Ionic liquids have received considerable attention as an alternative electrolyte for rechargeable battery systems. The goal of this investigation is to develop an understanding on the electrodeposition behavior of zinc within ionic liquid electrolytes and determine whether the unique properties of ionic liquids may allow for enhanced cyclability of the zinc electrode for rechargeable battery systems.

Three different analysis techniques are employed for the investigation of the zinc deposition behavior within an imidazolium based ionic liquid electrolyte. First, the electrochemical behavior of the electrodeposition behavior is analyzed by cyclic voltammetry and potential step methods. Second, in-situ atomic force microscopy (AFM) is conducted to investigate the morphological evolution of zinc during electrodeposition. Finally, in-situ ultra-small-angle X-ray scattering (USAXS) is conducted during the electrodeposition of zinc to understand how the electrode surface evolves during electrodeposition and help confirm the results obtained from the in-situ AFM analysis.

The ionic liquid electrolyte chosen for the investigation of zinc electrodeposition is an imidazolium based system consisting of zinc trifluoromethanesulfonate (Zn(OTf)₂) dissolved within 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate (BMIm OTf), and electrodeposition analysis is conducted on a Pt disk electrode. The behavior of Zn/Zn(II) within the ionic liquid electrolyte is analyzed at various deposition overpotentials, Zn(OTf)₂ concentrations, and temperatures.

Three distinct morphological behaviors are observed during the in-situ AFM analysis: growth of boulder like morphology, growth dominated by favorably oriented grains, and the formation of surface instabilities that manifested as agglomerate islands. The electrodeposition growth of Zn dominated by favorably oriented grains obtains a steady state where the surface roughness remained constant despite continued growth. The in-situ USAXS analysis confirms the results observed by the in-situ AFM analysis. In addition, the USAXS data shows that the zinc deposition behavior is hierarchical whereby the main scattering entities exhibited a sub-structure that remains constant in size with continued deposition.

The results of this research indicate that zinc deposition within an ionic liquid electrolyte can obtain a compact and dense morphology. Furthermore, the morphology can evolve under a steady state condition under certain deposition parameters identified by this research. The improved deposition morphology of zinc within ionic liquid electrolytes may help improve the cycling performance of the zinc electrode and help make zinc based rechargeable batteries a viable alternative for energy storage applications.

Rapid trends show a steady decrease in electronic device form factors, which are miniaturizing and flattening, while demonstrating an increase in device functionality, requiring complex and exacting power needs. This movement has motivated a shift in energy storage design and manufacture to accommodate novel and unconventional materials, new device geometries, and non-traditional fabrication methods. A combination of these strategies will lead to a revolution in the way energy storage components are designed, integrated, and utilized in electronic devices.

In this work, we present one possible strategy combining a materials innovation with simple engineering methods to fabricate and integrate batteries directly onto a device. A novel ionic liquid gel electrolyte compatible with zinc-metal oxide battery systems was synthesized. This gel electrolyte properties and its compatibility with the electrodes, current collector materials, packaging, and substrates were investigated.

A simple, low-cost, solution-based printing method for integrating energy storage components directly onto a device is demonstrated with a direct write dispenser printing system. The dispenser printer is able to pattern "inks" into multilayer devices with custom dimensions.

Printed 1 cm2 zinc-metal oxide microbatteries utilizing the ionic liquid gel electrolyte were fabricated and then various device quantities such as its storage capacity, power performance, self-discharge, and other properties were characterized. Prospective applications of this printable battery include flexible electronics and applications that need highly customized integrated or miniature energy storage such as printed circuit boards, permanent power supplies for autonomous wireless sensors, and active RFID tags.