Development of material design for advanced lithium-sulfur batteries via nucleophilic substitution chemistry

Abstract

For the last decade, in order to solve low energy density and specific capacity, which is a clear limitation of currently commercialized lithium secondary batteries, research and development has been positively implemented on secondary battery systems. Lithium-sulfur secondary batteries, which are evaluated as the most realistic of the next-generation secondary batteries, have advantages in terms of price and theoretical energy density, however, they have fundamental limitation of reducing lifespan characteristics due to lithium polysulfides dissolution and insulating nature of sulfur. In this Ph.D. dissertation, introducing one chemical approach to address the low conductivity and lithium polysulfides dissolution. The "nucleophilic aromatic substitution" is a synthesizing method of substituting fluorine functional group in an aromatic backbone to sulfur. This method achieves high reaction yields, conductivity, and lithium polysulfides adsorption capacity due to various heteroatoms and metals present in the aromatic molecule. Comprehensively, I have researched interaction between synthesized sulfur composites and lithium ion to reveal its electrochemical mechanisms.