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

为了实现更可持续的未来，电能储存是电力系统最关键的需求之一。锂硫(Li-S)电池由于使用了硫，具有更高的能量密度和更低的成本，是很有前途的候选电池。然而，李-S系统的一个关键限制是多硫化物穿梭。当多硫化物分子从阴极溶解到电解液中并穿梭通过隔膜与阳极材料反应时，就会发生穿梭。这一过程是不可逆的，并导致容量迅速衰落。本项目研究了多硫化锂在锂硫电池中的基本穿梭效应，重点是开发表面工程主体材料，以固定化多硫化锂并促进其转化。将开发一系列表面工程和形状控制的氧化铈，并对其进行表征，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、电动汽车以及利用太阳能和风能进行间歇性可再生能源储存的设备产生潜在的巨大影响。研究人员将继续通过为本科生提供独特的研究机会来支持STEM中优秀的少数族裔学生的招生、辅导和留住，并为他们提供持续奖学金以促进他们的留住。这项建议的总体目标是通过形状控制(纳米棒、纳米立方体和具有不同暴露晶面的纳米八面体：(110)、(100)和(111))和化学腐蚀处理来阐明表面工程极性CeO2作为主体材料添加作为主体材料对锂硫电池中多硫化物锂的固定、催化转化和电化学性能的影响。这些发现将提供对硫转化化学的基本理解，并为未来设计和筛选新的主体材料以实现锂硫电池的高硫负载/利用提供指导。研究人员推测，物理约束和具有不同端面结构的表面工程极性CeO2将有效地存储和捕获硫物种，以防止中间多硫化物锂的溶解和迁移，避免在电化学循环过程中的穿梭效应和容量下降。此外，还将利用非原位/原位电子显微镜和电子能量损失谱表征技术来更深入地了解锂多硫化物/CeO2界面的动态吸附/脱附、液/固和固/固相互作用以及结构/成分的变化。对多硫化物/CeO2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。在硫氧化物添加剂相互作用的电池化学方面获得的知识保证了长寿命和高能量/功率密度的锂硫电池。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。

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.