Collaborative Research: Promoting Lithium Sulfides Redox Cycle via Atomically Dispersed Active Sites for Batteries

电池在信息技术、能源储存和减少碳排放方面发挥着关键作用。锂硫电池使用地球上丰富的硫作为阴极材料，提供比当前电池更多的能量，因此它被认为是下一代技术之一。然而，其在硫和硫化锂之间的化学转化是一个非常复杂的过程，并且具有导致低容量和短电池寿命的基本问题，例如中间产物的溶解及其在两个电极之间的穿梭。 最近的证据表明，单原子催化剂在促进这一转化过程和随后提高电池性能方面起着关键作用，但对活性催化位点和反应机理的基本理解仍然非常模糊。 这阻碍了具有显著改善的性能的催化剂官能化阴极结构的开发。目前的项目将填补这一知识空白，从而加快实用锂硫电池技术的开发，以服务于国家在关键储能应用方面的利益。该项目还将产生更广泛的社会影响。在单原子催化剂上获得的知识可以应用于其他电化学系统。研究生和本科生，包括那些来自代表性不足的群体，将在先进材料科学和电池技术领域的培训。研究成果将纳入选修课程。 研究团队将深入当地社区，招募高中生进行研究，并向当地公共图书馆提供有关新电池技术的公开讲座。本合作基础研究计划将对原子分散催化剂在促进硫化锂氧化还原循环中的结构-性能相关性进行理论理解和实验验证，并将这些理解转化为优化的硫阴极设计。该项目假设，由金属中心及其局部配位决定的单原子催化剂的电子结构可以调整，以结合多硫化物并以优化的强度激活Li-S和S-S键，从而显着改善硫化物转化的景观，同时防止多硫化物穿梭。为此，本项目将理论计算和建模与原位/非原位实验研究相结合，建立单原子催化剂在化学吸附多硫化物和活化Li-S和S-S键转化中的结构-性能相关性，并探测和可视化电极形貌及其化学分布在循环过程中的演变。因此，这些研究将提供有关金属中心的选择，其局部配位以及附近电解质的见解，并揭示它们对硫化锂氧化还原循环的影响。这些对单原子催化剂在硫化物结合和转化方面的功能的理解，在先进的表征工具的帮助下，将被用来设计先进的硫阴极结构，用单原子催化剂官能化，用于演示电池单元，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，被认为值得支持和更广泛的影响审查标准。

Batteries play a key role in information technology, energy storage, and reduction in carbon emissions. The lithium-sulfur battery uses earth-abundant sulfur as the cathode material and delivers more energy than the current batteries, thus it is considered as one of the next-generation technologies. However, its chemistry of converting between sulfur and lithium sulfides is a very complex process and has fundamental problems that result in low capacity and short battery lifetime, such as the dissolution of intermediate products and their shuttling between the two electrodes. Recent evidence has shown the critical role of single-atom catalysts in promoting this conversion process and subsequently boosting the battery performance, but the fundamental understanding of the active catalytic sites and the reaction mechanism remains very elusive. This hinders the development of a catalyst-functionalized cathode structure with much improved performance. The current project will fill this knowledge gap, thus accelerating the development of a practical lithium-sulfur battery technology to serve the national interest in the key energy storage applications. The project will also result in societal boarder impacts. The knowledge gained on single-atom catalysts can be applied to other electrochemical systems. Graduate and undergraduate students, including those from underrepresented groups, will be trained in the fields of advanced material science and battery technology. The research outcomes will be incorporated into the elective courses. The research teams will reach out to the local communities, recruiting high school students to conduct research and delivering public lectures on the new battery technology to local public libraries. This collaborative fundamental research project will attain theoretical understanding and experimental validation of the structure-property correlation of atomically dispersed catalysts in promoting lithium sulfides redox cycle, and to transform these understandings into an optimized sulfur cathode design. The project hypothesizes that the electronic structure of the single-atom catalyst, which is determined by both the metal center and its local coordination, can be tuned for binding polysulfides and activating the Li-S and S-S bonds with an optimized strength, thus significantly improving the landscape of sulfides conversion while preventing polysulfides shuttling. To this end, combining theoretical calculations and modeling with in-situ/ex-situ experimental studies, this project will establish the structure-property correlation of single-atom catalysts in chemisorbing polysulfides and activating the Li-S and S-S bonds for conversion, and probe and visualize the evolution of the electrode morphology and its chemical distribution during cycling. The studies will thus provide insights on the choice of the metal center, its local coordination, and the electrolyte in the proximity, and reveal their impacts on the lithium sulfides redox cycle. These understandings of single-atom catalyst functions on sulfides binding and conversion, both thermodynamically and kinetically, assisted by advanced characterization tools, will then be leveraged to design advanced sulfur cathode structures, functionalized with single-atom catalysts, for demonstration of battery cells with much-improved performance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.