Patent Application
20200091534
The present invention relates to a method for securing the layers of a fuel cell membranes assembly.
Proton exchange membrane fuel cells, known as PEMFCs, stand for “proton exchange membrane fuel cells” or “polymer electrolyte membrane fuel cells” and have particularly interesting compactness properties. Each cell includes a polymer electrolyte membrane that enables only the passage of protons and not the passage of electrons. The membrane is contacted with an anode on a first side and with a cathode on a second side to form a membrane/electrode assembly called MEA.
The above assembly is generally carried out by successive superposition of the different membranes and electrodes with an interposition of reinforcing membranes to support the assembly. In order to secure the different thicknesses together, it is possible to carry out a thermocompression operation of the assembly.
In practice, it can be seen that the superposition of the reinforcing membrane and the polymer electrolyte membrane can be difficult. Indeed, to carry out the assembling, it may be desirable to pre-assemble one of the first reinforcing membrane and the second reinforcing membrane with the polymer electrolyte membrane to facilitate the handling of the polymer electrolyte membrane and the centering of the different membranes with each other. However, it appears that the polymer electrolyte membrane is very sensitive to the humidity variations resulting from temperature variations, the pressure being constant
This invention first of all relates to a method for manufacturing a polymer electrolyte membrane/electrode assembly for fuel cells comprising the following steps:
According to the invention, the pre-assembling of the polymer electrolyte membrane is carried out under first temperature conditions and handled under second temperature and humidity conditions in which the membrane is capable of expansion. In this way, it can be ensured that the polymer electrolyte membrane does not contract as long as the pre-assembly is subjected to the second temperature and humidity conditions. In practice, when the pressure is the atmospheric pressure and the humidity of the air is constant, step c) is performed at a temperature T1 higher than the temperature T2 to which the pre-assembly is subjected when placed on a support.
This support can be that of a storage magazine for the reinforcing membrane polymer electrolyte membrane assembly or the static support of a press that is arranged opposite a piston of said press.
In the first case, it is thus possible to guarantee the flatness of the pre-assembly of the reinforcing membrane with the polymer electrolyte membrane, which makes it easier to grip this pre-assembly, particularly by a suction frame. In addition, the guarantee of the flatness of the pre-assembly makes it easier to stack the other layers of the polymer electrolyte membrane/electrode assembly one on top of the other.
In one particular embodiment of the invention, step d) may include the following steps:
According to yet another characteristic of the invention, steps (iii) and (iv) include the realization, for example using a laser beam, of a first closed welding contour of the polymer electrolyte membrane with the reinforcing membrane and a second closed welding contour of the polymer electrolyte membrane with the reinforcing membrane and cutting only the polymer electrolyte membrane, the second contour surrounding the first contour.
In another embodiment, steps iii) and iv) include the realization of a closed contour of the polymer electrolyte membrane welding with the reinforcing membrane and simultaneously cutting the polymer electrolyte membrane.
In a particular embodiment of the invention, the temperature of the first temperature and humidity conditions is 5 to 50° C. higher than the temperature of the second temperature and humidity conditions, preferably between 10 and 20° C., the humidity being substantially identical under the first and second conditions.
According to another characteristic, the method also includes the following steps:
The invention will be better understood and other details, characteristics and advantages of the invention will appear when reading the following description, which is given as a non-limiting example, with reference to the attached drawings.
First of all, reference is made to
It should be understood that in
Thus, the polymer electrolyte membrane 16 is completely fitted between the first 14 and second 18 reinforced membranes and thus insulates the polymer electrolyte membrane from the cooling liquid and pure gas passages. This type of assembly is known as “anti-wicking”. More precisely, the assembly presented in
The different layers, namely the first 14 and second 18 reinforcing membranes, the first 12 and second 20 electrodes and the polymer electrolyte membrane 16 can have a substantially rectangular shape. The openings 24 of the first 14 and second 18 reinforcing membranes can also be rectangular in shape. The polymer electrolyte membrane 16 has a larger surface area than the first electrode 12 and the second electrode 20.
As can be seen in
According to the invention, the polymer electrolyte membrane 16 is secured to the second reinforcing membrane 18 by means of the device 26 shown in
The welding and cutting means 48 arranged inside the box 36. These means 48 include an arm 50 movable in a plane parallel to the plane of the tray 40 which is movable along a vertical axis, i. e. perpendicular to the plane of movement of the arm 50. The arm 50 carries a laser 52 capable of emitting a beam towards the tray.
