Bipolar plate, bipolar plate arrangement and electrochemical unit

Abstract

In order to provide a bipolar plate for an electrochemical unit, which achieves optimized supply and / or removal of a fluid medium to and / or from a membrane electrode unit as well as optimized cooling of the membrane electrode units, it is proposed that this plate comprise a first plate body on which several flow channels are formed, which are mutually delimited by webs and form at least a first flow field for a first fluid medium, and at least a second plate body on which several flow channels are formed, which are mutually delimited by webs and form at least a second flow field for a second fluid medium.wherein the flow channels formed on the second plate body are each received in a corresponding web on the first plate body and a flow area for a third fluid medium is formed between a channel bottom of at least one flow channel formed on the second plate body and a web bottom of the corresponding web formed on the first plate body.

Description

[0001] The present invention relates to a bipolar plate for an electrochemical unit, a bipolar plate arrangement and an electrochemical unit.

[0002] The core of a fuel cell consists of the membrane electrode assemblies, which are separated from each other on the cathode and anode sides by bipolar plates. Bipolar plates have a channel structure that forms flow fields, through which reaction media are supplied to the membrane electrode assembly, reaction products are removed from the membrane electrode assembly, and the membrane electrode assemblies are cooled.

[0003] The present invention is based on the object of providing a bipolar plate and a bipolar plate arrangement that achieves optimized supply and / or removal of fluid media to and / or from a membrane electrode assembly, as well as optimized cooling of the membrane electrode assembly. Furthermore, the invention is an object of providing an electrochemical assembly with optimized performance potential.

[0004] This object is achieved according to the invention by a bipolar plate for an electrochemical unit, comprising a first plate body on which a plurality of flow channels are formed, wherein the flow channels are delimited by webs from one another and form at least one first flow field for a first fluid medium, at least one second plate body on which a plurality of flow channels are formed, wherein the flow channels are delimited by webs from one another and form at least one second flow field for a second fluid medium, wherein the first flow field and the second flow field are formed on opposite sides of the plate body and the flow channels formed on the second plate body are each received in a corresponding one of the webs on the first plate body,wherein a flow region for a third fluid medium is formed between a channel base of at least one flow channel formed on the second plate body and a web base of the corresponding web formed on the first plate body.

[0005] The bipolar plate is preferably formed from two layers of plate bodies or can also be formed from several layers of plate bodies.

[0006] The plate bodies can be made in particular of metal, graphite, a graphite-polymer compound or of ceramic.

[0007] The plate bodies can be provided with a coating, in particular with a conductive and / or corrosion-resistant coating. For example, the at least one plate body can be coated with or formed from gold, titanium, titanium nitride, carbon, chromium nitride, and / or a ceramic material.

[0008] The webs which form the flow fields for the first fluid medium and the second fluid medium can in particular be formed from the respective plate body, preferably formed from it, formed onto it or incorporated into it.

[0009] The flow channels preferably extend in a flow direction from an inlet-side end of the bipolar plate to an outlet-side end of the bipolar plate.

[0010] The flow area for the third fluid medium is preferably formed by a distance between the channel base of the at least one flow channel formed on the second plate body and the web base of the corresponding web formed on the first plate body.

[0011] Since the flow area for the third fluid medium is formed by the distance between the channel base and the web base, a flow cross-section of the flow area for the third fluid medium can be adapted in a defined manner by configuring the channel base and / or web base. In this way, for example, the flow cross-section of the flow area can be adapted to the operation of the electrochemical unit or to the properties of the third fluid medium.

[0012] The third fluid medium can preferably be a cooling medium. The flow cross-section of the flow area can, for example,

[0013] The evaporation properties of such a coolant must be adapted. This allows optimal cooling properties to be achieved during operation of the electrochemical unit.

[0014] Because the flow area for the third fluid medium is formed between the channel base and the web base, optimized cooling by the third fluid medium can be provided over the entire web base of the web formed on the first plate body.

[0015] The flow channels can provide both a co-directional flow of the fluid media and an opposite flow of the fluid media.

[0016] In particular, the bipolar plate can enable individual adaptation of flow cross sections of the flow channels on the first and second plate body as well as of the flow area between the channel base and the web base depending on the operating characteristics of the electrochemical unit.

[0017] The electrochemical unit is in particular a fuel cell unit or an electrolysis unit.

[0018] A further development of the bipolar plate can provide that at least one shoulder is provided on the channel base of the at least one flow channel formed on the second plate body in the direction of the web base of the web formed on the first plate body and the at least one shoulder reduces a flow cross-section of the flow region between the channel base and the web base and / or divides the flow region into at least two flow regions.

[0019] Optionally, the at least one step on the channel base extends partially or completely along the direction of extension of the flow channel.

[0020] The at least one shoulder can be formed from the plate body, in particular formed from it, formed into it, introduced into it or formed onto it.

[0021] The at least one shoulder can have any desired geometry. Advantageously, the at least one shoulder can have a trapezoidal or rectangular cross-section.

[0022] The at least one step can be designed in such a way that it extends from the channel bottom to the web bottom.

[0023] Advantageously, a contact surface facing the web base can be formed on the at least one shoulder, which contact surface bears against the web base, in particular in a supporting and / or fluid-tight manner.

[0024] The at least one shoulder can extend, viewed in the direction of extension, along a right and / or a left edge region of the channel base of the flow channel.

