channels (not shown) of the fuel cells 4 is formed in the connecting plate 15 and in the lower clamping plate 21. Furthermore, an outlet opening 49 for discharging recirculation fuel from the recirculation fuel channels (not shown) of the fuel cells 4 is formed in the connecting plate 15 and in the lower clamping plate 21.In the connecting plate 15 and the lower clamping plate 21 as the clamping element 18, a further inlet opening 48 and outlet opening 49 are formed for introducing oxidizing agent and for discharging oxidizing agent into and out of the channels (not shown) of the fuel cells 4 and a not shown inlet opening 48 and outlet opening 49 for introducing coolant and for discharging coolant into the channels (not shown) between two plates of a bipolar plate (not shown) of the fuel cells 4. Thus, a total of 6 inlet and outlet openings 48, 49 are formed in the connecting plate 15 and the lower clamping plate 21 (only partially shown in Fig. 1).

[0051] A fuel cell system 2 comprises, in addition to the fuel cell unit 1, an oxidant supply system 26 for supplying the fuel cell stack 3 with air as the oxidant. The oxidant supply system 26 comprises a gas delivery device 27, for example, a blower, a compressor, a turbocompressor driven by an electric motor and / or a turbine, and oxidant lines 28. In addition to the fuel cell unit 1, the fuel cell system 2 also comprises a fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as the fuel. The fuel supply system 29 comprises a pressure vessel 30, a fuel line 31 as a process fluid line, valves (not shown) for fuel, in particular an injector (not shown) for controlling the volume flow of fuel introduced from the fuel line 31 into a recirculation fuel line 32,a heat exchanger (not shown) for fuel, a pressure reducer (not shown), the recirculation fuel line 32 as a process fluid line, a recirculation fuel conveyor 33, an electric motor (not shown) for driving the recirculation fuel conveyor 33 and a water separator 34 for separating water from the recirculation fuel, a water tank (not shown) for collecting the water collected in the water separator 34,a drain valve (not shown) for draining water from the water tank, and a drain valve as a purge valve (not shown) for discharging recirculation fuel into the environment. In the fuel supply system 29 for supplying the fuel cell stack 3 with hydrogen as fuel, the hydrogen stored in the pressure vessel 30 at a high pressure of, for example, 400 bar is supplied to the fuel cells 4 through the fuel line 31. After the fuel has passed through the fuel cells 4, the hydrogen is not completely consumed.so that this hydrogen derived from the fuel cells 4 is fed back to the fuel cells 4 through the recirculation fuel line 32 in a circuit. The recirculation fuel conveying device 33 is used to convey the recirculation fuel through the recirculation fuel line 32. After the fuel has passed through the fuel cells 4, the moisture content of the fuel increases,To prevent an excessive water or moisture content in the recirculation fuel, the fuel supply system 29 includes the water separator 34. The water separated in the water separator 34 is collected in the water tank (not shown) and discharged into the environment through the drain valve (not shown). Excess recirculation fuel is discharged into the environment through the purge valve (not shown). In addition to the fuel cell unit 1, the fuel cell system 2 also includes a cooling system (not shown) for controlling the temperature of the fuel cell stack 3, i.e., for cooling the fuel cell stack 3. The cooling system for controlling the temperature of the fuel cell stack 3 includes coolant lines as process fluid lines,a heat exchanger and a pump for circulating the coolant. The coolant is passed through coolant channels in the bipolar plates of the fuel cells 4, and the heat is dissipated to the environment via the heat exchanger. The fuel cell system 2 includes, in addition to the fuel cell unit 1, the oxidant supply system 26, the fuel supply system 29, and the cooling system (not shown) as a coolant supply system.

[0052] The fuel cell unit 1 can, with modifications not shown, in particular valves, also optionally be used and operated as an electrolysis cell unit 11 (Fig. 2), i.e., it forms a reversible fuel cell unit 1. Some features are described below that enable the operation of the fuel cell unit 1 as an electrolysis cell unit 11. A liquid electrolyte, namely highly diluted sulfuric acid with a concentration of approximately c (H2SO4) = 1 mol / l, is used for the electrolysis. A sufficient concentration of oxonium ions HaO + in the liquid electrolyte is necessary for electrolysis. Figure 2 shows an electrolysis cell unit 11, which can only be used for electrolysis.

