Nontechnical Abstract: The structural integrity of a crystalline material is an important property that can greatly influence its ability to be utilized in practical applications. For electrochemical energy storage devices, daily operation involves the electrochemical insertion and extraction of ions, which is often accompanied by larger structural transformations that may cause the material to collapse. Hence, the search for new electrode materials is necessary in order for future energy storage demands to be realized. Clathrates are a class of materials with cage-like structures that can naturally hold guest ions, a feature that may be exploited in energy storage applications. However, different features in the clathrate bonding arrangement may affect its mechanical integrity. Key objectives of this project are to understand the electrochemical characteristics of these materials, how the structure of the clathrate changes upon electrochemical insertion of guest ions, and the development of new synthetic routes to obtain clathrates. Results from this project enable new knowledge on the intricate relationships among the clathrates? structures and their physical properties, electrochemical characteristics, and structural stability.
The objectives of this project are: (1) to investigate the electrochemical and structural properties of germanium and tin clathrates using first principles calculations and detailed structural characterization to understand the electrochemically obtained structures; and (2) to synthesize new clathrates containing lithium ions from novel precursors. The project uses a concerted approach combining the synthetic, structural and electrochemical characterization, and theoretical expertise of the investigators. The research enables a better understanding of the relationship between the clathrate structure and its physical properties, electrochemical characteristics, and phase stability. These achievements could lead to higher energy density lithium and sodium batteries. The studies also help to build up the predictive power of solid-state chemistry, establishing new ideas of why and how atoms assemble and form new compounds and structures with the desired electrochemical properties. Investigation of these materials involves a collaboration between two universities (Arizona State University and University of Delaware) and three different departments (materials science, chemistry, and physics), which exposes students to multidisciplinary research. Outreach and educational activities engaging students ranging from the middle school to undergraduate levels, with an emphasis on recruiting females into science and engineering and improving student learning and engagement in introductory undergraduate classes.
