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EP1206807A1 - Electrical bonding protected against oxidation on the gas combustion side of a high temperature fuel cell - Google Patents

Electrical bonding protected against oxidation on the gas combustion side of a high temperature fuel cell

Info

Publication number
EP1206807A1
EP1206807A1 EP00949131A EP00949131A EP1206807A1 EP 1206807 A1 EP1206807 A1 EP 1206807A1 EP 00949131 A EP00949131 A EP 00949131A EP 00949131 A EP00949131 A EP 00949131A EP 1206807 A1 EP1206807 A1 EP 1206807A1
Authority
EP
European Patent Office
Prior art keywords
fuel cell
network
nickel
cell according
oxidation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00949131A
Other languages
German (de)
French (fr)
Inventor
Thomas Jansing
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Siemens Corp
Original Assignee
Siemens AG
Siemens Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG, Siemens Corp filed Critical Siemens AG
Publication of EP1206807A1 publication Critical patent/EP1206807A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023—Porous and characterised by the material
    • H01M8/0236—Glass; Ceramics; Cermets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023—Porous and characterised by the material
    • H01M8/0232—Metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023—Porous and characterised by the material
    • H01M8/0241—Composites
    • H01M8/0245—Composites in the form of layered or coated products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0297—Arrangements for joining electrodes, reservoir layers, heat exchange units or bipolar separators to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M2008/1293—Fuel cells with solid oxide electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the invention relates to a fuel cell or a fuel cell stack with the further features of the preamble of patent claim 1.
  • Fuel cells result in a fuel cell stack (also referred to in the technical literature as a fuel cell stack), which in sequence consists of an interconnector plate, a protective layer, a contact layer, a cathode, an electrolyte, an anode, a further contact layer and a further interconnector plate.
  • the interconnector plate with the sprayed-on protective and contact layer forms a unit.
  • Cathode, electrolyte and anode form the electrolyte electrode unit.
  • the corresponding units are layered parallel to each other and repeated several times in the same order.
  • the cathode, electrolyte and anode form an electrolyte-electrode unit.
  • an electrolyte electrode unit lying between adjacent interconnector plates forms a high-temperature fuel cell with the contact and protective layers directly adjacent to the electrolyte electrode unit on both sides, to which the sides of each of the protective layers and contact layers also lie belong to both interconnector plates.
  • the interconnector plates usually consist of CrFe5 with 1% Y-oxide, a so-called ODS alloy.
  • Gas channels are introduced into the interconnector plate, through which the fuel gas, for example hydrogen or methane (natural gas), and oxygen or air are passed becomes.
  • the hydrogen is directed to the anode side, the oxygen or air to the cathode side.
  • These gases are passed through with a relatively low overpressure of less than 1 bar.
  • the planar concept of the high-temperature fuel cell requires that the electrodes be contacted as fully as possible in both gas spaces.
  • contacting of the electrode is ensured by a contact layer made of La Perovskite, for example LasSrOo, 2 Mn ⁇ 3 .
  • This perovskite is stable in air.
  • contacting the electrode i.e. the anode
  • complete contacting of the anode is necessary because of the low transverse conductivity of the anode.
  • the anode is produced in the screen printing process and is therefore not flat over the entire surface, which is why flexible contacting is required which is very good electrical conductivity and whose resistance must be guaranteed over an operating period of approximately 40,000 hours
  • the prior art provides for the use of nickel networks as flexible contacts. For example, a finely meshed and a coarsely meshed nickel mesh are placed on top of one another, spot-welded to one another, so that a flexible intermediate layer with good contact is created.
  • a disadvantage of the prior art has turned out to be that when the fuel cell stack is soldered and when the fuel cell or the fuel cell stack is operated in the direct contact area of nickel network / CrFe5, an oxide layer that waxes out of Cr 2 ⁇ 3 in the non-material contact (Cr ⁇ O ⁇ ) and probably in material contact
  • NiO nickel-II-oxide
  • the nickel wires sinter together, so that there is a reduction in the desired flexibility as well as a reduction in the thickness, which is undesirable.
  • the reduction in thickness can also lead to contact breaks, which can cause component damage.
  • the invention is based on the object of developing a fuel cell or a fuel cell stack with the features of the preamble of patent claim 1 in such a way that the reduction in the thickness and the flexibility of the Nikkeinetze (s) is avoided, so that the most complete possible contact the anode and the interconnector plate is possible.
  • At least one metallic network which is protected against oxidation, is inserted for flexible contacting between the anode and the interconnector plate.