[0025] Alternatively, the at least one step can extend along a central region of the channel base, viewed in the direction of extension. In this way, the flow area for the third fluid medium can be divided into two separate flow areas.

[0026] An advantageous development of the bipolar plate can provide that at least one of the flow channels formed on the second plate body has, at least in sections, a channel depth which is 2 / 3 or less, preferably 1 / 2 or less, particularly preferably 1 / 3 or less, of a channel depth of the flow channels formed on the first plate body.

[0027] The at least one of the flow channels formed on the second plate body can thereby be formed with a smaller channel depth than the flow channels formed on the first plate body.

[0028] Due to the smaller channel depth of at least one of the flow channels formed on the second plate body, a flow cross-section can be smaller than a flow cross-section of the flow channels formed on the first plate body.

[0029] An embodiment of the bipolar plate can also provide that the flow region for the third fluid medium has a flow cross-section of 50% or less, preferably 25% or less, particularly preferably 10% or less, of a flow cross-section of the flow channels for the first fluid medium and / or the flow channels for the second fluid medium.

[0030] Preferably, the flow cross-section of the flow region for the third fluid medium can be smaller than the flow cross-section of the flow channels on the second plate body for the second fluid medium and preferably the flow cross-section of the flow channels on the second plate body for the second fluid medium can be smaller than the flow cross-section of the flow channels on the first plate body for the first fluid medium.

[0031] In a further development of the bipolar plate, at least one of the flow channels formed on the second plate body can have a varying channel depth along a flow direction, so that varying flow cross sections for the second fluid medium and for the third fluid medium are formed in the flow channel and in the flow region between the channel base and the web base.

[0032] Preferably, the varying channel depth along the flow direction can be formed by a wave-like change in the channel depth of the flow channels. That is, in the side view of the bipolar plate, by an oscillating change in the channel depth along the flow direction of the flow channels.

[0033] In this case, a reduction in the channel depth of the flow channels formed on the second plate body can cause an increase in the flow cross-section of the flow area for the third fluid medium.

[0034] Increasing the channel depth of the flow channels formed on the second plate body can cause a reduction in the flow cross-section of the flow area for the third fluid medium.

[0035] A further advantageous embodiment of the bipolar plate can also provide that at least one fluid connection is formed between adjacent flow regions for the third fluid medium, in that the first plate body and the second plate body are provided spaced apart from one another at least in regions between the adjacent flow regions.

[0036] By means of the at least one fluid connection, an overflow of the third fluid medium from one flow region of the third fluid medium to an adjacent flow region of the third fluid medium can be provided.

[0037] The fluid connection is preferably formed by the flow over a flow channel formed on the first plate body between the adjacent flow regions of the third fluid medium.

[0038] Advantageously, the bipolar plate can be provided with a plurality of fluid connections between adjacent flow regions for the third fluid medium, wherein the fluid connections are arranged in such a way that a meandering overflow path for the third fluid medium is formed between two adjacent flow regions and / or a defined overflow path is formed between a plurality of adjacent flow regions.

[0039] In particular, the meandering overflow path between the adjacent flow regions is formed by arranging the plurality of fluid connections spaced apart from one another along the flow direction between the adjacent flow regions for the third fluid medium.

[0040] Alternatively, the plurality of fluid connections may be formed between a plurality of adjacent flow regions for the third fluid medium, so that a plurality of regions are formed in which an overflow of the flow channels formed on the first plate body is provided between a plurality of adjacent flow regions.

[0041] In one embodiment of the bipolar plate, the first plate body and / or the second plate body can be provided with a hydrophobic surface and / or a hydrophobic coating outside the flow region for the third fluid medium.

[0042] If the third fluid medium forms a coolant, the coolant flow through the hydrophobic surface and / or hydrophobic coating can be limited to the flow area for the third fluid medium. Evaporated coolant can remain on the hydrophobic surface and / or hydrophobic coating, allowing controlled evaporation and thus a controlled temperature profile for cooling the membrane electrode assembly.

[0043] A further embodiment of the bipolar plate can provide that web side walls of the webs formed on the first plate body have a steeper angle of attack than channel side walls of the flow channels formed on the second plate body, which are accommodated in the webs.

[0044] This allows a clearance to be provided so that the flow channels formed on the second plate body can be inserted into the webs formed on the first plate body.

[0045] Preferably, a difference in the angle of incidence of approximately 5° or less, preferably approximately 2° or less, can be formed between the mutually facing web side walls of the webs formed on the first plate body and the channel side walls of the flow channels formed on the second plate body.

[0046] In order for the flow channels formed on the second plate body to be insertable into the webs formed on the first plate body, it is preferably provided that the channel base of the flow channels formed on the second plate body has a smaller width than the web base of the webs formed on the first plate body.

[0047] Likewise, it can preferably be provided that the channel base of the flow channels formed on the first plate body has a smaller width than the web base of the webs formed on the second plate body.

[0048] Preferably, it can be provided that a flow cross-section of the flow channels formed on the second plate body is smaller than a flow cross-section of the flow channels formed on the first plate body.

[0049] Particularly preferably, it can be provided that the second flow field for hydrogen (anode side) is provided as the second fluid medium through the flow channels formed on the second plate body with the smaller flow cross section.

[0050] Due to the flow channels formed on the first plate body with the larger flow cross-section, the first flow field for oxygen (cathode side) can preferably be provided as the first fluid medium.

[0051] In other words, in the flow channels formed on the second plate body with the smaller flow cross-section, a larger web width is preferably formed, which in particular forms the anode side with contact to the membrane electrode unit.

