A Bicontinuous Nanostructure Induced in Lithiated Iron Fluoride Electrodes of Lithium-ion Batteries Investigated by Small-Angle X-ray Scattering

Abstract

In a conversion-type electrode material of lithium-ion batteries, a phase separation phenomenon is induced by charge-discharge reaction. In this study, the spatial periodicity of phase-separated nanostructures induced in the discharged ferrous fluoride (FeF₂) electrodes were investigated using the small-angle X-ray scattering (SAXS) method. The SAXS results of discharged FeF₂ resembled the scattering results of the bicontinuous structures via spinodal decomposition. Thus, the SAXS results showed that the discharged FeF₂ electrodes were modulated nanostructures with a spatial periodicity. SAXS measurements also showed that the size of the discharged FeF₂ nanostructures was dependent on the cycle number. These SAXS finding on the morphological evolution of the nanoscale structure of conversion electrodes should be useful to reveal the mechanism of conversion reactions.