Developing Sulfur Cathode Materials for Electrochemical Energy Storage

提高电动汽车的储能技术和可再生能源电网储能的大规模集成是提高国内能源安全的迫切需要。目前，锂离子电池等最先进的储能技术还不足以满足广泛使用所需的成本和能量密度等性能要求。使用高能量密度电极的电池化学可以为这些应用提供提高能量密度和耐用性的途径。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，即反复使用后能量衰减。这种衰变的一个原因是称为锂多硫化物的反应中间体，它在电池电解质中溶解和迁移，导致活性物质的损失。这个项目用实验和理论相结合的方法来解决这个问题，开发新的材料，不仅可以限制锂多硫化物，而且可以加速它们的转换，以储存或释放能量。这些材料有可能在不影响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科学之路项目开展外展活动，涉及初中和高中的大学预科学生。研究人员将在该计划下开展一项涉及电池主题的夏季研讨会。这是一个基础工程项目，通过在分子水平上理解化学相互作用，并在电极/多硫界面上实现电催化，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多硫化物锂的化学结合机制和电化学氧化还原行为，并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配合物。将确定能有效结合锂多硫化物并催化其电化学转化反应的合适位点。反应途径、能垒和限速步骤将被计算和实验检验。基于这些新知识，将设计和合成三元结构材料和超薄保护层，以使高容量和长周期硫电极在应用相关条件下工作。该奖项反映了美国国家科学基金会的法定使命，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.