Fuel cell

Abstract

A fuel cell including a plurality of elementary modules stacked on each other, at least one of the elementary modules including an oxidation unit generating electrons by oxidation of a fuel with an oxidant, an anode block including a fuel transporter support, for transporting an anode feed flow containing the fuel to an anode chamber, onto which is attached an anode electron collector, a cathode block including an oxidant transporter support, for transporting a cathode feed flow containing the oxidant to a cathode chamber, onto which is attached a cathode electron collector, the elementary module defining the anode chamber, respectively, the cathode chamber between the oxidation unit and the fuel transporter support, respectively, the oxidant transporter support, and being such that, prior to the assembly of the elementary module in said plurality, the anode block, respectively, the cathode block and the oxidation unit are attached to each other.

Claims

1. A fuel cell including a plurality of elementary modules stacked on each other in a stacking direction, at least one of the elementary modules of the plurality including: an oxidation unit configured to generate electrons by means of the oxidation of a fuel with an oxidant the oxidation unit including an anode and a cathode sandwiching an electrolytic membrane, an anode block including a fuel transporter support suitable for transporting an anode feed flow containing the fuel to an anode chamber, and an anode electron collector attached to the fuel transporter support, a cathode block including an oxidant transporter support suitable for transporting a cathode feed flow containing the oxidant to a cathode chamber, and a cathode electron collector attached to the oxidant transporter support, the at least one elementary module being configured so as to define the anode chamber between the oxidation unit and the fuel transport support, and the cathode chamber, between the oxidation unit and the oxidant transporter support, the at least one elementary module being such that, prior to the assembly of the at least one elementary module in the plurality of elementary modules of the fuel cell, the anode block is attached to the oxidation unit, and the cathode block is attached to the oxidation unit.

2. The fuel cell as claimed in claim 1, in which each elementary module extends in a longitudinal plane perpendicular to the stacking direction.

3. The fuel cell as claimed in claim 2, in which the anode block and the oxidation unit are attached by bonding and electrically connected to each other by means of an anode conductive bridge, containing an electrically conductive adhesive in which the cathode block and the oxidation unit are attached by bonding and electrically connected to each other by a cathode conductive bridge containing the electrically conductive adhesive.

4. The fuel cell as claimed in claim 3, in which the anode conductive bridge and the anode electron collector, respectively, the cathode conductive bridge and the cathode electron collector are both attached by bonding and electrically connected to each other.

5. The fuel cell as claimed in claim 1, in which the oxidation unit and the fuel transporter support are both attached by bonding to each other and electrically insulated from each other by means of an anode leakproofing bridge containing a fuel-leaktight electrically insulating adhesive, the anode leakproofing bridge being configured so that the anode feed flow transported to the anode chamber flows essentially directly from the fuel transporter support to the anode.

6. The fuel cell as claimed in claim 1, being free of means for compressing the plurality of elementary modules.

7. The fuel cell as claimed in claim 1, in which the elementary modules are electrically connected together in parallel or in series.

8. The fuel cell as claimed in claim 1, in which two consecutive elementary modules are placed head to tail in the stacking direction.

9. The fuel cell as claimed in claim 1, the cell being configured to define at least one cathode feed channel configured to feed the at least one elementary module with a cathode feed flow containing the oxidant, and at least one cooling channel configured to transport a cooling flow including a heat transfer fluid so as to exchange heat by convection with the at least one elementary module.

10. The fuel cell as claimed in claim 9, in which the at least one elementary module is placed between the cathode feed channel and the cooling channel.

11. The fuel cell as claimed in claim 9, in which the cathode feed channel extends in an extension direction perpendicular to the direction in which cooling the channel extends, and/or the plane in which the cathode feed channel extends is different and parallel to the plane in which the cooling channel extend.

