journal menu
abstracts
Conversion based electrode materials offer increased energy storage compared to conventional intercalation materials due to the multiple electrons that reacts per metal ion. However, loss in capacities upon repeated cycling has limited the development of this technology for commercial application. Most structural studies focus on the first discharge-charge cycle [1,2,3]. To understand the loss in capacities with repeated cycling, studies must be extended beyond the first cycle. In conversion reactions, large structural transformations occur such that the electrode is reduced to the nanoscale. Pair distribution function (PDF) analysis is well suited to characterize the structural changes occurring in such nanomaterials. Conversion based iron fluorides (FeF3, FeF2, and FeOF) have been a focus of both structural and mechanistic studies [1,2,3]. An in-depth PDF analysis of what happens beyond the first cycle will be presented for these.
abstracts
Batteries are complex multicomponent devices wherein mesoscale phenomena-the nanoscale structure and chemistry of different components, and interactions thereof-drive functionality and performance. For example, electron/ion transport within the composite electrodes relies on bi-continuous nanostructuring to form electrically and ionicly conductive paths. Electrochemical conversion of different salts of a given metal yields a common and ostensibly identical product: the zero valent metal. For example, maximal lithiation of iron-based electrodes produces metallic iron nanoparticles for oxide, fluoride, and oxyfluoride electrodes alike. Accordingly, these provide an opportunity to explore the coupling of nanostructure development and anion chemistry, and correlate these with electrochemical performance. We combine synchrotron-based small angle X-ray scattering (SAXS) and pair distribution function (PDF) measurements to probe metallic iron formed by electrochemical conversion of different iron compounds across multiple length-scales and decouple the influence of anion chemistry and reaction temperature on the atomic structure and nanoscale morphology.
