DE4016157A1 - High temp. fuel cell stack - with cells series-connected by separator plates and elastic current collectors - Google Patents

Abstract

A device, for converting the chemical energy content of a gaseous fuel into electrical energy, includes a stack of series-connected, flat, zirconia solid electrolyte-based, high temp. fuel cells (1,2,3) with current transfer components inserted between adjacent cells. The novelty is that each inserted component consists of a central, electrically conductive, gastight, flat separator plate (4) sandwiched between electrically conductive, elastic current collectors (6,7) having contact points for the separator plate (4) and the adjacent cell electrode (2,3), the contact points being permanently subjected to pressure perpendicular to the plate plane. The periphery of the separator plates and fuel cells is provided with flat insulating spacer frames (9), elastic seals (10) and corresponding gaseous medium feed and discharge systems. The entire stack is held together under pressure perpendicular to the plate plane by elastic ti-rods or stirrups located at the periphery of or outisde the fuel cells and separator plates. ADVANTAGE - The device has an extremely high of many fuel cells and good current transfer between cells with minimal losses. and has a design allowing mass prodn.

Description

Technical field

High temperature fuel cells for converting chemical Energy in electrical energy. The electrochemical Energy conversion and the devices required for this purpose win thanks to their good efficiency compared to others types of change in importance.

The invention relates to the further development of the elek high temperature trochem cells using kera mix solid electrolytes as ion conductors, the cell len should be largely independent of the fuel used len and should provide a space-saving arrangement.

In particular, the invention relates to a device for order conversion of existing in a gaseous fuel mixer energy into electrical energy by means of an arrangement in the form of a stack of flat highs connected in series temperature fuel cells based on zirconium oxide Solid electrolyte with between neighboring fuel cells switched components for electrical power transmission.

State of the art

High-temperature fuel cells with ceramic solid electrolyte are known from numerous publications. The actual elements for such cells can have a wide variety of shapes and dimensions. In order to keep the ohmic voltage losses small, every effort is made to keep the thickness of the electrolyte layer as low as possible. The shape and dimensions of the elements also depend on the requirement of the possibility of series electrical connection of a large number of cells in order to achieve the necessary clamping voltage and to keep the currents comparatively low. There are elements in the form of:
Cylindrical tubes (Westinghouse),
Conical tubes, similar to "horsetail" (Dornier),
Trapezoidal waves (Argonne),
Circular plates (ZTEK).

In the development of fuel cells with ceramic hard So far, there has been almost no improvement in the substance electrolyte tion and cheapening of the ceramic components in the form of tubular fuel cell elements. About ge suitable arrangements for the best possible use of space and the achievement of high voltages by suitable, for the series circuit of the individual cells advantageous configuration there are practically no clues.

The following publications become state of the art called:

• - O. Antonsen, W. Baukal and W. Fischer, "High temperature Fuel battery with ceramic electrolyte ", Brown Boveri Announcements January / February 1966, pages 21-30,
• - US-A 46 92 274,
• - US-A 43 95 468,
• - W. J. Dollard and W. G. Parker, "An overview of the Westinghouse Electric Corporation solid oxide fuel cell program ", Extended Abstracts, Fuel Cell Technology and Applications, International Seminar, The Hague, Nieder land, October 26-29, 1987,
• - F.J. Rohr, High-Temperature Fuel Cells, Solid Electroly tes, 1978 by Academic Press, Inc., page 431 ff,  
• - D.C. Fee et al., Monolithic Fuel Cell Development, Ar gonne National Laboratory, Paper presented at the 1986 Fuel Cell Seminar, Oct. 26-29, 1986 Tucson, AZ, U.S. Department of Energy, The University of Chicago.

The known basic elements used for fuel cells are usually characterized by the comparatively complicated Geometry from the construction of compact, space-saving systems difficult. It is also proposed Form rational production on an industrial scale hardly possible. In particular, one is missing for an optimal series circuit of single cells usable configuration, which can be realized with simple manufacturing means.

There is therefore a great need for further development, Simplification and rationalization of the structure and the manufacture provision of basic components and their optimal counterpart arrangement based on ceramic high-temperature firing fabric cells.