The method according to the invention includes the following steps: An operator places a reinforcing membrane, namely the second reinforcing membrane 14 on the plate 40. In a second step, the operator pulls on the reel strip in order to cover the opening 18a of the second reinforcing membrane 18. The suction means 44 are then put into operation in order to maintain the second reinforcing membrane 18 and the polymer electrolyte membrane 16 on the plate 40. In a subsequent step, the polymer electrolyte membrane 16 is cut into a substantially rectangular shape and attached to the second reinforcing membrane 18.
The polymer electrolyte membrane 16 is cut and attached to the second reinforcing membrane 18 using laser welding. First, the two layers are secured together by making a first closed contour 54 of the polymer electrolyte membrane 16 welding to the inner edge 18b of the second reinforcing membrane 18. In a second step, a second closed contour 56 of the polymer electrolyte membrane 16 welding is made on the inner edge 18b of the second reinforcing membrane 18, the second contour 58 surrounding the first contour 54. The power of laser when making the first welding contour 54 is such that it allows the polymer electrolyte membrane 16 to be secured to the second reinforcing membrane 18 without cutting it. The realization of the second contour 56 is sufficient to allow a welding of the polymer electrolytic membrane 16 on the second reinforcing membrane 18 while allowing a cutting of the electrolytic membrane 16 only, i. e. without cutting the second reinforcing membrane. It should be noted that a single closed contour 54 could also be used to weld the electrolyte membrane with the reinforcing membrane and cut the polymer electrolyte membrane simultaneously.
Inside the box 36, the polymer electrolyte membrane 16 and the second reinforcing membrane 18 are subjected to first conditions of temperature and humidity. For air with a substantially constant absolute humidity, it is possible to vary the relative humidity or degree of hygrometry by varying the temperature. For a closed air volume, the decrease in relative humidity is obtained by increasing the temperature. Thus, to vary the degree of humidity to which the polymer electrolyte membrane 16 is subjected, it is sufficient to vary the temperature. To this end, the temperature of the enclosure or box 36 and more particularly that of the plate is maintained at a temperature T1 higher than a temperature T2 at which the polymer electrolyte membrane will be handled together with the second reinforcing membrane 18 to which it is secured.
In a particular embodiment of the invention, the temperature of the first temperature and humidity conditions is 5 to 50° C. higher than the temperature of the second temperature and humidity conditions, preferably between 10 and 20° C., the humidity being substantially identical under the first and second conditions.
The realization of the polymer electrolyte membrane—second reinforcing membrane assembly at a temperature higher than that at which said assembly is then handled—allows the membrane when subjected to temperature T2 relative to its state at temperature T1. Thus, the polymer electrolyte membrane, which is highly sensitive to moisture variations, does not induce any stress on the second reinforcing membrane 18, which can thus be kept in a flat state for subsequent assembly with the first 12 and second 20 electrodes and the first reinforcing membrane 14.
For example, for reference ambient air with a relative humidity (RH) of 50% at 20° C., the housing can be regulated to a temperature of 35° C. In this case, the air is locally at 22% relative humidity. The thinness of the membranes (10-50 μm) makes it possible to consider that the temperature rise time of the polymer electrolyte membrane 16 and the water stabilisation time of the polymer electrolyte membrane 16 are less than the positioning and initialization time of the welding/cutting cycle.
At 35° C. 22% RH, the membrane initially at 20° C. 50% RH undergoes a thermal expansion of 0.5% and a “water” shrinkage of 7.8%, i.e. an overall shrinkage of 7.3%. After welding and cutting the membrane, the double layer thus formed is returned to ambient condition and the polymer electrolyte membrane 16 undergoes a reverse deformation (expansion) of 7.3%. Consequently, the membrane does not generate any stress on the reinforcement to which it is secured.
Similarly, the placement of the polymer electrolyte membrane 16 secured to the second reinforcing membrane 18 in the environment of the MEA machine, in particular on a static support of a press that is 25° C. and therefore at 38% RH, will cause a new deformation of the membrane but limited to:
Since the polymer electrolyte membrane 16 is expanded by 7.3%, a shrinkage of 3.2% will not generate any stress on the reinforcing membrane, which will therefore remain perfectly positioned on the press support. This reasoning also applies to the handling of the polymer electrolyte membrane 16—second reinforcing membrane 18 double layer which is easier to achieve with a suction frame when said double layer is perfectly flat.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1753913 | May 2017 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2018/051110 | 5/3/2018 | WO | 00 |
