DESIGN, SYNTHESIS, AND CHARACTERIZATION OF NOVEL MATERIALS FOR HIGH-PERFORMANCE LITHIUM-SULFUR BATTERIES

Abstract

With ever-increasing energy demands, tremendous efforts have been devoted to developing rechargeable batteries. Conventional lithium-ion batteries have been widely used for decades, but are approaching their theoretical limit and are unable to meet the rising energy demands. Lithium–sulfur (Li–S) batteries are being actively pursued owing to their high energy density and cost-effectiveness. However, the commercial implementation of Li–S batteries has been impeded by the challenges associated with the sulfur cathodes, including extremely low conductivity, large volumetric expansion and rapid capacity loss arising from the dissolution of the intermediates, and the Li anode, owing to the uncontrollable formation of Li dendrites. To fulfill the promise of Li–S batteries as high-energy devices, it is necessary to solve these issues. In this dissertation, effective materials as sulfur hosts have been studied and possible strategies to improve the performance of the sulfur cathode proposed. These involve designing the structure of the host material to efficiently accommodate sulfur and, at the same time, applying the strong adsorption properties between the active material and the host. As to the Li anode, approaches to suppress the growth of Li dendrites were demonstrated by coating the surface of the anode current collector. These strategies were successful in inhibiting Li dendrites and significantly improve the performance of Li anodes. These studies provide promising results for high-performance Li–S batteries for future large-scale applications.