EP3747072A1 - Plaque bipolaire pour éléments d'une unité de pile à combustible et son procédé de fabrication, unité de pile à combustible la comportant et pile à combustible comportant cette unité - Google Patents
Plaque bipolaire pour éléments d'une unité de pile à combustible et son procédé de fabrication, unité de pile à combustible la comportant et pile à combustible comportant cette unitéInfo
- Publication number
- EP3747072A1 EP3747072A1 EP18705497.8A EP18705497A EP3747072A1 EP 3747072 A1 EP3747072 A1 EP 3747072A1 EP 18705497 A EP18705497 A EP 18705497A EP 3747072 A1 EP3747072 A1 EP 3747072A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- layer
- substrate
- bipolar plate
- oxygen
- compound
- 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- Withdrawn
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Classifications
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- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0206—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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0206—Metals or alloys
- H01M8/0208—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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0206—Metals or alloys
- H01M8/0208—Alloys
- H01M8/021—Alloys based on iron
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- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0215—Glass; Ceramic materials
- H01M8/0217—Complex oxides, optionally doped, of the type AMO3, A being an alkaline earth metal or rare earth metal and M being a metal, e.g. perovskites
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- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0223—Composites
-
- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0223—Composites
- H01M8/0226—Composites in the form of mixtures
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- 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
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0223—Composites
- H01M8/0228—Composites in the form of layered or coated products
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- 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
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- 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
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
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- 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
- Bipolar plate for elements of a unit of fuel hollows and its manufacturing process, fuel cell unit comprising it and battery
- the present invention relates to the manufacture of a strip or foil and the strip or sheet thus produced, which applies more particularly to the manufacture of elements of fuel cell units.
- PEMFC fuel cells that is to say proton exchange membrane
- battery units each consisting of an anode / electroiyte / cathode assembly, also called MBA ("membrane eiectrode assembiy" in English).
- gas diffusion layers also called GDL (“gas diffusion layer” in English)
- the bipolar plates assemble together the elements of the battery unit. They also define fluid circulation channels, distribute gas, coolant and evacuate the water generated in the cell which allows to control the moisture of the proton exchange membrane. They also have the function of collecting the current generated at the electrodes.
- ICR Interfacial Contact Resistance
- WO-A-2016/151356 and WO-A-2016/151358 have proposed a method of manufacturing a metal strip or sheet particularly suitable for the manufacture of bipolar plates, comprising the provision of a substrate made of stainless steel and the deposition of a chromium nitride layer on the substrate by physical vapor deposition (PVD) in a deposition installation comprising a vacuum-settable deposition chamber and also being fed with a mixture of inert gas such as argon and nitrogen.
- the enclosure also comprises a chromium target disposed above the upper face (for example) of the substrate, the substrate traveling through the deposition chamber in a longitudinal direction. A suitable potential difference is applied between the target and the substrate.
- the deposition chamber comprises a deposition zone whose length is strictly less than the length of the deposition chamber, taken according to the longitudinal direction and at least a first "forbidden zone", adjacent to the deposition zone in the longitudinal direction, and in which, during deposition, the chromium nitride is deposited on the substrate only in the deposition zone H does not produces no deposit of chromium nitride on the substrate in the first "forbidden zone"
- the first "forbidden zone” may be located downstream of the target on the path of the substrate.
- the chromium deposition rate on the substrate may be greater than or equal to a predetermined threshold in the deposition zone, downstream of the target.
- the deposition chamber comprises a downstream cache, impermeable to chromium atoms preventing the projection of chromium nitride on the substrate in the first "forbidden zone" and allowing the projection of chromium nitride on the substrate in the deposition zone
- the downstream mask is typically interposed on the trajectory of the chromium atoms projected towards the first zone, and is arranged in the deposition chamber so as to prevent the deposition on the substrate of the chromium atoms resulting from the target whose rate of deposition on the substrate would be strictly less than the predetermined threshold.
- the deposition chamber may furthermore comprise a second "forbidden zone" in which there is no chromium nitride deposit on the substrate during the deposition step, the second "forbidden zone” being adjacent to the deposition zone. deposit zone so that the first "forbidden zone” (downstream zone) and the second “prohibited zone” (upstream zone) frame the deposit zone in the longitudinal direction of travel of the strip or sheet.
- the enclosure then comprises, in addition, an upstream cache, impervious to chromium atoms, said upstream cache being disposed in the enclosure and interposed on the trajectory of chromium atoms projected towards the second "prohibited zone" to from the target, so as to allow the projection of chromium nitride on the substrate in the deposition zone and to prevent the projection of chromium nitride on the substrate in the second "forbidden zone".