12. The fuel cell as claimed in claim 9, in which the cathode feed channel is placed between the respective cathode blocks of at least two consecutive elementary modules of the plurality of elementary modules in the stacking direction, and is configured to transport the cathode feed flow to the oxidant transporter support of each of said two respective elementary modules, and/or the cooling channel is placed between at least two consecutive elementary modules of the plurality of elementary modules in the stacking direction and is configured so as to transport the cooling flow so as to exchange heat by convection with said two elementary modules.

13. The fuel cell as claimed in claim 9, in which: the cathode feed channel has at least one inlet aperture, respectively, at least one outlet aperture, for the flow at the cell inlet, respectively, at the cell outlet of the cathode feed flow, and the cooling channel has at least one inlet aperture, respectively, at least one outlet aperture, for the flow at the cell inlet, respectively, at the cell outlet of the cooling flow, the inlet apertures and outlet apertures of said cathode feed channels and cooling channels being configured so that the cell inlet and outlet cathode feed flows flow in at least one direction perpendicular to the at least one direction of flow of the cell inlet and outlet cooling flows, and/or the inlet apertures and outlet apertures of said cathode feed channel and cooling channel are configured so that the direction(s) of flow of the cell inlet and outlet cathode feed flows and the direction(s) of flow of the cooling flows are contained in different and parallel planes.

14. The fuel cell as claimed in claim 9, including: a plurality of cathode feed channels, each cathode feed channel being configured to feed at least one elementary module with cathode feed flow, a cathode feed probe placed in a channel of the plurality of cathode feed channels and configured to measure at least one cathode feed property chosen from the humidity, the temperature and the pressure, a cathode feed flow generator configured to generate the cathode feed flow to be transported in said channel or in another channel of the plurality of cathode feed channels, and a unit for controlling said cathode feed flow generator, which is configured to regulate, as a function of the measurement of the cathode feed property, at least one parameter of said cathode feed flow to be transported in said channel and/or said cathode feed flow to be transported in the other channel, and/or a plurality of cooling channels, each cooling channel being configured to transport a cooling flow so as to exchange heat by convection with at least one elementary module, a cooling probe placed in a channel of the plurality of cooling channels and configured to measure at least one cooling property chosen from the humidity, the temperature and the pressure, a cooling flow generator configured to generate the cooling flow to be transported in said channel or in another channel of the plurality of cooling channels, and a unit for controlling said cooling flow generator, which is configured to regulate, as a function of the measurement of the cooling property, at least one parameter of said cooling flow to be transported in said channel and/or said cooling flow to be transported in the other channel.

15. The fuel cell as claimed in claim 14, including a sensor placed in an elementary module in fluid communication with the cathode feed channel in which is placed the cathode feed probe and/or which is capable of exchanging heat by convection with a cooling flow flowing in the cooling channel in which is placed the cooling probe, said sensor being configured to measure an electrical resistance chosen from an internal resistance of the elementary module, the polarization resistance of the elementary module, or the total resistance of the elementary module, the unit for controlling said cathode feed flow generator being configured to regulate, as a function of the measurement of the cathode feed property and of the measurement of the electrical resistance, at least one parameter of said cathode feed flow to be transported in said cathode feed channel and/or said cathode feed flow to be transported in the other cathode feed channel, and/or the unit for controlling said cooling flow generator being configured to regulate, as a function of the measurement of the cooling property and of the measurement of the electrical resistance, at least one parameter of said cooling flow to be transported in said cooling channel and/or said cooling flow to be transported in the other cooling channel.

16. A process for manufacturing a fuel cell as claimed in claim 1, including a step of manufacturing at least one elementary module including a step to attach the anode block to the oxidation unit and a step to attach the cathode block to the oxidation unit.

17. The process as claimed in claim 16, in which at least two elementary modules are manufactured, and the elementary modules are stacked on top of each other in a stacking direction.

