Electrochemical device

Abstract

To form an electrochemical device comprising several electrochemical units, to create an electrochemical unit comprising at least one media separator and at least one frame on which the media separator is held, in which the frames of the electrochemical units can be manufactured in a manner suitable for mass production and yet have sufficient chemical resistance to the operating media of the electrochemical device and sufficient mechanical strength to withstand the pressure loads occurring during operation in the axial and radial directions, it is proposed that the frame comprise a media guidance area that comes into contact with at least one operating medium of the electrochemical device and a stabilization area that does not come into contact with any operating medium of the electrochemical device. wherein the media guidance area comprises a first plastic material and the stabilization area comprises a second plastic material, where the first plastic material and the second plastic material are different from each other, wherein the first plastic material has a higher chemical resistance to at least one of the operating media than the second plastic material and wherein the second plastic material has a higher strength, a higher stiffness and / or a higher creep resistance than the first plastic material.

Description

[0001] The present invention relates to an electrochemical device comprising several electrochemical units arranged in a stacking direction, wherein each electrochemical unit comprises at least one media separator and at least one frame to which the media separator is held in the assembled state of the electrochemical device.

[0002] Such an electrochemical device can in particular be a device in which a chemical reaction (such as in an electrolyzer) or an energy transfer (such as in a redox flow storage device) takes place with the help of an electric current.

[0003] The electrochemical device can be designed in particular as an electrolyzer or as a redox flow storage device.

[0004] An electrolyzer can, for example, be designed as an alkaline water electrolyzer.

[0005] In this case, each of the electrochemical units or cells of the electrochemical device comprises a cathode and an anode, with a cathode-side fluid chamber and an anode-side fluid chamber separated from each other by a membrane. The cathode-side fluid chamber and the anode-side fluid chamber each contain a mixture of water and potassium hydroxide, the so-called electrolyte. If the voltage applied between the cathode and the anode is higher than the sum of the electrochemical decomposition potential for water and the overvoltage required to overcome the electrical resistances of the circuit, an electric current flows through the electrochemical unit. At the cathode, a hydrogen gas molecule is formed from water molecules, creating a hydroxide ion. The hydrogen molecules form bubbles of hydrogen gas that detach from the electrode surface.From a lower edge to an upper edge of the electrode surface, the gas content in the mixture of water and potassium hydroxide solution increases continuously. This mixture, along with the hydrogen gas, is discharged from the electrochemical units, whereby the hydrogen gas is separated from the potassium hydroxide solution outside the electrochemical units by means of a hydrogen gas separator.

[0006] The hydroxide ions formed at the cathode during the reaction are transported across the membrane from the cathode to the anode due to the voltage difference between the electrodes of the electrochemical unit. At the anode surface, the hydroxide ions recombine with hydrogen atoms from the water to form water. Oxygen atoms remain, which combine to form oxygen molecules and create oxygen gas bubbles rising from the electrode. These gas bubbles, along with the potassium hydroxide solution, are carried out of the electrochemical units and separated outside the units by an oxygen gas separator.

[0007] To achieve a high gas production output, many electrochemical units are electrically and process-technically combined to form an electrolysis block.

[0008] The electrochemical units in the electrolysis block are separated from each other by bipolar plates.

[0009] The media in the electrochemical units are thus separated from each other by membranes and by bipolar plates, so that both the membrane and the bipolar plates can be regarded as media separators of the electrochemical device.

[0010] The frames to which the media separators are held in the assembled state of the electrochemical device are, according to the state of the art, made of metallic alloys in alkaline electrolyzers.

[0011] It is assumed that the significant expansion of renewable energy use will lead to water electrolysis, as a component of so-called "power-to-gas" plants, becoming increasingly important for the production of synthesis gas. This will result in a substantial increase in the required quantity of frames for electrolyzers.

[0012] Frames suitable for mass production could, for example, be made from a plastic material. The cost-effectiveness of frames made from a plastic material increases with the number of frames produced.

[0013] The operating conditions in an alkaline electrolyzer (overpressure on the order of 30 barg, a temperature around 90 °C, contact with a mixture of demineralized water (DI water) and 30% potassium hydroxide (KOH) by weight) necessitate the use of plastic materials that are resistant to these conditions, but are expensive. In addition to their high cost, these chemically resistant plastic materials have the further disadvantage of often possessing only limited mechanical strength to withstand the pressure loads present in the electrochemical device. Therefore, relatively thick walls must be used to absorb the axial and radial pressure forces.

[0014] The present invention is based on the objective of creating an electrochemical device of the type mentioned above in which the frames of the electrochemical units can be manufactured in a manner suitable for mass production and yet have sufficient chemical resistance to the operating media of the electrochemical device and sufficient mechanical strength to absorb the pressure loads occurring in the axial direction and in the radial direction of the stack of electrochemical units during the operation of the electrochemical device.