Presentation of the invention

The invention has for its object an arrangement of Fuel cells based on a high temperature solid Specify stabilized zirconia electrolytes based on smallest space achieves the highest possible performance, one wall-mounted series connection of a variety of fuel cells and a good current transfer between neighboring cells lowest losses guaranteed and a block by block positions to large power units. The up construction and the arrangement of the fuel cells and the rest Components should be a rational large-scale production guarantee.

This object is achieved in that in the beginning he mentioned device of each of said components from one  centrally located, electrically conductive, gastight levels Separating plate and electrically conductive on both sides fully elastic current collectors with a variety ofcon cycle points opposite the partition plate and the neighboring one Electrode of the opposite fuel cell exists where at the contact points thanks to the elasticity pressure is applied perpendicular to the plate plane, that further on the circumference of the partition plates and the fuel cell len level insulating means for feeding and discharging the gaseous media are provided, and that the entire Sta pel through on the circumference or outside of the fuel cells and Partition plates arranged elastic tie rods or stirrups lower is held tightly together under pressure to the plate level.

Way of carrying out the invention

The invention is illustrated by the following figures described exemplary embodiments. It shows

Fig. 1 is a sectional view (elevation) of the basic structure of the series of fuel cells, and intervening components,

Fig. 2 shows a section through lamellar current collectors,

Fig. 3 is a section elastically bedded by a partition plate with beidseiti gen packings particles,

Fig. 4 serving an exploded schematic diagram of fuel cells and intervening components including guide the gaseous Me,

Fig. 5 is a perspective view of a stack of fuel cells and in between Schaltgen components with external elastic tie rods.

In Fig. 1 a section (elevation) is shown through the basic structure of the sequence of fuel cells and components connected in between. 1 is a ceramic solid electrolyte formed as a flat plate on the basis of doped, stabilized ZrO ₂ , 2 is the porous (positive) oxygen electrode made of La / Mn perovskite and 3 is the corresponding porous (negative) fuel electrode of a Ni / ZrO ₂ cermet. 4 is a gas-tight, electrically conductive separating plate consisting of a ceramic or metallic material, which carries a conductive, oxidation-resistant, one-sided surface layer 5 on the oxygen side. In the present case, the surface layer 5 consists of La / Mn perovskite or of doped SnO ₂ . 6 is a fully elastic, on the oxygen side arranged current collector made of metallic, oxidation-resistant or ceramic material. In the present case, the current collector 6 is shown, for example, as a ceramic fleece. 7 is the corresponding vollela tical, arranged on the fuel side current collector, which is generally made of a metallic material be. In the present case, the current collector 7 is shown for example as metal wool. 8 are for the current transfer perpendicular to the plane of the plate between the separating plate 4 and the electrodes 2 and 3 on the one hand and the current collectors 6 and 7 on the other hand decisive contact points (pressure points). 9 is an electrically insulating spacer frame between the separating plate 4 on the one hand and the respective opposite electrode 2 or 3 on the other. Between a spacer frame 9 and the adjacent components, a frame-shaped elastic seal 10 (for example consisting of a ceramic material) is additionally arranged. A large number of such fuel cells with components connected between them is combined to form a stack-like structure. The sequence shown in FIG. 1 can be expanded in the vertical direction.

Fig. 2 shows a section through lamella-like Stromkollekto ren, the different variants a), b) and c) are shown. The partition plate 4 ( Fig. 1) consists of a metallic material. In variant a) a central sheet 11 is provided as the actual partition plate. 12 represents the sheet metal current collector provided with stamped elastic tabs (lamella) on the oxygen side. The oxidation-resistant surface layer 5 is applied in such a way that it covers the said oxygen side. 13 is the sheet metal current collector with stamped elastic tabs (lamella) on the fuel side. In variant b) there is also a central plate 11 as the actual separating plate. 14 is the sheet metal current collector made of soldered elastic lap pen (lamella) on the oxygen side. 15 the sheet metal current collector also applied on the fuel side. 16 are the solderings between 14 and 11 or 15 and 11 . The oxygen side is provided with the oxidation-resistant surface layer 5 . In variant c) there is no central plate. The partition plate 4 ( Fig. 1) is formed by two mutually offset, punched sheets ge. 17 is a sheet metal current collector with punched elec trical lobes (fins), oxygen side. The oxydationsbe permanent surface layer 5 is applied such that the entire oxygen side is covered. 18 is the sheet metal current collector on the fuel side, which is also equipped with punched elastic tabs (fins).