[0052] In the case of the flow channels formed on the first plate body with the larger flow cross-section, a smaller web width is preferably formed, which in particular forms the cathode side with contact to the membrane electrode unit.

[0053] Advantageously, the first plate body and the second plate body can be spaced apart from one another at least in regions between the adjacent flow regions to form the fluid connection in such a way that a channel side wall of the flow channel formed on the second plate body does not abut the corresponding web side wall of the web formed on the first plate body, and that an adjacent channel side wall of the adjacent flow channel formed on the second plate body does not abut the corresponding web side wall of the web formed on the first plate body.

[0054] In a further development of the bipolar plate, the webs formed on the first plate body and the flow channels formed on the second plate body, which are accommodated in the webs, can have a mutually corresponding wave-shaped course along the direction of extension.

[0055] The wave-shaped course of the webs on the first plate body and the wave-shaped course of the flow channels on the second plate body can form a periodic course.

[0056] Preferably, the webs on the first plate body and the flow channels on the second plate body have the same wave-shaped course.

[0057] Advantageously, the wave-shaped course of the webs on the first plate body and the flow channels on the second plate body can be uniformly formed.

[0058] For example, the corresponding webs on the first plate body and flow channels on the second plate body can have a wave-like course in which they oscillate symmetrically around a common imaginary center line.

[0059] The imaginary centerline is defined as a line / straight line that runs midway between the maximum and minimum points of the wave-shaped webs and / or flow channels.

[0060] A preferred use of the bipolar plate according to the invention is, according to a further development of the invention, a bipolar plate arrangement comprising a plurality of bipolar plates arranged in a stack according to one of the preceding claims, wherein a membrane electrode unit is provided between adjacent bipolar plates and adjacent bipolar plates are supported relative to one another at least in regions by the webs formed on the bipolar plates.

[0061] The membrane electrode assembly (MEA) is arranged between the adjacent bipolar plates. The bipolar plates, with the membrane electrode assembly arranged between them, form a fuel cell.

[0062] A fuel cell unit consists of several bipolar plates arranged in a stack with membrane electrode assemblies arranged between them. The fuel cell unit can also be formed by several fuel cell stacks.

[0063] A further development of the bipolar plate arrangement can provide that flat support sections are formed at least in sections on the upper sides of the webs, by means of which the adjacent bipolar plates are mutually supported, and preferably the webs, preferably the flat support sections, have a width of 1.2 mm or less, preferably 0.8 mm or less, particularly preferably 0.5 mm or less.

[0064] It can be provided that the webs, in particular the flat support sections, on the cathode side have a smaller width than the webs, in particular the flat support sections, on the anode side. For example, the width of the webs on the cathode side can be 0.8 mm or less, preferably 0.5 mm or less, particularly preferably 0.3 mm or less, while the width of the webs on the anode side can be 1.2 mm or less, preferably 0.8 mm or less, particularly preferably 0.5 mm or less.

[0065] The webs, preferably the flat support sections of the webs, can have different widths from one another. In particular, the webs, preferably the flat support sections, of one bipolar plate and the webs, preferably the flat support sections, of the adjacent bipolar plate can have at least partially different widths from one another.

[0066] In a further embodiment of the bipolar plate arrangement, the wave-shaped course of the webs and flow channels formed on one bipolar plate and the wave-shaped course of the webs and flow channels formed on the adjacent bipolar plate can be phase-shifted from one another along the flow direction.

[0067] Preferably, the wave-shaped course of the webs and flow channels formed on one bipolar plate and the wave-shaped course of the webs and flow channels formed on the adjacent bipolar plate can have the same wavelengths or different wavelengths from one another.

[0068] Alternatively, it can also be provided that the wave-shaped course of the webs and flow channels formed on one bipolar plate and the wave-shaped course of the webs and flow channels formed on the adjacent bipolar plate have a defined wavelength ratio to one another.

[0069] Advantageously, the wave-shaped course of the webs and flow channels formed on one bipolar plate and the wave-shaped course of the webs and flow channels formed on the adjacent bipolar plate can have an integer wavelength ratio to one another, for example, the integer wavelength ratio can be formed by a ratio of 1:3, 1:5, 1:7 or the like.

[0070] An integer wavelength ratio is in particular a wavelength ratio for which a natural number (for example 1, 2, 3, etc.) results when the larger of the two numbers is divided by the smaller of the two numbers.

[0071] A non-integer wavelength ratio is in particular a wavelength ratio for which no natural number (e.g. 1.5; 2.5; 3.5; etc.) results when the larger of the two numbers is divided by the smaller of the two numbers.

[0072] The wave-like course of the webs and flow channels formed on one bipolar plate and the wave-like course of the webs and flow channels formed on the adjacent bipolar plate can have the same wave heights as well as different wave heights, ie amplitude heights, from each other.

[0073] Advantageously, the wave-shaped courses of the webs and flow channels formed on one bipolar plate and the webs and flow channels formed on the adjacent bipolar plate can oscillate symmetrically around a common imaginary center line.

[0074] In this case, the wave-shaped courses of the webs and flow channels formed on one bipolar plate and the webs and flow channels formed on the adjacent bipolar plate can have varying wave heights, ie amplitude height, and / or varying wavelengths, ie amplitude lengths, which result in correspondingly varying channel widths, in particular varying channel widths of the cathode channels.

