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MEA Manufacturing Technology

Scale-up
Methods for manufacturing functional layer systems (membrane electrode assemblies, or MEAs) are usually developed on the laboratory scale. New ideas and methods can thus be tested using small amounts of material on the gram or milliliter scale. Whenever a method seems promising, material volumes of up to several kilograms are needed for larger-scale experiments, i.e. pilot plant tests. Often the laboratory methods cannot be used for these large-scale tests because the materials exhibit different behaviors. For example, a laboratory-manufactured catalyst–solvent dispersion can be processed within minutes into a layer of several square centimeters. Manufacturing a layer of several square meters, in contrast, can take well over an hour. Thus, the time scale for manufacturing materials in a laboratory is very different to a technical facility. A dispersion that is only stable for 10 minutes may be suitable for laboratory applications, but not for larger-scale approaches. The issue of scale-up, i.e. adapting MEA manufacturing methods to larger (temporal and spatial) scales, is thus relevant for several activities at IEK-14, including manufacturing polymer electrolyte electrolyzers and fuel cells.

Maßstabsübertragung für die Herstellung von Membran-Elektroden-EinheitenMaßstabsübertragung für die Herstellung von Membran-Elektroden-Einheiten


Correlation between process parameters and MEA properties
Scale-up requires knowledge of the correlation between the material, process, and performance parameters of the MEA produced. To identify scale-up rules, it must be known which of these parameters influence the MEA performance. For this purpose, extensive process analytics are being developed at IEK-14 that focus on the following process steps:

Prozessschritte für die Herstellung einer MEA über das TransferverfahrenProzessschritte für die Herstellung einer MEA über das Transferverfahren


The structure formed during this manufacturing process is decisive for the electrochemical performance of the MEA because it has a large influence on the physico-chemical processes in the electrode.

Korrelation zwischen Struktur und Leistungsfähigkeit bei einer Polymer-Elektrolyt-Membran WasserelektrolyseKorrelation zwischen Struktur und Leistungsfähigkeit bei einer Polymer-Elektrolyt-Membran Wasserelektrolyse


Structure formation processes
The structure in the electrodes results from factors such as the rheological structure in the dispersion used for manufacturing and its behavior during the coating and drying processes.

Rheology of the dispersion
Depending on the rheological structure in the dispersion and the free surface energy of the substrate, the coating process leads to different changes in the dispersion. Using rheological and tensiometric investigations, these influences on the dispersion can be clarified.

Analysemethoden für die Aufklärung der DispersionsstrukturAnalysemethoden für die Aufklärung der Dispersionsstruktur


Drying the dispersion
During the drying process, the solvents vaporize at different drying rates, which causes the solids in the dispersion to agglomerate to porous structures. This layer formation process is closely interconnected to the time-dependent progression of the chemical composition of the wet layer all the way to the dry electrode. By adapting thermodynamic parameters, this progression can be controlled so that crack formation can be influenced, for example. To analyze these processes, a spectroscopy-based measurement technique was developed at IEK-14, which simultaneously enables the reproducibility of the electrode manufacturing to be examined.

Analyse der Trocknungsverlaufskurven in Abhängigkeit von der DispersionszusammensetzungAnalyse der Trocknungsverlaufskurven in Abhängigkeit von der Dispersionszusammensetzung


The analyses of the correlation between dispersion composition, rheology and tensiometry of the dispersion, and the dispersion drying behavior are priorities that are thoroughly investigated at IEK-14.


Understanding structure formation processes is the key to identifying scale-up rules. This permits the transfer of the results from laboratory development to large-scale production. Furthermore, these insights are used to develop new manufacturing methods to make the production of MEAs simpler, faster, and therefore cheaper. For example, an MEA manufacturing method was developed at IEK-14 that requires fewer process steps than conventional production methods while at the same time producing less waste. This “completely coated MEA” method (CC-MEA) involves producing the two electrode layers and the membrane solely via slot-nozzle processes, which dispenses with the need for a separate membrane and the assembly step.

Prozessschritte für die Herstellung einer komplett gegossenen CC-MEAProzessschritte für die Herstellung einer komplett gegossenen CC-MEA


References:

A. Stähler, M. Stähler, F. Scheepers, M. Carmo, D. Stolten
Reusability of decal substrates for the fabrication of catalyst coated membranes
Int. J. Adhesion and Adhesives (2019)
https://doi.org/10.1016/j.ijadhadh.2019.102473

 F. Scheepers, A. Stähler, I. Friedrich, M. Stähler, M. Carmo, W. Lehnert, D. Stolten
Steering and In-situ Monitoring of Drying Phenomena during Film Fabrication
J. Coat. Technol. 16 (2019) 1213-1221
https://doi.org/10.1007/s11998-019-00206-5

 M. Stähler, A. Stähler, F. Scheepers, M. Carmo, D. Stolten
A completely slot die coated membrane electrode Assembly
Int. J. Hydrogen Energy 44 (2019 ) 7053-7058
https://doi.org/10.1016/j.ijhydene.2019.02.016

 F. Scheepers, A. Stähler, M. Stähler, M. Carmo, W. Lehnert, D. Stolten
Layer Formation from Polymer Carbon-Black Dispersions
Coatings 8 (2018) 450
 https://doi.org/10.3390/coatings8120450

A. Burdzik, M. Stähler, M. Carmo, D. Stolten
Impact of reference values used for surface free energy determination: An uncertainty analysis
Int. J. Adhesion and Adhesives 82 (2018) 1–7
https://doi.org/10.1016/j.ijadhadh.2017.12.002

F. Scheepers, A. Stähler, M. Stähler, M. Carmo, W. Lehnert, D. Stolten
A New Setup for the Quantitative Analysis of Drying by the use of gas phase FTIR-spectroscopy
Review of Scientific Instruments 89 (8), (2018) 083102
https://doi.org/10.1063/1.5036817

A. Burdzik , M. Stähler, I. Friedrich, M. Carmo, D. Stolten
Homogeneity analysis of square meter-sized electrodes for PEM electrolysis and PEM fuel cells
J. Coat. Technol. Res. 15 (2018) 1423-1432
https://doi.org/10.1007/s11998-018-0074-3

 M. Stähler, I. Friedrich
Statistical investigations of basis weight and thickness distribution of continuously produced fuel cell electrode
J. Power Sources 242 (2013) 425-437
ttps://doi.org/10.1016/j.jpowsour.2013.05.073