DE102007035830A1 - Bipolar plate for a fuel cell, in particular for the arrangement between two adjacent membrane-electrode assemblies in a fuel cell stack - Google Patents

Abstract

The invention relates to a bipolar plate (1) for a fuel cell, in particular for arrangement between two adjacent membrane-electrode assemblies in a fuel cell stack, having at least two plates arranged parallel to one another, one of which as an anode plate (2) and the other as a cathode plate ( 3), on the outer sides of which an anode flow field (F1) or a cathode flow field (F2) is formed by channel structures with anode channels (K1) or cathode channels (K2) introduced into the anode plate (2) or into the cathode plate (3) in which at least one coolant channel (K3) is formed between the anode plate (2) and the cathode plate (3) on their insides by negative structures of the channel structures. According to the invention, between the anode plate (2) and the cathode plate (3), at least one addition channel (K4) is additionally formed on its insides, which is fluidically connected to the anode channel (K1) or the cathode channel (K2).

Description

The The invention relates to a bipolar plate for a fuel cell, in particular for the arrangement between two adjacent membrane-electrode assemblies in a fuel cell stack according to the preamble of claim 1 and claim 10.

One Fuel cell stack (also called stack for short) consists of several, electrically connected in series, plane-parallel one above the other Stacked arranged fuel cells. Each fuel cell points an anode, a cathode and an electrolyte therebetween on, for example in the form of a polymer electrolyte membrane (short PEM), which together form a membrane-electrode assembly (MEA short) form. Between those in the fuel cell stack adjacent membrane electrode assemblies are each a bipolar plate (also called bipolar separator plate unit) arranged. The Bipolarplatte serves the spacing of adjacent membrane electrode assemblies, distributing reactants for the fuel cell like fuel and oxidant over the adjacent ones Membrane electrode assemblies and the removal of the reactants in this provided, respectively to the membrane-electrode assemblies out open channels, the removal of the heat of reaction via a guided in separate coolant channels Coolant and the production of an electrical connection between the anode and the cathode of adjacent membrane-electrode assemblies.

When Reactants are a fuel and an oxidant used. Most gaseous reactants (in short: reaction gases) are used, z. B. hydrogen or a hydrogen-containing gas (eg, reformate gas) as fuel and oxygen or an oxygen-containing gas (eg. As air) as an oxidizing agent. Under Reactants are all understood substances involved in the electrochemical reaction, including the reaction products, such as. B. water.

The respective bipolar plate consists of two plane-parallel with each other connected moldings, in particular plates - an anode plate for connection to the anode of a membrane-electrode assembly and a cathode plate for connection to the cathode of the others The membrane electrode assembly. At the one membrane electrode assembly facing surface of the anode plate are anode channels for distributing a fuel along the membrane-electrode assembly arranged on the other of the membrane electrode assembly facing surface of the cathode plate cathode channels for distributing the oxidizing agent over the other membrane-electrode assembly are arranged. The cathode channels and the anode channels have no connection with each other. Form the anode channels an anode flow field (also called anode flowfield), the cathode channels a cathode flow field (also Called cathode flowfield).

The Cathode and anode channels are thereby by surveys mutually separate recesses on each of the membrane-electrode assemblies facing surfaces of the anode and cathode plate educated. The cathode and anode plates are preferably shaped especially hollow shaped. The surveys and depressions for example, discontinuously by forming, deep-drawing, Extrusion or the like, or continuously Rolling or drawing made. By connecting the anode plate and the cathode plate channel bottom at the channel bottom are through to the Generation of the anode and cathode channels in the anode plate or the cathode plate molded elevations and depressions between the anode plate and the cathode plate coolant channels formed for the passage of coolant.

Certain Fuel cell electrolytes need it In addition, a certain water content to a sufficient ion conductivity exhibit. This is especially true for polymer electrolyte membrane fuel cells to, whose electrolytes on fluorinated sulfonic acids based materials exist, such. Nafion. For a homogeneous moisture distribution it is known to achieve, for example, humid cathode exhaust gas to dose.