[0015] This problem is solved according to the invention in an electrochemical device with the features of the preamble of claim 1 by the fact that the frame comprises a media guidance area which comes into contact with at least one operating medium of the electrochemical device during operation, and a stabilization area which does not come into contact with an operating medium of the electrochemical device during operation. wherein the media guidance area comprises a first plastic material and the stabilization area comprises a second plastic material, where the first plastic material and the second plastic material are different from each other, wherein the first plastic material has a higher chemical resistance to at least one of the operating media with which the media guide area comes into contact during the operation of the electrochemical device than the second plastic material and wherein the second plastic material has a higher strength, a higher stiffness and / or a higher creep resistance than the first plastic material.

[0016] The present invention is therefore based on the concept that the various functions of the frame of an electrochemical unit, namely on the one hand the media guidance and on the other hand the load bearing, are provided by two different components of the frame, each comprising different plastic materials.

[0017] This makes it possible to use a high-priced plastic material that has high chemical resistance and, in particular, low water absorption from the operating media of the electrochemical device only in the media guidance area of ​​the frame.

[0018] The media guidance area can be encased in a stabilization area made of mechanically high-strength, but less chemically resistant, plastic material.

[0019] The stabilization area is able to absorb the strains generated by the pressure loads acting on the frame at a very low creep modulus.

[0020] Within the framework of the electrochemical device according to the invention, at least two different plastic materials are combined with each other, with each plastic material being used in such a way that it optimally supports the function to be fulfilled by the respective component of the frame.

[0021] In particular, it may be provided that an internal media guidance area of ​​the frame, i.e., located closer to the central longitudinal axis of the electrochemical device, is surrounded by a mechanically high-strength stabilizing area capable of absorbing pressure loads.

[0022] For example, it may be planned that the media guidance area is overmolded with the stabilization area.

[0023] The stabilizing area can include a fiber-reinforced plastic material.

[0024] The media guidance area is preferably designed such that the boundary surfaces of the passage openings, at which the media guidance area comes into contact with one of the operating media of the electrochemical device during operation, are as small as possible.

[0025] The two-component frame of the electrochemical device according to the invention is characterized by lower manufacturing and material costs compared to corresponding frames made of metal.

[0026] The media guidance area, which comprises the first plastic material and is preferably formed substantially from the first plastic material, exhibits a lower water absorption from the operating media of the electrochemical device and a high chemical resistance to the operating media of the electrochemical device.

[0027] The stabilization area, which comprises the second plastic material and is preferably formed substantially from the second plastic material, exhibits high mechanical strength, high stiffness and high creep resistance to absorb the compressive forces acting during operation of the electrochemical device in the radial direction and in the axial direction of a longitudinal central axis of the stack of electrochemical units over the entire lifetime of the electrochemical device.

[0028] The first plastic material may include, for example, a polyphenylene sulfone (PPSU) material, a polysulfone (PSU) material, a polyethersulfone (PES or PESU) material, a polyphenylene sulfide (PPS) material and / or a polyphthalamide (PPA) material.

[0029] It is particularly advantageous if the first plastic material is essentially made entirely from a polyphenylenesulfone (PPSU) material, a polysulfone (PSU) material, a polyethersulfone (PES or PESU) material, a polyphenylene sulfide (PPS) material, or a polyphthalamide (PPA) material.

[0030] The second plastic material preferably comprises a polyamide (PA) material and / or a polypropylene (PP) material.

[0031] Preferably, the second plastic material is formed essentially entirely from a polyamide (PA) material or from a polypropylene (PP) material.

[0032] If the second plastic material comprises a polyamide (PA) material, then this polyamide (PA) material preferably comprises a polycaprolactam (PA6) material and / or a polyamide 66 (PA66) material.

[0033] Preferably, in this case, the polyamide(PA) material contained in the second plastic material is formed essentially entirely from a polycaprolactam(PA6) material or from a polyamide-66(PA66) material.

[0034] The mechanical stiffness of the stabilization area is preferably characterized by the modulus of elasticity (E-modulus) of the material from which the stabilization area is formed.

[0035] The modulus of elasticity of the material in the stabilization area is preferably at least 5 GPa, in particular at least 10 GPa, especially preferably at least 15 GPa, for example at least 20 GPa.

[0036] The mechanical strength of the stabilization area can be characterized, for example, by the tensile stress and / or the elongation at break of the material from which the stabilization area is formed.

[0037] The tensile strength of the material in the stabilization area is preferably at least 50 MPa, in particular at least 100 MPa, especially preferably at least 150 MPa, for example at least 200 MPa.

[0038] The elongation at break of the material from which the stabilization area is formed is preferably at least 1%, particularly at least 2%, most preferably at least 3%, and advantageously at least 4%, for example at least 5%.

[0039] The creep resistance of the stabilization area can be characterized, for example, by the tensile creep modulus of the material from which the stabilization area is formed.

[0040] The tensile creep modulus is defined as the ratio between the tensile stress and the deformation due to tensile strain under long-term loading (within the scope of this application and the attached claims, a loading period of 1000 hours is assumed).

[0041] After a loading period of 1000 hours, the tensile creep modulus of the material from which the stabilization area is formed is preferably at least 1000 MPa, in particular at least 2000 MPa, particularly preferably at least 3000 MPa, advantageously at least 4000 MPa, for example at least 5000 MPa.