18. The process as claimed in claim 16, in which at least one adhesive composition is deposited on the anode block, and/or on the oxidation unit, and the anode block is then assembled with the oxidation unit so as to form an adhesive attachment bridge rigidly attached to the anode and to the oxidation unit, in which at least one adhesive composition is deposited on the cathode block and/or on the oxidation unit, and the cathode block is then assembled with the oxidation unit so as to form an adhesive attachment bridge rigidly attached to the cathode block and to the oxidation unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the invention will also emerge on reading the detailed description that follows and from the attached drawing, in which:

(2) FIG. 1 schematically represents, in cross section view, an elementary module according to the invention,

(3) FIG. 2 schematically represents, in cross section view, another elementary module according to the invention;

(4) FIG. 3 schematically represents, in cross section view, another elementary module according to the invention;

(5) FIG. 4 schematically represents, in cross section vice, another elementary module according to the invention;

(6) FIG. 5 schematically represents, in cross section view, another elementary module according to the invention;

(7) FIG. 6 schematically represents a fuel cell including a plurality of elementary modules according to the invention, in cross section view along the stacking direction of the elementary modules,

(8) FIG. 7 represents a perspective variant of the fuel cells according to the invention,

(9) FIG. 8 represents another perspective variant of the fuel cells according to the invention,

(10) FIG. 9 represents another perspective variant of the fuel cells according to the invention, and

(11) FIG. 10 is a photograph of a cell according to one embodiment of the invention.

DETAILED DESCRIPTION

(12) In the various figures, identical references are used to denote identical or similar members.

(13) The elementary module 5 of FIG. 1 extends in a longitudinal plane P including a longitudinal direction X. It includes an oxidation unit 10 formed from a stack constituted successively of an anode 15, of an electrolytic membrane 20 and of a cathode 25, all three each being in the form of a plate extending in a plane parallel to the longitudinal plane. The electrolysis unit is placed between an oxidant transporter support 30 and a fuel transporter support 35, each being in the form of a porous plate extending in a plane parallel to the longitudinal plane of the elementary module.

(14) A cathode electron collector 40, in the form of a strip projecting in a transverse direction T relative to the longitudinal plane, is attached to the oxidant transporter support, thus defining with the oxidant transporter support a cathode block 45. It is attached to the cathode by means of a cathode conductive bridge 50 formed from an electrically conductive adhesive. The cathode conductive bridge extends in the transverse direction between two opposite faces 55 and 60, one of them 55 being in contact with the cathode electron collector, the other 60 being in contact with the cathode. Thus, the oxidation unit and the cathode block are attached to each other by bonding and electrically connected.

(15) Moreover, the oxidant transporter support, the cathode electron collector, the cathode conductive bridge and the cathode define a cathode chamber 65. Thus, during functioning, the cathode feed flow, for example generated by a fan and transported in a cathode feed channel, as will be described hereinbelow, passes through the porous oxidant transporter support, as indicated by the arrow O to penetrate into the cathode chamber and come into contact with the cathode so as to ensure the oxidation reaction of the fuel. The cathode electrons resulting from the oxidation reaction which are formed at the cathode may be collected and then, as indicated by the arrow Ec, may then be transferred by means of the cathode collector bridge to the cathode electron collector.

(16) An anode electron collector 70, in the form of a strip projecting in the transverse direction, is attached to the fuel transporter support 35, thus defining with the fuel transporter support an anode block 75. The anode electron collector is attached to the anode by means of an anode conductive bridge 80 formed from an electrically conductive adhesive. The anode conductive bridge extends in the transverse direction between two opposite faces 85 and 90, one of them 90 being in contact with the anode electron collector, the other 85 being in contact with the anode. Thus, the oxidation unit and the anode block are attached to each other by bonding. In addition, the anode electrons resulting from the oxidation reaction of the fuel, which are formed at the anode, may be collected and then, as indicated by the arrow Ea, may then be transferred by means of the anode conductive bridge to the anode electron collector.