  • Such networks as a contact layer have the advantage that they can no longer oxidize, so that the increase in thickness is also eliminated. Since no oxidation has taken place, there is also no need to reduce the metallic nets and the associated disadvantages, such as, for example, contact breaks during the thickness reduction or loss of flexibility, do not arise. Due to the fact that the oxidation / reduction change process does not take place, the original thickness and flexibility of the networks protected against oxidation are retained, so that a good contacting contact layer is created between the anode and the interconnector. In addition, a reduction in the thickness of the metallic networks is prevented with an ongoing operating period.
  • the metallic nets are expediently coated with an oxidation-resistant protective layer.
  • the metallic networks e.g. Nickel networks remain unaffected both in their composition and in their mechanical and electrical properties, i.e. et al they remain largely flexible, do not cause any change in thickness and essentially retain their advantageous properties. It is advantageous that the metallic nets are subjected to the coating process before being introduced as a flexible contact layer. The assembly with the other components as well as the soldering must then be carried out in the usual way.
  • Coated nickel nets can be provided as metallic nets.
  • the nickel networks meet the requirements with regard to flexibility as well as electrical conductivity.
  • Coated stainless steel nets can also be provided as metallic nets, which have the property that they only oxidize to a depth of approx.
  • the stainless steel nets are also coated with an oxidation-resistant protective layer.
  • Another advantage of Stainless steel networks consist in that their thermal expansion coefficient is well adapted to the thermal behavior of the components of the fuel stack. This property is of considerable advantage especially when the fuel cell is operated at high temperatures.
  • the protective layer advantageously contains chromium and is therefore matched to the chemical composition of the interconnector plate.
  • the protective layer advantageously consists of chromium carbide, which is highly electrically conductive and adheres very well to the metallic network.
  • a chromium carbide layer is also very corrosion-resistant against corresponding partial oxygen pressures on the fuel gas side. Furthermore, these are
  • Layers are stable using methane or coal-derived gases, which are later used media on the fuel gas side of the high-temperature fuel cell.
  • Another advantage of coating with chromium carbide is that when using carbon-derived gases which are passed through the gas channels on the anode side of the interconnect plates, small amounts of the protective layers are reworked by the carbon-derived gases.
  • the chromium carbide layer is therefore particularly thermodynamically favorable.
  • C 3 C 2 , CrC, Cr7C3 or Cr23C6 can be used as chromium carbide.
  • the protective layer of the metallic mesh may consist of chromium nitride.
  • the protective layer expediently has a thickness d of 0.1-10 ⁇ m, so that, on the one hand, there is sufficient protection against oxidation and, on the other hand, the flexibility of the metallic networks is hardly restricted.
  • FIG. 1 shows a schematic cross-sectional representation of the layers of a fuel cell
  • FIG. 2 shows an enlarged, schematic cross-sectional representation of a coated nickel mesh.
  • the fuel cell stack of the fuel cell 1 consists of an interconnector plate 5 ', a protective layer 8, a contact layer 9, a cathode 2, an electrolyte 3, an anode 4, two nickel meshes 6, 6' lying on top of one another and an interconnector plate 5 , wherein these components are arranged in layers parallel to each other.
  • the nickel mesh 6 is thinner than the nickel mesh 6 '.
  • the nickel nets 6, 6 ' are protected against oxidation in order to avoid an oxidation of these nets, which usually occurs when the entire fuel stack is soldered.
  • the oxidation of the nickel mesh is linked to an increase in thickness, the original thickness of the mesh packet being generated again in the subsequent reduction process. This can lead to contact breaks, which can cause component damage.
  • the nickel wires sinter together after the reduction, so that a reduction in the desired flexibility results.
  • the oxidation-protected networks accordingly avoid the oxidation / reduction process of the network packet and the associated disadvantages.
  • the original flexibility and the thickness of the nets can be retained, so that full-surface contacting of the anode 4 and the contact layer of the nickel nets 6, 6 'and the interconnector plate 5 is created.
  • the nickel networks 6, 6 ′ are coated with an oxidation-resistant protective layer 7. This coating can be done before assembling the individual components.
  • stainless steel networks can also be provided, which have the advantage that their thermal expansion coefficient is adapted to the components of the high-temperature fuel cell.
  • the protective layer 7 consists of chromium carbide, which has the advantage that when using carbon-derived gases which are introduced through the gas channels on the anode side of the interconnector plates 5, 5 ', vanishing constituents from the protective layers are improved again by the carbon-derived gases.
  • C3C 2 CrC, Cr 7 C3 or Cr 2 3C ⁇ or similar chromium carbides with different valences can be used as chromium carbides.
  • the protective layer 7 has a thickness d of 0.1-10 ⁇ m in order to reliably prevent oxidation and to hardly influence the flexibility of the nickel networks 6, 6 '.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Composite Materials (AREA)
  • Fuel Cell (AREA)