Fig. 3 relates to a section through a partition plate with bilateral beds of elastically embedded particles as current collectors. 2 is the porous oxygen electrode (La / Mn perovskite), 3 is the porous fuel electrode (Ni / ZrO ₂ cermet). 4 shows the gas-tight, electrically conductive separating plate, which carries a conductive, oxidation-resistant surface layer 5 made of, for example, La / Mn perovskite or doped SnO ₂ on the oxygen side. 19 represents an elastically behaving bed of pieces of wire on the oxygen side, which forms the oxygen-side current collector made of oxidation-resistant material. 20 is the corresponding fuel-side current collector in the form of an elastic bed of grains made of electrically conductive material.

FIG. 4 shows an exploded schematic illustration of fuel cells and components connected between them, including guidance of the gaseous media. The individual construction elements are drawn axially apart in the disassembled state. The seals are shown laterally shifted. 1 is the ceramic solid electrolyte, 2 the porous oxygen electrode and 3 the porous fuel electrode of the actual fuel cell. 4 is the gas-tight, electrically conductive separating plate with the conductive oxidation-resistant surface layer 5 on the oxygen side. 6 is a fully elastic, packet-like current collector in the form of a ceramic fleece on the oxygen side, 7 a corre sponding current collector in the form of a metal wool on the fuel side. 9 is the insulating spacer frame with the feed-through slots for the gaseous media. 10 is the elastic seal. The arrow pointing to the right indicates that the seal 10 is to be inserted between two adjacent components. All components have openings in the 4 corners for the passage of the gaseous media, which, when connected in series, form complete continuous channels. These openings form partially closed holes 25 , which are perpendicular to the plate plane. On the other hand, openings form bores 26 with a radial longitudinal slot (perpendicular to the plate plane) for the passage of the gaseous media. The leadership of the latter is shown by dash-dotted lines of different manners. 21 represents the supply of the gaseous oxygen carriers (e.g. air): symbol O ₂ . The oxygen carrier passes through the fuel cell (shown as a diagonal) and is collected in the opposite channel. 23 is the removal of the residual oxygen and the ballast gas (nitrogen): symbol (O ₂ ); N ₂ .

22 is the supply of the gaseous fuel (e.g. methane): symbol CH ₄ . The fuel passes through the fuel cell (shown as a diagonal) and is collected in the opposite channel. 24 is the removal of the residual fuel and the gaseous reaction products (carbon dioxide, water vapor): symbol (CH ₄ ); CO ₂ ; H ₂ O.

In Fig. 5 a perspective view is shown of a stack of fuel cells and intervening devices with external elastic tie rods. The reference numerals 21 and 22 for the supply and 23 and 24 for the discharge of the gaseous media correspond exactly to those in FIG. 4. The same applies to the symbols. 27 is a stack of fuel cells and partition plates with associated current collectors, spacers and seals. 28 is an end plate, which limits the stack 27 above and below. The whole stack 27 is held on the end plates 28 according to the filter press principle on the tie rods 29 arranged in the corners, which represent the longitudinal structure. The Zugan ker 29 transfer their longitudinal force elastically to the upper end plate 28 via the spring elements 30 in the form of screw springs.

Embodiment 1 See Figs. 1 and 4

A test device for energy conversion consisting of a stack of 100 fuel cells, separating plates with current collectors and seals similar to FIG. 5 was constructed. The fuel cells had the shape of flat plates with a square outline of 60 mm side length and each consist of a ceramic solid electrolyte 1 (doped, stabilized ZrO ₂ ) of 0.3 mm thickness, a porous oxygen electrode (La / Mn perovskite) 0.1 mm thick and a porous fuel electrode (Ni / ZrO ₂ cermet) 0.06 mm thick. Spacers 9 with plane-parallel ground surfaces made of Al ₂ O _{3 were} provided for spacing, guiding the gaseous media and closing the edge from the environment.

