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

1604908 PI：Guo职务：溶剂化作用对亚纳米约束下锂硫电化学过程的动力学影响与市售锂离子电池相比，锂硫（Li-S）电池具有以更低成本提供更高能量密度的潜力。与仅涉及固态锂化-脱锂反应的锂离子电池相反，Li-S电池涉及能够溶解多硫化锂（LPS）化合物的液体电解质中的反应，以便克服由硫的高度绝缘性质造成的障碍。目前，Li-S电池的性能受到Li-S电化学反应和LPS扩散的时间尺度差异的限制。 该项目的总体目标是研究新的电极设计，使硫限制在亚纳米结构中，并消除LPS溶解引起的问题。该项目的主要科学目标是了解限制对微孔碳和单壁碳纳米管中硫电化学行为的影响，以提高锂硫电池的性能。在Li-S电池中，锂化-脱锂过程需要一系列固-液-固反应。液体电解质必须溶解中间体LPS化合物以获得高硫利用率，但在每个循环中通过扩散离开电极而损失一些LPS。亚纳米限制可以通过阻止溶剂进入硫电极上的孔来克服这一挑战，因此Li+离子只能通过去溶剂化进入孔，有效地固定电极表面上的Li-S反应。拟议的研究将通过协调一致的实验和建模工作来研究具有亚纳米限制的Li-S电化学的基本机制。 除了培训研究生外，PI还计划让本科生参与研究，并提出一项外联工作，重点是吸引里亚托联合学区高中代表性不足的少数民族学生。该研究项目的成果可能对多孔纳米结构中的亚纳米限制领域产生更广泛的影响。

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.