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，锂离子电池等最先进的储能技术不足以满足广泛使用所需的性能要求，如成本和能量密度。使用高能量密度电极的电池化学可以为这些应用提供一条在能量密度和耐用性方面获得收益的途径。该项目致力于使用锂硫电池作为一种潜在的高能量密度和低成本的选择。锂硫电池的主要制约因素是循环稳定性差，即反复使用时能量衰减。这种衰变的一个原因是称为多硫化锂的反应中间产物，它们在电池电解液中溶解和迁移，导致活性物质的损失。该项目通过实验和理论相结合的方法来解决这个问题，以开发不仅可以限制多硫化锂，而且可以加速它们的转换以储存或释放能量的新材料。这些材料有可能在不影响其能量密度的情况下延长锂硫电池的寿命。该项目还通过耶鲁大学通向科学之路计划，在初中和高中的大学预科学生中开展外联活动。研究人员将在该计划下为一个涉及电池主题的夏季研讨会启动一项新的外展活动。这是一个基础工程项目，通过在分子水平上了解化学相互作用并在电极/多硫化物界面上实现电催化，合理设计高性能硫电极，解决锂硫电池面临的循环寿命挑战。通过实验和计算研究了锂多硫化物的化学结合机理和电化学氧化还原行为，该模型材料体系包括无机纳米颗粒和结构可控的金属络合物。可以有效地结合多硫化锂并催化其电化学反应的合适位置将被确定。将计算反应路径、势垒和限速步骤，并进行实验检验。在新知识的基础上，将设计和合成三元结构材料和超薄保护层，以使大容量和长周期的硫电极能够在与应用相关的条件下运行。该奖项反映了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。

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.