[0042] If the stabilization area is essentially entirely composed of the second plastic material, then the values ​​given above for the modulus of elasticity (E-modulus), the tensile stress, the elongation at break and the tensile creep modulus apply to the second plastic material.

[0043] To increase the strength, stiffness and / or creep resistance of the material in the stabilization area, the second plastic material may include fibers, preferably glass fibers.

[0044] The proportion of fibers in the second plastic material is preferably at least 20% by weight, particularly preferably at least 30% by weight.

[0045] In principle, the fibers contained in the second plastic material (especially glass fibers) can include short fibers, long fibers and / or continuous fibers.

[0046] Short fibers are defined as those with a fiber length of up to 1 mm. Preferably, these short fibers have a fiber length of at least 0.1 mm.

[0047] Long fibers have a fiber length of more than 1 mm up to 50 mm.

[0048] Continuous fibers have a fiber length of more than 50 mm.

[0049] In a preferred embodiment of the invention, it is provided that the fibers, in particular glass fibers, in the second plastic material have at least partially a fiber length of more than 1 mm.

[0050] It is particularly advantageous if all fibers, especially glass fibers, of the second plastic material have a fiber length of more than 1 mm.

[0051] In a particularly preferred embodiment of the invention, it is provided that the fibers, in particular glass fibers, in the second plastic material comprise continuous fibers.

[0052] To increase the mechanical stability of the stabilization area, it has proven particularly advantageous if the second plastic material comprises continuous fibers wound around at least one fixed point.

[0053] In this process, the continuous fibers impregnated with a matrix are wound around at least one fixed point before the continuous fibers are overmolded with the other components of the second plastic material.

[0054] Continuous fiber bundles in a thermoplastic matrix can, for example, be wound as a circle with a defined radius.

[0055] The structure, wound from continuous fibers, is placed into an injection mold before the cavity of the injection mold is filled with the remaining components of the second plastic material.

[0056] In principle, it can also be provided that the first plastic material comprises fibers, preferably glass fibers.

[0057] The proportion of fibers in the first plastic material is preferably at most 20% by weight, particularly preferably at most 10% by weight.

[0058] For example, a polyphenylene sulfide (PPS) material with a fiber content, preferably glass fiber content, of approximately 20% by weight can be used as the first plastic material.

[0059] The fibers contained in the first plastic material can have the same properties as the fibers contained in the second plastic material, which have been described above.

[0060] In a preferred embodiment of the invention, it is provided that the media guidance area and / or the stabilization area of ​​the frame is produced by an injection molding process.

[0061] Furthermore, it may be provided that the media guidance area and / or the stabilization area of ​​the frame includes ribs and recesses bounded by the ribs.

[0062] In particular, the media guidance area of ​​the frame can be provided with recesses in those areas where it does not come into contact with the operating media of the electrochemical device, which further reduces the material usage and can lead to a homogeneous wall thickness distribution, which can improve manufacturability - especially in an injection molding process - by reducing distortions occurring during production.

[0063] However, material can also be saved in the stabilization area by providing recesses limited by ribs, and manufacturability – especially in an injection molding process – can be improved by a more homogeneous wall thickness distribution, which leads to less distortion.

[0064] By providing several recesses bounded by the ribs in the media guidance area and / or in the stabilization area of ​​the frame, a skeletal structure can be formed in the media guidance area or in the stabilization area, which leads to a particularly high material efficiency with regard to the sealing functions to be performed by the media guidance area or with regard to the pressure absorption functions to be performed by the stabilization area in the radial and axial direction of the electrochemical device.

[0065] The media guidance area of ​​the frame is preferably provided with at least one passage opening for an operating medium of the electrochemical device.

[0066] Such an operating medium can in particular be an electrolyte, for example an aqueous solution of an alkali hydroxide, in particular a potassium hydroxide, or a gas produced by electrochemical reaction in the electrochemical device, for example a hydrogen gas or an oxygen gas.

[0067] At least one of the openings for a working medium can be designed as an elongated hole extending along a circumferential direction of the frame.

[0068] In a preferred embodiment of the invention, it is provided that several passage openings for operating media of the electrochemical device, which are provided in the media guidance area, are each designed as an elongated hole extending along a circumferential direction of the frame.

[0069] The openings for the operating media of the electrochemical device preferably consist of supply channels and discharge channels for the operating media of the electrochemical device, which extend parallel to a longitudinal central axis of the electrochemical device through the electrochemical units of the electrochemical device.

[0070] In addition to these passageways for the operating media of the electrochemical device, the media guidance area of ​​the frame of an electrochemical device preferably includes a central passageway, for example having a circular cross-section, which accommodates, for example, an anode-side fluid chamber or a cathode-side fluid chamber of the respective electrochemical unit. In the assembled state of the electrochemical device, the anode-side fluid chamber or the cathode-side fluid chamber is bounded on one side by a bipolar plate and on the other side by a membrane of the electrochemical unit or an adjacent electrochemical unit.

[0071] To increase the mechanical stability of the stabilizing area of ​​the frame, it may be provided that the stabilizing area of ​​the frame includes a clamping ring embedded in the second plastic material.

