Microsupercapacitors (with footprints from -mm up to -cm scale) have attracted attention for use as electrochemical energy storage devices to power wearables, IoT, and other small microsystems due to their high power density, excellent charge/discharge reversibility, and long cycle stability. Additive fabrication, with its spatial accuracy and versatile material manipulation capabilities will facilitate easy integration of these devices into a range of ubiquitous microsystem platforms.
This thesis demonstrates the additive fabrication of hybrid microsupercapacitors, which simultaneously, benefit from electrical double-layer capacitance (EDLC) and pseudocapacitance charge storage mechanisms. We have been able to elucidate the charge storage mechanism contributions of the microsupercapacitors, which are found to be dependent on the composition of the electrode and electrolytes. For the first time, this thesis reports the complete integration of such a microsupercapacitor through additive fabrication, including all component layers and encapsulation. We report on several novel materials, including electrodes based on edge-oxide graphene oxide (EOGO)/Cerium Oxide nanocomposites) and electrolytes based on (poly (ethylene glycol) diacrylate (PEGDA) + LiCl + lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). Our results show that, through optimization of all component structures within a microsupercapacitor, it is possible to realize unprecedented levels of performance. We systematically study the dimensional scaling of the microsupercapacitors in the sub-mm3 range and investigate how this scaling affects the performance of the microsupercapacitors.
The research outcomes of this thesis include realization of the smallest microsupercapacitors that are fully additively fabricated reported to date, with the highest levels of observed performance. We report on scaling behavior in these devices for the first time as well. Thus, this thesis provides important steps towards realization of additive fabrication of high-performance microsupercapacitors for embedded energy applications.