[0075] It can also be provided that the wave-shaped courses of the webs and flow channels formed on one bipolar plate and the webs and flow channels formed on the adjacent bipolar plate are arranged offset from one another transversely to the flow direction.

[0076] An advantageous embodiment of the bipolar plate arrangement can also provide that the flow channels and / or webs formed on the plate bodies are provided mirror-symmetrically and that supply regions, discharge regions and / or edge regions formed on the plate bodies are provided point-symmetrically.

[0077] Preferably, the flow fields formed on the plate bodies can each have a mirror-symmetrical design.

[0078] In addition, the supply and discharge areas for the fluid media formed on the plate bodies, which are arranged on the plate bodies in particular opposite one another, and / or the edge areas can preferably have a point-symmetrical design.

[0079] A particularly advantageous application of the bipolar plate or bipolar plate arrangement according to the invention is, according to a further development of the invention, an electrochemical unit comprising at least one membrane electrode unit and at least one bipolar plate according to one of the previously described embodiments or comprising a bipolar plate arrangement according to one of the previously described embodiments.

[0080] The electrochemical unit is in particular a fuel cell unit or an electrolysis unit.

[0081] The fuel cell unit comprises any fuel cell having bipolar plates to form a fuel cell stack. For example, the fuel cell unit may comprise a polymer electrolyte fuel cell (PMFC), alkaline fuel cell (AFC), direct methanol fuel cell (DMFC), or phosphoric acid fuel cell (PAFC).

[0082] In particular, the fuel cell unit comprised a plurality of membrane electrode assemblies stacked in a stacking direction to form a fuel cell stack, wherein the membrane electrode assemblies are each provided between bipolar plates.

[0083] In particular, a bipolar plate is arranged on one anode side and one cathode side of the membrane electrode assembly.

[0084] The at least one bipolar plate or the bipolar plate arrangement forms an anode chamber on the anode side and a cathode chamber on the cathode side, via which the fluid media (e.g. process gases) for the fuel cell reaction are supplied and / or discharged.

[0085] A fuel cell unit with such a bipolar plate or bipolar plate arrangement can provide improved supply and removal of fluid media to the membrane electrode assembly and optimized cooling of the membrane electrode assembly, thereby achieving optimized performance potential of the fuel cell unit. The at least one bipolar plate or the bipolar plate arrangement can thus maximize the power density of the membrane electrode assembly, allowing the fuel cell unit to achieve improved efficiency.

[0086] Further preferred features and / or advantages of the invention are the subject of the following description and the drawings of exemplary embodiments.

[0087] In the figures shows: Fig. 1 is a schematic sectional view of adjacent bipolar plates of a bipolar plate arrangement according to a first embodiment of the disclosure; Fig. 2 is a schematic sectional view of a bipolar plate of the bipolar plate assembly according to an alternative embodiment; Fig. 3 is a schematic sectional view of a bipolar plate of the bipolar plate arrangement according to another alternative embodiment; Fig. 4 a schematic partial view of one of the bipolar plates of the bipolar plate arrangement in Fig. 1; Fig. 5 a schematic partial view of the bipolar plate arrangement in Fig. 1; Fig. 6 is a schematic partial view of a bipolar plate according to another embodiment of the disclosure; Fig. 7 a schematic sectional view of the further development of the bipolar plate according to the section AA in Fig. 6; Fig. 8 a schematic sectional view of the further development of the bipolar plate according to the section BB in Fig. 6; Fig. 9 a schematic sectional view of the further development of the bipolar plate according to the section CC in Fig. 6.

[0088] Identical or functionally equivalent elements are provided with the same reference numerals in all figures.

[0089] Fig. 1 shows a schematic sectional view of a bipolar plate arrangement, designated as a whole by 100, using the example of two adjacent bipolar plates 102 for an electrochemical unit not shown in detail, in particular for a fuel cell unit or an electrolysis unit, according to a first embodiment according to the disclosure.

[0090] The fuel cell unit comprises one or more fuel cell stacks, each formed by a plurality of fuel cells arranged in a stack. The fuel cell stack, also referred to as a fuel cell stack, comprises a plurality of such bipolar plate assemblies 100.

[0091] The fuel cell can be any fuel cell that includes bipolar plates to form the fuel cell stack, for example a polymer electrolyte fuel cell (PMFC), alkaline fuel cell (AFC), direct methanol fuel cell (DMFC) or phosphoric acid fuel cell (PAFC).

[0092] The fuel cell comprises a supply line for supplying fluid media to the fuel cell, in particular a fuel, fuel mixture (fuel-exhaust gas mixture), oxidizer, and / or coolant. The exhaust gas, fuel, oxidizer, and / or coolant are removed via a fuel cell outlet.

[0093] The fuel cell stack comprises a plurality of membrane electrode assemblies 104 stacked in a stacking direction. The membrane electrode assemblies 104 are each arranged between the bipolar plates 102. That is, one bipolar plate 102 is arranged on each anode side and one cathode side of a membrane electrode assembly 104.

[0094] In other words, the bipolar plate 102 forms the anode side of one membrane electrode assembly 104 and the cathode side of an adjacent membrane electrode assembly 104.

[0095] The membrane electrode assemblies 104 comprise a catalyst-coated membrane with an anode-side gas diffusion layer and a cathode-side gas diffusion layer.

[0096] The anode-side and cathode-side gas diffusion layers are each provided with an anode-side and cathode-side microporous layer towards the catalyst-coated membrane.

