Electrolytes and its additives used in aluminum reduction cell: a review

The electrolyte is considered to play the role of blood in an aluminum reduction cell and performs several vital functions as the charge transfer, the mass dissolution and transfer, the electrode products separation and the electrical work dissipation. The proper performance of listed functions is completely determined by the physical and chemical properties, which namely are the electrical conductivity, the viscosity, the vapor pressure, the liquidus and solidus temperatures, the density, the surface tension, the solubility and the dissolution rate of oxides, aluminum, carbon and the various connections and by operating conditions, which namely are the temperature, the current density, the anode-cathode distance, etc. The electrolyte affects the current efficiency and the cell voltage, which determines the specific energy consumption and the total cost of aluminum. This is the reason why different electrolytes and additives have been in the spotlight of the researchers and the enterprises for decades. This article presents the brief information about the influence of additives in the cell utilizing traditionally used sodium cryolite and different low-temperature electrolytes on physical-chemical properties and concentrates on the latest works which have not been included in widely known textbooks. The article also contains new experimental results obtained by the authors and devoted to the effective electrical conductivity of suspended unconventional electrolytes.