The electrochemical behavior of cathodic process was investigated by means of cyclic voltammetry

electrochemical impedance spectroscopy and square wave voltammetry in both Na3AlF6-Al2O3 and Na3AlF6-Al2O3-KF systems. The results showed that the reduction peaks shifted negatively and oxidation peak shifted positively with the increase of scan rate from the measurement of cyclic voltammetry. The reaction process was irreversible under the condition of lower scan rate

and the reaction was relatively flat and stable

but the reduction process became reversible gradually with the increase of scan rate. Because of polymerization phenomenon at the electrode-site

inductance phenomenon appeared in the high frequency area when KF was absent in the molten salt. Under the condition of containing KF

the reaction was predominantly controlled by charge transfer and diffusion. The growth of the concentration of KF could decrease diffusion impedance coefficient and increase reaction current. The charge transfer process gradually replaced the diffusion process and accelerated oxidation rate. Meanwhile the reduction and oxidation process became reversible. Adding KF also suppressed the deposition of aluminum and alloying effect was obvious. Through Gaussian fitting for the cathodic prewave

electron transfer numbers of Al ion were 1.19

1.02 and 0.75 in different systems of KF concentration（0，3%，5%）respectively.