The frame 9 had been cut out of the plates with the laser beam. The thickness of the frame 9 was 5 mm on the oxygen side and 2 mm on the fuel side. Roughness and unevenness as well as thickness tolerance were approx. ± 0.05 mm. The holes 25 and 26 running perpendicular to the plane of the plate had a diameter of 6 mm on the oxygen side and 5 mm on the fuel side. The longitudinal slots of the bores 26 had a clear width of 1 mm. The seals 10 in the form of a square frame consisted of an Al ₂ O ₃ nonwoven type APA-3 with a thickness of 0.3 mm from Cirbas Products (USA). The gas-tight, electrically conductive partition plate 4 was manufactured from a 1 mm thick sheet of heat-resistant Cr / Al steel with the material number 1.4742 of the German standard (DIN X10CrAl18) from Thyssen. The steel had the following composition:

Cr = 18% by weight
Al = 1% by weight
Si = 0.9% by weight
Mn = 0.9% by weight
C 0.12% by weight
P 0.04% by weight
S 0.03% by weight
Fe = rest.

Thanks to the Cr content, stable protective layers of Cr ₂ O _{3 are formed} on the surface at an operating temperature of 800-1000 ° C, which largely prevent further oxidation of the underlying material. Since the partition plates 4 practically have no supporting function, but only serve to separate gaseous media, the heat resistance need not be high. The partition plates 4 had the same external dimensions as the fuel cells and had corresponding holes aligned with the holes 25 and 26 , respectively. Thickness tolerance + unevenness were approx. ± 0.07 mm. The fuel side of the partition plate 4 was covered with a 20 micron thick nickel layer. On the oxygen side, a conductive, oxidation-resistant surface layer 5 was applied in the form of a 25 μm thick gold plating (in deviation from the name of this layer in FIGS. 1, 2 and 3, where La / mn perovskite or doped SnO _{2 were} specified). The nickel layer and the gold plating proved their worth for short-term tests at 850 ° C for up to 100 h by fulfilling their protective and contact functions.

The material for the fully elastic current collectors 6 and 7 was used on both sides of the partition plate or the fuel cell ( 1; 2; 3 ) commercially available so-called scrubbing wool made of steel shavings. In particular, the scrubbing wool consisted of a wire mixture with a mesh size of 6 mm and a wire spacing of 2.5 mm of a flat wire with a cross section of 1 × 0.08 mm. The current collectors 6 and 7 were cut out of a "stocking" scrubbing wool by means of a laser beam, so that they just fit into the cavities within the spacer frames 9 . For the fuel side (collector 7 ) one, for the oxygen side (collector 6 ) two layers of scrubbing wool were used and pressed together in front so perpendicular to the plane of the plate that after removing the load, the thickness of the current collector 7 was about 3.2 mm and that of the current collector 6 was 6.2 mm. Taking into account the thickness of the seals 10 of 0.3 mm each and a setting under preload of approx. 0.1 mm, a vertical path (⟂ to the plate level) of approx. 0.7 mm was thus available for the spring action.

Now a total of 100 fuel cells and the associated components connected there have been assembled into a compact stack and held together by 4 tie rods over 2.5 mm thick end plates made of Al ₂ O ₃ . In the latter, the connections for the gaseous media were embedded in the form of metal tubes using ceramic adhesive. The electrical connections were made via the two terminal partition plates 4 . Contrary to FIG. 5, the tie rods consisting of 2 mm thick heat-resistant rods were not arranged outside the stack, but were placed coaxially to the bores 25 and 26 directly in the channels formed by the latter, perpendicular to the plane of the plate. Instead of the spring preload, a weight preload was chosen by loading the upper end plate with a mass of 500 g. The entire loaded stack was installed in a heat-insulated (adiabatic) container made of a heat-resistant and oxidation-resistant alloy.

