Exploration and Optimization of Thiol-containing Conductive Polymer and Covalent Organic Frameworks as Cathode Materials in Lithium-Sulfur Batteries: Synthesis, Operando Analysis, and Simulation

锂硫(Li-S)电池有望实现未来的储能，其中聚(4-(噻吩基)苯硫醇)(PTBT)等聚合物将发挥关键作用。然而，实现高硫负载量和保持最佳导电性是面临的挑战。共价有机骨架(COF)提供了潜在的解决方案，为硫的储存和运输提供了多孔结构。尽管最初的研究很有希望，但诸如硫和COF之间的电化学相互作用以及孔结构对硫负载的影响等基本问题仍然没有被探索。除了科学上的挑战外，还需要解决实际方面的问题，如可伸缩性、与工业过程的兼容性以及向与工业相关的单元格式过渡期间的降解机制。先进的表征技术和操作方法有助于更深入地了解电极材料的电化学机理，尽管COF在多方法模拟研究中的接触有限。本研究通过实验和理论研究相结合的方法，对PTBT和硫醇功能化碳纤维(SH-COF)作为正极材料进行优化，旨在提高锂S电池的效率、稳定性和能量密度。该工作计划包括实验调查、全面的操作手分析以及使用模拟和理论计算进行的机理研究。该计划包括优化用于储袋电池的PTBT基硫阴极的放大合成，创建具有可控孔径和-SH基团的SH-COF，对Li-S电池(硬币电池和储袋电池)进行多峰操作分析，以及从理论上理解含硫醇的COF基硫宿主。X射线成像等技术将跟踪活性物质的分布，而光谱方法将研究电池循环过程中多硫化物物种释放到电解液中的情况。基于多尺度模拟和理论模型的含硫醇COF的机理研究将提供对这些材料的微观理解。将研究分子结构、动力学以及不同溶剂组成和孔径大小的影响。

Lithium-sulfur (Li-S) batteries hold promise for future energy storage, with polymers like poly(4-(thiophene-3-yl) benzenethiol) (PTBT) playing key roles. However, achieving high sulfur loading and maintaining optimal conductivity present challenges. Covalent organic frameworks (COFs) provide potential solutions, offering porous structures for sulfur storage and transport. Despite promising initial studies, fundamental issues such as electrochemical interactions between sulfur and COFs and the impact of pore structures on sulfur loading remain unexplored. In addition to the scientific challenges, practical aspects such as scalability, compatibility with industrial processes, and degradation mechanisms during transition to industrially relevant cell formats need addressing. Advanced characterization technologies and operando methods offer deeper understanding of electrochemical mechanisms in electrode materials, though COFs have had limited exposure to multi-method modeling studies. The proposed research combines experimental and theoretical investigations to optimize PTBT and thiol-functionalized COFs (SH-COFs) as cathode materials, aiming to enhance the efficiency, stability, and energy density of Li-S batteries. The work program includes experimental investigations, comprehensive operando analysis, and mechanistic studies using simulations and theoretical calculations. The program involves optimizing the up-scale synthesis of PTBT-based sulfur cathodes for pouch cell application, creating SH-COFs with controllable pore size and -SH groups, performing multimodal operando analysis of Li-S cells (both coin cells and pouch cells), and attaining a theoretical understanding of thiol-containing COF-based sulfur hosts. Techniques like X-ray imaging will track active material distributions, while spectroscopic methods will study the release of polysulfide species into the electrolyte during cell cycling. A mechanistic study of thiol-containing COFs, based on multiscale simulations and theoretical modeling, will provide a microscopic understanding of these materials. Molecular structure, dynamics, and the impact of varied solvent compositions and pore sizes will be investigated.