Surface Engineered and Highly Redox Active Polar Oxide Host Materials Immobilizing Lithium Polysulfides for Long-Life and High-Performance Li-S Batteries

电能存储是电力系统实现可持续发展的最关键需求之一。锂硫（Li-S）电池由于其较高的能量密度和由于使用硫而降低的成本而成为有希望的候选者。然而，Li-S系统的关键限制是多硫化物穿梭。当来自阴极的多硫化物分子溶解到电解质中并穿梭穿过隔板与阳极材料反应时，发生穿梭。这个过程是不可逆的，导致容量迅速衰减。本项目研究锂硫电池中多硫化锂的基本穿梭效应，重点是开发用于固定多硫化锂并促进其转化的表面工程主体材料。一系列表面工程和形状控制的氧化铈将被开发和表征，以了解哪些结构特征最能限制多硫化物的关闭。这些知识对于设计新型主体材料和长寿命储能系统至关重要，这将对便携式电子产品，电动汽车以及太阳能和风能间歇性可再生能源存储设备产生潜在的巨大影响。该研究员将继续支持优秀的招聘，指导，并通过提供独特的研究机会，为本科生，早在他们的大一和持续的奖学金，以促进他们的保留少数学生在STEM的保留。本提案的总体目标是阐明表面工程极性CeO 2添加作为主体材料通过形状控制的效果（具有不同暴露晶面的纳米棒、纳米立方体和纳米八面体：（110）、（100）和（111））和化学蚀刻处理对锂硫电池中的多硫化锂固定、催化转化和电化学性能的影响。这些发现将为硫转化化学的基本理解提供深入了解，并为未来设计和筛选新的主体材料以实现锂硫电池中的高硫负载/利用率提供指导。研究人员假设，具有不同终止表面结构的物理限制和表面工程极性CeO 2将有效地储存和捕获硫物质，以防止中间体多硫化锂的溶解和迁移，避免在电化学循环期间的穿梭效应和容量下降。此外，非原位/原位透射电子显微镜和电子能量损失谱表征技术将被用来实现更深入的了解动态吸附/脱附，液/固和固/固相互作用，和结构/组成的变化在多硫化锂/CeO 2界面。对多硫化锂/CeO 2界面结构的新见解（定量动态原子级结构和化学表征）将为促进或抑制各种界面现象提供强有力的实用策略。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。

Electrical energy storage is one of the most critical needs in power systems for a more sustainable future. Lithium–sulfur (Li-S) batteries are promising candidates because of their higher energy density and reduced cost due to the use of sulfur. However, a key limitation of the Li-S system is polysulfide shuttling. Shuttling occurs when polysulfide molecules from the cathode dissolve into the electrolyte and shuttle across the separator to react with the anode materials. This process is irreversible and leads to a rapidly fading capacity. This project addresses the fundamental shuttle effect of lithium polysulfides in lithium sulfur batteries with emphasis on developing surface engineered host materials for immobilizing lithium polysulfides and promoting their conversion. A series of surface engineered and shape-controlled cerium oxides will be developed and characterized to understand which structural features best limit polysulfide shutting. Such knowledge is critical for designing novel host materials and long-life energy storage systems, which will have a potentially immense impact on portable electronics, electric vehicles, and devices for intermittent renewable energy storage from solar and wind resources. The investigator will continue to support the outstanding recruitment, mentoring, and retention of minority students in STEM by providing unique research opportunities for undergraduates as early as their freshman year and with continuing scholarships to promote their retention.The overall objective of this proposal is to elucidate the effect of surface engineered polar CeO2 addition as a host material via shape control (nanorods, nanocubes, and nanoctahedra with different exposed crystal planes: (110), (100) and (111)) and chemical etching treatment on the lithium polysulfides immobilization, catalytic conversion, and electrochemical performance in lithium-sulfur batteries. These findings will provide insight into a fundamental understanding of sulfur conversion chemistry and act as a guide for the future design and screening of new host materials toward achieving high sulfur loading/utilization in lithium-sulfur batteries. The investigators hypothesize that physical confinement and surface engineered polar CeO2 with distinct termination surface structures would effectively store and entrap sulfur species to prevent the dissolution and migration of intermediate lithium polysulfides avoiding the shuttle effect and capacity degradation during the electrochemical cycling. In addition, ex situ/in situ transmission electron microscopy and electron energy loss spectroscopy characterization techniques will be employed to achieve a deeper understanding of dynamic adsorption/desorption, liquid/solid and solid/solid interactions, and structural/compositional changes at the lithium polysulfides/CeO2 interface. New insights (quantitative dynamic atomic-level structural and chemical characterizations) into lithium polysulfides/CeO2 interfacial structures will provide powerful practical strategies to promote or suppress various kinds of interface phenomena. The obtained knowledge on battery chemistry of sulfur-oxide additive interaction promises long-life and high energy/power density lithium-sulfur batteries.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.