The investigations showed that the leakage leakage occurring in the seals and joints during operation partly less than 2% of the respective volume flow of the gas feed medium. The whole stack gave at a tempe a power of 100 W from 850 ° C. The efficiency was approximately 60%.

Embodiment 2 See Figs. 1 and 4

Another experimental device was that the metallic current collectors 6 and 7 of Example 1 were replaced by ceramic materials. All other components such as fuel cells ( 1; 2; 3 ), spacer frame 9 and seals 10 and the entire structure of the stack corresponded to those in Example 1. For the current collector 6 on the oxygen side, a ceramic fiber felt with the trade designation 48/1260 of the form G was + H Montage, Ludwigshafen / Rh, Germany selected. The corresponding ceramic fiber had a diameter of approx. 3 µm with an average length of 6 mm. The composition of the long-term stable ceramic fiber in an oxidizing atmosphere up to a temperature of 1200 ° C was as follows:

SiO ₂ = 54% by weight
Al ₂ O ₃ = 45.5% by weight
Fe ₂ O ₃ = 0.2% by weight
Na ₂ O = 0.2% by weight.

The current collector 6 was cut out from a mat of felt of 6.4 mm in thickness by means of a laser and coated with an electrically conductive SnO ₂ doped with Sb ₂ O ₃ using a pyro-lytic co-deposition process. Thanks to the felt-like structure of the current collector 6 , the distance between adjacent contact points in the plate plane was only 0.1 to 0.5 mm. This dense network of contact points and the elasticity of the fiber ensured excellent current transfer. During assembly, the 6.4 mm thick felt was pressed together to 5.5 mm. For the current collector 7 on the fuel side, a ceramic filament fabric with the trade name K 1100 from the aforementioned company G + H Montage was used. The ceramic fiber had a diameter of approx. 4 µm. Numerous fibers were twisted into a yarn of approx. 1 mm thickness and this was again processed into a coarse fabric - similar to coarse-mesh wool. To increase the tensile strength, the yarn was provided with an approximately 0.1 mm thick core made of a Cr / Ni alloy. The long-term stable ceramic fiber up to temperatures of 1280 ° C had the following composition:

SiO ₂ = 51.7% by weight
Al ₂ O ₃ = 47.9% by weight
Fe ₂ O ₃ = 0.04% by weight
TiO ₂ = 0.002% by weight
MgO = 0.01% by weight
CaO = 0.02% by weight
Na ₂ O = 0.1% by weight.

The current collector 7 was cut out of a tissue with a thickness of 3 mm by means of a laser and coated with electrically conductive SnO ₂ doped with Sb ₂ O ₃ . Due to the fabric-like construction of the current collector 7 , a network of contact points with an average distance in the plate plane of about 3 mm was created. The 3 mm thick fabric was compressed to 2.5 mm during assembly. The separating plate 4 consisted, similarly to example 1, of a Cr / Al steel, with both sides now being provided with a 30 μm thick layer of conductive SnO ₂ doped with Sb ₂ O ₃ instead of nickel and gold. Thanks to the stability of the SnO ₂ and its own property, practically not diffusing into the core material of the partition plate 4, a long service life can be expected for this arrangement.

In trial operation, the stack was able to stand at 850 ° C for 500 h be operated trouble-free. The power was 120 W. The Efficiency was approximately 55%.

Embodiment 3 See Figs. 2 and 4

The device was built up on the partition plate 4 and the current collectors 6 and 7 exactly the same as specified in Example 1. An embodiment according to FIG. 2a) was chosen for the combination separating plate / current collectors. The central plate 11 of the separating plate was 0.7 mm thick and had the same composition according to DIN substance number 1.4742 as the separating plate 4 in example 1. Since the plate 11 only has a separating function, it may be flexible and the environment - to a certain extent Degree also plastic - adjust. The sheet metal current collector 12 or 13 with stamped elastic tabs (contact fingers) must have a high heat resistance and must not lose its resilient properties even at operating temperature. Therefore, a 2 mm thick sheet made of the dispersion-hardened iron-based superalloy with the trade name MA 956 from Inco was assumed. The alloy had the following composition:

Cr = 20% by weight
Al = 4.5% by weight
Ti = 0.5% by weight
Y ₂ O ₃ = 0.5% by weight
Fe = rest.

