Structure Property Relations in Ceramic Composites for Energy Conversion and Storage
Mixed ionic-electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Lower resistance to ionic transport may improve the performance of many electrochemical devices (batteries, fuel cells). In model ceramic systems consisting of an ionic conductive phase and an electronic conductive phase we recently reported the concept of targeted phase formation that serves to enhance the grain boundary ionic conductivity. The formation of an emergent phase successfully avoided segregation of the Gd dopant and depletion of oxygen vacancies at the Ce0.8Gd0.2O2-δ-Ce0.8Gd0.2O2-δ grain boundary. This resulted in superior grain boundary ionic conductivity as demonstrated by the enhanced oxygen permeation flux. This work illustrates the control of mesoscale level transport properties in mixed ionic-electronic conductor composites through processing induced modifications of the grain boundary defect distribution. Current work is focused on application of these principles to the fabrication and testing of solid-state lithium ion battery electrolytes such as Li7La3Zr2O12. This is an opportunity to conduct fundamental research on ceramic materials used for energy conversion and storage, with broad implications on topics ranging from batteries and fuel cells to nuclear waste immobilization.
The REU student will work towards understanding the link between composition, processing, microstructure and performance of these materials. The goal of the REU project will be to understand the combined effects of composition and processing induced microstructural modifications to the electrical properties of the material. The REU students will be 1) responsible for fabricating electrolyte materials from solid state and chemical solution processing routes 2) optimize the time and temperature conditions for phase formation and densification, 3) measure the crystal structure of the primary and any associated secondary phases and 4) examine the local chemical composition and microstructure with Scanning Electron Microscopy techniques and 5) measure the temperature dependent conductivity of the samples using AC impedance spectroscopy. The REU student will participate in REU: Surfaces and Interfaces activities, as well as Brinkman Research Group activities. The REU student will collect, analyze, and regularly present data in a highly active research environment. Finally, the REU student will receive high-quality mentoring from a Postdoctoral researcher and Dr. Brinkman.