- the deposition rate of the chromium atoms on the substrate during deposition is preferably greater than or equal to the predetermined threshold
- the method further comprises, prior to the deposition step, a step of determining the predetermined threshold, for a given deposition installation, by calibration, the predetermined threshold corresponding to the minimum deposition rate for which a coating layer is obtained. having a desired contact resistance.
- the strip or metal sheet is made of stainless steel, its thickness is typically of the order of 0.1 mm but can be even lower, and it initially comprises, on its surface, a passive oxidation layer which is completely eliminated at less in the areas to be coated with the coating layer so that in these areas no passive layer remains at the beginning of the deposition step.
- a deposit on both sides of the strip or sheet is possible if the enclosure has two chrome targets arranged on either side of the strip or sheet and away from each other on the course of the tape or sheet, and the cache or caches associated with each target.
- a strip or metal sheet comprising a stainless steel substrate and a coating layer on at least one of its faces, based on chromium nitride, the coating layer optionally comprising oxygen, said layer of coating being obtained by physical vapor deposition (PVD).
- PVD physical vapor deposition
- the coating layer comprises, on its surface, a surface area with an atomic oxygen content strictly below its atomic nitrogen content.
- the surface area has a height less than or equal to 15% of the total thickness of the coating layer.
- the coating layer comprises, at the interface with the substrate, an interface zone comprising an atomic oxygen content strictly below its atomic nitrogen content. Typically, it has a height less than or equal to 15% of the total thickness of the coating layer;
- the coating layer can thus have a contact resistance (ICR) of less than 10 m ⁇ .em 2 to 100 N. cm 2 .
- the coating layer is formed directly on the stainless steel substrate without interposition of a passive layer between the coating layer and the stainless steel of the substrate.
- the coating layer is textured, and in particular has an epitaxial relationship with the stainless steel of the substrate. This epitaxy must remain present after the shaping of the plate. The differences in mechanical properties between the substrate and the coating make this condition maintained, at the cost of localized ruptures of the CrN layer, which are not really troublesome.
- the passivation layer is reconstituted and prevents significant corrosion of the plate, especially since the surrounding medium is relatively acidic (pH of the order of 4 or 5).
- bipolar fuel cell plate comprising at least one plate obtained by deformation of a sheet or blank cut from a strip as aforesaid.
- a plate coated with a CrN-based coating layer is prepared on only one of its faces.
- only one PVD target can be found in the enclosure. overhangs the scrolling path of the strip or sheet, above the face to be coated.
- CrN CrN which is deposited on the opposite side of the strip or sheet scrolling in the treatment chamber, which is not a problem in itself.
- the CrN is not the most efficient material for forming the textured coating layer, and there is little margin for reliably obtaining a lower contact resistance in all parts of the plate. at the prescribed threshold of 10 mQ.cm 2 to 100 N. cm 2 .
- a single-sided coating of the plate is adequate if, to achieve the assembly of the bipolar plates, the plates are welded to each other after their deformation, the welding being effected on the uncoated faces, because the material welding contributes to the electrical conductivity of the whole. But if the assembly is carried out by another means, there is a degradation of the contact resistance at the areas where the metal was exposed in the shaping of the plates by causing the reconstitution of the passivation layer . The performance of the assembly in terms of electrical conductivity are therefore degraded.
- Said layer therefore contains at most a quantity of oxygen at%, measured by X-ray photoelectron spectrometry (XPS) over the upper 10 nm of said layer, which does not exceed 1.5 times the content of at% oxygen which, based on the content of at% of T1 measured, would correspond to a coating which would be composed entirely of TiO.
- XPS X-ray photoelectron spectrometry
- such a coating may be present on both sides of the strip or sheet, or only on one of them, the other face remaining bare or having on its banks only a deposit parasite of compound (s) of bivalent or thvalent Ti, or being covered with a deposit of another nature, such as CrN.
- the object of the invention is to provide a strip or metal foil for the constitution of a bipolar fuel cell element plate, having on at least one of its faces a deposit consisting essentially of at least one compound bivalent or trivial Ti, or CrN, which make it possible to manufacture fuel cell units having a duration of use under satisfactory optimal conditions.