(17) In this way, the attachments by bonding of the anode and cathode blocks by means of the respective anode and cathode conductive bridges to the oxidation unit ensure the mechanical strength of the elementary module, without it being necessary to insert permanent compression means for this purpose.

(18) Moreover, an anode leakproofing bridge 100, formed from a fuel-leaktight electrically insulating adhesive seal, is sandwiched between the anode block and the fuel transporter support and holds them a distance from each other, defining an anode chamber 105 extending in a plane parallel to the longitudinal plane. The anode leakproofing bridge forms a leakproofing seal extending between the faces facing the anode and the fuel transporter support, in a transverse direction relative to the longitudinal plane. The anode leakproofing bridge surrounds said anode chamber in a plane parallel to the longitudinal plane. Besides its leakproofing function described hereinbelow, it reinforces the mechanical strength of the elementary module, by adding an additional attachment between the anode block and the oxidation unit. During functioning, the attachment of the oxidation unit by means of the anode leakproofing bridge and the anode conductive bridge allows the elementary module to withstand the fuel pressure in the anode chamber, which is above atmospheric pressure.

(19) Moreover, the elementary module includes a reservoir 108, defining an internal volume 110, including a filling orifice 115 for feeding the reservoir with fuel. The fuel transporter support moreover defines a wall 118 separating the anode chamber from the internal volume of the reservoir.

(20) During functioning, a compressor can inject a fuel flow into the internal volume of the reservoir via the filling orifice, in which the fuel is thus stored. The anode feed flow containing the fuel then passes through the fuel transporter support, which is porous, and penetrates into the anode chamber where it flows, in a transverse direction relative to the longitudinal direction, until it comes into contact with the anode, as indicated by the arrow C. The anode leakproofing bridge limits the flow of the fuel flow in the chamber in any direction contained in the longitudinal plane, as indicated by the arrows L.sub.1 and L.sub.2, and thus reduces the leaks of fuel out of the anode chamber.

(21) The elementary module of FIG. 2 differs from the elementary module of FIG. 1 in that an anode collecting layer 120 and a cathode collecting layer 125 are placed on the faces 130 and 135 of the anode and cathode, respectively, placed facing the anode and cathode chambers, respectively.

(22) The anode and cathode collecting layers improve the collection of the anode and cathode electrons generated remotely from the anode and cathode electron collectors, respectively.

(23) In order for the fuel and the oxidant to be able to come into contact with the anode and the cathode, respectively, the electron collecting layers may partially cover said faces of the anode and cathode and, for example, may be fuel-leaktight or oxidant-leaktight, respectively. In this variant, the fuel and the oxidant may come into contact with the anode and the cathode, respectively, in the zones of said faces of the anodes and cathodes that are not covered with the anode and cathode collecting layers, respectively. The anode and cathode collecting layers may also be in the form of a film that is porous with respect to the fuel and to the oxidant, respectively, and which covers, for example entirely, said faces of the anode and cathode, respectively.

(24) In the example of FIG. 2, the anode conductive bridge 80 and the anode leakproofing bridge 100 are attached by bonding to the anode layer.

(25) Moreover, to further reinforce the mechanical strength of the elementary module, the elementary module of FIG. 2 includes a cathode attachment bridge 140 formed from an electrically insulating adhesive, extending between two opposite faces of the cathode chamber in a transverse direction relative to the longitudinal plane, one of the faces 145 of the cathode attachment bridge being bonded to the oxidant transporter support, the other face 150 of said bridge being bonded to the cathode collecting layer 125.

(26) Although this is not illustrated, the elementary module of FIG. 1 may include such a cathode attachment bridge bonded both to the fuel transporter support and to the cathode.

(27) The elementary module of FIG. 3 differs from the elementary module of FIG. 2 in that the anode, respectively, the cathode includes an anode window 155, respectively, a cathode window 160, passing through the anode, respectively, the cathode, in its thickness, and lying on the electrolytic membrane. The anode conductive bridge 80, respectively, the cathode conductive bridge 50 is housed in the anode window, respectively, in the cathode window, and is attached by bonding to the electrolytic membrane 10.