[0053] The polarity of the electrodes with electrolysis when operated as an electrolysis cell unit 11 is the opposite (not shown) to when operated as a fuel cell unit 1, so that hydrogen H2 is formed at the cathodes in the channels for fuel of the electrochemical cells 24, through which the liquid electrolyte is passed, and the hydrogen H2 is absorbed by the liquid electrolyte and transported along in dissolved form. Analogously, the liquid electrolyte is passed through the channels for oxidizing agents and oxygen O2 is formed at the anodes or at the channels for oxidizing agents. When operated as an electrolysis cell unit 11, the fuel cells 2 of the fuel cell unit 1 function as electrolysis cells 9 with channels for the electrolyte. The fuel cells 2 and electrolysis cells 9 thus form electrochemical cells 24. The electrolysis cells 9 are arranged in alignment as an electrolysis cell stack 8 as a cell stack 12.The oxygen O2 formed is absorbed by the liquid electrolyte and transported in dissolved form. The hydrogen H2 formed is absorbed by the liquid electrolyte and transported in dissolved form. The liquid electrolyte is stored in a storage container 35 and is passed by a pump 37 and through electrolyte lines 36 through the channels in the electrolysis cell stack 8 or generally as cell stack 12 or cell stack 12. For a reversible fuel cell unit 1 (not shown) according to Fig. 1, two 3-way valves (not shown) are provided on the recirculation fuel line 32 and the oxidant line 28 and are switched over during operation as electrolysis cell unit 11, so that not recirculation fuel and oxidant, but the liquid electrolyte is introduced by the pump 37 from the storage container 35 into the recirculation fuel line 32 and the oxidant line 28 as electrolyte line 36.A hydrogen separator 38 separates the hydrogen obtained from electrolysis from the electrolyte. An oxygen separator 39 separates the oxygen obtained from electrolysis from the electrolyte. The electrolyte is circulated through the electrolysis cell unit 11, and sulfuric acid is added according to consumption using a device not shown. An electrolysis cell system 7 includes, in addition to the electrolysis cell unit 11, an electrolyte supply system 10 comprising the storage tank 35, the electrolyte lines 36, and the pump 37, as well as the hydrogen separator 38 and the oxygen separator 39.

[0054] In the fuel cell system 2, process fluids, namely the oxidant, the fuel, and the coolant, are conveyed through lines, namely the oxidant line 28, the fuel line 31, and a coolant line (not shown), forming process fluid lines. Similarly, in the electrolysis cell system 7, the electrolyte is conveyed as process fluid through electrolyte lines 36, forming process fluid lines. In an electrochemical cell system 40, i.e., the fuel cell system 2 and / or the electrolysis cell system 7, process fluid lines are thus necessary for conveying process fluids.

[0055] The process fluids are to be introduced into and discharged from the fuel cell stack 3 or the electrolysis cell stack 8, generally as a cell stack 12. In the cell stack 12 of the electrochemical cell unit 25, both the upper clamping plate 20 and the lower clamping plate 21 function as a clamping plate 19 and also as an end plate 47, because the clamping plates 19 form the end of the cell stack 12 in a direction perpendicular to the fictitious planes 41, ie in an axial direction 42 with respect to an inlet channel 50 and a outlet channel 51. In a cell stack 12 without prestressing of the electrochemical cells 24 and without connecting devices 22, the end plates 47 thus only form end plates 47 and not clamping plates 19 (not shown). A current plate 45 and an insulating plate 46 are formed between the end plates 47 and the electrochemical cells 24. The lower insulating plate 46 lies directly on the lower end plate 47 and the lower current plate 45.The lower current plate 45 rests directly on the lowest electrochemical cell 24. In a similar manner, the upper insulating plate 46 is arranged between the upper end plate 47 and the upper current plate 45. In a fuel cell unit 1, the current plates 45 conduct the electrical current generated in the fuel cells 4 via current lines (not shown). In an electrolysis cell unit 11, the current plates 45 are subjected to a voltage difference via current lines (not shown) for the corresponding voltage difference for the electrolysis in the electrolysis cells 9. The housing 13 and the connection plate 45 have no electrical potential and are grounded, so that the insulating plate 46 serves to electrically insulate the cell stack 12 from the environment because the end plate 47 is electrically conductively connected to the connection plate 15.

