Session 18: Printing Technology
Flexible and Printable Li-ion Batteries
Thursday, June 22, 2017
8:45 AM - 9:05 AM
Printable energy storage facilitates innovation in the manufacture of flexible electronics in that it will enable direct integration of a power source into a device during the fabrication process. To enable such advancement, we demonstrate a universal approach to develop free-standing and flexible electrodes for printable, high-performance Li-ion batteries. This simple approach utilizes a well-dispersed and directly castable mixture of active material, carbon nanofibers, and polymer to make printable electrode inks. Free-standing electrodes of three common Li-ion battery active materials (Li4Ti5O12, LiFePO4, LiCoO2) are prepared, each showing excellent cyclability and rate capability. To complement this component, we demonstrate a dry phase inversion technique representing a step toward controlled, printed porosity in Li-ion battery electrolytes. Our approach utilizes a solvent/weak non-solvent system to generate porosity within a polymer matrix and a ceramic Al2O3 filler to fine tune the pore size distribution to impart desirable tortuosity within the membrane. In other words, no additional processing steps such as coagulation baths, stretching, or etching are required for full functionality of our electrolyte, which makes it a viable candidate to enable completely additively manufactured Li-ion batteries. Compared to commercial polyolefin separators, these electrolytes demonstrate comparable high rate electrochemical performance (e.g. 5C), but possess better wetting characteristics and enhanced thermal stability. Finally, sequentially printing this electrolyte ink over a composite electrode via a direct write extrusion technique has been demonstrated while maintaining expected functionality in both layers. These ink formulations are an enabling step towards completely printed batteries and could allow direct integration of a flexible power source in restricted device areas or on non-planar surfaces.
Ryan Kohlmeyer is currently a Research Scientist in the Air Force Research Laboratory (AFRL) Soft Matter Materials Branch. Dr. Kohlmeyer joined AFRL in 2013 under the direction of Dr. Michael Durstock and was awarded a National Research Council Postdoctoral Fellowship. He has worked extensively on the development of next generation Li-ion batteries with topics ranging from flexible/creasable batteries, 3D-printed batteries, and high temperature batteries. Previously, he earned a B.S. in Chemistry from the University of Wisconsin-Whitewater and a Ph.D. in Chemistry from the University of Wisconsin-Milwaukee.
Air Force Research Laboratory