Method for the production of an electrochemical cell
The present invention relates to a new method for the production of electrochemical cells, in particular individual cells for fuel cells and stacks, in which the individual components of a membrane electrode assembly are compressed and bonded by use of ultrasonic waves and the absence of any further additional heating. The method according to the invention allows faster cycles during the lamination of the membrane electrode assemblies.
1. A method for the production of an individual electrochemical cell, wherein said electrochemical cell comprises
(i) at least one proton-conducting polymer electrolyte membrane matrix that includes an acid which is not covalently bonded to the polymer,
(ii) at least one electrically conductive gas diffusion layer on each side of the proton-conducting polymer electrolyte membrane matrix,
(iii) at least one catalyst layer arranged
(a) on both sides of the proton-conducting polymer electrolyte membrane matrix or
(b) on each side of the electrically conductive gas diffusion layers facing towards the proton-conducting polymer electrolyte membrane matrix, and
(iv) optionally a first subgasket film frame which overlaps (a) the outer peripheral area of the electrically conductive gas diffusion layer and (b) the outer peripheral area of the proton-conducting polymer electrolyte membrane matrix on the anode side and a second subgasket film frame which overlaps (a) the outer peripheral area of the electrically conductive gas diffusion layer and (b) the outer peripheral area of the proton-conducting polymer electrolyte membrane matrix on the cathode side, said first subgasket film frame and said second subgasket film frame extending beyond the proton-conducting polymer electrolyte membrane matrix and beyond the electrically conductive gas diffusion layers, said first subgasket film frame and said second subgasket film frame further being in flat contact with each other,
said method comprising:
a) supplying and depositing:
(i) a gas diffusion layer or
(ii) a gas diffusion layer which has at least one catalyst layer on that side facing upwards
and depositing the gas diffusion layer on an anvil, and
b) supplying and depositing:
(i) a proton-conducting polymer electrolyte membrane matrix on the surface of the gas diffusion layer having a catalyst layer facing upward or
(ii) a catalyst coated proton-conducting polymer electrolyte membrane matrix on the surface of the gas diffusion layer, the catalyst coated side of the membrane matrix facing towards the gas diffusion layer, and
c) supplying and depositing:
(i) a second gas diffusion layer if the proton-conducting polymer electrolyte membrane matrix is catalyst coated or
(ii) a second gas diffusion layer which has at least one catalyst layer on that side facing towards the proton-conducting polymer electrolyte membrane matrix, and
d) compressing the components obtained in accordance with step a), b) and c) up to a preset pressure or up to a preset compression, and
bonding the proton-conducting polymer electrolyte membrane matrix to the gas diffusion layers during the compression in step d) or subsequently after the compression while the components are still in the compressed state, with ultrasonic waves having an energy flux from 0.1 J/mm 2 to 1.5 J/mm2 to heat the gas diffusion layers, and the proton-conducting polymer electrolyte membrane matrix, to an interfacial temperature of less than the melting point of the layers and the electrolyte membrane matrix.
2. The method of claim 1 , wherein the individual electrochemical cell is an individual membrane electrode assembly for use in fuel cells.
3. The method of claim 1 , wherein the compression in step d) no additional heating is performed in step d) other than the heat provided by the ultrasonic waves.
4. The method of claim 1 , wherein the gas diffusion layer is coated with a catalyst layer.
5. The method of claim 1 , wherein the proton-conducting polymer electrolyte membrane matrix is coated with a catalyst layer.
6. The method of claim 1 , wherein the first subgasket film frame is provided between step a) and step b) and the second subgasket film frame is provided between step b) and step c).
7. The method of claim 1 , wherein the assembling described in steps a) to c) is performed separately and on any surface not limited to an anvil and the assembled, non-laminated, layered structure is placed on the anvil for compression and bonding in step d).
