Understanding the conversion mechanism and performance of monodisperse FeF2 nanocrystal cathodes

Researchers in Professor Nicole Grobert's and Professor Mauro Pasta's groups present a new system for mechanistic study, as set out in this paper published in Nature Materials.

The colloidal synthesis of single-crystalline, monodisperse iron fluoride nanorods was explored.  High-resolution analytical transmission electron microscopy revealed intricate morphological features, lattice orientation relationships and oxidation state changes that comprehensively described the conversion mechanism.  Phase evolution, diffusion kinetics and cell failure were critically influenced by surface-specific reactions.

The reversibility of the conversion reaction was governed by topotactic cation diffusion through an invariant lattice of fluoride anions and the nucleation of metallic particles on semicoherent interfaces.