UCLA

This dissertation focuses on the fundamental problems in the lithium-sulfur battery, which is one of the most promising candidates for next-generation electric energy storage. Despite years of research, the electrochemical process in lithium-sulfur batteries remains ambiguous. The first part of this dissertation discusses the geometric and electronic band structures of related sulfur species, and how these intrinsic properties determine their electrochemical behaviors. The second part introduces the concept of regenerative polysulfide-scavenging layers which mitigate the shuttling phenomenon of polysulfides. It also details the interactions between various metal oxides and lithium polysulfides in terms of physisorption and chemisorption. The third part illustrates the working mechanism of redox mediators for sulfur species and their expedited electrochemical behaviors. The last section presents the design of a hybrid silicate coating for lithium metal anode to suppress the formation of dendritic structures. These investigations unveil the fundamental limitations of lithium-sulfur batteries, and present practical strategies to achieve higher energy density, extended cycling life, and better safety.