Solid State NMR Studies of Disordered Solids: Ionic Conductors and Battery Materials

技术解释 为了降低固体氧化物燃料电池（SOFC）的工作温度，需要具有更高离子电导率的新型固态电解质。在本研究项目中，将研究两种在低温下限制离子电导率或可能有助于在中等温度下设计具有非常高电导率的材料的现象。 具体地，固态NMR光谱将用于（i）研究两相之间的界面处的结构和离子迁移率（例如，异质层形成的CaF 2和BaF 2）或在纳米粒子的表面上，和（ii）确定附近的氧离子空位在中度氧离子导体，掺杂镓酸镧（La0.9Sr0.1Ga0.9Mg0.1O3）的阳离子位点，以探讨所产生的效果，由于镁（Mg 2+）和锶（Sr 2+）掺杂形成的陷阱空位掺杂剂集群。 将使用氟-19（19 F）和氧-17（17 O）NMR研究局部结构和迁移率;将使用镓-71（71 Ga）和镁-25（25 Mg）魔角自旋（MAS）核磁共振（NMR）光谱探测阳离子周围的局部环境。 最后，MAS NMR方法将用于研究一系列电池电极材料和相关化合物。 这些材料中的许多显示出金属行为，并且工作的一个目的是开发用于从这些化合物的NMR光谱中提取结构/电子信息的直接方法。 该研究计划将纳入涉及高中生、大学生和整个社区的外联活动。 私家侦探为少数民族学生开设了一个高中课程，该课程侧重于电源，学生们在那里合成电池电极（例如，锂锰），并测试自己的电池。 非技术性解释迫切需要具有更高功率密度的改进的电池和燃料电池，以帮助促进从基于石油的经济向基于更多样化能源的经济的转变。 为了降低固体氧化物燃料电池（SOFC）的工作温度，并降低这些装置的成本，需要允许氧离子快速传输通过固体的新材料。 该研究计划的第一部分的目的是通过使用固态NMR方法来识别限制膜中氧离子电导率和两种不同材料之间界面的现象。固态NMR方法允许直接观察在固体中移动的离子，并测量它们的迁移率。 该计划的结果将有助于设计改进的燃料电池和其他氧传导很重要的设备（例如，氧/氮分离和氧传感器）。在研究计划的第二部分中，NMR方法将用于研究一系列电池电极材料和相关化合物，以了解这些材料的功能。 该研究计划将纳入涉及高中和初中学生，本科生和整个社区的外联活动。 私家侦探为少数民族学生开设了一个高中项目，重点是电源，学生们自己制作和测试电池。

TECHNICAL EXPLANATION New solid-state electrolytes with higher ionic conductivities are required in order to lower the operating temperatures of a solid oxide fuel cell (SOFC). In this research project, two phenomena that limit ionic conductivity at low temperatures or that may help in the design of materials with very high conductivities at moderate temperatures will be investigated. Specifically, solid-state NMR spectroscopy will be used to (i) investigate structure and ionic mobility at the interfaces between two phases (e.g., heterolayers formed of CaF2 and BaF2) or at the surfaces of nanoparticles, and (ii) identify the cation sites that are nearby the oxygen-ion vacancies in the moderate oxygen-ion conductor, doped lanthanum gallate (La0.9Sr0.1Ga0.9Mg0.1O3), in order to explore effects arising from trapped vacancy-dopant clusters formed due to magnesium (Mg2+) and strontium (Sr2+) doping. Fluorine-19 (19F) and oxygen-17 (17O) NMR will be used to investigate local structure and mobility; the local environments surrounding the cations will be probed by using gallium-71 (71Ga) and magnesium-25 (25Mg) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. Finally, MAS NMR methods will be used to study a series of battery electrode materials and related compounds. Many of these materials show metallic behavior and one aim of the work is to develop straightforward approaches for extracting structural/electronic information from the NMR spectra of these compounds. The research program will be incorporated into outreach activities involving both high and middle school students, undergraduates and the community at large. The P.I. runs a high-school program for minority students, which focuses on power sources, where the students synthesize battery electrodes (e.g., lithium manganese) and test their own batteries. NON-TECHNICAL EXPLANATIONImproved batteries and fuel cells with higher power densities are critically needed to help facilitate the move from an oil-based economy, to an economy based on a more diverse range of energy sources. New materials are required which will allow rapid transport of oxygen ions through a solid in order to lower the operating temperatures of a solid oxide fuel cell (SOFC), and reduce the costs of these devices. The aim of the first part of this research program is to identify, via the use of solid-state NMR methods, phenomena that limit conductivity of oxygen ions in membranes and at the interfaces between two different materials. Solid-state NMR methods allow the ions that move in a solid to be observed directly, and their mobility to be measured. The results from this program will help in the design of improved fuel cells and other devices where oxygen conduction is important (e.g., oxygen/nitrogen separations and oxygen sensors). In the second part of the research program, NMR methods will be used to study a series of battery electrode materials and related compounds in order to understand how these materials function. The research program will be incorporated into outreach activities involving both high school and middle school students, undergraduates and the community at large. The P.I. runs a high-school program for minority students, which focuses on power sources, where the students make and test their own batteries.