- the subject of the invention is a bipolar plate for assembling the elements of a fuel cell unit constituted by a stainless steel substrate coated on at least one of its two faces by a layer of an electrically conductive material, characterized in that said material is selected from CrN and a bivalent or trivalent Ti compound or a mixture of such compounds, in that said electrically conductive material is a compound of Bivalent or trivalent Ti or a mixture of such compounds, said layer contains at most a quantity of oxygen at%, measured by X-ray photoelectron spectrometry (XPS) on the upper 10 nm of said layer, which does not exceed 1, 5 times the content of at% oxygen which, according to the content of at% of Ti measured, corresponds to a coating which is entirely composed of TiO, and in that between said substrate and said layer of electrically conductive material is interposed at least one intermediate layer of a metal or a metal alloy, the thickness of the said layer of metallic material being at least 1 nm, preferably at least 5 nm, better still at
- Said metal or metal alloy may be selected from Ti, Al, Cr, alloys based on Ti or Al or Cr, a stainless steel.
- the ductility of the at least one layer of a metal or metal alloy may be intermediate between that of the substrate and that of the layer of a compound or a mixture of divalent Ti compounds.
- the bipolar plate may comprise a plurality of superposed intermediate layers, and the respective ductilities of said superposed layers may create a ductility gradient within the layers, the respective ductilities of said superposed intermediate layers being progressively closer to that of the layer of conductive material.
- Said Ti compound if divalent, may be selected from TiN, TiO and mixtures thereof.
- the two faces of said plate may each be coated with a layer of at least one bivalent or trivalent Ti compound, each of said layers containing at most a quantity of oxygen, measured by X-ray photoelectron spectrometry (XRS) over the upper 10 nm of said layer, which does not exceed 1.5 times the content of at% oxygen which, based on the content of at% of Ti measured, would correspond to a coating which would be composed entirely of TiO.
- XRS X-ray photoelectron spectrometry
- the conductive layer of one of the faces of the plate may be a divalent or trivalent T1 compound or a mixture of such compounds, containing at most a quantity of oxygen, measured by X-ray photoelectron spectrometry (XPS) over the upper 10 nm of said layer, which does not exceed 1.5 times the content of at% oxygen which, according to the content of at% of Ti measured, would correspond to a coating which would be composed entirely of TiO, and the conductive layer of the other side can then be CrN.
- XPS X-ray photoelectron spectrometry
- the invention also relates to a method for manufacturing a bipolar plate for assembling the elements of a fuel cell unit, constituted by a stainless steel substrate coated on at least one of its two faces by an electrically conductive material, characterized in that said material is selected from CrN and a bivalent or trivalent Ti compound or a mixture of such compounds, in that said layer, if it consists of a Ti compound bivalent or trivalent or a mixture of such compounds, contains at most an amount of oxygen, measured by X-ray photoelectron spectrometry (XPS) on the upper 10 nm of said layer, which does not exceed 1.5 times the content of at% oxygen which, based on the measured Ti content of%, would correspond to a coating which would be composed entirely of TiO, and in that:
- XPS X-ray photoelectron spectrometry
- a stainless steel substrate is provided in the form of a strip or a sheet;
- At least one of the faces of the substrate is deposited at least one layer of a metal or a metal alloy
- At least one of the faces of the plate is deposited with a layer (5) of a compound or a mixture of divalent II compounds by physical vapor deposition (PVD) in a deposition installation comprising at least one enclosure depositing, means for scrolling the substrate within said enclosure in a longitudinal direction, means for limiting or controlling the amount of air and oxygen introduced into the chamber, and at least one Ti target ;
- PVD physical vapor deposition
- Said metal or metal alloy may be selected from Ti, Al, Cr, alloys based on Ti or Al or Cr, a stainless steel.
- the ductility of the at least one layer of a metal or metal alloy may be intermediate between that of the substrate and that of the layer of a compound or a mixture of divalent Ti compounds.
- Said Ti compound if it is bivalent, can be selected from TIN, TiO and mixtures thereof.
- One of the faces of the substrate may be coated with a conductive material consisting of a bivalent or trivalent Ti compound or a mixture of such compounds, and the other side may be coated with a conductive Crn material.
- the invention also relates to a fuel cell unit PEMFC type, consisting of an anode / electroiyte / cathode assembly, the anode and the cathode having at least one bipolar plate comprising a stainless steel substrate coated on at least one of its faces by an electrically conductive material, characterized in that at least one of the anode and the cathode comprises at least one bipolar plate of the above type.
- the invention also relates to a fuel cell comprising bipolar plate units for assembling the elements of its units, characterized in that at least one of said units is a unit of the above type.
- the invention is based on the presence, between the stainless steel substrate and the coating of bivalent and / or trivalent Ti compound (s), of an intermediate layer of metallic Ti, a metal such as Cr and Al, or, more generally, a metal or a metal alloy which has deformation properties similar to those of stainless steel due to the proximity of their ductilities.
