UC San Diego

Energy storage and conversion devices need to continue to develop to keep up with the demands that come along with the ever-increasing global energy consumption. As the percentage of energy coming from renewable sources continues to rise, a cost-effective and safe solution to store the generated energy must also be implemented. In this regard, all-solid-state batteries (ASSBs), which do not contain the flammable and corrosive liquid electrolyte, have been highly sought after, as they have the potential for enhanced energy density and safety in addition to lowered cost and lowered maintenance considerations.Many classes of lithium-ion-conducting and sodium-ion-conducting solid-state electrolytes (SSEs) have been developed and reported over the years. Na-based ASSBs have the potential for additional cost savings is one main driving force. Since there now exist many different solid electrolytes with adequate ionic conductivity, our research focus turns to studying cell degradation mechanisms at both the anode/SSE interface and the cathode/SSE interface; understanding these mechanisms will allow for the selection of compatible chemistries to ultimately enable the design of longer-lasting ASSBs. In terms of energy conversion, Thin Film Solid Oxide Fuel Cells (TF-SOFCs) are of research interest as they can operate at lower temperatures than conventional SOFCs. This will allow for a wider range of materials and lowered maintenance costs, while still maintaining and far surpassing the fuel-to-electricity conversion efficiency of conventional fossil fuel sources. Applications for such high-power devices range from transportation to large-scale power plants. In this thesis, for the Na solid-state battery system, the reactivity between the Na anode and the Na3SbS4 electrolyte was studied to gain insight on cell degradation, and on the cathode side, a new, stable, halide chemistry, Na3-xY1-xZrxCl6, was evaluated for its compatibility when paired with the oxide cathode NaCrO2. For the Li-based solid-state system, the properties of a dry-processed protective lithium borate coating on the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode were investigated, and lastly, a sputtering platform to fabricate an entire TF-SOFC was developed and tested in order to enable a more practical and scalable SOFC fabrication method.