At 'Printed Electronics USA,' EDI to focus on specialised coating and film capabilities already proven in solar and battery uses
Multi-layer flexible or thin-film structures will play a central role in coming generations of both photovoltaic (PV) and metal-ion battery technologies.
At Stand 55 during Printed Electronics USA / Photovoltaics USA, Extrusion Dies Industries, LLC (EDI) will highlight film and coating die systems that it has developed for such structures—systems already applied successfully in both solar and battery applications.
Dies are the shaping tools used by manufacturers to transform molten plastic into film or apply functional coatings, such as fluidized anode and cathode materials, onto film or other substrates.
"Because a flexible PV or battery structure involves many film layers and coating applications, advanced die technologies are essential for minimizing costs and ensuring consistent, reliable, and safe end-product performance," said Mark D. Miller, manager of EDI's New Development Group. "Particularly important are coating technologies for 'printing' electrodes onto continuous substrates, making possible the reel-to-reel production that is the key to economies of scale."
As an example of die systems developed by EDI specifically for electrode printing, Miller cited slot dies designed to carry out two-sided coating. In this technique, two dies simultaneously apply anode and cathode slurries to both sides of a substrate. A variation of this system is "lane coating," which applies continuous coated lanes in the machine direction, alternating with uncoated lanes. Lane coating has been employed successfully in applications of up to 48 separate lanes, each 20 mm wide and separate from other lanes by 10 mm gaps. The coating fluid has been applied in register on both sides—critical for preventing unbalanced energy densities.
EDI's work on lithium-ion batteries began in 2002 with the first of four U.S. Department of Defense contracts for optimizing production of batteries for devices carried by soldiers. The company built and operated a pilot coating line specifically for battery development. Since then EDI has provided film and coating die technology to producers of batteries for a range of consumer electronics applications and is now also working with suppliers to the automotive industry.
At the same time, this coating technology proved valuable for PV applications. EDI supplies slot coating die systems to manufacturers of rigid, discrete glass-panel solar systems and is working with companies that are developing flexible, continuous-web systems
Advantages of slot die coating over conventional electrode printing
A slot die is comprised of two stainless steel body sections that enclose a precision-engineered flow channel, or manifold, that has been machined into one of the sections. A fluid delivery system or pump meters the fluid to be applied to the substrate into the manifold. The fluid flows through the manifold and exits at a slit-like opening between "lips" formed by the two body sections. The substrate to be coated is a film or foil that moves from reel to reel in a continuous strip.
Compared with vacuum deposition, spray coating, ink jet printing, and roll coating, slot die coating provides higher production speeds, better control over coat weight and distribution, and more effective raw material management. Unlike spray and roll coating, slot die coating is a closed system with metered fluid delivery, preventing waste, contamination of the fluid, and contamination of the factory environment
EDI supplies two types of slot die coating systems:
Ultracoat adjustable-lip dies apply fluid directly to a substrate, using the die lip to "wipe" the coating fluid onto it. Coating thicknesses as low as 0.00075 inch (18 microns) are achievable. The adjustable lip is important for applying electrode slurries, since slurry viscosity changes over the course of a production run and the die needs to be adjusted accordingly.
Liberty fixed-lip dies are used for "draw coating," which involves allowing the fluid to traverse a short distance between the lips of the die and the substrate, and using the rotation of the backing roll to draw the fluid down to very low thickness. Coating thicknesses achieved can be as low as 0.00004 inch (1 micron). Besides its capability for very thin coatings, draw coating is better suited for the optically clear applications required for many flexible PV layer components.
EXTRUSION DIES INDUSTRIES, LLC
EDI is a leading international supplier of flat dies for sheet, film, extrusion coating, fluid coating, and pelletizing.
The company designs and manufactures dies, feedblocks, deckling systems, vacuum boxes, and related equipment.
Its subsidiaries include EDI GmbH in Reichshof-Wehnrath, Germany, and EDI China in Shanghai. In the U.S.A., Germany, and China, EDI operates facilities dedicated to reworking its own dies and those built by other suppliers, and it has licensed a fourth rework facility in Japan.
Headquartered in Chippewa Falls, Wisconsin, U.S.A., EDI is focused on supplying the global market.