This document discusses using focused flow co-extrusion to print battery electrodes. It can print microscopic widths of multiple materials through a single nozzle. This technique has been used to print gridlines for solar cells, increasing their efficiency by 1%. It could also print battery electrodes by extruding many thin lines next to each other to form a layer, rather than coating. This would offer advantages like enhancing ionic/electronic conduction, increasing electrode thickness and storage density, reducing shorting and production time.

1. Focused flow co-extrusionfor battery electrode manufacture Scott Elrod, Vice President, Palo Alto Research Center elrod@parc.com, (650) 812-5060

2. Silver Ink Sacrificial material Fluid Flow in 1 Nozzle It works by focusing a ink flows, using a multiple materials, to get microscopic widths Solar cell gridline application: The “Outer Material” shapes theinner (e.g. silver) line PARC | 2

3. The technology has already been developed for printing gridlines in PV cells By getting more height on the gridlines, they can be made thinner compared to screen printing, thus cover less of the surface area of the PV cell Using the technique has shown a 1% increase in absolute efficiency of PV cells (i.e. around 6% relative), for tests done by a PV Manufacturer in the DOE Solar America Initiative Screen printed front side metallization Co-extruded front-side metallization PARC | 3

4. Electrode Extrusion printed gridlines: Extrusion printed electrode: 100 µm Battery electrodes are made by coating a layer of electrode material (about 10-100 µm thick) onto a metal sheet: The coating could possibly be replaced by extrusion printing many ‘lines’ next to each other to form a layer: Reduce distance between lines Metal sheet Coating machine Another potential use of the technology is for making battery electrode PARC | 4

5. Advantages for Advanced Battery Electrodes Enhance ionic conduction path Higher power/energy density Enhance electronic conduction path Higher power/energy density Increase electrode thickness Higher volumetric storage density Reduce yield loss due to shorting Reduce separator cost Reduce production time Less winding, less coated area Porous regions to accommodate cathodic byproducts Relevant to Lithium/Air and Lithium/Sulfur batteries Interdigitated – Multi material electrode 5 PARC | 5