Rechargeable batteries with higher energy densities are fundamental to meeting the ever-increasing requirements of consumer electronics, electric vehicles, and a burgeoning renewable energy economy. Fluoride ion batteries (FIBs) exhibit among the highest theoretical volumetric energy densities of any lithium or post-lithium ion technology under consideration. This potential capability arises from the coupling of highly dense anode (metal) and cathode (metal fluoride) materials through use of an anionic charge carrier (F-). However, at this incipient stage, the discharge/charge mechanism at both electrodes is still poorly understood; furthermore, the design of a liquid electrolyte system for long-term cycling stability has not been fully realized. In studying the behavior of transition metal fluorides in lithium ion batteries, our group has achieved a comprehensive mechanistic evaluation and stable long-term cycling through the use of monodisperse, nanocrystalline metal fluoride cathodes and ionic liquid electrolytes. This same methodology lends itself to the study of fluoride ion batteries.
In this project, the student will study the electrochemical phase evolution and mass/charge transport of transition metal fluoride cathodes in fluoride ion batteries. To this end, the student is expected to become experienced in advanced nanoparticle synthesis techniques and the use of ex-situ TEM/SEM to characterize structural and morphological changes during battery cycling. In addition, the student will aid in the development of new in-situ TEM and X-ray techniques for collection of time-resolved structural and chemical data under realistic battery conditions. Complementary to understanding the mechanism of FIB cathode reactions, this project seeks to engineer high performance FIB chemistries. The student will work closely with other group members to optimize electrolyte compositions for stability and ionic conductivity and to tailor electrode surface compositions to mitigate dissolution and side reactions. This work will involve use of surface/interfacial characterization techniques including impedance spectroscopy, XPS, Raman, and SEM-EDX.