Study on the electrochemical behaviour of Al3+ in LiCl‐KCl‐AlCl3 melt

Abstract

AbstractThe electrochemical behaviour of Al3+ reduction on a tungsten electrode in LiCl‐KCl‐AlCl3 molten salt was investigated by electrochemical techniques. Using cyclic voltammetry (CV) and square wave voltammetry (SWV), Al3+ was reduced to Al in one step, and Li was deposited on Al to form Al‐Li alloys of different compositions. According to chronoamperometry (CA), co‐deposition of Li‐Al alloys can be obtained at cathode current densities greater than 0.045 A cm−2 or cathode potentials lower than −2.28 V (vs. Ag/AgCl). The apparent standard potential was calculated using the equilibrium electrode potential obtained from the open‐circuit chronopotentiometry. Al3+ diffusion coefficient calculated by CV at 703 K is 0.82 × 10−5 cm2/s. In addition, the diffusion activation energy of Al3+ in LiCl‐KCl‐AlCl3 molten salt was also obtained using the Arrhenius equation. The linear polarization was used to calculate exchange current density at different temperatures. Based on the theoretical model of metal nucleation deposition developed by Scharifker and Hills, the nucleation process of Al3+ involves instantaneous nucleation in the range of 673~763 K.