Such provided with a metering fuel cell is for example from the DE 10 2005 035 098 A1 known. In this case, a separating plate is provided in addition to the bipolar plate, which separates a part of the cathode space as Zudosierungsraum. The disadvantage here is that an additional plate is required. In addition, the additional plate must be electrically conductive. For this purpose, it may, for. B. be coated with a precious metal. Usually, the additional plate is connected to the plates of the bipolar plate, in particular laser welded. As a result, the fuel cell produced from three electrically conductive plates - separating plate and two plates of the bipolar plate - is very complicated and expensive to produce.

Of the Invention is therefore based on the object, a bipolar plate for to provide a fuel cell, which adds a simple metering simultaneously reduced production costs.

The object is achieved according to the invention by the features specified in claim 1 or in claim 10.

advantageous Further developments of the invention are the subject of the dependent claims.

The Bipolar plate for a fuel cell, in particular for Arrangement between two adjacent membrane-electrode assemblies in a fuel cell stack comprises in a conventional manner at least two planes arranged parallel to each other, of one as an anode plate and the other as a cathode plate is formed, on the outer sides of an anode flow field or a cathode flow field through into the anode plate or introduced into the cathode plate channel structures with anode channels or cathode channels is formed, wherein between the anode plate and the cathode plate on their insides by negative structures the channel structures formed at least one coolant channel is. According to the invention, between the anode plate and the cathode plate on their insides in addition formed at least one metered addition, the fluidically with the Anodenkanal or the cathode channel is connected.

By such a bipolar plate with between the anode and the cathode plate arranged coolant channels and Dosing channels is no additional plate for Separation of cathode compartment and dosing space or anode compartment and dosing space required. Thus, the from the state of Technically known third, designed as a partition plate sure avoided. This results in a simple manufacturing process, because only two plates connected, z. B. welded, become. In this case, by such an embodiment of Bipolar plate without additional dividing plate wider channels - cathode or Anode channel - required.

In One possible embodiment is between the anode plate and the cathode plate of the dosing channel and the coolant channel alternately and adjacent to each other arranged. This is about the respective flow field a largely uniform cooling achieved at the same time sufficiently good addition. This is adjacent Metered into the anode flow field of each anode channel or when metered into the cathode flow field each Cathode channel preferably laterally to a coolant channel and a metering channel. The boundary channels border the anode flow field or the cathode flow field preferably only to one metering channel.

A possible embodiment provides that at a Metering into the anode flow field or the cathode flow field the channel structure, in particular the channel shape, the anode plate or the cathode plate along the Zudosierungskanals along whose longitudinal extent varies from input to output. In particular, by changing the channel shape, i. H. the introduced by deformation channel contours, including the cross-sectional area both the metering channel and the cathode channel or the anode channel varied. Preferably, such a varying channel structure is introduced, through which the metering channel in the entrance area a smaller Cross-section than in the exit area. Furthermore can the ratio of the cross sectional areas of the Dosing channel to the cathode or anode channel in longitudinal extension vary. In other words, the varying cross-section of the metering channel and the varying aspect ratios condition varying along the longitudinal extent of the metering channel Channel heights, whereby when flowing through the Zudosierungskanals Flow parameters, such. The flow rate, the flow rate and / or pressure, accordingly are adjustable. It is based on the varying cross-sectional ratios ensured that despite varying cross-section of the metering channel the total height of dosing channel and cathode or Anode channel is the same. It should be noted that the dosage range over the entire length of the channels - the Anode channel and the cathode channel - can extend so that the end of the metering region in the region of the cathode output located. This can be in the dosing and adjacent Cathode space pressure ratios are set, the with respect to the course of the relative humidity in the metering area advantageous inflow of the oxidizing agent from the metering channel allow in the cathode channel.