[0072] Such a clamping ring can, for example, be wound from continuous fibers, especially continuous glass fibers.

[0073] The electrochemical device according to the invention is particularly suitable as an electrolyzer, especially as an alkaline electrolyzer, or as a redox flow storage device.

[0074] Further features and advantages of the invention are the subject of the following description and the graphic representation of an exemplary embodiment.

[0075] The drawings show: Fig. 1 a schematic perspective representation of an electrochemical device, for example an electrolyzer, comprising several electrochemical units, for example electrolysis units, which follow one another along a stacking direction, wherein each electrochemical unit comprises at least one media separator, preferably two media separators, for example a membrane and a bipolar plate, and at least one frame on which the at least one media separator is held in the assembled state of the electrochemical device, wherein the frame comprises a media guidance area which comes into contact with at least one operating medium of the electrochemical device during operation, and a stabilization area which, during operation of the electrochemical device does not come into contact with an operating medium of the electrochemical device, comprising the media guidance area comprising a first plastic material and the stabilization area comprising a second plastic material, where the first plastic material and the second plastic material are different from each other, wherein the first plastic material has a higher chemical resistance to at least one of the operating media with which the media guide area comes into contact during the operation of the electrochemical device than the second plastic material and / or wherein the second plastic material has a higher strength, a higher stiffness and / or a higher creep resistance than the first plastic material; Fig. 2 a schematic longitudinal section through the electrochemical device Fig. 1, along the stacking direction of the electrochemical device; Fig. 3. A top view of a frame of one of the electrochemical units of the electrochemical device from the Fig. 1 and Fig. 2, with the viewing direction along the stacking direction; and Fig. 4 a longitudinal section through the frame made of Fig. 3 along a connecting channel between a fluid chamber of the electrochemical unit and a medium channel of the electrochemical device, along line 4-4 in Fig. 3.

[0076] Identical or functionally equivalent elements are designated with the same reference symbols in all figures.

[0077] One in the Fig. The electrochemical device shown in Figures 1 to 4 and designated as a whole by 100 is, for example, designed as an electrolyzer, in particular as an alkaline electrolyzer.

[0078] The electrochemical device 100 comprises a stack 102 of several electrochemical units 104, which follow one another along a stacking direction 106 of the electrochemical device 100.

[0079] The stack 102 of electrochemical units 104 is arranged between two end plates 108.

[0080] How best to Fig. As can be seen in Figure 2, the electrochemical device 100 comprises a clamping device 110 by means of which the two end plates 108 and the intermediate stack 102 of electrochemical units 104 can be clamped.

[0081] The clamping device 110 comprises several clamping elements 112, which extend essentially parallel to the stacking direction 106 and follow one another along the circumferential direction of the end plates 108.

[0082] During the Fig. In the embodiment of an electrochemical device 100 shown in figures 1 to 4, for example, 24 clamping elements 112 are provided, of which, however, for the sake of clarity (especially in Fig. 1) only every second one is shown graphically.

[0083] Each of the clamping elements 112 can each include a clamping rod 114.

[0084] Each of the tension rods 114 can, for example, be designed as a threaded rod 116 which is provided with an external thread 118.

[0085] A clamping nut 120 is provided at each end region of a clamping rod 114, wherein each clamping nut 120 is assigned to one of the end plates 108 and is arranged on the side of the respective end plate 108 facing away from the other end plate 108'.

[0086] Each of the clamping nuts 120 has an internal thread which engages in the external thread 118 of the respective associated clamping rod 114.

[0087] Furthermore, each of the clamping elements 112 is provided with an insulating sleeve 122, which is made of an electrically insulating material and prevents contact between the clamping element 112 in question and one of the end plates 108.

[0088] Between the other end plate 108' and the clamping nut 120' of the clamping element 112 associated with that other end plate 108', at least one spring element 124 is arranged, which is under elastic preload and thereby holds the adjacent clamping nut 120' at a distance from the end plate 108' associated with it. This elastic preload of the at least one spring element 124 pulls the clamping nut 120 associated with the other end plate 108 against the other end plate 108 (however, the insulating sleeve 122 prevents direct contact between this other clamping nut 120 and the other end plate 108).

[0089] The at least one spring element 124, which elastically clamps a clamping element 112, can, for example, be designed as a disc spring 126.

[0090] Each of the electrochemical units 104 of the electrochemical device 100 comprises two frames 128 and 128', a membrane 130 held between the two frames 128 and 128', and a bipolar plate 132 held between one of the frames 128' and a frame 128' of an adjacent electrochemical unit 104.

[0091] The bipolar plate 132 can be provided with an anode on one side and a cathode on the other side.

[0092] The membrane 130 and the bipolar plate 132 each form a media separator 133 of an electrochemical unit, which separates an anode-side fluid space 136a and a cathode-side fluid space 136b from each other and is held on at least one frame 128 of an electrochemical unit 104.

[0093] One of the frames 128 of an electrochemical unit 104 is in Fig. 3 shown in a top view along the stacking direction 106.