Abstract

The invention concerns a fuel cell (1) or a stack of fuel cells comprising cathodes (2), electrolytes (3), anodes (4) and interconnection plates (5, 5') arranged in parallel layers, and at least a metal lattice (6, 6') inserted between the anode (4) and the interconnection plate (5) for a flexible bonding. The inventive fuel cell is characterised in that the metal lattice (6, 6') is protected against oxidation.

Description

Beschreibung description

Oxidationsgeschützte elektrische Kontaktierung auf der Brenngasseite der Hochtemperatur-BrennstoffzelleOxidation-protected electrical contacts on the fuel gas side of the high-temperature fuel cell

Die Erfindung betrifft eine Brennstoffzelle bzw. einen Brennstoffzellenstack mit den weiteren Merkmalen des Oberbegriffs des Patentanspruchs 1.The invention relates to a fuel cell or a fuel cell stack with the further features of the preamble of patent claim 1.

Es ist bekannt, daß die Hintereinanderschaltung mehrererIt is known that the series connection of several

Brennstoffzellen einen Brennstoffzellenstapel ergibt (in der Fachliteratur auch als Brennstoffzellenstack bezeichnet) , welcher der Reihenfolge nach aus einer Interkonnektorplatte, einer Schutzschicht, einer Kontaktschicht, einer Kathode, ei- nem Elektrolyten, einer Anode, einer weiteren Kontaktschicht sowie einer weiteren Interkonnektorplatte besteht. Die Interkonnektorplatte mit der jeweils aufgespritzten Schutz- und Kontaktschicht bildet eine Einheit. Kathode, Elektrolyt urd Anode bilden die Elektrolyt-Elektroden-Einheit. Die entspre- chenden Einheiten sind schichtweise parallel aufeinander gelegt sind und sich in der derselben Reihenfolge mehrmals wiederholen.Fuel cells result in a fuel cell stack (also referred to in the technical literature as a fuel cell stack), which in sequence consists of an interconnector plate, a protective layer, a contact layer, a cathode, an electrolyte, an anode, a further contact layer and a further interconnector plate. The interconnector plate with the sprayed-on protective and contact layer forms a unit. Cathode, electrolyte and anode form the electrolyte electrode unit. The corresponding units are layered parallel to each other and repeated several times in the same order.

Kathode, Elektrolyt und Anode bilden eine Elektrolyt-Elektro- den-Einheit. Dabei bildet jeweils eine zwischen benachbarten Interkonnektorplatten liegende Elektrolyt-Elektroden-Einheit mit den beidseitig an der Elektrolyt-Elektroden-Einheit unmittelbar anliegenden Kontakt- und Schutzschichten eine Hochtemperatur-Brennstoffzelle, zu der auch noch die an der Schutzschicht bzw. den Kontaktschichten anliegenden Seiten jeder der beiden Interkonnektorplatten gehören. Die Interkonnektorplatten bestehen üblicherweise aus CrFe5 mit 1 % Y- Oxid, einer sogenannten ODS-Legierung.The cathode, electrolyte and anode form an electrolyte-electrode unit. In each case, an electrolyte electrode unit lying between adjacent interconnector plates forms a high-temperature fuel cell with the contact and protective layers directly adjacent to the electrolyte electrode unit on both sides, to which the sides of each of the protective layers and contact layers also lie belong to both interconnector plates. The interconnector plates usually consist of CrFe5 with 1% Y-oxide, a so-called ODS alloy.

In die Interkonnektorplatte sind Gaskanäle eingebracht, durch die zum einen das Brenngas z.B. Wasserstoff oder Methan (Erdgas) und zum anderen Sauerstoff bzw. Luft hindurchgeleitet wird. Der Wasserstoff wird dabei an die Anodenseite, der Sauerstoff bzw. die Luft an die Kathodenseite geleitet. Die Hin- durchleitung dieser Gase geschieht mit relativ geringem Überdruck von kleiner 1 bar.Gas channels are introduced into the interconnector plate, through which the fuel gas, for example hydrogen or methane (natural gas), and oxygen or air are passed becomes. The hydrogen is directed to the anode side, the oxygen or air to the cathode side. These gases are passed through with a relatively low overpressure of less than 1 bar.

Das planare Konzept der Hochtemperatur-Brennstoffzelle verlangt eine möglichst vollflachige Kontaktierung der Elektroden in beiden Gasraumen. Auf der Kathodenseite wird die Kontaktierung der Elektrode durch eine Kontaktschicht aus La- Perowskit gewährleistet, z.B. LasSrOo,2Mnθ3. Dieser Perowskit ist an Luft stabil. Auf der Brenngasseite dagegen gestaltet sich die Kontaktierung der Elektrode, also der Anode, schwieriger. Die vollständige Kontaktierung der Anode ist jedoch wegen der geringen Querleitfahigkeit der Anode notwendig. Die Anode wird im Siebdruckprozeß hergestellt und ist daher nicht vollflachig eben, weshalb eine flexible Kontaktierung erforderlich ist, die sehr gut elektrisch leitend ist und deren Beständigkeit über eine Betriebsdauer von etwa 40.000 h gewährleistet sein mußThe planar concept of the high-temperature fuel cell requires that the electrodes be contacted as fully as possible in both gas spaces. On the cathode side, contacting of the electrode is ensured by a contact layer made of La Perovskite, for example LasSrOo, 2 Mnθ 3 . This perovskite is stable in air. On the other hand, on the fuel gas side, contacting the electrode, i.e. the anode, is more difficult. However, complete contacting of the anode is necessary because of the low transverse conductivity of the anode. The anode is produced in the screen printing process and is therefore not flat over the entire surface, which is why flexible contacting is required which is very good electrical conductivity and whose resistance must be guaranteed over an operating period of approximately 40,000 hours