In one possible embodiment, the metering channel is formed of at least two recesses and an elevation of one or both plates arranged therebetween - anode and cathode plate. Conveniently, in each case at least one recess is introduced in the region of the elevation, in particular in its lateral webs. The recess serves as an input port for metering and connects the Zudosierungskanal with the cathode channel or the anode channel. In this case, bores are introduced into the bottoms and / or the webs of the anode channel or the cathode channel along the Zudosierungskanals in the relevant anode or cathode plate as recesses. The diameter of the holes are expediently designed so that the pressure loss when flowing through the holes is much higher than the pressure drop during the flow along the Zudosierungskanals. For example, holes with a diameter of 0.3 mm suitable. The diameter of the holes is substantially the same size. As a result, the gas volume, which flows through a bore per unit time, approximately the same size for all holes, so that the amount of oxidant to be metered in a simple manner by the number of holes is specified.

In Another embodiment is at a metering into the anode flow field or the cathode flow field the channel structure of the anode plate or the cathode plate, in particular in Area of the metering channel, partially graduated elevations and partially stepped depressions formed. this makes possible a simple variation of the cross-section of the metering channel.

at the channels - dosing channel, anode channel and Cathode channel - can, due to production limits, such as minimum dimensions for radii and angles of webs and side walls during forming, the respective channel shape, z. B. the channel height or the channel cross-section, not arbitrary be made small. Appropriately, is the channel shape is larger than the minimum dimension. In one possible embodiment is therefore for a variation of the channel shape of the cathode channel and / or the anode channel in Support area, for example in the range of two consecutive arranged channel bottoms of the cathode channel and the anode channel, in section at least in sections and / or at least partially filled. This allows a change the cross section of the cathode channel or anode channel and thus a possibility of changing the aspect ratios to the metering channel and an adjustment of flow parameters, like pressure, speed and quantity. Alternatively or in addition is at least one of the Zudosierungskanäle in cross section partially completely or at least partially filled.

Regarding the coolant channel is the channel structure of the anode plate and the cathode plate expediently in the range the coolant channel in each case at least one survey educated. This results in a largely round or oval channel and flow cross section over the length of the Coolant channel is largely the same.

to Obtaining a bipolar plate with simple addition and simultaneous low production cost is in an alternative embodiment the bipolar plate in a conventional manner from the two plane-parallel formed to each other arranged plates, one of which as Anode plate and the other is designed as a cathode plate, on whose outer sides are an anode flow field or a cathode flow field through into the anode plate or introduced into the cathode plate channel structures with anode channels or cathode channels is formed, wherein between the anode plate and the cathode plate on their insides by negative structures the channel structures formed at least one coolant channel is. On the outside of the anode plate or the cathode plate a separating plate is arranged, which from the anode channel or cathode channel at least in sections, preferably over the entire length the anode or cathode channel separates a metering channel, the fluidically connected to the anode channel and the cathode channel is. According to the invention, the partition plate with openings provided, through which the anode plate or the cathode plate protrudes. In contrast to the conventional partition plate is the separation plate according to the invention, for example separating the cathode compartment and the metering compartment from each other, so formed so that they at least in the channel bottom area and / or in the Sidewall area is provided with apertures, so that the protruding from these breakthrough cathode plate electrically and mechanically with the adjacent membrane-electrode assembly can be connected. By the electrical connection of cathode plate and membrane electrode assembly allows that the partition itself from a non-electrically conductive material can be formed. The partition plate may for example be made of plastic or to be an uncoated metal. This is the partition plate over the known from the prior art, precious metal coated separating plate particularly simple and inexpensive executed. In addition, the partition plate does not have to with the other Plates are welded. In general, the individual Plates of a metallic bipolar plate welded together, to seal the plates against each other and the electrical resistance for the power line to reduce.

Of Further is when metered into the anode flow field or the cathode flow field, the anode plate or the Cathode plate formed such that a connecting web of a Cathode channel or anode channel to the adjacent cathode channel or Anode channel is given. This will separate the separation Cathode or anode and metering space in a component, d. H. with the partition plate, reached. Alternatively, for everyone Zudosierungskanal provided an associated separating element be. This would be very long and narrow separation elements result, z. B. currently with a length corresponding to the Flow field of about 300 mm to 1000 mm and a channel width of about 0.5 mm to 2 mm.