[0094] The frame 128 comprises a media guidance area 134, which surrounds a fluid space 136 (for example, a cathode-side fluid space 136b) of the electrochemical unit 104, and a stabilization area 138, which surrounds the media guidance area 134 and forms an outer boundary of the frame 128 towards an environment 140 of the electrochemical device 100.

[0095] In the assembled state of the electrochemical device 100, the media guidance area 134 of the frame 128 rests against the media guidance area 134 of an adjacent frame 128' via sealing elements 135 (see Fig. 4).

[0096] Furthermore, in the assembled state of the electrochemical device 100, the media guidance area 134 of the frame 128 rests on a bipolar plate 132 via sealing elements 137 and the media guidance area 134 of the frame 128' rests on a membrane 130 via sealing elements 137'.

[0097] The media guidance area 134 of the frame 128 is provided with several passage openings 142, which penetrate the media guidance area 134 and thus the frame 128 along the stacking direction 106.

[0098] This includes in particular an anode-side supply opening 144, a cathode-side supply opening 146, an anode-side discharge opening 148 and a cathode-side discharge opening 150.

[0099] The passage openings 142 can, for example, be designed as elongated holes 143, which extend along the circumferential direction of the frame 128.

[0100] Each of the passage openings 142 of the media routing area 134 is connected via a connecting channel 152 (see, for example, Fig. 4) in connection with an anode-side fluid space 136a or in connection with a cathode-side fluid space 136b of an electrochemical unit 104, wherein the anode-side fluid space 136a and the cathode-side fluid space 136b of each electrochemical unit 104 are separated from each other by the membrane 130 of the respective electrochemical unit 104.

[0101] The second frame 128' of an electrochemical unit 104 comprises a media guidance area 134, which surrounds an anode-side fluid space 136a of the electrochemical unit 104.

[0102] The passage openings 142 into the media guidance area 134 of the frames 128, 128' together form media channels 154, which penetrate the stack 102 of electrochemical units 104 along the stack direction 106 and also one of the end plates 108 in order to supply the electrochemical units 104 with an operating medium or to discharge an operating medium from the electrochemical units 104.

[0103] If the electrochemical device 100 is, for example, an alkaline electrolyzer, then during operation the electrochemical units 104 of the alkaline electrolyzer are supplied with, for example, a 30% aqueous solution of potassium hydroxide (KOH) via an anode-side supply medium channel 154a and via a cathode-side supply medium channel 154b.

[0104] The anode-side supply medium channel 154a is formed by the anode-side supply openings 144 of the medium guidance areas 134 of the electrochemical units 104, while the cathode-side supply medium channel 154b is formed by the cathode-side supply openings 146 of the media guidance areas 134 of the electrochemical units 104.

[0105] The anode-side supply medium channel 154a is in fluid communication via a (not shown) connecting channel with each anode-side fluid space 136a of the electrochemical units 104, while the cathode-side supply medium channel 154b is in fluid communication via a (also not shown) connecting channel with a cathode-side fluid space 136b of the electrochemical units 104.

[0106] The anode-side fluid space 136a of each electrochemical unit 104 is in fluid communication with an anode-side discharge medium channel 154a via a (not shown) connecting channel.

[0107] During operation of the alkaline electrolyzer, for example a 30% aqueous solution of potassium hydroxide (KOH) together with oxygen, which has been formed by the electrochemical reactions in the respective electrochemical unit 104, passes through this connecting channel from the anode-side fluid space 136a of the respective electrochemical unit 104 into the anode-side discharge medium channel 154a.

[0108] By means of an anodic gas separator (not shown) of the electrochemical device 100, the oxygen is separated from this mixture and fed to an oxygen collection container.

[0109] The cathode-side fluid space 136b of each electrochemical unit 104 is located above a (in Fig. 4 shown) connecting channel 152 in fluid connection with a cathode-side discharge medium channel 154d, so that via this connecting channel 152 in the operation of the alkaline electrolyzer a mixture of 30% aqueous solution of potassium hydroxide (KOH) and of hydrogen, which has been formed by the electrochemical reactions in the respective electrochemical unit 104, can be discharged from the cathode-side fluid space 136b of the electrochemical unit 104 into the cathode-side discharge medium channel 154d.

[0110] From this mixture, the hydrogen can be separated by means of a (not shown) cathodic gas separator of the electrochemical device 100 and fed into a hydrogen collection container.

[0111] During the operation of the electrochemical device 100, electrochemical reactions take place at the electrodes of the electrochemical units 104, which lead to the formation of gaseous hydrogen and gaseous oxygen.

[0112] In the case of an alkaline electrolyzer, the following reaction takes place at the cathode of each electrochemical unit 104: 2 H2O + 2e - → H2 + 2 OH - .

[0113] The following reaction takes place at the anode of each electrochemical unit 104 during the operation of the alkaline electrolyzer: 2 OH - → 1 / 2 O2 + H2O + 2 e - .

[0114] The hydroxide ions produced during the cathode reaction migrate through the membrane 130 of the electrochemical unit 104 from the cathode-side fluid space 136b to the anode-side fluid space 136a, where the hydroxide ions are then consumed in the anode reaction.