- the inventors have found that if the bipolar plates constituted, according to the prior art, by a stainless steel substrate coated with a conductive layer of TiN and / or TiO and / or Ti 2 O 3 (or Ti compound bivalent or trivalent in general) did not always have optimal performance during a satisfactory period of use, this was due to the fact that these conductive layers tended to crack excessively during the stamping which gives the membrane its desired shape. This cracking, when pronounced to the point of concern, in places, the entire thickness of the conductive layer, increases the risk of contamination of the proton exchange membrane by Fe, Cr or other ions released by the substrate since it is found bare in the cracked areas over the entire thickness of the coating.
- Stamping if it leads to a very substantial change in the shape of the coated sheet, introduces mechanical stresses in the coatings which tend to crack or even endanger their adhesion to the substrate, and to shorten the duration of use in good conditions of the fuel cell to which the element enclosing the defective membrane is integrated.
- the inventors have therefore devised to carry out, prior to the deposition of the layer (s) of Ti or CrN, the deposition, by any method, of at least one ductile metal layer, said layer (or the lower layer). there are several) having good adhesion to the stainless steel substrate. It is therefore on this metal layer or this set of metal layers that the deposition of either CrN or Ti compound (s) takes place according to the methods set forth in application PCT / IB2017 / 056925 and that one will remember here in detail.
- the metal Ti for example, has the advantage of deforming, during the drawing, in a manner very similar to that of the stainless steel substrate, in any case substantially better than does the conductive layer of compound (s) non-metallic Ti bivalent or trivalent which determines the ICR of the cell membrane to fuel which is the preferred application of this type of material.
- the ductility of the metal layer relative to that of the substrate is one of the main criteria to be respected, as well as its adhesion to both the substrate and the conductive layer of Ti bi or trivalent which will then be deposited.
- the ductility of a deposited metallic material can be represented by its elongation at break.
- the elongation at break property of the underlayer (s) present between the stainless steel substrate and the surface conductive layer is preferably chosen such that the elongation at break of each layer is intermediate. between the elongation at break of the layer on which it is deposited (or the elongation at break of the substrate in the case of the first deposited metal layer) and that of the layer which is deposited on it (or of the layer conductive in the case of the last deposited metal layer).
- the experiment will confirm that the chosen materials (especially in the case where one would deposit several successively, especially to create a ductility gradient in the deposit) are indeed suitable, given the thickness of the coating and the deformations that it undergoes during a given formatting.
- any metal or metal alloy layer will in any case have a sufficiently close ductility to that of the stainless steel substrate so that its deposit is already a progress in solving the problems mentioned, compared to the case where the Conductive layer of CrN or bivalent or trivalent Ti compound (s) would be deposited directly onto the substrate.
- the presence of several intermediate metal layers of different natures and preferably having a ductility gradient is only one variant of the invention.
- Figure 1 which shows a cross-sectional micrograph of the upper surface of a bipolar plate according to the prior art, wherein a stainless steel substrate is coated with a double layer of TIN;
- FIG. 2 which shows the analysis of the superficial zone of this bipolar plate according to the prior art, carried out by dispersion spectrometry X-ray energy (Energy dispersive X-Ray, EDX), the distance from the surface of the plate being expressed in nanometers (abscissa);
- EDX dispersion spectrometry X-ray energy
- Figure 3 which shows a photomicrograph in cross section of the upper surface of a bipolar plate according to the invention, where a stainless steel substrate is coated successively with a layer of metallic Ti and a TiN layer;
- FIG. 4 which shows the analysis of the superficial zone of this bipolar plate according to the invention, carried out by X-ray energy dispersive spectrometry, the distance from the surface of the plate being expressed in nanometers (abscissa);
- FIG 5 which shows the upper surface of the bipolar plate of Figure 3 after deformation by stamping
- FIG. 6 which shows the upper surface of the bipolar plate of FIG. 3 after a deformation by stamping greater than that undergone in the case of FIG.
- the substrate is a stainless steel of known type SUS 316L, where the intermediate coating is substantially pure Ti (that is to say without alloying elements voluntarily added) and wherein the conductive coating determining HCR is TIN, the other components possibly present relatively marginally in the coating (for example various oxides of Ti bi, tri or tetravalent) having been formed only involuntarily.
- FIG. 1 represents by reference a micrograph of a section according to the thickness of the substrate 1, which is a austenitic stainless steel of conventional SUS 316L grade. It has been covered by PVD, in the example represented, with a double layer 2, composed essentially of TIN with a thickness of about 45 nm. But a single layer of TIN would be just as suitable.
- the growth of TiN 2 is carried out columnarly from substrate 1.
