Unraveling the influences of electrolyte on sulfur redox behaviors in lithium sulfur batteries 

Yi-Chun Lu*

The Chinese University of Hong Kong 

Abstract: Lithium sulfur (Li−S) battery has the potential to provide a two to three times higher specific energy than conventional lithium ion batteries. The development of Li−S batteries is limited by the dissolution, diffusion, and side reactions of soluble polysulfides in the electrolyte. The search and development for effective electrolytes has been impeded by the lack of understanding of how solvent and salt properties affect the Li-S redox chemistry. In this study, we examine a series of nonaqeuous solvents covering a wide range of solvent properties, viz.,in dielectric constant (ε), in Gutmann donor number (DN), and in acceptor number (AN). This enables us to examine the influence of these three solvent characteristics on the Li-S chemistry. In addition, we will discuss synergistic interactions between polysulfides and other redox-active species as a new strategy to improve Li-S batteries. We exploit operando UV-Vis spectroscopy coupling with cyclic voltammetry and rotating ring-disk electrode (RRDE) techniques to correlate the chemical stability of polysulfides with their electrochemical activities and behaviors in the Li-S batteries.

Biography: Prof. Yi-Chun Lu received her Ph.D. degree in Materials Science & Engineering from the Massachusetts Institute of Technology in 2012. She is currently an Assistant Professor in the Department of Mechanical and Automation Engineering at The Chinese University of Hong Kong (CUHK). She was the recipient of the Hong Kong SAR Research Grants Council Early Career Award (2014), Young Researcher Award (2016), University Education Award, (2016), Vice-Chancellor's Exemplary Teaching Award (2014). Prof. Lu's research interest centers on developing fundamental understandings and material design principles for clean energy storage and conversion. Specifically, her research group is studying: Electrode and electrolyte design for high-energy metal-air and metal sulfur batteries; Redox-active components and solution chemistry for redox-flow batteries. Electrocatalysts and electrode design for low-temperature fuel cells and electrolyzers; Mechanistic understanding of interfacial phenomena governing electrochemical energy conversion and storage processes.