[0115] The gaseous hydrogen produced during the cathode reaction passes from the cathode-side fluid chamber 136b through the connecting channel into the cathode-side discharge medium channel 154d.

[0116] The gaseous oxygen produced during the anode reaction passes from the anode-side fluid chamber 136a through a connecting channel into the anode-side discharge medium channel 154c.

[0117] The media guidance area 134 of each frame 128 of one of the electrochemical units 104 comes into contact with the aqueous solution of potassium hydroxide (KOH) in the area of ​​the anode-side supply passage opening 144, in the area of ​​the cathode-side supply passage opening 146, in the area of ​​the anode-side discharge passage opening 148 and in the area of ​​the cathode-side discharge passage opening 150 as well as in the area of ​​the boundary of the central anode-side fluid space 136a or the central cathode-side fluid space 136b.

[0118] Furthermore, the media guidance area 134 of each of the electrochemical units 104 comes into contact with the gaseous oxygen formed by the electrochemical reactions in the operation of the electrochemical device 100 in the area of ​​the boundary of the central anode-side fluid space 136a, in the area of ​​the connecting channel between the anodic fluid space 136a and the anode-side discharge opening 148 and in the area of ​​the anode-side discharge opening 148.

[0119] Furthermore, the media guidance area 134 of each electrochemical unit 104 comes into contact with the gaseous hydrogen formed during the electrochemical reactions in the area of ​​the boundary of the central cathode-side fluid space 136b, in the area of ​​the connecting channel 152 between the cathode-side fluid space 136b and the cathode-side discharge opening 150, and in the area of ​​the cathode-side discharge opening 150.

[0120] The media guidance area 134 of each frame 128, 128' of an electrochemical unit 104 is therefore preferably formed from a first plastic material which has a high chemical resistance to the operating media of the electrochemical device 100, i.e. to the aqueous solution of potassium hydroxide (KOH), to gaseous oxygen and to gaseous hydrogen.

[0121] For example, the first plastic material may include a polyphenylene sulfone (PPSU) material, a polysulfone (PSU) material, a polyethersulfone (PES or PESU) material, a polyphenylene sulfide (PPS) material and / or a polyphthalamide (PPA) material.

[0122] It is particularly advantageous if the first plastic material comprises a polyphenylene sulfone (PPSU) material, a polysulfone (PSU) material, a polyethersulfone (PES or PESU) material, a polyphenylene sulfide (PPS) material or a polyphthalamide (PPA) material as its main component, that is, as the component with the highest weight percentage.

[0123] It is particularly advantageous if the first plastic material is essentially made entirely from a polyphenylenesulfone (PPSU) material, a polysulfone (PSU) material, a polyethersulfone (PES or PESU) material, a polyphenylene sulfide (PPS) material, or a polyphthalamide (PPA) material.

[0124] In contrast, the stabilization area 138 of each frame 128 of an electrochemical unit 104 has no openings through which an operating medium of the electrochemical device 100 flows during operation of the electrochemical device 100.

[0125] Rather, the stabilization area 138 only has clamping element passage openings 156, which extend through the stabilization area 138 in the axial direction of the respective frame 128, 128' parallel to the stacking direction 106.

[0126] The number of clamping element passage openings 156 preferably corresponds to the number of clamping elements 112 of the clamping device 110 of the electrochemical device 100.

[0127] In the assembled state of the electrochemical device 100, one of the clamping elements 112, for example in the form of a clamping rod 114, extends through each of the clamping element passage openings 156.

[0128] The clamping element passage openings 156 of the stabilization area 138 follow one another along the circumferential direction of the frame 128.

[0129] The clamping element through-openings 156 can all have the same distance from the central longitudinal axis 158 of the frame 128.

[0130] Alternatively, it can also be provided that the clamping element passage openings 156 have different distances from the central longitudinal axis 158 of the frame 128.

[0131] For example, it may be provided that the clamping element passage openings 156a, which are arranged adjacent to the passage openings 142 of the media guidance area 134 of the frame 128, have a greater distance from the longitudinal center axis 158 of the frame 128 than the clamping element passage openings 156b, which are arranged in areas of the frame 128 that are not adjacent to any of the passage openings 142 of the media guidance area 134.

[0132] During operation of the electrochemical device 100, an internal pressure p prevails in the fluid-carrying areas of the electrochemical device 100, which is significantly higher than the external pressure in the environment 140 of the electrochemical device 100.

[0133] For example, it can be provided that the internal pressure p in the fluid-carrying areas of the electrochemical units 104 is at least 20 barg, particularly preferably at least 30 barg (and is therefore at least 20 bar or at least 30 bar above the atmospheric pressure prevailing in the environment 140 of the electrochemical device 100).

[0134] During operation of the electrochemical device 100, this pressure presses the radially located areas of the frame 128 within the clamping element openings 156 against the clamping elements 112 of the electrochemical device 100 which penetrate these clamping element openings 156, so that the frame 128 expands under the operating load in the radial direction of the longitudinal center axis 158.

[0135] The clamping elements 112 thus serve, in addition to applying the necessary surface pressure in the axial direction of the electrochemical device 100, to support the radial compressive forces which occur in the electrochemical units 104.