This material still has a service life (creep limit) of over 1000 h at 900 ° C under a load of 100 MPa. The 2 mm thick sheet was rolled down between heated rolls of 700 ° C in 6 passes with intermediate annealing at 1100 ° C / ½ h to a final thickness of 0.2 ± 0.01 mm. In the absence of a punch, a large number of 5 mm long and 1.5 mm wide tongues were cut into square pieces of sheet metal with a side length of 60 mm, with a narrow side of 1.5 mm remaining. These tongues were then bent to form an angle of approximately 30 ° with respect to the plate plane (contact finger) (see FIGS. 12 and 13 in FIG. 2a). Care was taken to ensure that the ends of the tabs were exactly the same height with respect to the plane of the plate. The sharp-edged cut edges were rounded off by sandblasting. Now the ends of the rags were electroplated with gold. The average thickness of the gold layer was 50 µm. Now the sheet metal current collectors ver with gold-plated rags 12 and 13 were joined together with the central sheet 11 of the separating plate to form a whole and the electrical contact between all three sheets was ensured by spot welding.

From the usual components fuel cell ( 1; 2; 3 ), partition plate / current collector ( 11; 12; 13 ), spacer frame 9 and seals 10 , a stack was assembled according to Example 1. Since the elastic resilient flaps of elements 12 and 13 were comparatively stiffer than braid, fleece or felt, the end plate had to be loaded with a higher mass (approx. 2.5 kg) in order to achieve sufficient tightness in the edge areas.

The device was operated at a temperature of 950 ° C 500 h operated, the power 140 W and the efficiency Was 63%. Because gold is bad with the iron-based alloy alloyed, the diffusion was relatively low.

In deviation from Fig. 2a) for the combination separating plate / current collector, the variants according to Fig. 2 b) (sheet current collectors with soldered tabs 14; 15; 16 ) and Fig. 2c) (sheet current collectors offset against each other for gas-tightness) 17; 18 ) executed. The assembly was done in the usual way. The results were practically identical to those of the structure shown in FIG. 2a).

 Embodiment 4 See Figure 3

The structure of the device was basically similar to that given in Example 1. Instead of metal mesh, fleeces or felts, loose material was used to build the current collectors. On the oxygen side there was a bed of corrugated wire pieces (similar to 19 in FIG. 3), on the fuel side there was a bed of thin-walled elastic sheet metal tubes (instead of grains 20 in FIG. 3). The corrugated wire pieces consisted of a nickel-based superalloy and were gold-plated with a thickness of 20 µm. The super alloy with the trade name IN 625 from Inco had the following composition:

Cr = 21.5% by weight
Mo = 9.0% by weight
Nb = 3.6% by weight
Al = 0.2% by weight
Ti = 0.2% by weight
Fe = 2.5% by weight
Mn = 0.2% by weight
Si = 0.2% by weight
C = 0.05% by weight
Ni = rest.

The elastic sheet metal tubes consisted of a nickel-based Super alloy and were nickel-plated 50 µm thick. The superle Inco with the trade name IN 105 from Inco following composition:

Cr = 13.5% by weight
Co = 18% by weight
Ti = 0.9% by weight
Al = 4.2% by weight
Mo = 4.5% by weight
Si = 1% by weight
Mn = 1% by weight
Ni = rest.

As a result of the substantially lower resilience (higher spring constant) of the beds 19 and 20 serving as current collectors, the components determining the geometry had to be manufactured particularly precisely and with a low surface roughness. In addition, a larger mass of approx. 10 kg was necessary as a load on the stack.

The one operated at a temperature of 900 ° C for 200 h Device gave a power of 95 W. The efficiency be carried about 55%.