[0097] The bipolar plate arrangement 100 is designed to ensure a uniform supply and distribution of the fluid media to the membrane electrode units 104 and an optimal removal of the fluid media as well as to provide a coordinated cooling of the membrane electrode units 104.

[0098] The membrane electrode assembly 104 may preferably have a gas diffusion layer having a flexural rigidity of 0.4 GPa or more.

[0099] Preferably, the gas diffusion layer may have a flexural rigidity of 0.6 GPa or more.

[0100] Particularly preferably, the gas diffusion layer may have a flexural rigidity of 1.0 GPa or more

[0101] A shear modulus of the gas diffusion layer can be 1 MPa or more.

[0102] Preferably, the shear modulus of the gas diffusion layer may be 2 MPa or more.

[0103] The bipolar plates 102 of the bipolar plate arrangement 100 are each formed from a first plate body 106 and at least one second plate body 108.

[0104] A first flow field 110 for a first fluid medium is formed on the first plate body 106. The first flow field 110 is formed by a plurality of flow channels 112 formed on the first plate body 106, wherein the flow channels 112 are each delimited from one another by webs 114 formed on the first plate body 106.

[0105] A second flow field 116 for a second fluid medium is formed on the at least one second plate body 108. The second flow field 116 is formed by a plurality of flow channels 112 formed on the second plate body 106, wherein the flow channels 112 are each delimited from one another by webs 114 formed on the second plate body 108.

[0106] The first flow field 110 for the first fluid medium formed on the first plate body 106 and the second flow field 116 for the second fluid medium formed on the second plate body 108 are formed on opposite sides of the plate bodies 106, 108.

[0107] The plate bodies 106, 108 can be made of metal, graphite, a graphite-polymer compound or ceramic.

[0108] The surface of the plate bodies 106, 108 can be provided with a coating, in particular with a conductive and / or corrosion-resistant coating. For example, the plate bodies 106, 108 can be coated with or formed from gold, titanium, titanium nitride, carbon, chromium nitride, and / or a ceramic material.

[0109] The surface of the plate bodies 106, 108 can be provided at least in some areas with a hydrophobic surface and / or a hydrophobic coating.

[0110] The flow channels 112 are preferably formed from the respective plate body 106, 108, in particular they are formed from them, formed onto them or introduced into them.

[0111] The webs 114 are preferably formed from the respective plate body 106, 108, in particular they are formed from them, formed onto them or introduced into them.

[0112] Adjacent bipolar plates 102 are supported relative to one another via the webs 114. For this purpose, the webs 114 are flattened on their upper sides, so that flat support sections 118 are formed on these upper sides.

[0113] The membrane electrode assembly 104 is arranged between the flat support sections 118 of the webs 114 on the first plate body 106 and the flat support sections 118 of the webs 114 on the second plate body 108.

[0114] This provides that the flat support sections 118 of the webs 114 on the first plate body 106 and the flat support sections 118 of the webs 114 on the second plate body 108 each rest on opposite sides of the membrane electrode assembly 104.

[0115] The flat support sections 118 of the webs 114 on the first plate body 106 and the flat support sections 118 of the webs 114 on the second plate body 108 thus support each other with the membrane electrode assembly 104 in between.

[0116] Preferably, the planar support sections 118 are formed along the longitudinal extent of the webs 114 on their respective upper sides.

[0117] If the bipolar plates 102 are stacked one above the other in a stack, the webs 114 are arranged at least in sections corresponding to one another, so that the adjacent bipolar plates 102 are mutually supported on one another via the support sections 118 of the webs 114.

[0118] The webs 114, preferably the flat support sections 118, may have a width of 0.8 mm or less.

[0119] Preferably, the webs 114, preferably the planar support sections 118, may have a width of 0.5 mm or less.

[0120] Particularly preferably, the webs 114, preferably the flat support sections 118, may have a width of 0.3 mm or less.

[0121] The webs 114 of the bipolar plates 102 can have different widths, preferably being formed by support sections 118 of different widths.

[0122] As in Fig. 1, the flow channels 112 formed on the second plate body 108 are each received in a corresponding one of the webs 114 on the first plate body 106.

[0123] Preferably, the flow channels 112 formed on the second plate body 108 are each received in a corresponding one of the webs 114 on the first plate body 106 and the flow channels 112 formed on the first plate body 106 are each received in a corresponding one of the webs 114 on the second plate body 106.

[0124] In other words, the flow channels 112 formed on the second plate body 108 are each inserted into the corresponding webs 114 on the first plate body 106, and the flow channels 112 formed on the first plate body 106 are each inserted into the corresponding webs 114 on the second plate body 106.

[0125] A gap is formed between a channel bottom 120 of each flow channel 112 on the second plate body 108 and a web bottom 122 of the corresponding web 114 formed on the first plate body 106.

[0126] The channel bottom 120 forms a bottom section of the flow channel 112.

[0127] The channel base 120 can preferably be formed as a flat bottom section of the flow channel 112.

[0128] The web bottom 122 forms a bottom section of each web 114.

[0129] The web bottom 122 may preferably be formed as a flat bottom section of the web 114.

[0130] A flow area 124 for a third fluid medium is formed by the space between the channel base 120 of the flow channel 112 and the web base 122 of the web 114.

[0131] Preferably, the third fluid medium is a coolant.