(28) In the variant in which the mechanical connection between the anode, respectively, the cathode and the electrolytic membrane is weak, the mechanical strength of the elementary module is improved, the connections of the anode and cathode blocks, respectively, by means of the anode and cathode conductive bridges, respectively, with the oxidation unit being made directly with the electrolytic membrane.

(29) The anode conductive bridge 80, respectively, the cathode conductive bridge 50 has a relief 165, respectively, 170 projecting longitudinally and being placed in contact with the anode collecting layer, respectively, with the cathode collecting layer. The relief of the anode conductive bridge, respectively, of the cathode conductive bridge places the anode, respectively, the cathode in electrical contact with the anode electron collector, respectively, with the cathode electron collector.

(30) FIG. 4 illustrates an embodiment of the fuel cell including several elementary modules 5.sub.1, 5.sub.2 sharing the same electrolytic membrane 20. Relative to a cell constituted of two modules each placed on different electrolytic membranes, each of said modules being as illustrated in FIG. 3, the arrangement illustrated in FIG. 4 makes it possible to increase the voltage delivered by the cell for the same power generated. The fuel cell of FIG. 4 includes elementary modules as illustrated in FIG. 3, which may obviously be combined and/or replaced with one or more elementary modules, for example as illustrated in FIGS. 1 and 2. Moreover, in a variant not shown, the elementary modules may share the same fuel transporter support and/or the same insulating transporter support. They may or may not share the same reservoir.

(31) FIG. 5 illustrates a fuel cell including an elementary module as illustrated in FIG. 2, also including a superposed porous gas diffusion layer 170 which is in contact with the face of the oxidant transporter support opposite the face that is facing the anode chamber. Moreover, the gas diffusion layer is placed between the oxidant transporter support and a porous grate 175 with which it is in contact.

(32) The fuel cell of FIG. 5 also includes a first hollow tube 180, one wall of which is at least partially formed by the grate 175, which defines a cathode feed channel 185 for transporting a cathode feed flow including the oxidant. The hollow tube includes an inlet aperture 190 for the cathode feed flow, as indicated by the arrow O.sub.E, which is placed facing a fan 200 that is capable of generating said cathode feed flow. The hollow tube moreover includes an outlet aperture 205, via which the cathode feed flow can escape, as indicated by the arrow O.sub.S after it has passed through the porous grate 175 and the gas diffusion layer and after having fed, as indicated by the arrow O, the cathode chamber 65 of the elementary module, and after having been charged with oxidation reaction products. In particular, in the case where the oxidant is dioxygen and the fuel is dihydrogen, the oxidation reaction produces water vapor which is evacuated from the anode chamber to the outlet aperture by the cathode feed flow, in the present case a flow of air.

(33) The fuel cell also has a second hollow tube 210 placed such that the elementary module 5 is sandwiched between the first 185 and second 210 hollow tubes. The second hollow tube has a wall in common with the reservoir. It defines a cooling channel 212 having an inlet aperture 215 configured for the inlet of a cooling flow R including a heat transfer fluid such as air, placed facing a fan 220 configured to generate and distribute said cooling flow to said inlet aperture.

(34) When it flows in the cooling channel as indicated according to the arrow R, the elementary module exchanges heat generated by the exothermic oxidation reaction by convection on the wall 225 common to the module and to the second hollow tube. The cooling flow thus heated flows to an outlet aperture 230 placed opposite the inlet aperture, via which it is evacuated from the fuel cell.

(35) As may be seen in FIG. 5, in order to avoid any interaction between the cathode feed flow O and the cooling flow R, the cathode feed channel and the cooling channel extend in different planes P.sub.1 and P.sub.2 parallel to the longitudinal plane.

