Electrochemical characterization of multicomponent sodium cryolite electrolytes with high content of aluminium fluoride

Electrochemical impedance spectroscopy is a suitable measurement method for the investigation of electrical conductivity of new types of aluminium electrolytes. Low-temperature electrolytes together with inert electrodes represent an innovation of the aluminium electrolysis process. Electrical conductivity, as one of the most important properties of electrolytes, has been investigated and described as part of the studied area of low-temperature sodium cryolite mixtures. Electrolytes used in this study contained high content of aluminium fluoride, up to 45 mol %; the molar ratio of NaF to AlF3 in the melts varied from 2.0 to 1.2. Mutual influence of commonly used additives in industrial electrolytes (AlF3, Al2O3, CaF2, MgF2, LiF) and their temperature dependence was determined. Electrical conductivity was measured using a tube-type cell with stationary electrodes applying AC-techniques with a sine wave signal in the high frequency range. Concentration and temperature dependences of the electrical conductivity for all the studied low-temperature multi-component systems were described by the regression equation.