Der Stand der Technik sieht vor, als flexible Kontaktierungen Nickelnetze einzusetzen. So werden beispielsweise ein feinmaschigeres und ein grobmaschigeres Nickelnetz übereinander gelegt, miteinander punktverschweißt, so daß eine flexible Zwi- schenlage mit einer guten Kontaktierung geschaffen wird.The prior art provides for the use of nickel networks as flexible contacts. For example, a finely meshed and a coarsely meshed nickel mesh are placed on top of one another, spot-welded to one another, so that a flexible intermediate layer with good contact is created.

Als Nachteil hat sich beim Stand der Technik herausgestellt, daß sowohl beim Verlöten der Brennstoffzellenstapel als auch beim Betrieb der Brennstoffzelle bzw. des Brennstoffzellen- Stacks im direkten Kontaktbereich Nιckelnetz/CrFe5 eine Oxid- schicht aufwachst, die im nicht stoffschlüssigen Kontakt aus Cr2θ3 (CrχOγ) und im stoffschlüssigen Kontakt wahrscheinlichA disadvantage of the prior art has turned out to be that when the fuel cell stack is soldered and when the fuel cell or the fuel cell stack is operated in the direct contact area of nickel network / CrFe5, an oxide layer that waxes out of Cr 2 θ 3 in the non-material contact (CrχOγ) and probably in material contact

aus einem CrNi-Spinell besteht. Diese Oxidschichten sind maß- geblich verantwortlich für die zu hohen Serienwiderstande der Hochtemperaturbrennstoffzellen. Die elektrische Leistung wird dadurch stark negativ beeinflußt. Außerdem oxidiert das Nickelnetz beim Verlöten des BrennstoffZellenstacks mit einem Glaslot an Luftatmosphäre an der Oberfläche der Drähte einige um in das Drahtinnere hinein. Durch die Bildung von Nickel-II-Oxid (NiO) , das ein etwa 16 % größeres Volumen als Nickel aufweist, erfolgt eine Dickezunahme des gesamten Netzpaketes um etwa 10 - 40 μm (je nach Lötbedingungen) . Die Dickenzunahme beträgt im oxidierten Bereich des Drahtes mehr als 16 %, da das entstandene NiO porös ist. Bei der Oxidierung versintern die Nickelnetze sowie de- ren Drähte miteinander. Bei der späteren Reduktion des Nikkeinetzes wird die ursprüngliche Dicke des Netzpaketes wieder erzeugt bzw. unter Umständen sogar noch reduziert.consists of a CrNi spinel. These oxide layers are largely responsible for the high series resistance of the high-temperature fuel cells. This has a very negative influence on the electrical performance. In addition, when the fuel cell stack is soldered to the surface of the wires, the nickel mesh oxidizes a few microns into the inside of the wire with a glass solder in an air atmosphere. The formation of nickel-II-oxide (NiO), which has an approximately 16% larger volume than nickel, leads to a thickness increase of the entire network package by approximately 10 - 40 μm (depending on the soldering conditions). The increase in thickness in the oxidized area of the wire is more than 16% because the NiO formed is porous. During the oxidation, the nickel nets and their wires sinter together. When the Nikka network is reduced later, the original thickness of the network package is generated again or, in some circumstances, even reduced.

Bei dieser Reduzierung versintern die Nickeldrähte iteinan- der, so daß eine Reduktion der angestrebten Flexibilität als auch eine Reduzierung der Dicke eintritt, die unerwünscht ist. Die Dickenreduzierung kann außerdem zu Kontaktabrissen führen, welche Komponentenschädigungen erzeugen können.With this reduction, the nickel wires sinter together, so that there is a reduction in the desired flexibility as well as a reduction in the thickness, which is undesirable. The reduction in thickness can also lead to contact breaks, which can cause component damage.

