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

电池在信息技术、储能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正极材料，比现有的电池提供更多的能量，被认为是下一代技术之一。然而，它在硫磺和锂硫化物之间的转化是一个非常复杂的过程，并且存在导致容量低和电池寿命短的根本问题，如中间产物的溶解和它们在两个电极之间穿梭。最近的证据表明，单原子催化剂在促进这一转化过程并随后提高电池性能方面发挥了关键作用，但对其活性催化部位和反应机理的基本了解仍然很难理解。这阻碍了具有更高性能的催化剂功能化正极结构的发展。目前的项目将填补这一知识空白，从而加快发展实用的锂硫电池技术，服务于国家利益的关键储能应用。该项目还将产生更多的社会影响。所获得的单原子催化剂方面的知识可应用于其他电化学体系。研究生和本科生，包括那些来自代表性不足的群体的学生，将接受先进材料科学和电池技术领域的培训。研究成果将被纳入选修课。研究团队将接触当地社区，招募高中生进行研究，并向当地公共图书馆提供关于新电池技术的公开讲座。这一合作的基础研究项目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，并将这些认识转化为优化的硫磺阴极设计。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被调节，以结合多硫化物，并以优化的强度激活Li-S和S-S键，从而显著改善硫化物转化的格局，同时防止多硫化物穿梭。为此，本项目将理论计算和模拟与现场/非现场实验研究相结合，建立单原子催化剂化学吸附多硫化物并激活Li-S和S-S键进行转化的结构-性质关联，并探索和可视化循环过程中电极形态及其化学分布的演变。这些研究将为金属中心的选择、局部配位以及附近电解液的选择提供见解，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热力学和动力学功能的理解，在先进的表征工具的辅助下，将被用来设计先进的硫阴极结构，用单原子催化剂功能化，以展示性能大大改善的电池单元。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.