[0132] Due to the flow through the flow region 124 between the channel base 120 of the flow channel 112 and the web base 122 of the web 114 with the third fluid medium, cooling of the membrane electrode unit 104 can be provided in particular.

[0133] The flow region 124 comprises an inlet (not shown in detail) for supplying and an outlet for discharging the third fluid medium.

[0134] The flow channels 112 formed on the second plate body 108 can preferably have a channel depth that is 2 / 3 or less, preferably 1 / 2 or less, particularly preferably 1 / 3 or less, of the channel depth of the flow channels 112 formed on the first plate body 106. In this way, the flow channels 112 formed on the second plate body 108 can be formed with a smaller channel depth than the flow channels 122 formed on the first plate body 106.

[0135] Due to the smaller channel depth of the flow channels 122 formed on the second plate body 108, a flow cross-section can be smaller than a flow cross-section of the flow channels 122 formed on the first plate body 106.

[0136] The flow channels 112 formed on the second plate body 108 can have a varying channel depth along the flow direction S. Varying flow cross sections for the second fluid medium and for the third fluid medium can thus be formed in the flow channels 112 formed on the second plate body 108 and in the flow regions 124 between the channel base 120 and the web base 122.

[0137] Preferably, a reduction in the channel depth of the flow channels 122 formed on the second plate body 108 causes an increase in the flow cross-section of the flow regions 124 for the third fluid medium and, conversely, an increase in the channel depth of the flow channels 112 formed on the second plate body 108 causes a reduction in the flow cross-section of the flow regions 124 for the third fluid medium.

[0138] In particular, the varying channel depth along the flow direction S can be formed by a wave-shaped changing channel depth of the flow channels 112.

[0139] Fig. 2 shows a schematic sectional view of a bipolar plate 102 of the bipolar plate assembly 100 according to an alternative embodiment.

[0140] In this alternative embodiment, a shoulder 126 is provided on the channel base 120 of the flow channels 112 formed on the second plate body 108 in the direction of the web base 122 of the web 114 formed on the first plate body 106.

[0141] The shoulder 126 formed on the flow channels 112 provides for a reduction of a flow cross-section of the flow region 124.

[0142] In particular, the shoulder 126 extends completely along the direction of extension of the channel base 120 of the flow channels 112. Alternatively, the shoulder 126 can also extend in sections along the channel base 120 of the flow channels 112.

[0143] The shoulder 126 is preferably formed from the second plate body 108, but can also be formed into, incorporated into, or molded onto it.

[0144] The shoulder 126 can have any geometry. Advantageously, the shoulder 126 can have a trapezoidal or rectangular cross-section.

[0145] Advantageously, the shoulder 126 can extend from the channel base 120 of the flow channels 112 formed on the second plate body 108 to the web base 122 of the webs 114 formed on the first plate body 106.

[0146] A contact surface facing the web base 122 can be formed on the shoulder 126, which contact surface preferably rests against the web base 122.

[0147] The shoulder 126 can extend, as seen in the direction of extension, along a right and / or along a left edge region of the channel base 120 of the flow channels 112.

[0148] Fig. 3 shows a schematic sectional view of a bipolar plate 102 of the bipolar plate assembly 100 according to another alternative embodiment.

[0149] In this embodiment, the shoulder 126 extends in a central region along the channel base 120 of the flow channels 112, as seen in the direction of extension of the flow channels 112.

[0150] In this way, two separate flow areas 124 for the third fluid medium can be formed between the channel bottom 120 and the web bottom 122.

[0151] Fig. 4 shows a schematic partial view of the bipolar plate 102 of the bipolar plate arrangement 100 in Fig. 1, wherein the illustration essentially illustrates the course of the flow channels 112 on the second plate body 108 and the course of the webs 114 on the first plate body 106.

[0152] The webs 114 formed on the first plate body 106 and the flow channels 112 formed on the second plate body 108 and accommodated in the webs 114 can have a mutually corresponding wave-shaped course along the direction of extension.

[0153] The wave-shaped course of the webs 114 formed on the first plate body 106 and the flow channels 112 formed on the second plate body 108 and accommodated in the webs 114 can have any wave height and / or wavelength along the direction of extension; preferably, it can be a uniform or periodic wave-shaped course of the flow channels 112 on the second plate body 108 and webs 114 on the first plate body 106.

[0154] In particular, the flow channels 112 on the second plate body 108 and the webs 114 on the first plate body 106 have the same wave-shaped course.

[0155] For example, mutually corresponding flow channels 112 on the second plate body 108 and webs 114 on the first plate body 106 can have a wave-like course in which they oscillate symmetrically around a common imaginary center line.

[0156] In an alternative embodiment of the bipolar plate 102, it can also be provided that the webs 114 formed on the first plate body 106 and the flow channels 112 formed on the second plate body 108 and accommodated in the webs 114 have a mutually corresponding rectilinear course along the direction of extension.

[0157] In Fig. 5 is a schematic partial view of the bipolar plate assembly 100 in Fig. 1, wherein the illustration essentially illustrates the wave-shaped course of the flow channels 112 and webs 114 of a bipolar plate 102 as well as the wave-shaped course of the flow channels 112 and webs 114 of an adjacent bipolar plate 102.

[0158] It is preferably provided that the wave-shaped course of the flow channels 112 and webs 114 of one bipolar plate 102 and the wave-shaped course of the flow channels 112 and webs 114 of the adjacent bipolar plate 102 are provided with a phase shift relative to one another.