Der Erfindung liegt die Aufgabe zugrunde, eine Brennstoffzelle bzw. einen Brennstoffzellenstack mit den Merkmalen des Oberbegriffs des Patentanspruchs 1 derart weiterzubilden, daß die Reduzierung der Dicke und der Flexibilität des/der Nikkeinetze (s) vermieden wird, so daß eine möglichst vollstän- dige Kontaktierung der Anode und der Interkonnektorplatte möglich ist.The invention is based on the object of developing a fuel cell or a fuel cell stack with the features of the preamble of patent claim 1 in such a way that the reduction in the thickness and the flexibility of the Nikkeinetze (s) is avoided, so that the most complete possible contact the anode and the interconnector plate is possible.

Diese Aufgabe wird durch die kennzeichnenden Merkmale des Patentanspruchs 1 gelöst. Vorteilhafte Weiterbildungen der Brennstoffzelle ergeben sich aus den Unteransprüchen 2 - 8.This object is achieved by the characterizing features of patent claim 1. Advantageous further developments of the fuel cell result from subclaims 2-8.

Als Kern der Erfindung wird es angesehen, daß zur flexiblen Kontaktierung zwischen Anode und Interkonnektorplatte mindestens ein metallisches Netz, das oxidationsgeschützt ist, eingefügt ist. Derartige Netze als Kontaktschicht haben den Vorteil, daß diese nicht mehr oxidieren können, so daß auch die Dickenzunahme entfallt. Indem keine Oxidation stattgefunden hat, ist auch kein Reduktionsvorgang der metallischen Netze notwendig und die damit verbundenen Nachteile, wie z.B. Kontaktabrisse bei der Dickenreduzierung oder Flexibilitatsembußen, entstehen nicht. Aufgrund des nicht stattfindenden Wechselprozesses Oxidation/Reduktion bleibt die ursprüngliche Dicke und Flexibilität der oxidationsgeschutzten Netze erhalten, so daß eine gut kontaktierende Kontaktschicht zwischen Anode und Inter- konnektor geschaffen wird. Außerdem wird eine Dickereduzie- rung der metallischen Netze mit fortlaufender Betriebsdauer verhindert .It is regarded as the essence of the invention that at least one metallic network, which is protected against oxidation, is inserted for flexible contacting between the anode and the interconnector plate. Such networks as a contact layer have the advantage that they can no longer oxidize, so that the increase in thickness is also eliminated. Since no oxidation has taken place, there is also no need to reduce the metallic nets and the associated disadvantages, such as, for example, contact breaks during the thickness reduction or loss of flexibility, do not arise. Due to the fact that the oxidation / reduction change process does not take place, the original thickness and flexibility of the networks protected against oxidation are retained, so that a good contacting contact layer is created between the anode and the interconnector. In addition, a reduction in the thickness of the metallic networks is prevented with an ongoing operating period.

Zweckmaßigerweise sind die metallischen Netze mit einer oxi- dationsresistenten Schutzschicht beschichtet. Die metallischen Netze, z.B. Nickelnetze, bleiben auf diese Weise sowohl in ihrer Zusammensetzung als auch in ihren mechanischen und elektrischen Eigenschaften unbeeinflußt, d.h. u.a. sie blei- ben weitgehend flexibel, fuhren keine Dickenanderung herbei und behalten im wesentlichen ihre vorteilhaften Eigenschaften bei. Vorteilhaft ist dabei, daß vor dem Einbringen als flexible Kontaktschicht die metallischen Netze dem Beschichtungs- prozeß unterzogen werden. Die Zusammenfugung mit den anderen Bauteilen sowie das Verlöten ist anschließend in üblicher Weise durchzufuhren.The metallic nets are expediently coated with an oxidation-resistant protective layer. The metallic networks, e.g. Nickel networks remain unaffected both in their composition and in their mechanical and electrical properties, i.e. et al they remain largely flexible, do not cause any change in thickness and essentially retain their advantageous properties. It is advantageous that the metallic nets are subjected to the coating process before being introduced as a flexible contact layer. The assembly with the other components as well as the soldering must then be carried out in the usual way.

Als metallische Netze können beschichtete Nickelnetze vorgesehen sein. Die Nickelnetze erfüllen dabei die Anforderungen hinsichtlich der Flexibilität als auch der elektrischen Leitfähigkeit .Coated nickel nets can be provided as metallic nets. The nickel networks meet the requirements with regard to flexibility as well as electrical conductivity.

Als metallische Netze können auch beschichtete Edelstahlnetze vorgesehen sein, welche die Eigenschaft haben, daß sie nur oberflächlich bis m eine Tiefe von ca. 5 μm oxidieren. Die Edelstahlnetze sind dabei ebenfalls mit einer oxidationsresi- stenten Schutzschicht beschichtet. Ein weiterer Vorteil der Edelstahlnetze besteht darin, daß deren thermischer Ausdehnungskoeffizient an das thermische Verhalten der Komponenten des BrennstoffZeilenstacks gut angepaßt ist. Vor allem beim Hochtemperaturbetrieb der Brennstoffzelle ist diese Eigenschaft von erheblichem Vorteil.Coated stainless steel nets can also be provided as metallic nets, which have the property that they only oxidize to a depth of approx. The stainless steel nets are also coated with an oxidation-resistant protective layer. Another advantage of Stainless steel networks consist in that their thermal expansion coefficient is well adapted to the thermal behavior of the components of the fuel stack. This property is of considerable advantage especially when the fuel cell is operated at high temperatures.

