Dynamics of solvation effects on lithium-sulfur electrochemical processes in sub-nano confinement

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1604908 PI: GuoTitle: Dynamics of solvation effects on lithium-sulfur electrochemical processes in sub-nano confinementLithium-sulfur (Li-S) batteries have the potential of providing higher energy density at a lower cost, when compared to the commercially available lithium-ion batteries. In contrast to Li-ion batteries that involve only solid state lithiation-delithiation reactions, Li-S batteries involve reactions in liquid electrolytes capable of dissolving lithium polysulfide (LPS) compounds in order to overcome the barriers posed by the highly insulating nature of sulfur. The performance of Li-S batteries is currently limited by the difference in the time scales of Li-S electrochemical reactions and LPS diffusion. The overarching goal of the proposed project is to investigate new electrode designs that enable the confinement of sulfur in sub-nanometer structures and eliminate the problems arising from LPS dissolution. The key scientific objective of the proposed project is to understand the effects of confinement on the electrochemical behavior of sulfur in microporous carbon and single-walled carbon nanonutubes in order to improve the performance of Li-S batteries. In Li-S batteries, the lithiation-delithiation process requires a sequence of solid-liquid-solid reactions. The liquid electrolyte must dissolve the intermediate LPS compounds for high sulfur utilization, but some LPS is lost in each cycle through diffusion away from the electrode. Sub-nano confinement could overcome this challenge by blocking the solvent from entering the pores on the sulfur electrode, so Li+ ions can only enter the pores through desolvation, effectively immobilizing the Li-S reaction on the electrode surface. The proposed research will examine the fundamental mechanisms of Li-S electrochemistry with sub-nano confinement through a concerted experimental and modeling effort. In addition to training graduate students, the PIs plan to involve undergraduate students in research and propose an outreach effort focused at engaging underrepresented minority students from the Rialto Unified School District High Schools. The outcome of this research project may have a broader impact on the field of sub-nano confinement in porous nanostructures.