For a simple metering, the separating plate is provided with a number of recesses in the area of the metering channel along its longitudinal extent. The recesses are, for example, holes. In addition, the recesses are preferably variable with each other rendem distance along the longitudinal extent of Zudosierungskanals introduced into the separation plate. As a result, appropriate parameters, such as metered amount and pressure, adjustable. Thus, for example, more recesses are in the entrance area of the metering channels than in the exit area or vice versa. For this purpose, the hole spacing between two adjacent recesses is varied accordingly. The hole spacing is independent of the shape, size and position of the connecting webs.

embodiments The invention will be explained in more detail with reference to drawings.

there demonstrate:

1 1 schematically a bipolar plate with an anode plate and a cathode plate, between which a coolant channel and a metering channel are arranged in cavities,

2 1 schematically shows a further embodiment of a bipolar plate with an anode plate and a cathode plate, between which a coolant channel and a metering channel are arranged in cavities,

3 schematically an alternative embodiment of a bipolar plate having an anode plate and a cathode plate and a partition plate which separates a cathode space from a metering space.

4 schematically a cross section through the bipolar plate according to 3 , and

5 schematically a further cross section through the bipolar plate according to 4 ,

each other corresponding parts are in all figures with the same reference numerals Mistake.

1 shows schematically in cross section a section of a bipolar plate 1 for a fuel cell, not shown, for the arrangement between two adjacent, not-shown membrane-electrode assemblies in a fuel cell stack, not shown.

The bipolar plate 1 includes an anode plate 2 and a cathode plate 3 ,

The anode plate 2 and the cathode plate 3 are arranged plane-parallel to each other. The anode plate 2 and the cathode plate 3 are molded parts, eg. B. thin metal sheets, which have elevations and depressions that form the outside, ie the respective associated membrane-electrode assembly, an anode flow field F1 and a cathode flow field F2 with anode channels K1 and cathode channels K2. During operation of the fuel cell, an anode flows through the anode channels K1 of the anode flow field F1 and the cathode channels K2 of the cathode flow field F2 through an oxidizing agent.

Between the anode plate 2 and the cathode plate 3 and thus on the inside, at least one coolant channel K3 and one metering channel K4 are formed by negative structures of the outer channel structures. Here are the anode plate 2 and the cathode plate 3 For example, such channel bottom placed on the channel bottom to each other, that form the side walls and webs inside coolant channels K3 and Zudosierungskanäle K4. Preferred are in cross section of the bipolar plate 1 seen a coolant passage K3 and a Zudosierungskanal K4 arranged alternately side by side. In this way, each anode channel K1 and each cathode channel K2 adjoins laterally on a coolant channel K3 and a metered addition channel K4. In the edge region of the bipolar plate, not shown 1 For example, the edge channels of the anode flow field F1 and of the cathode flow field F2 can adjoin only one metering channel K4 or coolant channel K3.

The one or more coolant channels K3 and the or the metering channels K4 can be in the longitudinal extension of the bipolar plate 1 in a manner not shown in sections or completely over the entire length of the bipolar plate 1 extend.

In the exemplary embodiment with a metered addition into the cathode flow field F2, the metering channels K4 are fluidically connected to the cathode channels K2. This is the cathode plate 2 in the area of the metering channels K4 with recesses 4 , z. B. holes provided.

To set predeterminable pressure ratios and flow rates in the cathode flow field F2 and thus in the cathode channels K2 and the metered addition channels K4, the channel shape of both channels can vary along their course. 1 and 2 show different cross-sectional shapes for the cathode channels K2 and the metering channels K4, wherein 1 shows a large cross-section for the metering channel K4 and a corresponding cross-sectional ratio in the inlet region of the cathode flow field F2, wherein the cross section of the metering channel K4 becomes smaller in the course of the channel and the cross-sectional ratio changes accordingly, so that in the exit region of the cathode flow field F2 the in 2 shown small cross-section is given for the metering channel K4.