Vorteilhafterweise enthält die Schutzschicht Chrom und ist damit an die chemische Zusammensetzung der Interkonnektorplatte angepaßt.The protective layer advantageously contains chromium and is therefore matched to the chemical composition of the interconnector plate.

Die Schutzschicht besteht vorteilhafterweise aus Chromcarbid, welches in hohem Maße elektrisch leitend ist und sehr gut am metallischen Netz haftet. Eine Chromcarbidschicht ist außerdem sehr korrosionsbeständig gegen entsprechende Sauerstoff- partialdrücke auf der Brenngasseite. Ferner sind dieseThe protective layer advantageously consists of chromium carbide, which is highly electrically conductive and adheres very well to the metallic network. A chromium carbide layer is also very corrosion-resistant against corresponding partial oxygen pressures on the fuel gas side. Furthermore, these are

Schichten stabil unter Verwendung von Methan bzw. kohlestämmigen Gasen, welche spätere Einsatzmedien auf der Brenngasseite der Hochtemperatur-Brennstoffzelle sind.Layers are stable using methane or coal-derived gases, which are later used media on the fuel gas side of the high-temperature fuel cell.

Ein weiterer Vorteil der Beschichtung mit Chromcarbid besteht darin, daß bei Verwendung von kohlestämmigen Gasen, die durch die Gaskanäle der Anodenseite der Interkonnektoplatten hindurch geleitet werden, geringe Bestandteile aus den Schutzschichten durch die kohlestämmigen Gase wieder nachgebessert werden. Die Chromcarbidschicht ist daher thermodynamisch besonders günstig.Another advantage of coating with chromium carbide is that when using carbon-derived gases which are passed through the gas channels on the anode side of the interconnect plates, small amounts of the protective layers are reworked by the carbon-derived gases. The chromium carbide layer is therefore particularly thermodynamically favorable.

Als Chromcarbid können z.B. C3C2, CrC, Cr7C3 oder Cr23C6 verwendet werden.For example, C 3 C 2 , CrC, Cr7C3 or Cr23C6 can be used as chromium carbide.

Es ist auch möglich, daß die Schutzschicht der metallischen Netze aus Chromnitrid besteht.It is also possible for the protective layer of the metallic mesh to consist of chromium nitride.

Zweckmäßigerweise weist die Schutzschicht eine Dicke d von 0,1 - 10 μm auf, so daß einerseits ein ausreichender Oxidati- onsschutz vorhanden ist und andererseits die Flexibilität der metallischen Netze kaum eingeschränkt wird. Die Erfindung ist anhand eines vorteilhaften Ausführungsbei- spiels in den Zeichnungsfiguren näher erläutert. Diese zeigen:The protective layer expediently has a thickness d of 0.1-10 μm, so that, on the one hand, there is sufficient protection against oxidation and, on the other hand, the flexibility of the metallic networks is hardly restricted. The invention is explained in more detail using an advantageous exemplary embodiment in the drawing figures. These show:

FIG 1 eine schematische Querschnittsdarstellung der Schichten einer Brennstoffzelle sowie1 shows a schematic cross-sectional representation of the layers of a fuel cell and

FIG 2 eine vergrößerte, schematische Querschnittsdarstellung eines beschichteten Nickelnetzes.2 shows an enlarged, schematic cross-sectional representation of a coated nickel mesh.

Der Brennstoffzellenstapel der Brennstoffzelle 1 entsprechend der schematischen Darstellung in FIG 1 besteht aus einer Interkonnektorplatte 5', einer Schutzschicht 8, einer Kontaktschicht 9, einer Kathode 2, einem Elektrolyten 3, einer Anode 4, zwei aufeinanderliegenden Nickelnetzen 6, 6' sowie einer Interkonnektorplatte 5, wobei diese Bauteile schichtweise aufeinander parallel angeordnet sind. Das Nickelnetz 6 ist dünner als das Nickelnetz 6' .The fuel cell stack of the fuel cell 1 according to the schematic representation in FIG. 1 consists of an interconnector plate 5 ', a protective layer 8, a contact layer 9, a cathode 2, an electrolyte 3, an anode 4, two nickel meshes 6, 6' lying on top of one another and an interconnector plate 5 , wherein these components are arranged in layers parallel to each other. The nickel mesh 6 is thinner than the nickel mesh 6 '.

