The Design and Characterization of Advanced Li Metal Anodes for Next-Generation Batteries
Abstract
Li metal batteries have been widely regarded as the next stage of energy storage technology, which is enabled by the low electrochemical potential (-3.04 V vs. the standard hydrogen electrode) and high specific capacity (3860 mAh g-1) of the Li metal anode. However, the implementation of Li metal anodes has been hindered by several issues including parasitic side reactions with electrolyte, large volume fluctuations, and dendrite formation which can cause short-circuits and safety issues. This thesis will cover some novel Li anode stabilization strategies while using advanced characterization techniques to provide critical information on the working mechanisms of Li metal anodes and their modes of failure.
The first part of this thesis covers the design of a conductive 3D copper nanowire host for Li metal. A simple and facile fabrication process yields a lithiophilic surface that enables molten Li infusion into the 3D host. The 3D structure is shown to lower the localized current density and minimize electrode volume change, thus allowing for high performance and long-life Li metal anodes.
The second part of this thesis investigates the temperature-dependent behavior and failure mechanisms of Li metal anodes in carbonate electrolytes. Several electrochemical testing methodologies are used to study the cycling behavior of Li metal anodes cycled between 0-60 °C. Furthermore, advanced synchrotron characterization techniques including in-situ X-ray tomography and energy-dependent X-ray fluorescence mapping are used for the first time to study Li metal anode chemical and physical structure changes under different operating conditions.
The third part of this thesis explores the application of molecular layer deposition (MLD) Zircone films on Li metal anodes. The nanoscale zircone coatings are able to improve the air stability and processability of the Li metal anode while enabling operation at higher current densities with improved stability. The application of the coating is shown in Li-O2 batteries which have a 10-fold improvement in cycle life.
The fourth part of this thesis investigates the mechanism of atomic layer deposition (ALD) coating growth on Li metal anodes and compares it to Cu current collectors for anode-free applications. The chemical and physical structure of the coatings are explored and it is shown that the reactive Li surface results in non-ideal surface structures with unexpected chemical compositions that differ from other substrates with the same deposition parameters.
The final part of this thesis studies three superionic halide solid-state electrolytes and their electrochemical reactivity towards Li metal anodes. The reactions are studied through advanced characterization techniques and their failure modes are explored.