In detail, for example, the metering channel K4 is formed in the input region of the cathode flow field F2 from partially stepped depressions and elevation. In stepwise formed depressions and elevations for channel formation, the fluidic connection of metering channel K4 and cathode channel K2 can be formed by recesses introduced in the channel bottom area 4 take place (see 1 ). Additionally or alternatively, the metered addition can take place via recesses introduced into side walls. In order to vary the channel shapes of the metering channel K4 and / or of the cathode channel K2, they can, at least in sections, with a filling, alternatively or in addition to the contour change in the respective channel bottom area 5 be provided. This ensures that when varying the channel contours and dimensions of the overall height and thus the thickness of the bipolar plate 1 stays the same. In a further possible embodiment, one or more of the metering channels K 4 can be partially or completely filled with a filling 5 be filled. In this case, the filling of the bottom region of the metering channel K4 and / or of the cathode channel K2 takes place, for example, by screen printing or powder coating.

Is the metering channel K4, as in 2 shown, formed only from a monotonous elevation with lateral depressions, so the fluidic connection by introduced into side walls recesses 4 respectively.

3 schematically shows an alternative embodiment for a bipolar plate 1 in top view and in the 4 and 5 this bipolar plate 1 in two cross sections.

In addition to the anode plate 2 and cathode plate 3 includes the bipolar plate 1 in this embodiment, a partition plate 6 , which separates a cathode space, in particular the cathode channel K2, from a metering space, in particular the metering channel K4. Alternatively, the partition plate 6 in a manner not shown also the separation of a dosing space in the anode flow field F1 serve.

In detail is the partition plate 6 formed in sections such that the cathode plate 3 through breakthroughs 7 protrudes. The breakthroughs 7 may be formed as shown as a longitudinal recess or as holes (not shown). About in the form of holes formed recesses 4 in the cathode plate 3 the metering channel K4 is fluidically connected to the cathode channel K2. The breakthroughs are preferred 7 at the channel webs of the coolant channel K1 open at the top, so that the cathode plate projecting therefrom 3 can be electrically and mechanically connected in a manner not shown with the adjacent membrane-electrode assembly.

Due to the direct connection of cathode plate 3 and membrane electrode assembly may be the separator plate 6 be made of an electrically non-conductive material, in particular of plastic or an uncoated metal. Also, instead of a partition plate 6 for each of the Zudosierungskanäle K4 an associated not shown in detail separating element can be used.

Depending on the specification, both the number of recesses 4 for adjusting the dosage as well as the number of breakthroughs 7 vary for electrical connection. In addition, the distance from adjacent recesses 4 and / or breakthroughs 7 vary.

1

bipolar

2

anode plate

3

cathode plate

4

recess

5

filling

6

separating plate

7

breakthroughs

F1

Anode flow field

F2

Cathode flow field

K1

anode channel

K2

cathode channel

K3

Coolant channel

K4

Zudosierungskanal

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102005035098 A1 [0007]

Claims (16)