- FIG. 2 shows the analytical spectrum produced by the process known as "X-ray energy dispersive spectrometry” (X-Ray energy dispersive spectrometry, EDX) and which makes it possible to determine, on the ordinate, the respective at% contents of the various elements mentioned on the diagram and their evolution from the surface of a deposit 2 of TiN (zero abscissa) to a depth of about 60 nm, made on another sample and a little thicker than the depot shown in Figure 1. It can be seen that the extreme surface has a high content of both Ti and O, because Ti has absorbed, in this extreme surface, residual oxygen. The presence of Fe and Cr at the extreme surface indicated by this diagram is, in fact, an aberration of analysis. The XPS analyzes do not confirm this presence.
- X-ray energy dispersive spectrometry X-Ray energy dispersive spectrometry
- the nominal composition of the deposit 2 is established, with essentially TiN and a marginal presence of oxygen. From about 50.5 nm of depth, the Fe and Cr contents of the deposit increase, sign that the deposition 2 of TiN and the steel of the substrate 1 begin to interpenetrate. From about 55 nm, one finds on the substrate 1 stainless steel as shown by the very predominant presence of Fe, Cr, Ni, mixed with oxygen which is integrated in the passive layer whose spontaneous formation is usual in the extreme surface area of stainless steels and which gives them their resistance to corrosion.
- This passive oxidized layer at the extreme surface of stainless steel 1 is not, however, favorable to the adhesion of TiN (or other non-metallic coatings based on divalent Ti or trivents that can be used in the invention, alone or in mixing) it is therefore desirable, in this reference configuration, to eliminate it as much as possible prior to the deposition of the conductive layer 2 on the substrate 1.
- the conductive layer on the surface of bipolar plates according to the invention may have the characteristics described in WO-A-2016/151356, WOA-2016/151358 or PCT / IB2017 / 056925).
- this layer is formed predominantly of bivalent or trivalent titanium compounds, especially TiN and / or TiO, deposited by PVD, on one or, preferably, on both sides of the strip or sheet.
- TiN for example, would indeed be a more suitable material than the CrN used, in particular in WO-A-2016/151356 and WO-A-2018/151358, since it is suitable for obtaining ICR. from less than 5 cm 2 to 100 N. cm 2 .
- the TiO's ICR is of the same order of magnitude as that of the TiN.
- the strip or sheet is coated with a material essentially based on bivalent or trivalent Ti, which is, for example, TiN, TiO or a mixture of these two compounds.
- Bivalent Ti is the character bivalent or trivalent compounds of Ti deposited on the web or sheet which is fundamental to the performance of the bipolar plate, and TiN, TiO and mixtures thereof are quite substantially equally suitable for providing low contact resistance, typically less than 5 cm 2 to 100 N cm 2 .
- Trivalent Ti conductive compounds such as Ti 2 O 3 are also suitable
- the bivalent or trivalent Ti-based coating must have, on this superficial thickness of 10 nm, an overall content of at% oxygen% (that is to say expressed in atomic percentages) which must not not exceed by more than half (ie not more than 1, 5 times) the oxygen content measured in at% which, in view of the measured Ti content, also at%, would correspond to a coating which would be integrally formed of TiO, based on an analysis of the coating carried out by the so-called "XPS" method of X-ray photoelectron spectroscopy
- TiN is a high performance material in terms of contact resistance. It has been found that the method of deposition of CrN by PVD, carried out under conditions comparable to those described in the prior art documents cited in the introduction, was also suitable for deposition of TiN. However, it is necessary that the surface of the metal support is very well cleaned before the deposition of the TiN, and it is advisable to clean it by a conventional method of chemical etching adapted to the material used. For stainless steel, it will thus be preferable to use an argon plasma etching.
- the coating deposit in the downstream part may be accompanied by a parasitic coating deposit on the face which had already been coated in the upstream part of the enclosure. the enclosure and which is likely to degrade its properties.
- the strip or sheet is coated on both sides by a layer composed of bivalent (s) and / or trivalent (s) Ti
- the caches defining the prohibited areas and the areas authorized for the deposition of the layers on each face are also arranged symmetrically with respect to the strip or sheet. In this way, both faces are coated substantially at the same time and with the same parameters. If parasitic deposits occur, they occur very similarly on both sides, which minimizes their influence on the final properties of the coated material, the two faces of which are thus coated in substantially identical ways.
- TiO is a conductive phase in the same way as TiN, and its presence within the TiN layer, or on its surface, or at the substrate / TiN interface does not lead to deterioration of the contact resistance. .
- TiO may even be the exclusive or quasi-exclusive component of the conductive phase, which essentially consists of bivalent Ti (TiN, TiO) as opposed to non-conductive tetravalent Ti compounds such as TiO 2.