Die Nickelnetze 6, 6' sind oxidationsgeschützt, um eine Oxi- dation dieser Netze , welche üblicherweise beim Verlöten des gesamten BrennstoffZeilenstacks auftritt, zu vermeiden. Die Oxidation der Nickelnetze ist mit einer Dickenzunahme verknüpft, wobei bei dem späteren Reduktionsvorgang die ur- sprüngliche Dicke des Netzpaketes wieder erzeugt wird. Dies kann zu Kontaktabrissen führen, welche Komponentenschädigungen erzeugen können. Außerdem versintern die Nickeldrähte nach der Reduzierung miteinander, so daß eine Reduktion der angestrebten Flexibilität resultiert. Die oxidationsgeschütz- ten Netze vermeiden demnach den Oxidations-/Reduktionsprozeß des Netzpaketes und die damit verbundenen Nachteile. Die ursprüngliche Flexibilität sowie die Dicke der Netze kann beibehalten werden, so daß eine vollflächige Kontaktierung von Anode 4 und der Kontaktschicht der Nickelnetze 6, 6' sowie der Interkonnektorplatte 5 geschaffen wird. Außerdem wird eine Dickenreduzierung der Nickelnetze 6, 6' beim Betrieb der Brennstoffzelle 1 verhindert. Wie in FIG 1 und FIG 2 verdeutlicht, sind die Nickelnetze 6, 6' mit einer oxidationsresistenten Schutzschicht 7 beschichtet. Diese Beschichtung kann vor dem Zusammenbau der einzelnen Komponenten vorgenommen werden. Die Nickelnetze 6, 6' werden somit in ihren ursprünglichen, vorteilhaften Eigenschaften nicht durch einen Oxidations- und einen anschließenden Reduktionsprozeß verändert. FIG 2 zeigt in einem vergrößerten Ausschnitt die Beschichtung von einem Nickelnetz 6 bzw. 6' .The nickel nets 6, 6 'are protected against oxidation in order to avoid an oxidation of these nets, which usually occurs when the entire fuel stack is soldered. The oxidation of the nickel mesh is linked to an increase in thickness, the original thickness of the mesh packet being generated again in the subsequent reduction process. This can lead to contact breaks, which can cause component damage. In addition, the nickel wires sinter together after the reduction, so that a reduction in the desired flexibility results. The oxidation-protected networks accordingly avoid the oxidation / reduction process of the network packet and the associated disadvantages. The original flexibility and the thickness of the nets can be retained, so that full-surface contacting of the anode 4 and the contact layer of the nickel nets 6, 6 'and the interconnector plate 5 is created. In addition, a reduction in the thickness of the nickel networks 6, 6 ′ during operation of the fuel cell 1 is prevented. As illustrated in FIG. 1 and FIG. 2, the nickel networks 6, 6 'are coated with an oxidation-resistant protective layer 7. This coating can be done before assembling the individual components. The nickel meshes 6, 6 'are thus not changed in their original, advantageous properties by an oxidation and a subsequent reduction process. 2 shows an enlarged detail of the coating of a nickel mesh 6 or 6 '.

Anstatt der Nickelnetze 6, 6' können auch Edelstahlnetze vorgesehen sein, welche den Vorteil haben, daß deren thermischer Längenausdehnungskoeffizient an die Komponenten der Hochtemperatur-Brennstoffzelle angepaßt ist.Instead of the nickel networks 6, 6 ', stainless steel networks can also be provided, which have the advantage that their thermal expansion coefficient is adapted to the components of the high-temperature fuel cell.

Die Schutzschicht 7 besteht aus Chromcarbid, welches den Vorteil hat, daß bei Verwendung von kohlestämmigen Gasen, die durch die Gaskanäle der Anodenseite der Interkonnektorplatten 5, 5' eingeleitet werden, verschwindende Bestandteile aus den Schutzschichten durch die kohlestämmigen Gase wieder nachgebessert werden.The protective layer 7 consists of chromium carbide, which has the advantage that when using carbon-derived gases which are introduced through the gas channels on the anode side of the interconnector plates 5, 5 ', vanishing constituents from the protective layers are improved again by the carbon-derived gases.

Als Chromcarbide können C3C2 CrC, Cr7C3 oder Cr23Cδ oder ähnliche Chromcarbide mit unterschiedlichen Wertigkeiten ver- wendet werden.C3C 2 CrC, Cr 7 C3 or Cr 2 3Cδ or similar chromium carbides with different valences can be used as chromium carbides.

Die Schutzschicht 7 weist eine Dicke d von 0,1 - 10 μm auf, um eine Oxidation zuverlässig zu verhindern und die Flexibilität der Nickelnetze 6, 6' kaum zu beeinflussen. The protective layer 7 has a thickness d of 0.1-10 μm in order to reliably prevent oxidation and to hardly influence the flexibility of the nickel networks 6, 6 '.