(36) Moreover, in the example of FIG. 5, the fan for generating the cooling flow and the fan for generating the cathode feed flow including the oxidant are placed facing the same side face 235, parallel to the stacking direction D.sub.E of the fuel cell. As a variant, the fan for generating the cooling flow may be placed on the side face opposite the one to which the fan for generating the cathode feed flow is placed facing.

(37) In a variant not shown, and notably when the cell is intended for generating an electric current within a limited operating temperature range, the cell may be free of means as described, for example, in FIG. 5, for cooling the cell by means of a cooling flow.

(38) The fuel cell 250 of FIG. 6 includes a plurality of four elementary modules 5a-d stacked on each other in a stacking direction D.sub.E.

(39) Each elementary module of the plurality is identical to that illustrated in FIG. 5, with the exception that the apertures and outlets of the cooling channels are formed on faces perpendicular to those on which are formed the apertures and outlets of the cathode feed channels. The stacking direction D.sub.E is perpendicular to the longitudinal plane P of each elementary module.

(40) The fuel cell is configured such that each pair of two consecutive elementary modules of the stack is such that said two elementary modules, for example 5a and 5b, are arranged head to tail relative to each other in the stacking direction.

(41) The modules of the stack are electrically connected by means of an electrical circuit, not shown, connecting an anode electron collector of one elementary module to a cathode electron collector of an adjacent elementary module.

(42) In the stack of FIG. 6, two consecutive elementary modules having cathode blocks placed facing each other are separated by a cathode feed channel 255.sub.1-2 extending in a transverse plane relative to the stacking direction. Thus, by means of a single cathode feed channel, the cathode chambers 65a-d of the two elementary modules are fed with a single cathode feed flow at the inlet O.

(43) Moreover, two consecutive elementary modules whose anode blocks, for example 75b and 75c, are placed facing each other and are separated by a cooling channel 260 extending in a transverse plane relative to the stacking direction. Thus, by means of a single cooling channel, the two elementary modules 5b and 5c are cooled by convective exchange with the cooling flow R flowing in the channel.

(44) In this way, the fuel cell 250 of FIG. 6 is configured such that the cathode feed channel and the cooling channel are placed a distance from each other and in alternance along the stacking direction D.sub.E. In this way, the interactions between the cathode feed flow O and the cooling flow R are limited.

(45) As regards the generation of the cathode feed flows and of the cooling flows, the fuel cell of FIG. 6 includes two cathode feed fans 200.sub.1-2 configured so as each to feed a respective cathode feed channel 255.sub.1-2 with associated cathode feed flows and three cooling fans 220.sub.1-3 configured so as each to feed a cooling channel with associated cooling flows. Moreover, the cathode feed fans and the cooling fans are placed facing side faces 270, 275 of the cell that are perpendicular to each other. In this way, the cathode feed flows and the cooling flows flow in respectively oblique flow directions. The interaction between said flows is limited, which optimizes the energy yield of the cell.

(46) Moreover, the fuel cell illustrated in FIG. 6 includes a cathode feed probe 280 placed in one of the cathode feed channels to measure the temperature of the cathode feed flow in said channel. The cathode feed probe is electrically connected to a unit 285 for controlling the anode feed fans of the cell, via connection means not shown, said control unit being configured to regulate, as a function of the temperature measured by the cathode feed probe, for example, the flow rate of the cathode feed flow at the outlet of each of the cathode feed fans of the fuel cell.

(47) In this way, by means of a single cathode feed probe, the flow rate of the cathode feed flows of the plurality of cathode feed channels of the cell can be easily regulated.

(48) The fuel cell of FIG. 6 also includes a cooling probe 292 placed in one of the cooling channels consecutive to the cathode feed channel in which is placed the cathode feed probe, to measure the temperature of the cooling flow in said cooling channel. The cooling probe is electrically connected to a unit for controlling the cooling fans 298 of the fuel cell, via connection means not shown, said control unit being configured to regulate, as a function of the temperature measured by the cooling probe, for example, the flow rate of the cooling flow at the outlet of each of the cooling fans of the fuel cell.