[0159] In this case, any desired phase offset can be provided between the flow channels 112 and webs 114 of one bipolar plate 102 and the flow channels 112 and webs 114 of the adjacent bipolar plate 102, preferably a phase offset of 180°.

[0160] For example, this can be realized by designing an overall layout of the bipolar plate arrangement 100 with point symmetry with respect to opposing edge regions, in particular the supply and discharge lines, while the flow field paths, in particular the flow channels 112 and / or webs 114, are mirror symmetrical.

[0161] Advantageously, it can be provided that the mutually corresponding flow channels 112 and webs 114 of one bipolar plate 102 and the flow channels 112 and webs 114 of the adjacent bipolar plate 102 oscillate around a common imaginary center line.

[0162] As a result, the corresponding flow channels 112 and webs 114 of one bipolar plate 102 and the flow channels 112 and webs 114 of the adjacent bipolar plate 102 can be arranged centrally one above the other with a corresponding phase offset. In this way, uniform support of the adjacent bipolar plates 102 can be achieved via the webs 114.

[0163] The flow channels 112 can have varying channel depths along the flow direction S.

[0164] Preferably, the varying channel depths in the flow channels 112 can be formed by a wave-like changing channel depth. As a result, alternating regions can be provided along the flow direction S of the flow channels 112 in which a maximum channel depth and a minimum channel depth are formed.

[0165] Preferably, the regions with minimum channel depth of one bipolar plate 102 are arranged substantially congruent with regions with minimum channel depth of the adjacent bipolar plate 102, so that the bipolar plate 102 can be additionally supported via the regions with minimum channel depth.

[0166] Preferably, a further development can provide that the extension lengths of the maximum channel depth and / or the minimum channel depth along the flow direction S are shortened step by step.

[0167] Alternatively or additionally, it can be provided that the channel depths are designed in such a way that the maximum channel depth and / or the minimum channel depth increases or decreases step by step along the flow direction S, so that the flow cross-section increases or decreases accordingly in the corresponding areas.

[0168] Particularly preferably, it can be provided that the maximum channel depth along the flow channels 106 remains constant, while only the minimum channel depth along the flow channels 106 is designed to decrease. In this way, the contact surfaces formed by the maximum channel depths between adjacent bipolar plates 102 can be maintained.

[0169] Fig. 6 shows a schematic partial view of a bipolar plate 102 according to a further embodiment according to the disclosure, wherein the illustration essentially illustrates the course of the flow channels 112 on the second plate body 108 and the course of the webs 114 on the first plate body 106.

[0170] The further development of the bipolar plate 102 according to Fig. 6 can be applied to a bipolar plate 102 according to Fig. 4 may be applied.

[0171] For the bipolar plate 102 according to Fig. 6, it is provided that several fluid connections 128 are formed between adjacent flow regions 124 for the third fluid medium.

[0172] Through the fluid connections 128, the third fluid medium can flow between one flow region 124 and an adjacent flow region 124.

[0173] The fluid connections 128 are arranged in such a way that a meandering overflow path 130 for the third fluid medium is formed between two adjacent flow regions 124.

[0174] Alternatively, it can also be provided that fluid connections 128 are formed between a plurality of adjacent flow regions 124, so that a defined overflow path 130 is formed between these flow regions 124.

[0175] Fig. 7 shows a schematic sectional view of this further development of the bipolar plate 102 according to the section AA in Fig. 6, Fig. Figure 8 shows a schematic sectional view of the further development of the bipolar plate 102 according to the section BB in Fig. 6 and Fig. 9 shows a schematic sectional view of the further development of the bipolar plate 102 according to the section CC in Fig. 6.

[0176] From the Fig. 7 and Fig. 9 it becomes clear that the flow channels 112 accommodated in the webs 114 on the second plate body 108 are formed with the previously described varying channel depth.

[0177] It is provided that every second flow channel 112 is formed with the same channel depth, wherein the varying channel depths of adjacent flow channels 112 are each provided with a phase shift relative to one another in the flow direction S.

[0178] In this way, in every second flow channel 112, the flow region 124 is formed between the channel base 120 and the web base 122 by providing a minimum channel depth of the corresponding flow channel 112, and in the corresponding sections of the respectively adjacent flow channels 112, a maximum channel depth is formed, in which no flow region 124 is formed between the channel base 120 and the web base 122, as shown in Fig. 7 according to section AA in Fig. 6 and in Fig. 9 according to section CC in Fig. 6 is shown.

[0179] Fig. 8 illustrates according to the section BB in Fig. 6, that the fluid connections 128 are formed in a transition region between these phase-shifted channel depths in that the first plate body 106 and the second plate body 108 are provided spaced apart from one another in some areas between adjacent flow regions 124 in this transition region.

[0180] In this way, the third fluid medium can be provided to flow over the flow channel 112 formed on the first plate body 106 and arranged between the adjacent flow regions 124.

[0181] By forming such fluid connections 128 along the flow direction S multiple times between adjacent flow areas 124, the meandering overflow path 130 can be formed as shown in Fig. 6 is shown.