- Trivalent Ti compounds such as Ti 2 O 3 are also suitable.
- the criterion to be taken into account is that the bivalent or trivalent Ti coating must have, on a superficial thickness of 10 nm, an overall content of at% oxygen which should not be greater than 1, 5 times the oxygen content measured in at% which, in view of the measured Ti content, also at%, would correspond to a coating which would be integrally formed of TiO, on the basis of a coating analysis performed by XPS.
- thermodynamics and kinetics of the formation of Ti oxides mean that the TIO is formed in a privileged way, and that the TiO 2 which is to be avoided is only significantly formed if the quantity of available oxygen is sufficient for this purpose, relationship with the temperature at which the deposit takes place.
- WO-A-2016/151356 and WO-A-2016/151358 give examples of quantitative indications on Cr, N and O-containing layer compositions that would be suitable.
- Another advantage of a biface deposit is that the manufacturer of the fuel cell units can minimize or eliminate the step of welding the microchannels together.
- the analysis of the deposition can be carried out by any suitable method which would give a direct or indirect indication of the chemical nature of the deposit and the excessive presence of Ti tétr series in the form of pure Ti0 2 .
- spectrometry photoelectron X XPS
- XPS spectrometry photoelectron X
- the analysis of the first 10 nm of the outer surface of the layer is sufficient to determine whether the coating would have the necessary qualities, as on the one hand are the most important for obtaining a good contact resistance, and secondly those are those for which the pollution by oxygen leading to excessive oxidation of Ti would be maximum.
- the target (s) in Ti are not located too close to the entrance of the band moving in the enclosure, so that the oxygen and the water absorbed have time to be evacuated by the pumping facility before the portion of the band from which it originated reaches the formation of the TiN / TiO coating, optionally also containing trivalent Ti compounds such as Ti 2 O 3 .
- the reactive gas can be a nitrogen / oxygen mixture whose composition and the flow rate will be adjusted by the man of craft with the power of sputtering and the geometry of its installation, so as not to observe tetravalent titanium on the surface of its deposit as described above.
- the installation comprises all that is necessary and customary for producing a PVD coating deposit on a moving substrate in a controlled atmosphere chamber.
- means for moving the substrate inside the enclosure in a longitudinal direction if the substrate is a moving strip means imposing a suitable potential difference between the targets and the substrate, etc.
- the mechanical properties of the TiN and the TiO are not fundamentally different from those of the CrN, so that they do not react more adversely than the CrN to the cuts and the shaping of the strips or sheets for the production of the plates. They also develop from the surface of the substrate with a remarkable epitaxy, forming columns to the right of the grains of the substrate. This epitaxy can be observed on X-ray diffraction examinations in area selection by transmission electron microscopy: there is a very good coincidence of the diffraction spots due to TiN and TiO with those due to the grains of the substrate.
- both sides of the sheet or web can be coated with two different bivalent Ti materials, both of which would meet the requirements of the invention (for example, one side has a substantially composed of TiN and the other face has a coating consisting essentially of TiO, or both sides are coated with a TiN-TiO mixture but in different proportions on each side ).
- two different bivalent Ti materials for example, one side has a substantially composed of TiN and the other face has a coating consisting essentially of TiO, or both sides are coated with a TiN-TiO mixture but in different proportions on each side .
- Another variant consists in coating one side of the substrate with a coating based on divalent Ti compounds (typically T ⁇ N, TiO or mixtures thereof) or trivalent and coating the other side with CrN as it is known, for example from the manner described in WO-A-2016/151356 and WO-A-2016/151358.
- the two deposits are made in different enclosures. It is obviously preferable that, in this case, the two enclosures are connected to each other (with a sufficient seal between them so that their atmospheres do not influence each other too much) and that the substrate (scrolling or not) ) is not exposed to free air during its transfer, which could lead to pollution of its surfaces which would disturb the deposit in the second enclosure.
- caches can be used in each enclosure to limit the risk of spurious deposits on the face of the substrate that should not be concerned.
- the two faces are made identifiable in any way by the operator, in view of the correct assembly of the fuel cell membrane.
- the strip or sheet is conditioned as is usual to obtain a bipolar plate of shape and dimensions adapted to the use that will be made, by cutting and shaping, using conventional methods for this purpose, such as cold deformation, in particular by stamping.
- This type of coating is applicable to the coating of any stainless steel known to be suitable for use as a bipolar plate substrate, in particular because of its mechanical properties governing its ability to be properly shaped.
- Non-limiting examples include stainless steel 4404 (AIS 316L), 14306 (AISI 304L), 1.4510 (AISI 409) and 14509 (AISI 441), both austenitic stainless steels and stainless steels. ferritic.