[0136] The clamping elements 112, in particular the clamping rods 114, are preferably made of a metallic material, for example of a steel material.

[0137] In order to reliably and permanently absorb the axial and radial compressive forces acting on the frames 128, 128' during the operation of the electrochemical device 100, the stabilization area 138 of each frame 128 of the electrochemical units 104 preferably comprises a second plastic material which has a higher strength, a higher stiffness and / or a higher creep resistance than the first plastic material which the media guidance area 134 of the frame 128 includes.

[0138] For example, it may be provided that the second plastic material comprises a polyamide (PA) material and / or a polypropylene (PP) material.

[0139] It is advantageous if the second plastic material comprises a polyamide (PA) material or a polypropylene (PP) material as its main component, that is, as the component with the highest weight percentage.

[0140] It is particularly advantageous if the second plastic material is essentially made entirely of a polyamide (PA) material or a polypropylene (PP) material.

[0141] If the second plastic material comprises a polyamide (PA) material, it may be provided that this portion of the second plastic material comprises a polycaprolactam (PA6) material and / or a polyamide 66 (PA66) material.

[0142] It is particularly advantageous if, in this case, the polyamide (PA) material component of the second plastic material comprises a polycaprolactam (PA6) material or a polyamide-66 (PA66) material as the main component, that is, as the component with the highest weight percentage.

[0143] In a preferred embodiment of the invention, the polyamide (PA) material component of the second plastic material is essentially formed entirely from a polycaprolactam (PA6) material or from a polyamide 66 (PA66) material.

[0144] The mechanical stiffness of the stabilization area is preferably characterized by the modulus of elasticity (E-modulus) of the material from which the stabilization area is formed.

[0145] The modulus of elasticity of the material in the stabilization area is preferably at least 5 GPa, in particular at least 10 GPa, especially preferably at least 15 GPa, for example at least 20 GPa.

[0146] The mechanical strength of the stabilization area can be characterized, for example, by the tensile stress and / or the elongation at break of the material from which the stabilization area is formed.

[0147] The tensile strength of the material in the stabilization area is preferably at least 50 MPa, in particular at least 100 MPa, especially preferably at least 150 MPa, for example at least 200 MPa.

[0148] The elongation at break of the material from which the stabilization area is formed is preferably at least 1%, particularly at least 2%, most preferably at least 3%, and advantageously at least 4%, for example at least 5%.

[0149] The creep resistance of the stabilization area can be characterized, for example, by the tensile creep modulus of the material from which the stabilization area is formed.

[0150] The tensile creep modulus is defined as the ratio between the tensile stress and the deformation due to tensile strain under long-term loading (within the scope of this application and the attached claims, a loading period of 1000 hours is assumed).

[0151] After a loading period of 1000 hours, the tensile creep modulus of the material from which the stabilization area is formed is preferably at least 1000 MPa, in particular at least 2000 MPa, particularly preferably at least 3000 MPa, advantageously at least 4000 MPa, for example at least 5000 MPa.

[0152] If the stabilization area is essentially entirely composed of the second plastic material, then the values ​​given above for the modulus of elasticity (E-modulus), the tensile stress, the elongation at break and the tensile creep modulus apply to the second plastic material.

[0153] Furthermore, it has proven advantageous to increase the mechanical strength, stiffness and creep resistance of the second plastic material if the second plastic material includes glass fibers.

[0154] It is particularly advantageous if the proportion of glass fibers in the second plastic material is at least 20% by weight, and preferably at least 30% by weight.

[0155] In this case, it is also advantageous if the second plastic material, besides the glass fibers, essentially contains only a polyamide (PA) material and / or a polypropylene (PP) material.

[0156] The glass fibers of the second plastic material can generally include short fibers (with a fiber length of 0.1 mm to 1 mm), long fibers (with a fiber length of more than 1 mm to 50 mm) and / or continuous fibers (with a fiber length of more than 50 mm).

[0157] It has proven advantageous if the glass fibers of the second plastic material have at least a partial fiber length of more than 1 mm.

[0158] Furthermore, it is advantageous if the glass fibers of the second plastic material comprise continuous fibers.

[0159] In particular, it may be provided that the second plastic material comprises continuous fibers wound around at least one fixed point.

[0160] The stabilizing area 138 of a frame 128, 128' of an electrochemical unit 103 of the electrochemical device 100 can comprise a clamping ring 166 embedded in the second plastic material (see Fig. 4).

[0161] Such a clamping ring 166 can, for example, be wound from continuous glass fibers.

[0162] The glass fibers of the second plastic material can preferably be formed at least partially from a so-called "electric glass".

[0163] Such an “electric glass” is an aluminum borosilicate glass with a weight fraction of less than 2% alkali oxides.

[0164] In principle, it is also possible that the first plastic material includes glass fibers.

[0165] The proportion of glass fibers in the first plastic material is preferably at most 20% by weight, particularly preferably at most 10% by weight.

[0166] For example, a polyphenylene sulfide (PPS) material with a glass fiber content of approximately 20% by weight can be used as the first plastic material.

