Developing Sulfur Cathode Materials for Electrochemical Energy Storage

迫切需要改进电动汽车的储能技术，并大规模整合可再生电网储能，以提高国内能源安全。目前，最先进的能量存储技术，如锂离子电池，不足以提供所需的性能要求，如成本和能量密度，以实现广泛的使用。使用高能量密度电极的电池化学可以为这些应用提供获得能量密度和耐久性的途径。该项目将锂硫电池作为一种潜在的高能量密度和低成本选择。锂硫电池的主要限制是其循环稳定性差，即重复使用时能量衰减。这种衰变的一个原因是称为多硫化锂的反应中间体，其溶解并迁移到电池电解质中，导致活性材料的损失。该项目通过实验和理论相结合的方法来解决这个问题，开发新材料，不仅可以限制多硫化锂，还可以加速其转化以储存或释放能量。这些材料有可能延长锂硫电池的寿命，而不会影响其能量密度。该项目还通过耶鲁大学科学之路项目开展外联活动，涉及初中和高中的大学预科学生。研究人员将在该项目下开展一项新的外展活动，即一个涉及电池主题的夏季研讨会。这是一个基础工程项目，旨在通过基于对化学相互作用的分子水平理解合理设计高性能硫电极，并在电极/多硫化物界面实现电催化，解决锂硫电池面临的循环寿命挑战。采用不同的模型材料体系，包括无机纳米颗粒和具有良好控制和系统变化结构的金属络合物，对多硫化锂的化学结合机制以及电化学氧化还原行为进行了实验和计算研究。合适的网站，可以有效地结合锂多硫化物和催化其电化学转化反应将被确定。反应途径，能量障碍和限速步骤将被计算和实验研究。基于这些新知识，将设计和合成三元结构材料和硫保护层，以实现在应用相关条件下运行的高容量和长周期硫电极。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

There is a critical need for improved energy storage technologies for electric vehicles and large-scale integration of renewable electricity grid storage to improve domestic energy security. Currently, state-of-the-art energy storage technologies such as lithium ion batteries are insufficient in providing the performance requirements needed such as cost and energy density to enable broad use. Battery chemistries using high energy density electrodes could provide an avenue towards gains in energy density and durability for these applications. This project addresses the use of lithium-sulfur batteries as a potential high energy density and lower cost option. The major constraint of lithium-sulfur batteries is their poor cycling stability, namely the energy decay upon repeated use. One cause for this decay is reaction intermediates called lithium polysulfides, which dissolve and migrate in the battery electrolyte causing loss in active material. This project addresses the issue with a combined experimental and theoretical approach to develop new materials that can not only confine lithium polysulfides, but also accelerate their conversion to store or release energy. These materials have the potential to extend the life time of lithium-sulfur batteries without compromising their energy density. The project also conducts outreach through the Yale University Pathways to Science Program involving pre-college students in middle school and high school. The investigators will enable a new outreach activity under this program for a summer workshop involving battery topics.This is a fundamental engineering project that addresses the cycle life challenge facing lithium-sulfur batteries by rationally designing high-performance sulfur electrodes based on molecular-level understanding of the chemical interactions and enabling electrocatalysis at the electrode/polysulfide interface. The chemical binding mechanisms as well as the electrochemical redox behaviors of lithium polysulfides are studied both experimentally and computationally with distinct model material systems comprising inorganic nanoparticles and metal complexes with well-controlled and systematically-varied structures. Suitable sites that can effectively bind lithium polysulfides and catalyze their electrochemical conversion reactions will be identified. Reaction pathways, energy barriers and rate-limiting steps will be calculated and experimentally examined. Based on the new knowledge, ternary-structured materials and ultrathin protection layers will be designed and synthesized to enable high-capacity and long-cycle sulfur electrodes operating under application-relevant conditions.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.