UC San Diego

A variety of renewable energy sources are needed to support the modern electrical grid. Lithium metal batteries and fuel cells are high-energy-density, high-power technologies that are needed to meet the demand for immediate power delivery, such as electrified vehicles or portable electronics. The lifetime and power output of these technologies can be improved via the efficient usage of their material components. This dissertation investigates the mechanisms and morphologies of metal plating and stripping inside two relevant clean energy technologies. Firstly, the conformal plating of a Ni/P alloy on a high-aspect ratio porous oxide substrate was studied for solid oxide fuel cells (SOFCs). The fabrication of a porous conductive interface improves the power output of thin-film SOFCs. Secondly, the effect of low temperature on the stripping of lithium metal anodes was studied. Improved homogeneity of the stripped interface and the spontaneous formation of faceted crystals under low-reactivity conditions lead to the formation of a high-surface area cycled morphology. The application of external pressure was found to decrease the impedance of this interface without significant compression, leading to a wide range of appropriate pressures that allowed Li/SPAN full cells to be cycled without shorting. Finally, the effects of temperature on the formation of isolated lithium in lithium metal was studied quantitatively. The total round-trip efficiency of lithium metal anodes cycled in a highly inorganic electrolyte was studied as a function of temperature. This study demonstrated that low temperature has a narrow window where efficiency is improved via the lowered reactivity of the electrolyte/lithium interface, below which high-surface-area growth leads to the permanent isolation of lithium. This dissertation leverages the micro- and nano-scale mechanisms at play in both fuel cells and lithium metal batteries to reduce impedance and increase efficiency, power output and cell lifetime.