- the grain size of the substrate is less than 50 ⁇ m, preferably between 10 and 30 ⁇ m.
- this substrate when this substrate is subject to deformation, for example stamping, to give the bipolar plate, coated on one or both sides, its desired final shape, the coating can crack and the conductive upper layer loses its effectiveness.
- one or both faces of the stainless steel substrate are then coated with a metal or a metal alloy before the conductive deposit of CrN or bi Ti compound is made on the face or faces.
- a metal or a metal alloy or trivalent (TiN, TiO, Ti 2 O 3 , typically).
- This metal deposit preferably has a ductility intermediate between that of the stainless steel substrate and that of the future conductive upper layer to limit the stress concentrations in the coating during stamping.
- this deposition is carried out by a PVD method using at least one target of the material to be deposited, therefore identical or comparable to the method of depositing the conductive upper layer.
- This intermediate metal deposit makes it possible to "dampen" the deformations of the upper conductive layer relative to those undergone by the substrate and thus to limit the risk of excessive cracking of the conductive layer.
- This intermediate metal deposit must also have good adhesion with, of a on the other hand, the stainless steel substrate and, on the other hand, with the surface conductive layer.
- stainless steels, Ti, Cr, Al and alloys based on these metals are preferred (but not exclusive) examples as it has been shown that they do not not age too sensitive during the use of the membrane.
- Their great avidity for oxygen in particular, makes them immediately saturated with oxygen during their deposition process, and their composition does not change over time.
- Their mode of crystallization prevents oxygen from passing through the network and eventually altering the surface of the substrate by degrading the conductivity at the interface and the adhesion of the metal layer.
- the adhesions of CrN, and TiN, TiO, TiO 2 and mixtures thereof on these metals and alloys are also suitable for demanding conditions for shaping the membrane.
- a very small thickness of metal layer is sufficient.
- a 13 nm thick layer of metallic Ti deposited on a 0.1 mm or 0.075 mm thick stainless steel sheet is typical.
- the first atoms of the underlayer metal deposition according to the invention provide an improvement in the deformability of the coating of the stainless steel substrate, compared to a solution where this coating consists only of the conductive layer of CrN or of divalent or trivalent Ti compound (s).
- This immediate improvement is related to the improvement of the adhesion on the areas of the substrate where passive layer residues could remain.
- This adhesion improvement on a substrate not completely freed of its passive layer increases until the formation of a covering undercoat. Then, beyond the minimum thickness ensuring complete coverage of the substrate, it is the ductility gradient phenomenon that takes precedence.
- Those skilled in the art will determine the optimal thickness of sub-layer necessary for shaping the channels of the membrane according to each target bipolar plate geometry.
- the lowest acceptable thicknesses according to the invention correspond to cases where the plate is not required to undergo very intense local deformations.
- FIG. 3 shows a micrograph of the surface of a sheet of stainless steel SUS 316L coated with PVD, according to the invention, with a layer 4 of metallic Ti whose thickness is, in the present case, substantially uniform and about 20 nm thick. It is therefore on this layer of Ti that was then deposited, according to a variant of the invention, a layer 5 of TiN.
- the epitaxial growth of the Ti layer 4 from the substrate 3 is good, and we also note the columnar structure of TiN deposition 5 which is one of the causes of its relative fragility during deformation when it adheres directly to the substrate.
- Note also the monodomain growth of the Ti layer which develops according to the orientation of the stainless steel substrate. It therefore perfectly follows the deformation of the substrate, and alleviates the stress exerted on the columnar layer of TiN during plate deformations.
- FIG. 4 The analysis in at% of the superficial zone (the first 6 nm) of the sheet 3 thus coated is shown in FIG. 4, in the same way as the analysis of FIG. 2 representative of the reference example of FIG. FIG. 1. It can be seen that over the first 20 nm of the surface, there is a TiN deposit containing, at the extreme surface, a little oxygen which was residual in the deposit chamber and which was captured by the Ti. Then over the next 15 nm, there is the Ti deposit made according to the invention, which has also captured a little residual oxygen from the deposition atmosphere. Some Cr also migrated into this layer from the substrate. Finally, from a depth of about 35 nm, there is the austenitic stainless steel substrate where Fe, Cr and Ni are predominant.
- Figures 5 and 6 show in the same way as Figure 3 the surface of a sheet 3 coated according to the invention, after it has undergone a stamping deformation in the area shown. It can be seen that in the case of FIG. 5, the deformations of the layers 4 of Ti and TiN 5 follow very well the deformations of the sheet 3. This is less true in the case of FIG. 6 where the deformation has been more important as in the case of Figure 5. Indeed, we see that in the area of greatest deformation, there was a sliding of the TiN layer 5 in the deformed area, which left the layer 4 of Ti cover only the substrate 3 in the zone of initiation of the deformation.