(49) In this way, by means of a single cooling probe, the flow rate of the cooling flows of the plurality of cooling channels of the cell can be easily regulated.

(50) The fuel cell also includes a sensor 300 placed in an elementary module to measure, for example, the internal resistance of the elementary module. The sensor is connected to the units for controlling the cathode feed fan and cooling fan which are also each configured to regulate the flow rates of the cathode feed flow and the cooling flow as a function of the internal resistance measurement of the elementary module.

(51) FIG. 7 schematically shows a fuel cell 250 including six elementary modules 5a-f stacked in a stacking direction D.sub.E, each elementary module being thin and extending in a longitudinal plane P normal to the stacking direction.

(52) The elementary modules of the fuel cell are placed head to tail in pairs as in the example of FIG. 6.

(53) The fuel cell of FIG. 7 is in the general form of a right slab having four side faces 280a-d on which emerge the inlets and outlets of the various cathode feed channels and cooling channels. In the example of FIG. 7, each cathode feed channel, respectively, each cooling channel has an inlet aperture 290a-c, respectively, 295a-d emerging on a side face facing a cathode feed fan 300, respectively, a cooling fan 305, and has outlet apertures 310a-c, respectively, 315a-d emerging on each of the other three side faces of the cell.

(54) In the example of FIG. 7, one or more cathode feed fans 300 are placed facing a side face 280b perpendicular to another side face 280a towards which one or more cooling fans 305 are placed facing. Thus, the cathode feed flows O, on the one hand, and the cooling flows R, on the other hand, flow in the respective channels in substantially perpendicular directions.

(55) Thus, although each cathode feed channel and each cooling channel have apertures on the four side faces 280a-d of the cell, interactions with harmful consequences for the functioning of the fuel cell, between cathode feed flows and cooling flows, are limited.

(56) The fuel cell of FIG. 8 is an improved and preferred embodiment of the fuel cell of FIG. 7, in which, for each cathode feed channel, respectively, each cooling channel, the apertures formed on the faces perpendicular to those on which is formed the inlet aperture of said channel are closed by means of side walls. Thus, the flow of the cathode feed flow, respectively, of the cooling flow takes place in the direction of the outlet aperture 310, respectively, 315 emerging on the side face of the cell opposite the side face on which emerges the inlet aperture 290, respectively, 295. In this way, the cathode feed flows and cooling flows flow in perpendicular directions and at different heights in the stacking direction and do not interact. Such an arrangement promotes the functioning of the fuel cell over an extended operating temperature range.

(57) For example, to obtain the cell illustrated in FIG. 8, the side apertures of each cathode feed channel formed on one, or even on the two, side faces of the cell of FIG. 5, perpendicular to the side face on which is formed the inlet aperture for the cathode feed flow, may be closed so as to prevent the outlet of said flow, for example by means of masks referenced 320a-c between the dotted lines, for example made of polymer, notably formed from foam. Moreover, the side apertures of each cooling channel formed on one, or even on the two, side faces of the cell of FIG. 7, perpendicular to the side face on which is formed the inlet aperture for the cooling flow, may be closed so as to prevent the outlet of said flow, for example by means of masks referenced 325a-c between the dotted lines, for example made of polymer, notably formed from foam.

(58) In this way, the cathode feed flows and cooling flows flow in perpendicular directions and do not interfere with each other.

(59) In the example of FIG. 8, two consecutive elementary modules are placed head to tail. In a variant not shown, two consecutive elementary modules may be placed such that the anode block of the first elementary module is facing the cathode block of the second elementary module. Preferably then, in order to separate the cathode feed flow for feeding said cathode, from the cooling flow, a solid separating plate extending in a longitudinal direction is placed between the two consecutive elementary modules.

