Electrochemical impedance spectroscopy study on intercalation and anomalous diffusion of AlCl-4 ions into graphite in basic molten salt

Abstract

Electrochemical impedance spectroscopy (EIS) was employed to investigate diffusion of AlCl4- ions in basic (AlCl 3-NaCl-KCl) molten salt. Nyquist plots in different DC offset potentials showed finite and restricted aluminum ion diffusion due to insertion and blocking in the graphite electrode. The general Warburg, open Warburg, and short Warburg impedance in the complex Nyquist plot of this system showed the anomalous diffusion behavior of the ions in the graphite electrode. The diffusion coefficient of the AlCl4-ions was calculated from the slope of the Warburg line in a totally blocking film in the graphite electrode and was found to be 2.8 × 10-10 cm2/s.