CAREER: Designing Interfaces for Electrochemical Energy Storage: A Mechanistic Perspective

这个职业项目专注于锂硫(Li-S)电池，它承诺在下一代储能系统中成本更低、容量更大。先进的车用和储能锂电池可以提高国内能源安全性，但其使用主要受到电极/电解液界面不良化学副反应的限制。这个项目试图从根本上了解电池运行过程中这个界面上的反应。这一基本认识将有助于解决电池稳定性和整体电池性能问题。与该项目相关的教育和推广活动是：(I)为高中生和中学生提供实践经验；(Ii)让本科生参与前沿研究活动，重点是未被充分代表的学生参与STEM；以及(Iii)为研究生提供创新和创业机会。虽然锂-S电池已经得到了广泛的探索，但固/液电解液界面上多硫氧化还原反应的许多方面的机理仍不清楚。在缺乏详细的机理了解的情况下，电极结构的合理设计一直是困难的。本项目的技术目标是利用原位扫描电化学显微镜和拉曼光谱相结合的方法，绘制锂-S电池充放电过程中多硫化物形态的时空演变图。该研究计划基于两个指导性假设：(1)测量界面性质将允许从机理上阐明(电)化学反应途径，并提供关于多硫化物溶解-歧化-沉淀动力学的信息；(2)阐明反应机理将控制电化学界面，从而通过适当的材料设计实现多硫化物穿梭。该项目的成功完成有望(I)利用一种新的分析工具，在纳米尺度上以高时空分辨率加强对电极/电解液界面相互作用的基本了解，(Ii)以高时间分辨率绘制出过渡条件下多硫化物与电极表面和电解液溶剂的相互作用图，以及(Iii)确定催化剂的作用和整个多硫化物氧化还原过程中的限速步骤，以评估锂-S电池材料的优异性能。由此产生的硫(电)化学反应的机理阐明将为Li-S氧化还原化学提供新的见解，并将允许详细绘制多硫化物穿梭的空间和时间演化图，这是Li-S体系的核心问题。

This CAREER project focuses on lithium-sulfur (Li-S) batteries, which promise lower cost and higher capacity in next-generation energy storage systems. Advanced lithium batteries for vehicles and energy storage could improve domestic energy security, but their use is mainly limited by undesirable chemical side reactions at the electrode/electrolyte interface. This project seeks to fundamentally understand the reactions at this interface during battery operation. This fundamental understanding will help resolve the issues of battery stability and overall battery performance. The education and outreach activities associated with this project are to (i) provide hands-on experience to high school students and middle school students, (ii) engage undergraduate students in cutting-edge research activities with strong emphasis on the involvement of underrepresented students in STEM and (iii) provide innovation and entrepreneurship exposure to graduate students.While Li-S batteries have been extensively explored, many aspects of the mechanisms of polysulfide redox reactions at solid/liquid electrolyte interfaces remain unclear. In the absence of detailed mechanistic understanding, rational design of electrode architectures has been difficult. The technical objective of this project is to map the temporal and spatial evolution of polysulfide speciation during the charge/discharge process in a Li-S battery through use of in-situ scanning electrochemical microscopy methods coupled with Raman spectroscopy (SECM-Raman). The research program is underpinned by two guiding hypotheses; (1) measuring interfacial properties will allow for mechanistic elucidation of (electro)chemical reaction pathways and provide information on kinetics of polysulfide dissolution-disproportionation-precipitation and (2) elucidating the reaction mechanism will control the electrochemical interface and thereby polysulfide-shuttle with an appropriate material design. The successful completion of the project is expected to (i) enhance fundamental understanding of interactions at the electrode/electrolyte interface at the nanoscale level with high spatiotemporal resolution using a new analytical tool, (ii) map the interaction of polysulfides with the electrode surface and with electrolyte solvents under transient conditions with a high temporal resolution, and (iii) define the role of catalysts and the rate-limiting step in the overall polysulfide redox process to assess superior performance of materials for Li-S batteries. The resulting mechanistic elucidation of sulfur (electro)chemical reactions occurring at the interfaces will provide new insight into Li-S redox chemistry and will allow for detailed mapping of the spatial and temporal evolution of the polysulfide shuttle; a core issue in the Li-S system.