Embodiment 5 See Figure 3

The device was constructed in the same way as given in Example 4. This time, beds of small ceramic balls (instead of grains 20 in FIG. 3) were used as current collectors on both sides. The core of the 0.7 mm diameter balls was made of SiC. The ceramic balls arranged on the oxygen side had previously been galvanically coated with a 30 µm thick layer of palladium. The ceramic balls used on the fuel side had an electroplated nickel surface layer of 20 µm thickness. The usual structure of the device corresponds to that of Example 4.

The operating results after 500 h at one temperature of 950 ° C were: power 110 W, efficiency: 59%.

Embodiment 6 See Figs. 1 and 4

A test device was examined, the basic structure of which corresponded to Example 1. Corrugated wire mesh (metal mesh) was used as the fully elastic current collectors ( 6; 7 ). The diameter of a single wire was 0.15 mm, the mesh size 1 mm.

An oxidation-resistant iron-based alloy with the material number 1.4767 of the German standard (DIN CrAl20 5) from Thyssen with the following composition was used for the current collector 6 on the oxygen side:

Cr = 20% by weight
Al = 5% by weight
Si = 0.8% by weight
Mn = 0.8% by weight
C 0.10% by weight
P 0.045% by weight
S 0.03% by weight
Fe = rest.

For the current collector 7 on the fuel side, a heat-resistant heating conductor alloy with the material number 2.4869 of the German standard (DIN NiCr 80 20) from Thyssen with the following composition was used, even in a reducing atmosphere:

Ni = 76% by weight
Cr = 20% by weight
Cu = 0.5% by weight
Si = 1% by weight
Mn = 1% by weight
C 0.15% by weight
P 0.025% by weight
S 0.02% by weight
Fe = rest.

Both wire meshes were made using embossing tools forms that waves of approx. 2 mm wavelength and approx. 0.6 mm Am plitude (half total height) were formed. On the Sauer 6 layers of these wave meshes on the fabric side Fuel side 3 each stacked crosswise. There due to piles that were unloaded on the Total height (perpendicular to the plate plane) of 7.2 mm, on the fuel side 3.6 mm exhibited.

The wire mesh of the current collector 6 for the oxygen side is coated galvanically with each about 5 microns thick layers of Co, Ni and Pd in the angege surrounded order prior to installation in the spacer frame. 9 Then the whole was subjected to a heat treatment at 900 ° C / 1 h, whereby existing pores and hairline cracks were closed by sintering and diffusion processes. The separating plate 4 , consisting of the heat-resistant Cr / Al steel with the material number 1.4742, was provided in the same way on the oxygen side with a layer of Co, Ni and Pd.

All other components corresponded exactly to those from Bei game 1. The same was true of the operating conditions. The up Stacks operated at 850 ° C worked perfectly for 1000 hours, anyway he turned off several times and the temperature again was started up. Above all, the easy demon animalability and mountability without any change of the Components found that are special for the trial operation proven valuable and advantageous.

The power was 105 W, the efficiency 62%.

The invention is not based on the exemplary embodiments limits.

The device for converting chemical energy present in a gaseous fuel into electrical energy consists of an arrangement in the form of a stack of series-connected flat, planar high-temperature fuel cells ( 1; 2; 3 ) based on zirconium oxide as a solid electrolyte 1 elements connected between adjacent fuel cells for electrical power transmission, said elements from a centrally arranged, electrically conductive, gas-tight flat separating plate 4 and on both sides of orderly electrically conductive, fully elastic current collectors ( 6; 7 ) with a plurality of contact points 8 opposite the separating plate 4 and the adjacent electrode ( 2; 3 ) of the opposing fuel cell consist by constantly exerting a pressure perpendicular to the plate plane at the contact points 8 thanks to elasticity, and on the circumference of the separating plates 4 and the fuel cells plane insulating Di stanzrah Men 9 and elastic seals 10 and corresponding means for supplying and discharging the gaseous media are seen before and the entire stack is held together by pressure arranged on the circumference or outside of the fuel cells and separating plates elastic tie rods or brackets perpendicular to the plane of the plate. The partition plate 4 consists of a heat-resistant metallic material or a conductive ceramic material or a cermet, the oxygen side being provided with a conductive oxidation-resistant surface layer 5 .