[0056] For this purpose, an inlet channel 51 for introducing a process fluid and an outlet channel 51 for discharging a process fluid are formed in the cell stack 12. The inlet channel 50 is formed by aligned inlet openings 48 in the connection plate 15, the lower clamping plate 21 as end plate 47, the insulating plate 46 and the metal current plate 45, as well as in the electrochemical cells 24. The outlet channel 51 is formed by aligned outlet openings 49 in the connection plate 15, the lower clamping plate 21 as end plate 47, the insulating plate 46 and the current plate 45, as well as in the electrochemical cells 24. The inlet channel 50 and the outlet channel 51 are formed in the cell stack 12 as shown in Fig. 1 and Fig. 3 in all electrochemical cells 24, but not in the upper current plate 45 and not in the upper insulating plate 46 and thus also not in the upper end plate 47.By introducing the process fluid into the inlet channels 50, the process fluid is introduced into the channels of the electrochemical cells 24 and is discharged again from the channels (not shown) of the electrochemical cells 24 through the discharge channels 51 and is conducted through channels in the electrochemical cells 24 in a direction substantially parallel to the fictitious planes.

[0057] The insulating plate 46 is made of an electrically non-conductive plastic and is constructed in several parts. In the area of ​​one inlet opening 48 and one outlet opening 49 of the insulating plate 46, a process fluid region 53 of the insulating plate 46 is formed in the area of ​​the inlet opening 48 and the outlet opening 49, and a plate region 52 of the insulating plate 46 is formed outside the process fluid region 53. The process fluid region 53 is annular and designed as a sleeve 54 made of ceramic. With respect to the inlet channel 50 and the outlet channel 51, and thus also with respect to the inlet opening 48 and the outlet opening 49, the insulating plate 46 has a radial direction 43 parallel to the fictitious plane 41. A radial inner side of the sleeve 54 of the insulating plate 46 delimits the inlet opening 48 and the outlet opening 49 of the insulating plate 46.Between the radial outer side of the sleeve 54 and the remaining insulating plate 46 at the plate region 52, a distance 55 is provided as an annular gap 56 (Fig. 3). The hardness, as the Shore hardness, of the sleeve 54 is significantly greater than the Shore hardness of the plate region 52 of the insulating plate 46. For this reason, the distance 55, as the annular gap 56, between each sleeve 54 and the plate region 52 of the remaining insulating plate 46, is necessary to avoid compressive forces in the radial direction 43 between the plate region 52 and the process fluid region 53, as the sleeve 54.In the axial direction 42, the thickness or extension of the sleeve 54 as the process fluid region 53 is smaller than at the plate region 52 without prestressing with the connecting devices 22, because during prestressing, the thickness or extension of the plate region 52 of the insulating plate 46 decreases more sharply than at the sleeve 54 with a greater hardness and a greater modulus of elasticity. The modulus of elasticity at the process fluid region 53 defining the inlet opening 48 or the outlet opening 49 is thus greater than at the plate region 52.

[0058] In a further, not-shown embodiment of the insulating plate 46, the process fluid region 53 and the plate region 52 are formed as a single piece. When manufacturing the insulating plate 46 from plastic using two-component injection molding, the process fluid region 53 is first manufactured from a plastic with greater hardness, in particular greater Shore hardness, and greater modulus of elasticity, and then the remaining plate region 52 is manufactured from a plastic with lower hardness, in particular lower Shore hardness, and lower modulus of elasticity. However, the difference in the modulus of elasticity and hardness between the plate region 52 and the process fluid region 53 is selected such that no distance 55 is necessary between the process fluid region 53 and the plate region 52 if the forces within the entire insulating plate 46 are sufficiently small.