- the substrate 3 would have been naked in this zone of greater deformation and it could have gradually released into the electrolyte contaminating atoms for the cation exchange membrane.
- the presence persistence in this zone of the ductile layer 4 of Ti according to the invention makes it possible to avoid this disadvantage.
- the SUS 316L substrate can be replaced by any stainless steel capable of forming a bipolar plate.
- the Ti coating can be replaced by any metal coating, consisting of a pure metal or an alloy, with preferred examples, besides Ti, Cr, Al and stainless steels.
- two or more layers of different metals or alloys may be deposited successively prior to deposition of the conductive top layer.
- the different layers would preferably have different ductilities which would lead to the introduction of a ductility gradient within the deposit (the ductility is gradually approaching that of the conductive upper layer) thus ensuring a "smooth transition" of the ductility of the deposit, which would be more favorable to its good behavior during deformations.
- the metal or alloy deposited first on the substrate preferably has an excellent ability to adhere to the substrate while it has a lower ability to adhere to the conductive upper layer, and that the material deposited last before the deposition of the conductive upper layer has, him, a less good ability to adhere to the substrate, but a better ability to adhere to the conductive layer than the material deposited first. If, on the other hand, these two metallic materials have an excellent ability to adhere to one another (for example by virtue of a diffusion of the one into the other or any other mechanism), we obtain an optimal adhesion of the various materials to each other.
- the invention also relates to a PEMFC fuel cell and the units that compose it, conventionally comprising bipolar plates to assemble together units of the battery, at least one of said plates, and preferably all said plates of all said units being constituted according to the present invention.
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Abstract
Description
Claims
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/IB2018/050526 WO2019145759A1 (fr) | 2018-01-29 | 2018-01-29 | Plaque bipolaire pour éléments d'une unité de pile à combustible et son procédé de fabrication, unité de pile à combustible la comportant et pile à combustible comportant cette unité |
Publications (1)
Publication Number | Publication Date |
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EP3747072A1 true EP3747072A1 (fr) | 2020-12-09 |
Family
ID=61226620
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP18705497.8A Withdrawn EP3747072A1 (fr) | 2018-01-29 | 2018-01-29 | Plaque bipolaire pour éléments d'une unité de pile à combustible et son procédé de fabrication, unité de pile à combustible la comportant et pile à combustible comportant cette unité |
Country Status (5)
Country | Link |
---|---|
US (1) | US20210050603A1 (fr) |
EP (1) | EP3747072A1 (fr) |
KR (1) | KR20200111242A (fr) |
BR (1) | BR112020015372A2 (fr) |
WO (1) | WO2019145759A1 (fr) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2022260983A1 (fr) * | 2021-06-09 | 2022-12-15 | Ohmium International, Inc. | Plaques bipolaires d'électrolyseur et couche de diffusion de gaz poreuse ayant un revêtement électroconducteur et procédé de fabrication |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001022513A1 (fr) * | 1999-09-17 | 2001-03-29 | Matsushita Electric Industrial Co., Ltd. | Pile a combustible a electrolyte polymerique |
EP2608299B1 (fr) * | 2011-12-22 | 2014-04-09 | Feintool Intellectual Property AG | Dispositif et procédé de fabrication de plaques bipolaires métalliques |
WO2016151358A1 (fr) | 2015-03-20 | 2016-09-29 | Aperam | Bande ou feuille métallique présentant un revêtement à base de nitrure de chrome, plaque bipolaire et procédé de fabrication associé |
WO2016151356A1 (fr) | 2015-03-20 | 2016-09-29 | Aperam | Bande métallique, plaque bipolaire et procédé de fabrication associé |
-
2018
- 2018-01-29 EP EP18705497.8A patent/EP3747072A1/fr not_active Withdrawn
- 2018-01-29 US US16/965,561 patent/US20210050603A1/en not_active Abandoned
- 2018-01-29 WO PCT/IB2018/050526 patent/WO2019145759A1/fr unknown
- 2018-01-29 BR BR112020015372-9A patent/BR112020015372A2/pt not_active Application Discontinuation
- 2018-01-29 KR KR1020207024663A patent/KR20200111242A/ko unknown
Also Published As
Publication number | Publication date |
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BR112020015372A2 (pt) | 2020-12-08 |
US20210050603A1 (en) | 2021-02-18 |
KR20200111242A (ko) | 2020-09-28 |
WO2019145759A1 (fr) | 2019-08-01 |
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