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

技术说明：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，将研究两种限制低温下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。具体来说，固态核磁共振光谱将用于(i)研究两相界面（例如，由CaF2和BaF2形成的异质层）或纳米颗粒表面的结构和离子迁移率，以及（ii）确定中等氧离子导体(掺杂没食子酸镧（La0.9Sr0.1Ga0.9Mg0.1O3）中氧离子空位附近的阳离子位置。以探索由于镁（Mg2+）和锶（Sr2+）掺杂而形成的捕获空位掺杂团簇所产生的影响。氟-19 （19F）和氧-17 （17O）核磁共振将用于研究局部结构和迁移率；利用镓-71 （71Ga）和镁-25 （25Mg）幻角旋转（MAS）核磁共振（NMR）波谱技术探测阳离子周围的局部环境。最后，利用MAS NMR方法对一系列电池电极材料及相关化合物进行研究。这些材料中的许多都表现出金属行为，这项工作的一个目的是开发从这些化合物的核磁共振光谱中提取结构/电子信息的直接方法。该研究计划将纳入涉及高中和初中学生，大学生和广大社区的外展活动。P.I.为少数族裔学生开设了一个高中课程，重点是电源，学生们在那里合成电池电极（例如锂锰）并测试他们自己的电池。非技术解释为了促进从石油经济向基于更多样化能源的经济转变，改进电池和燃料电池具有更高的功率密度是非常必要的。为了降低固体氧化物燃料电池（SOFC）的工作温度，并降低这些设备的成本，需要能够使氧离子在固体中快速传输的新材料。本研究计划第一部分的目的是通过使用固态核磁共振方法，确定限制膜和两种不同材料之间界面上氧离子导电性的现象。固态核磁共振方法可以直接观察到在固体中移动的离子，并测量它们的迁移率。这个项目的结果将有助于改进燃料电池和其他设备的设计，其中氧气传导是重要的（例如，氧/氮分离和氧传感器）。在研究计划的第二部分，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。该研究计划将被纳入涉及高中和初中学生、本科生和整个社区的外展活动中。P.I.为少数族裔学生开设了一个高中项目，重点关注能源，学生们制作并测试自己的电池。

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.