The arranged on both sides of the partition plate 4 fully elastic current collectors ( 6; 7 ) are preferably as a sponge, felt, fleece, braid, grid, wool, fiber ball, fiber laminate or fabric or further as a corrugated or punched profiled plate body with resilient lamellar elevations, strips or rags educated. The fully elastic current collectors ( 6; 7 ) consist of a heat-resistant metallic material or a conductive ceramic material or a cermet, whereby the oxygen-side current collectors are made resistant to oxidation or are provided with oxidation-resistant surface layers.

For the partition plate 4 and / or for the current collectors ( 6; 7 ), ceramic conductive materials such as silicon carbide, tin oxide, La / Mn perovskite, Ni / ZrO ₂ cermet are advantageously also used.

The fully elastic current collectors ( 6; 7 ) are preferably electrically conductive and mechanically non-positively connected to the separating plate 4 and / or the electrode ( 2; 3 ) of the fuel cell, which is adjacent because of a high-temperature solder or a weld or a sintering, the Soldering, welding or sintering is oxidation-resistant or non-oxidizing and / or is provided with a protective oxide-forming cover layer.

Claims (9)

1. Device for converting chemical energy present in a gaseous fuel into electrical energy by means of an arrangement in the form of a stack of series-connected flat, planar high-temperature fuel cells ( 1; 2; 3 ) based on zirconium oxide as a solid electrolyte ( 1 ) with components connected between adjacent fuel cells for electrical power transmission, characterized in that each of said components from a centrally arranged, electrically conductive, gas-tight planar separating plate ( 4 ) and electrically conductive, fully elastic current collectors ( 6; 7 ) arranged on both sides with a lot number of contact points ( 8 ) with respect to the separating plate ( 4 ) and the adjacent electrode ( 2; 3 ) of the fuel cell lying opposite, whereby at the contact points ( 8 ), thanks to elasticity, a pressure directed perpendicular to the plate plane is continuously exerted, that further on the circumference of the dividing plates ( 4th ) and the fuel cell level insulating spacer frame ( 9 ) and elastic lines ( 10 ) and appropriate means for supplying and discharging the gaseous media are provided, and that the entire stack by means of elastic circumferential tie rods or brackets arranged on the circumference or outside the fuel cells and separating plates is held firmly together under pressure perpendicular to the plate plane. 2. Device according to claim 1, characterized in that the separating plate ( 4 ) consists of a heat-resistant metallic material or a conductive ceramic material or a cermet, the oxygen side being provided with a conductive, oxidation-resistant surface layer ( 5 ). 3. Device according to claim 1, characterized in that the both sides of the separating plate (4) arranged vollela stischen current collectors (6, 7) as a sponge. Felt, fleece, braid, grid, wool, ball of fiber, fiber laminate or fabric are formed. 4. The device according to claim 1, characterized in that the bilaterally the partition plate ( 4 ) arranged vollela-elastic current collectors ( 6; 7 ) are designed as corrugated or GE punched profiled plate body with resilient lamella-like elevations, strips or rags. 5. Apparatus according to claim 3 or 4, characterized in that the fully elastic current collectors ( 6; 7 ) consist of a heat-resistant metallic material or a lei tend ceramic material or a cermet, wherein the oxygen-side current collectors are made oxidation-resistant or with oxidation-resistant surface layers are provided. 6. The device according to claim 2, 3, 4 or 5, characterized in that for the partition plate ( 4 ) and / or for the current collectors ( 6; 7 ) ceramic conductive materials such as silicon carbide, tin oxide, La / Mn perovskite, Ni / ZrO ₂ - cermet can be used. 7. The device according to claim 1, characterized in that the fully elastic current collectors ( 6; 7 ) with the separating plate ( 4 ) and / or the electrode ( 2; 3 ) of the adjacent fuel cell in each case by a high-temperature solder or a weld or a Sin tion are electrically conductive and mechanically non-positively connected. 8. The device according to claim 7, characterized in that the soldering, welding or sintering are resistant to oxidation dig or non-oxidizing.   9. The device according to claim 7, characterized in that the soldering, welding or sintering with a protection oxide-forming cover layer is provided.