8. A method for the production of an individual electrochemical cell, wherein said electrochemical cell comprises
(i) at least one proton-conducting polymer electrolyte membrane that includes acid groups which are covalently bonded to a polymer,
(ii) at least one electrically conductive gas diffusion layer on each side of the proton-conducting polymer electrolyte membrane,
(iii) at least one catalyst layer arranged
(a) on both sides of the proton-conducting polymer electrolyte membrane or
(b) on each side of the electrically conductive gas diffusion layers facing towards the proton-conducting polymer electrolyte membrane, and
(iv) optionally a first subgasket film frame which overlaps (a) the outer peripheral area of the electrically conductive gas diffusion layer and (b) the outer peripheral area of the proton-conducting polymer electrolyte membrane on the anode side and a second subgasket film frame which overlaps (a) the outer peripheral area of the electrically conductive gas diffusion layer and (b) the outer peripheral area of the proton-conducting polymer electrolyte membrane on the cathode side, said first subgasket film frame and said second subgasket film frame extending beyond the proton-conducting polymer electrolyte membrane and beyond the electrically conductive gas diffusion layers, said first subgasket film frame and said second subgasket film frame further being in flat contact with each other,
said method comprising:
a) supplying and depositing:
(i) a gas diffusion layer or
(ii) a gas diffusion layer which has at least one catalyst layer on that side facing upwards
and depositing the gas diffusion layer on an anvil, and
b) supplying and depositing:
(i) a proton-conducting polymer electrolyte membrane on the surface of the gas diffusion layer having a catalyst layer facing upward or
(ii) a catalyst coated proton-conducting polymer electrolyte membrane on the surface of the gas diffusion layer, the catalyst coated side of the membrane facing towards the gas diffusion layer, and
c) supplying and depositing:
(i) a second gas diffusion layer if the proton-conducting polymer electrolyte membrane is catalyst coated or
(ii) a second gas diffusion layer which has at least one catalyst layer on that side facing towards the proton-conducting polymer electrolyte membrane, and
d) compressing the components obtained in accordance with step a), b) and c) up to a preset pressure or up to a preset compression, and
bonding the proton-conducting polymer electrolyte membrane to the gas diffusion layers during the compression in step d) or subsequently after the compression while the components are still in the compressed state, with ultrasonic waves having an energy flux from 0.5 J/mm 2 to 0.7 J/mm2 to heat the gas diffusion layers, and the proton-conducting polymer electrolyte membrane, to an interfacial temperature of less than the melting point of the layers and the electrolyte membrane.
9. The method of claim 8 , wherein the polymer electrolyte membrane comprises fluorinated or perfluorinated polymer having covalently bonded sulphonic acid and/or phosphonic acid groups.
10. The method of claim 1 , wherein the polymer electrolyte membrane comprises an alkaline polymer.
11. The method of claim 10 , wherein the alkaline polymer contains at least one nitrogen atom in a repeating unit of the polymer.
12. The method of claim 1 , wherein the preset compression is from 10 to 60%.
13. The method of claim 1 , wherein the preset compression in step d) is achieved by using one or more shims placed between pressure plates, or by path-control of pressure plates.
14. The method of claim 1 , wherein the ultrasonic waves have a vertical oscillation between 10 and 75 microns in amplitude, and a frequency of 15-20 kHz.
15. The method of claim 1 , wherein the preset pressure or preset compression used in step d) for polymer electrolyte membrane comprising an alkaline polymer is from 0.2/mm 2 to 1.0 N/mm 2 .
16. The method of claim 8 , wherein the preset pressure or preset compression used in step d) for polymer electrolyte membrane comprising fluorinated or perfluorinated polymer having covalently bonded sulphonic acid and/or phosphonic acid groups is from 2.0 N/mm 2 to 5.0 N/mm 2 .
17. The method of claim 1 , wherein the energy flux is from 0.2 J/mm 2 to 1.2 J/mm 2 .
18. The method of claim 1 , wherein the ultrasonic waves are applied by a horn.
19. The method of claim 15 , wherein the ultrasonic bonding process includes use of a horn and/or anvil with a knurled surface.
20. The method of claim 19 , wherein the horn and the anvil have female knurls on the surface.
21. The method of claim 19 , wherein the anvil has a support which is located between the anvil and a machine base, said support being compliant.
22. The method of claim 19 , wherein the anvil is actively cooled by a coolant.
23. The method of claim 21 , wherein the support is actively cooled by a coolant.
24. The method of claim 1 , wherein the preset compression includes a compression speed of 20 to 200 μm/s for a membrane electrode assembly with a thickness of 1 mm.
25. The method of claim 1 , wherein the acid is an inorganic Lewis or Bronsted acid.
26. The method of claim 1 , wherein the acid is selected from phosphoric acid, polyphosphoric acid or mixtures thereof.
27. The method of claim 6 , wherein the first and the second subgasket film frame is a fluoropolymer selected from poly(tetrafluoroethylene-co-hexafluoropropylene) FEP, polyvinylidine fluoride PVDF, perfluoroalkoxy polymer PFA, or poly(tetrafluoroethylene-co-perfluoro(methylvinyl ether) MFA.
28. The method of claim 6 , wherein the first and the second subgasket film frame is a polyimide.