[0182] In an alternative embodiment, the plurality of fluid connections 128 can also be formed between a plurality of adjacent flow regions 124 for the third fluid medium, whereby a plurality of overflow regions are formed, in which an overflow of the flow channels 112 formed on the first plate body 106 is provided between a plurality of adjacent flow regions 124 and a defined overflow path 130 is formed. List of reference symbols 100 bipolar plate arrangement 102 Bipolar plate 104 membrane electrode assemblies 106 first plate body 108 second plate body 110 first flow field 112 Flow channel 114 jetty 116 second flow field 118 support section 120 canal bottom 122 ridge floor 124 Flow area 126 paragraph 128 Fluid connection 130 Overflow path S Flow direction

Claims

[1] A bipolar plate (102) for an electrochemical unit, comprising a first plate body (106) on which a plurality of flow channels (112) are formed, wherein the flow channels (112) are delimited from one another by webs (114) and form at least one first flow field (110) for a first fluid medium, at least one second plate body (108) on which a plurality of flow channels (112) are formed, wherein the flow channels (112) are delimited from one another by webs (114) and form at least one second flow field (116) for a second fluid medium, wherein the first flow field (110) and the second flow field (116) are formed on opposite sides of the plate bodies (106, 108) and the flow channels (112) formed on the second plate body (108) are each received in a corresponding one of the webs (114) on the first plate body (106),wherein a flow region (124) for a third fluid medium is formed between a channel base (120) of at least one flow channel (112) formed on the second plate body (108) and a web base (122) of the corresponding web (114) formed on the first plate body (106). [2] Bipolar plate according to claim 1, characterized by that at least one shoulder (126) is provided on the channel base (120) of the at least one flow channel (112) formed on the second plate body (108) in the direction of the web base (122) of the web (114) formed on the first plate body (106), and the at least one shoulder (126) reduces a flow cross-section of the flow region (124) between the channel base (120) and the web base (122) and / or divides the flow region (124) into at least two flow regions. [3] Bipolar plate according to claim 1 or 2, characterized bythat at least one of the flow channels (112) formed on the second plate body (108) has, at least in sections, a channel depth which is 2 / 3 or less, preferably 1 / 2 or less, particularly preferably 1 / 3 or less, of a channel depth of the flow channels (112) formed on the first plate body (106). [4] Bipolar plate according to one of the preceding claims, characterized by that the flow region (124) for the third fluid medium has a flow cross-section of 50% or less, preferably 25% or less, particularly preferably 10% or less, of a flow cross-section of the flow channels (112) for the first fluid medium and / or the flow channels (112) for the second fluid medium. [5] Bipolar plate according to one of the preceding claims, characterized bythat at least one of the flow channels (112) formed on the second plate body (108) has a varying channel depth along a flow direction (S), so that varying flow cross sections for the second fluid medium and for the third fluid medium are formed in the flow channel (112) and in the flow region (124) between the channel base (120) and the web base (122). [6] Bipolar plate according to one of the preceding claims, characterized by that at least one fluid connection (128) is formed between adjacent flow regions (124) for the third fluid medium, in that the first plate body (106) and the second plate body (108) are provided spaced from one another at least in regions between the adjacent flow regions (124). [7] Bipolar plate according to claim 6, characterized bythat a plurality of fluid connections (128) are formed between adjacent flow regions (124) for the third fluid medium along the flow direction (S), wherein the fluid connections (128) are arranged in such a way that a meandering overflow path (130) for the third fluid medium is formed between two adjacent flow regions (124) and / or a defined overflow path (130) is formed between a plurality of adjacent flow regions (124). [8] Bipolar plate according to one of the preceding claims, characterized by that the first plate body (106) and / or the second plate body (108) are provided with a hydrophobic surface and / or a hydrophobic coating outside the flow region (124) for the third fluid medium. [9] Bipolar plate according to one of the preceding claims, characterized bythat web side walls of the webs (114) formed on the first plate body (106) have a steeper angle of attack than channel side walls of the flow channels (112) formed on the second plate body (108) which are accommodated in the webs (114). [10] Bipolar plate according to one of the preceding claims, characterized by that the webs (114) formed on the first plate body (106) and the flow channels (112) formed on the second plate body (108), which are accommodated in the webs (114), have a mutually corresponding wave-shaped course along the direction of extension. [11] Bipolar plate arrangement (100) for a fuel cell unit comprising a plurality of bipolar plates (102) arranged in a stack according to one of the preceding claims, wherein a membrane electrode unit (104) is provided between adjacent bipolar plates (102) and adjacent bipolar plates (102) are supported relative to one another at least in regions by the webs (114) formed on the bipolar plates (102). [12] Bipolar plate arrangement according to claim 11, characterized by that on upper sides of the webs (114) at least partially flat support sections (118) are formed, by which the adjacent bipolar plates (102) are mutually supported, and preferably the webs (114), preferably the flat support sections (118), have a width of 1.2 mm or less, preferably 0.8 mm or less, particularly preferably 0.5 mm or less. [13] Bipolar plate arrangement according to claim 11 or 12, characterized bythat the wave-shaped course of the webs (114) and flow channels (112) formed on a bipolar plate (102) and the wave-shaped course of the webs (114) and flow channels (112) formed on the adjacent bipolar plate (102) are phase-shifted from one another along the flow direction (S). [14] Bipolar plate arrangement according to one of claims 11 to 13, characterized by that the flow channels (112) and / or webs (114) formed on the plate bodies (106, 108) are provided with mirror symmetry and that the feed regions, discharge regions and / or edge regions formed on the plate bodies (106, 108) are provided with point symmetry. [15] Electrochemical unit comprising at least one membrane electrode assembly (104) and at least one bipolar plate (102) according to one of claims 1 to 10 or a bipolar plate arrangement (100) according to one of claims 11 to 14.

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