(60) Moreover, the stack of FIG. 8 may be obtained by placing two cross braces between two consecutive elementary modules. The cross braces are, for example, solid bars. They are spaced apart from each other so as to form the side walls of a cathode feed channel or of a cooling channel.

(61) The fuel cell of FIG. 9 differs from the fuel cell of FIG. 8 in that each module has a length L at least twice as long as the width 1. In order to ensure optimum cooling of the elementary modules, several fans are placed in the longitudinal direction X facing the side face 280 on which emerge the apertures 295a-d of the cooling channels. The discs 330.sub.1-6 schematically indicate the portion of the side face onto which is directed the cooling flow.

(62) Finally, none of the elementary modules described in FIGS. 1 to 4 and none of the fuel cells illustrated in FIGS. 5 to 9 includes means for compressing the plurality of elementary modules, such as clamping plates connected by compression tie rods.

EXAMPLE

(63) A fuel cell, a photograph of which is shown in FIG. 10, is formed by a stack of 12 elementary modules, each in the form of a thin right slab with a length of 117 mm, a width of 74 mm and a thickness of 2 mm. This fuel cell is configured to oxidize dihydrogen as fuel with atmospheric dioxygen.

(64) Each elementary module weighs 8 g and is capable of generating an electric power of 8 W. Two consecutive elementary modules are placed head to tail in the stacking direction and are spaced 1.2 mm apart, by means of a spacer formed by foam bars, the opposite faces of which, each in contact with one of said two consecutive modules, are covered with adhesive. The stack is in the form of a right slab, with a length of 117 mm, a width of 74 mm and a thickness of 45 mm.

(65) The fuel cell has a volume of 0.4 liter and a mass of less than 150 g. It is capable of generating an electric power of 100 W and has a power density per unit mass of 0.67 W.g.sup.−1. It is moreover suitable for generating electrical energy over a temperature range of between −20° C. and 50° C. The fuel cell has an internal resistance of 175 mΩ.cm.sup.2, similar to that of a cell of the prior art including end clamping plates and having a lower power density per unit mass for the same generated power. This internal resistance value indicates that the collection of electrons and the electrical connection of the elementary modules is of good quality.

(66) Moreover, the pressure resistance measurements indicate that the fuel cell can withstand a maximum dihydrogen pressure of 3 bar in the anode chamber of each elementary module. In addition, as regards the leaktightness of the anode chamber, the measurements of leaktightness by infiltration of helium indicate that the rate of leakage is low, less than 0.1 cm.sup.3/min

(67) For comparative purposes, the performance qualities of the present fuel cell may be compared with a fuel cell formed from a stack of modules compressed by end plates, sold by the company Horizon FC. This cell functions within a lower temperature range of between 0° C. and 40° C. and is capable of generating a power of 200 W. However, it has a mass of 470 g and thus a low power density per unit mass equal to 0.42 W.g.sup.−1 compared with the fuel cell of the invention.

(68) Needless to say, the invention is not limited to the embodiments and examples described above.

(69) For example, notably in the variant in which the cathode feed channel and/or the cooling channel have bent shapes, for example a coil or a plurality of parallel tubes, the cell may include a compressor, a distribution channel being connected to the compressor, the compressor being configured to distribute a cathode feed flow and/or a cooling flow at the inlet of the cathode feed channel and/or of the cooling channel, respectively.

(70) Moreover, preferably, the cooling flow may include a heat transfer fluid other than air, for example a liquid, for example water or an oil.

(71) Moreover, the fuel is not limited to dihydrogen. It may also be an alkane chosen, for example, from methane, propane, butane and mixtures thereof, or an alcohol in vapor form chosen, for example, from ethanol, methanol and mixtures thereof. The oxidant is not limited to dioxygen. It may also be a gas including dioxygen, for example air, or a mixture constituted of dioxygen and dinitrogen.

(72) Finally, the terms “comprising a”, “containing a” and “including a” are understood as equivalently meaning, respectively, “comprising at least one”, “containing at least one” and “including at least one”.