Bipolar plate ( 1 ) for a fuel cell, in particular for the arrangement between two adjacent membrane-electrode assemblies in a fuel cell stack, with at least two planes arranged parallel to one another, of which one as an anode plate ( 2 ) and the other as a cathode plate ( 3 ) is formed, on whose outer sides an anode flow field (F1) and / or a cathode flow field (F2) through into the anode plate ( 2 ) and / or in the cathode plate ( 3 ) introduced channel structures with anode channels (K1) and / or cathode channels (K2) is formed, wherein between the anode plate ( 2 ) and the cathode plate ( 3 ) on the insides of which is formed by negative structures of the channel structures at least one coolant channel (K3), characterized in that between the anode plate ( 2 ) and the cathode plate ( 3 ) is additionally formed on the inner sides of at least one Zudosierungskanal (K4), which is fluidly connected to the anode channel (K1) or the cathode channel (K2). Bipolar plate according to claim 1, characterized in that between the anode plate ( 2 ) and the cathode plate ( 3 ), the metering channel (K4) and the coolant channel (K3) are arranged alternately and adjacent to each other. Bipolar plate according to claim 1 or 2, characterized that each anode channel (K1) or each cathode channel (K2) laterally to a coolant channel (K3) and a metering channel (K4) adjoins. Bipolar plate according to one of Claims 1 to 3, characterized in that, when metered into the anode flow field (F1) or the cathode flow field (F2), the channel structure, in particular the channel shape, of the anode plate ( 2 ) and / or the cathode plate ( 3 ) in the region of the metering channel (K4) varies along its longitudinal extent from the inlet to the outlet. Bipolar plate according to one of claims 1 to 4, characterized in that when added to the anode flow field (F1) or the cathode flow field (F2), the channel structure of the anode plate ( 2 ) and / or the cathode plate ( 3 ) is formed in the region of the metering channel (K4) of at least two recesses and an elevation arranged therebetween. Bipolar plate according to one of claims 1 to 5, characterized in that when metered into the anode flow field (F1) or the cathode flow field (F2) in the channel side walls and / or in the channel bottom region of the anode plate ( 2 ) or the cathode plate ( 3 ) at least one recess ( 4 ) is introduced. Bipolar plate according to one of claims 1 to 6, characterized in that when added to the anode flow field (F1) or the cathode flow field (F2), the channel structure of the anode plate ( 2 ) and / or the cathode plate ( 3 ), in particular in the region of the metering channel (K4), is formed from partially stepped elevations and partially stepped depressions. Bipolar plate according to one of claims 1 to 7, characterized in that the cathode channel (K2) and / or the anode channel (K1) in the channel bottom region in cross section at least partially and / or at least partially filled. Bipolar plate according to one of claims 1 to 8, characterized in that at least one of the Zudosierungskanäle (K4) in sections in whole or at least partially is filled. Bipolar plate according to one of claims 1 to 9, characterized in that the channel structure of the anode plate ( 2 ) and the cathode plate ( 3 ) is formed in the region of the coolant channel (K3) in each case at least one elevation. Bipolar plate ( 1 ) for a fuel cell, in particular for the arrangement between two adjacent membrane-electrode assemblies in a fuel cell stack, with at least two planes arranged in parallel to one another, one of which being an anode plate ( 2 ) and the other as a cathode plate ( 3 ) is formed, on whose outer sides an anode flow field (F1) and / or a Ka thodenströmungsfeld (F2) through in the anode plate ( 2 ) and / or in the cathode plate ( 3 ) introduced channel structures with anode channels (K1) and / or cathode channels (K2) is formed, wherein between the anode plate ( 2 ) and the cathode plate ( 3 ) on its insides by negative structures of the channel structures at least one coolant channel (K3) is formed and the outside of the anode plate ( 2 ) or the cathode plate ( 3 ) a separating plate ( 6 ) is arranged, which at least in sections from the anode channel (K1) and / or cathode channel (K2) a Zudosierungskanal (K4) separates, which is fluidically connected to the anode channel (K1) and / or the cathode channel (K2), characterized in that the Partition plate ( 7 ) with breakthroughs ( 8th ), through which the anode plate ( 2 ) and / or the cathode plate ( 3 ) stands out. Bipolar plate according to claim 11, characterized in that the separating plate ( 6 ) is made of a non-electrically conductive material. Bipolar plate according to claim 11 or 12, as characterized in that the separating plate ( 3 ) is made of plastic. Bipolar plate according to one of claims 11 to 13, characterized in that when metered into the anode flow field (F1) or the cathode flow field (F2), the anode plate ( 2 ) and / or the cathode plate ( 3 ) is formed such that a connecting web of a cathode channel (K2) o the anode channel (K1) to the adjacent cathode channel (K2) and / or anode channel (K1) is given. Bipolar plate according to one of claims 10 to 12, characterized in that the separating plate ( 6 ) in the region of the metering channel (K4) along its longitudinal extent with a number of recesses ( 4 ) is provided. Bipolar plate according to claim 15, characterized in that the recesses ( 4 ) with mutually varying distance along the longitudinal extent of Zudosierungskanals (K4) in the separating plate ( 6 ) are introduced.