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Printed Electronics World
Posted on May 24, 2011 by  & 

Coextrusion printing of battery and fuel cell electrodes

PARC has demonstrated a manufacturing technology—co-extrusion printing—for depositing thick films of densely interdigitated functional materials. This is a promising method for making advanced battery and fuel cell electrodes, particularly air cathodes.
 
Metal air batteries and fuel cells have the potential to surpass the storage capability (i.e., energy density) of lithium ion batteries. Successful implementation depends on developing air cathodes that support the power density, particularly for vehicle applications. Toward this end, we introduce a novel, non-contact, high-throughput, mask-less technology for direct-printing high aspect ratio functional materials onto substrates of technological interest.
 
The current density in an air-breathing electrode is proportional to the amount of electro-catalytic surface area that is exposed to air. The PARC technology provides a directed-assembly printing method for producing a greater proportion of this "three-phase boundary" than conventional electrode manufacturing methods.
  • Up to 10x the air-breathing surface area of conventional electrodes.
The electrode material coating method works like a slot coater that extrudes pastes in a ribbon of interdigitated stripes or functional materials. These functional material pastes can contain hydrophobic air transport materials such as Teflon interleaved with hydrophilic electro-catalyst material. A post deposition processing step dries and sinters the deposit into the final electrode structure. The stripes can be as narrow as several microns wide and as tall as several hundred microns.
 
 
The first application of this technique has been for silver gridlines on the front surface of solar cells. Compared to screen-printed gridlines, the narrower and taller front gridlines created by this technique covered less solar cell surface area, resulting in increased absolute cell efficiency. The non-contact nature of the technology also increases the yield due to reduced breakage and supports cost reduction by enabling thinner wafers. The initial commercial application of this work is to provide a production-worthy drop-in alternative to screen printing to simultaneously increase solar cell yield and performance without requiring additional processing steps. A production prototype machine is currently under test at a customer site. To date an additional gain of up to 1% absolute cell efficiency and process speeds up to 200 mm/sec have been demonstrated.
 
For more attend Electric Vehicles Land Sea Air in June in Stuttgart, Germany. Never before has there been an opportunity in Europe for people in land, water and air electric vehicles and their components, infrastructure and test equipment to compare notes in one event. Delegates already signed up vary from Airbus, Hudson Power Sports and Hudson Yachts to Sony, the Bulgarian Electric Vehicle Association and Robert Bosch Venture Capital.
 
 
 
Source: PARC
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