Studies of Local Structure and Transport Properties of Anionic Conductors and Battery Materials with Solid State NMR

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9901308 GreySolid State Nuclear Magnetic Resonance (NMR) will be used to probe local structure in fluoride-anion conductors, ferroelectric oxyfluorides, and lithium manganese oxide cathode materials. These are all systems where knowledge of local structure, and how it changes with temperature (fluorides) or charging/discharging of the battery cell (lithium manganese oxides) is critical to the understanding of the function of these materials. Mechanisms of fluoride-ion conduction in fluorides and oxyfluorides will be determined. The role of disorder and fluroride ion mobility in controlling ferroelectric to paraelectric phase transitions in ferroelectrics will be investigated. Lithium manganese oxides may be used as cathode materials for lithium rechargeable or "rocking chair" batteries. Since these electrode materials, however, suffer from reproducibility problems, combined with a loss of capacity after repeated charging and discharging of the electrochemical cell, NMR will be used to follow the changes in local structures (atomic and electronic) of the cathode during the charging/discharging. The aim is to determine which local lithium environments are deintercalated at a spec fic voltage, and which lithium local environments remain trapped in the solid.%%%Moderate to fast ionic conduction is critical in a wide range of devices or applications, which include fuel cells, sensors, and solid state electrolytes (and cathode materials) in batteries. An understanding of the mechanisms of conduction will help in the design and search for new and improved materials for these applications. The rechargeable battery in many computers (and electronic devices) typically represents the first component of the system to fail: research in this area is critical in order to keep pace with society's increased demand for electrically driven (computer controlled) machinery. The manganate cathodes represent more environmentally-friendly and cheaper alternatives to batteries currently in production.