Claims

Patentansprüche claims 1. Brennstoffzelle (1) bzw. Brennstoffzellenstack mit schichtweise parallel angeordneten Kathoden (2), Elektrolyten (3), Anoden (4) und Interkonnektorplatten (5, 5 ) sowie mindestens einem metallischen Netz (6, 6'), das zwischen Anode (4) und Interkonnektorplatte (5) zur flexiblen Kontaktierung eingefügt ist, d a d u r c h g e k e n n z e i c h n e t, daß das minde- stens eine metallische Netz (6, 6') oxidationsgeschützt ist.1. fuel cell (1) or fuel cell stack with layers of parallel arranged cathodes (2), electrolytes (3), anodes (4) and interconnector plates (5, 5) and at least one metallic network (6, 6 ') which is between anode ( 4) and interconnector plate (5) is inserted for flexible contacting, characterized in that the at least one metallic network (6, 6 ') is protected against oxidation. 2. Brennstoffzelle nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t, daß das mindestens eine metallische Netz (6, 6') mit einer oxidationsresi- stenten Schutzschicht (7) beschichtet ist.2. Fuel cell according to claim 1, d a d u r c h g e k e n e z e i c h n e t that the at least one metallic network (6, 6 ') is coated with an oxidation-resistant protective layer (7). 3. Brennstoffzelle nach einem der Ansprüche 1 oder 2, d a d u r c h g e k e n n z e i c h n e t, daß das Netz (<?. 6') ein beschichtetes Nickelnetz ist.3. Fuel cell according to one of claims 1 or 2, so that the network (<?. 6 ') is a coated nickel network. 4. Brennstoffzelle nach einem der vorhergehenden Ansprüche, d a d u r c h g e k e n n z e i c h n e t, daß das Netz (6, 6') ein beschichtetes Edelstahlnetz ist.4. Fuel cell according to one of the preceding claims, that the network (6, 6 ') is a coated stainless steel network. 5. Brennstoffzelle nach den Ansprüchen 2 - 4, d a d u r c h g e k e n n z e i c h n e t, daß die Schutzschicht (7) Chrom enthält.5. Fuel cell according to claims 2-4, d a d u r c h g e k e n n z e i c h n e t that the protective layer (7) contains chromium. 6. Brennstoffzelle nach einem der vorhergehenden Ansprüche 2 - 5, d a d u r c h g e k e n n z e i c h n e t, daß die Schutzschicht (7) aus Chromcarbid besteht.6. Fuel cell according to one of the preceding claims 2-5, d a d u r c h g e k e n n z e i c h n e t that the protective layer (7) consists of chromium carbide. 7. Brennstoffzelle nach Anspruch 6, d a d u r c h g e k e n n z e i c h n e t, daß als Chromcarbid C3C2/ CrC, Cr7C3 oder Cr23C6 verwendet wird. 7. Fuel cell according to claim 6, characterized in that C 3 C 2 / CrC, Cr 7 C 3 or Cr2 3 C 6 is used as the chromium carbide. 8. Brennstoffzelle nach einem der vorhergehenden Ansprüche, d a d u r c h g e k e n n z e i c h n e t, daß die Schutzschicht (7) eine Dicke (d) von etwa 0,1 - 10 μ aufweist. 8. Fuel cell according to one of the preceding claims, that the protective layer (7) has a thickness (d) of approximately 0.1-10 μ.
EP00949131A 1999-07-09 2000-06-26 Electrical bonding protected against oxidation on the gas combustion side of a high temperature fuel cell Withdrawn EP1206807A1 (en)

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DE19932192 1999-07-09
PCT/DE2000/002071 WO2001004981A1 (en) 1999-07-09 2000-06-26 Electrical bonding protected against oxidation on the gas combustion side of a high temperature fuel cell

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DE10033898B4 (en) * 2000-07-12 2009-06-18 Forschungszentrum Jülich GmbH High temperature fuel cell and fuel cell stack
WO2005008816A2 (en) * 2003-07-18 2005-01-27 Versa Power Systems, Ltd. Electrically conductive fuel cell contact material
US7190568B2 (en) * 2004-11-16 2007-03-13 Versa Power Systems Ltd. Electrically conductive fuel cell contact materials
DE102005014077B4 (en) * 2005-03-23 2012-05-24 Forschungszentrum Jülich GmbH Interconnector for high-temperature fuel cells and method for its production and method for operating a fuel cell
DE102008036847A1 (en) * 2008-08-07 2010-02-11 Elringklinger Ag Fuel cell unit and method for making an electrically conductive connection between an electrode and a bipolar plate
CN116247234A (en) * 2023-03-14 2023-06-09 合肥工业大学 Antioxidant metal net and preparation method and application thereof

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DE4016157A1 (en) * 1989-06-08 1990-12-13 Asea Brown Boveri High temp. fuel cell stack - with cells series-connected by separator plates and elastic current collectors
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