From Striped Toothpaste to Lithium-Ion Batteries
PARC, an NCMS member company, is a name you might not recognize but really is someone you do know. Xerox’s Palo Alto Research Centre (PARC) has been responsible for many innovations that have impacted how we do business and how the information technology sector has developed. They are responsible for the computer mouse, GUI, icons, windows, Ethernet and the laser printer.
Today, they are as innovative as ever and now work with companies, government agencies and other partners providing R&D services, technology, expertise, best practices, and intellectual property management. Much like NCMS, PARC creates new business options and accelerates the time to market while reducing risk for our clients.
Everyone from automakers to manufacturers and even homeowners are looking for cost-effective and portable energy storage. But to become ubiquitous, the development of more efficient batteries at low cost is crucial for the growth of the electric vehicle market and generally portable storage. To date, given the limited space available within a battery cell, performance is typically optimized for either power or energy density.
PARC’s Hardware Systems Lab is addressing this manufacturing challenge through the development of a lithium-ion battery for an electric vehicle that is capable of holding 20% more energy than traditional designs. With typical monolithic battery electrodes, increased power requires greater conductivity, thereby resulting in less available volume for energy storage. By structuring an electrode with conductive regions that are interweaved with storage regions, ion flow paths can be shortened without compromising capacity.
This basic idea is understood but the challenge has been to building the regions small enough, about 100 microns across for the storage medium, and ten for the conductor. The cathode of a typical electric car’s battery would need tens of thousands of these interweaved channels. Making such intricate weave with the correct precision could really only been done with photolithography which is expensive not really suitable for high speed manufacturing.
Their inspiration for the solution? Striped toothpaste of all things. In their new battery the two materials are mixed with an organic material to form pastes and fed into a print head containing tiny channels and nozzles. PARC has developed CoEx, an innovative coextrusion printing technique where dissimilar materials can be deposited side by side at high speed. 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.
PARC originally developed this technique to print metal gridlines with high aspect ratios on solar cells. Silver paste is co-extruded with a material that burns off when the cell is heated. The result is a wire a mere 20 microns across, instead of 50 microns. Narrow wires cast smaller shadows, so more sunlight reaches the cell. PARC has now transferred the technology for solar cell metallization to pilot production with a leading PV manufacturer.
This week PARC launched the Printed Integral Battery Project with the U.S. Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E) to demonstrate a lithium-ion battery manufacturing process that deposits the entire functional battery, not just the cathode, in a single pass. The conventional lithium-ion battery manufacturing process requires that the two halves 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. This will require five pastes—two each for the cathode and the anode, plus a separator. PARC's CoEx technology allows multiple materials to be deposited simultaneously while still maintaining fine features in the finished product. This new method has the dual benefit on reducing cost while improving battery performance.
The ARPA-E project will be done in partnership with Lawrence Berkeley National Laboratory and will address the development of 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. 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 projects the benefit of the process to include up to 30% increase in energy density; up to 30% improvement in power density; up to 30% reduction in cost ($/kWh); technology that is transferrable to mass manufacturing, scalable to manufacture higher capacity batteries and applicable to most mature battery chemistries.
PARC is already looking for new manufacturing applications in the areas of fuel cells, ultracapacitors and even the traditional catalytic converters. Keep an eye on Co-extrusion because it just might become if not a household name, definitely production name.