[0059] Overall, the electrochemical cell unit 25 according to the invention and the electrochemical cell system 40 according to the invention offer significant advantages. The mechanical, hydraulic, and chemical stress on the insulating plate 46 is greatest in the area of ​​the inlet opening 48 and the outlet opening 49. By designing the insulating plate 46 at the process fluid region 53 with different material properties, in particular a different material to delimit the inlet opening 48 or the outlet opening 49, a different material optimally tailored to the requirements can be used, even at higher material costs per unit volume. This advantageously prevents damage to the insulating plate 46 in the area of ​​the inlet opening 48 and the outlet opening 49.Such damage could lead to the conduction of electrical current to the end plate 47 or even to a short circuit, which can be advantageously avoided in a simple and inexpensive manner with this design solution.

Claims

Claims 1 . Electrochemical cell unit (25) for converting electrochemical energy into electrical energy as a fuel cell unit (1) and / or for converting electrical energy into electrochemical energy as an electrolysis cell unit (11) with a cell stack (3), the cell stack (3) comprising - stacked electrochemical cells (24) as a cell stack (3), - a current plate (45) for conducting current, - an end plate (47), - an insulating plate (46) electrically insulating the end plate (47) from the current plate (45) and the electrochemical cells (24), - at least one inlet channel formed in the cell stack (3) (50) for conducting a process fluid into the electrochemical cells (24) and the inlet channel (50) is formed by inlet openings (48) in the end plate (47), the insulating plate (46) and the current plate (45), - at least one discharge channel formed in the cell stack (3) (51) for conducting a process fluid from the electrochemical cells (24) and the discharge channel (51) is formed by discharge openings (49) in the end plate (47), the insulating plate (46) and the current plate (45), characterized in that the insulating plate (46) has different material properties in a process fluid region (53) delimiting the at least one inlet opening (48) and / or the at least one discharge opening (49) than in a plate region (52) of the insulating plate (46) outside this process fluid region (53).

2. Electrochemical cell unit according to claim 1, characterized in that the insulating plate (46) is formed from a different material on a process fluid region (53) delimiting the at least one inlet opening (48) and / or the at least one outlet opening (49) than on a plate region (52) of the insulating plate (46) outside this process fluid region (53).

3. Electrochemical cell unit according to claim 1 or 2, characterized in that the material of the process fluid region (53) of the insulating plate (46) has a greater modulus of elasticity than the plate region (52) of the insulating plate (46).

4. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the process fluid region (53) of the insulating plate (46) is completely continuous in the circumferential direction (44) of the inlet opening (48) and / or outlet opening (49).

5. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the components of the electrochemical cells (24) are formed in layers and span fictitious planes (41).

6. Electrochemical cell unit according to claim 5, characterized in that the process fluid region (53) of the insulating plate (46) in an axial direction (42) is formed perpendicular to the fictitious planes (41) at the at least one inlet opening (48) and / or the at least one outlet opening (49) to be completely continuous.

7. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the process fluid region (53) of the insulating plate (46) has a substantially constant extent in a radial direction (43) with respect to the at least one inlet opening (48) and / or the at least one outlet opening (49) of the insulating plate (46).

8. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the at least one inlet opening (48) and / or the at least one outlet opening (49) is substantially circular in cross-section.

9. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the process fluid region (53) is annular.

10. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the process fluid region (53) is designed as a sleeve (54).

11. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the process fluid region (53) of the insulating plate (46) and the plate region (52) of the insulating plate (46) are separate components (52, 53).

12. Electrochemical cell unit according to one or more of the preceding claims, characterized in that a distance is formed between the process fluid region (53) of the insulating plate (46) and the plate region (52) of the insulating plate (46).

13. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the plate region (52) of the insulating plate (46) is made of plastic.

14. Electrochemical cell unit according to one or more of the preceding claims, characterized in that the process fluid region (53) of the insulating plate (46) is formed at least partially, in particular completely, from ceramic.

15. Electrochemical cell system (40) for converting electrochemical energy into electrical energy as a fuel cell system (2) and / or for Conversion of electrical energy into electrochemical energy as an electrolysis cell system (7), comprising an electrochemical cell unit (25) as a fuel cell unit (1) and / or an electrolysis cell unit (11), at least one supply system (10, 26, 29) for at least one process fluid, characterized in that the electrochemical cell unit (25) is designed according to one or more of the preceding claims

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