Top-Down and Bottom-Up Fabrication of Key Components in Miniature Energy Storage Devices

The advent of miniature electronic devices demands power sources of commensurate form factors. This spurs the research of micro energy storage devices, e.g., 3D microbatteries. A 3D microbattery contains nonplanar microelectrodes with high aspect ratio and high surface area, separated by a nanoscale electrolyte. The device takes up a total volume as small as 10 mm3, allowing it to serve on a chip and to provide power in-situ. The marriage of nanotechnology and electrochemical energy storage makes microbattery research a fascinating field with both scientific excitement and application prospect. However, successful fabrication of well-functioned key components and the assembly of them require careful choice of both materials and processing technologies, which explains the rarity of reports on fully assembled 3D microbattery devices. In this Thesis, we exploited both top-down and bottom-up methods to produce nanostructured functional materials as either microelectrodes or nanoscale electrolytes. Project 1 introduces nanoimprinting as a promising strategy toward scalable fabrication of woodpile-like 3D microelectrodes out of well-dispersed TiO2 nanoparticles. Using sequential imprinting, we created electrode structures with different aspect ratios and correlated them to the improved charge storage capacity. One step forward, we applied imprinting to other electrode materials. In Project 2, we imprinted microelectrode using customized, ultrafine LiMn2O4 (LMO) and Li4Ti5O12 (LTO) nanoparticles. A dopamine-containing copolymer electrolyte was developed to enable the layer-by-layer assembly of microbattery full device. The synergistic effect of nanosized materials and micropatterning resulted in batteries with very high volumetric energy and power densities. Project 3 explores using vapor phase chemistry to deposit copolymer thin films onto 3D nanostructures and subsequently doping the neat dielectric films into “shrink-wrap” electrolytes. Correlations between deposition parameters, copolymer composition and the resultant dielectric and conducting properties were built. In the last project, we harnessed the self-assembly of bottlebrush block copolymers to template phenolic resin precursor and obtained nanoporous carbon electrodes that show promising performance in electrostatic double layer capacitors (EDLCs). By mixing electroactive Fe2O3 nanoparticles into the precursors, the electrodes become high-capacity lithium-ion battery anodes and more importantly, the precursor can be imprinted and undergo rapid photothermal curing. The combination of bottom-up assembly, top-down patterning and rapid curing makes them attractive for a variety of applications