PARC, a Xerox company, has launched a project with the US Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) under the 2012 Open Funding Opportunity. (Earlier post.) The Printed Integral Battery Project will leverage a PARC invented co-extrusion (CoEx) technology (earlier post) to demonstrate a lithium-ion battery manufacturing process that deposits the entire functional battery in a single pass.
The conventional lithium-ion battery manufacturing process requires that the two electrodes of a battery be made in two separate steps, and then combined together in a third step—each step adding cost that contributes to the high price of the final product. PARC’s Printed Integral Battery deposits the entire battery cell—cathode, separator, anode—in one single pass.
CoEx deposits thick films of pastes of disimilar functional materials side-by-side at high speed. For batteries, these functional material pastes would be the electrode active materials. This technique can directly deposit an interdigitated structure as small as 5μm in width with high aspect ratios.
By changing the print head geometry, the relative thickness, width, and length of the deposited structure can easily be modified. A post-deposition processing step dries and sinters the deposit into the final electrode structure.
Current batteries are typically optimized either for power or for energy density. With typical monolithic battery electrodes, tuning the battery for increased power requires greater conductivity, thus resulting in less available volume for energy storage.
However, structuring an electrode with conductive regions that are interleaved with storage regions can result in shortened ion flow paths without compromising capacity. PARC’s CoEx technique can fabricate such structures at high speed. The relative dimensions can be changed to achieve optimal performance in terms of both power and energy, customizing the benefits for batteries based on their specific application.
CoEx can be applied to battery chemistries in which electrodes are coated on metal foils from a slurry; its process speed, coating width, and reliability are equivalent to those of conventional battery coating equipment.
Single pass printing of the three layers will reduce costs in deposition, calendaring, laminating, and yield loss. Because it inherently incorporates CoEx technology, the structured electrodes can simultaneously increase energy density, or deliver equivalent energy density with less active material to reduce the overall cost even further.
PARC suggests that using CoEx manufacturing could result in up to a 30% increase in energy density; up to a 30% improvement in power density; and up to a 30% reduction in cost ($/kWh).
PARC has already fabricated LiCoO2 half cells using CoEx and measured improved energy and power; it is also conducting performance modeling with different battery chemistries, including alkaline, LixMn2O4, LiCoO2, Zn-air, and Ag-Zn. As an early example, the modeling of a CoEx structured cathode in a Li-ion battery resulted in a 10-20% improvement in energy density at the same power output. Applying the technique to anodes, additional improvements can be expected.
The ARPA-E-funded Printed Integral Battery Project will be executed with partner Lawrence Berkeley National Laboratory. Over the next twelve months, the team will develop the high-viscosity battery material inks capable of co-extrusion at high-speed; the three-dimensional print-head configuration that simultaneously prints structured layers of cathode, separator, and anode; and the process details to ensure a reliable and high-yield manufacturing capability.
PARC will then print integral batteries and document performance to help foster investment and adoption by battery manufacturers.
PARC originally developed this technique to print metal gridlines with high aspect ratios on solar cells. Implementing CoEx for solar, PARC has partnered with a solar company for mass manufacturing of silicon solar cell gridlines, and is currently seeking partnerships with battery manufacturers to use CoEx as a drop-in replacement for conventional electrode deposition equipment that can improve the performance of current battery chemistries by as much as 30%.
The Printed Integral Battery Project is part of a portfolio of research within the PARC Energy Technology Program aimed at developing practical solutions to make clean and abundant energy available across a wide range of applications. This includes a focus on improving energy storage for EVs, consumer electronics, and electric grid support through better ways to make, monitor, and manage batteries.