[0167] The media guidance area 134 and / or the stabilization area 138 of each frame 128 of an electrochemical unit 104 of the electrochemical device 100 is preferably produced by an injection molding process.

[0168] For example, it may be provided that in a first injection molding process structures made of wound continuous glass fibers are placed into the cavity of an injection molding tool, whereupon the cavity of the injection molding tool is filled with the second plastic material in order to overmold the structures made of the continuous glass fibers with the second plastic material.

[0169] After the stabilization area 138 of a frame 128 has been produced in this way, the media guidance area 134 can be injection molded onto the stabilization area 138 of the frame 128 from the first plastic material in a second injection molding process.

[0170] In one variant (not shown separately) of the one in the Fig. In the embodiment of an electrochemical device 100 illustrated in Figures 1 to 4, each frame 128, 128' of an electrochemical unit 104 is provided with recesses 160 in areas where there is no contact with an operating medium of the electrochemical device 100. These recesses 160 are in Fig. 4 are shown hatched and can be provided in the media guidance area 134 and / or in the stabilization area 138 of the frame 128.

[0171] In this variant, the recesses 160 are bounded by ribs 162, which together form a skeletal structure 164.

[0172] If the frames 128, 128' of the electrochemical units 104 have a skeletal structure 164 formed by such ribs 162, this offers the advantage that a small amount of the first plastic material is required for the formation of the media guidance area 134 and / or a smaller amount of the second plastic material is required for the formation of the stabilization area 138.

[0173] Furthermore, a skeletal structure 164 formed by such recesses 160 has a uniform wall thickness, which facilitates the production of the skeletal structure 164 by an injection molding process.

[0174] Moreover, this variant of the one in the Fig. The embodiment of an electrochemical device 100 shown in Figures 1 to 4 is comparable with respect to its structure, function and method of manufacture to that shown in the Fig. The embodiment shown in Figures 1 to 4 is identical, and reference is made to the preceding description of these figures.

Claims

[1] Electrochemical device comprising several electrochemical units (104) which follow one another along a stacking direction (106), wherein each electrochemical unit (104) comprises at least one media separator (133) and at least one frame (128) on which the media separator (133) is held in the assembled state of the electrochemical device (100), characterized by , that the frame (128) comprises a media guidance area (134) which, during operation of the electrochemical device (100), comes into contact with at least one operating medium of the electrochemical device (100), and a stabilization area (138) which, during operation of the electrochemical device (100), does not come into contact with an operating medium of the electrochemical device (100), wherein the media guidance area (134) comprises a first plastic material and the stabilization area (138) comprises a second plastic material, where the first plastic material and the second plastic material are different from each other, wherein the first plastic material has a higher chemical resistance to at least one of the operating media with which the media guide area (134) comes into contact during the operation of the electrochemical device (100) than the second plastic material and wherein the second plastic material has a higher strength, a higher stiffness and / or a higher creep resistance than the first plastic material. [2] Electrochemical device according to claim 1, characterized by that the media guidance area (134) is essentially formed from the first plastic material and / or that the stabilization area (138) is essentially formed from the second plastic material. [3] Electrochemical device according to claim 1 or 2, characterized by, that the first plastic material comprises a polyphenylene sulfone (PPSU) material, a polysulfone (PSU) material, a polyethersulfone (PES or PESU) material, a polyphenylene sulfide (PPS) material and / or a polyphthalamide (PPA) material. [4] Electrochemical device according to any one of claims 1 to 3, characterized by that the second plastic material comprises a polyamide (PA) material and / or a polypropylene (PP) material. [5] Electrochemical device according to claim 4, characterized by that the second plastic material comprises a polycaprolactam(PA6) material and / or a polyamide-66(PA66) material. [6] Electrochemical device according to any one of claims 1 to 5, characterized by that the first plastic material and / or the second plastic material includes fibers. [7] Electrochemical device according to claim 6, characterized bythat the proportion of fibers in the second plastic material is at least 20% by weight and / or that the proportion of fibers in the first plastic material is at most 20% by weight. [8] Electrochemical device according to one of claims 6 or 7, characterized by that the fibers have at least a partial fiber length of more than 1 mm. [9] Electrochemical device according to any one of claims 6 to 8, characterized by that the fibers comprise continuous fibers. [10] Electrochemical device according to claim 9, characterized by , that the second plastic material comprises continuous fibers wound around at least one fixed point. [11] Electrochemical device according to any one of claims 1 to 10, characterized by , that the media guidance area (134) and / or the stabilization area (138) of the frame (128) includes ribs (162) and recesses (160) bounded by the ribs (162). [12] Electrochemical device according to any one of claims 1 to 11, characterized by , that the media guidance area (134) is provided with at least one passage opening (142) for an operating medium of the electrochemical device (100). [13] Electrochemical device according to claim 12, characterized by , that at least one passage opening (142) of the media routing area (134) is designed as an elongated hole (143) extending along a circumferential direction of the frame (128). [14] Electrochemical device according to any one of claims 1 to 13, characterized by , that the stabilizing area (138) of the frame (128) includes a clamping ring (166) embedded in the second plastic material.

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