Study on the Initial Crystallization Temperature of the Na3AlF6-K3AlF6-Li3AlF6-AlF3-KF-Al2O3 Electrolyte System

The primary crystallization temperature of an electrolyte is a critical parameter in the aluminum electrolysis process, determining the operating temperature of the electrolytic process. Therefore, the initial crystallization temperature is one of the most critical physicochemical properties of the electrolyte in the electrolytic aluminum process. However, the Na 3 AlF 6 -AlF 3 electrolyte system, which is predominantly used in industrial electrolysis systems, operates at high temperatures. Lowering the electrolysis temperature would lead to numerous issues, including reduced current efficiency and increased cell voltage. Therefore, we propose low-temperature aluminum electrolysis in the Na 3 AlF 6 -K 3 AlF 6 -Li 3 AlF 6 -AlF 3 -KF-Al 2 O 3 electrolyte system. The synergistic effect of K 3 AlF 6 and Li 3 AlF 6 on the initial crystallization temperature within this system was investigated. Results indicate that at a cryolite molar ratio (CR) of 1.7–2, each unit of K 3 AlF 6 added reduces the initial crystallization temperature by an average of 2–4°C, while each unit of Li 3 AlF 6 added lowers it by an average of 0.5–3.5°C. Analysis of the cold-quenched electrolyte phases indicates the formation of phases such as Na 5 Al 3 F 14 , K 2 NaAlF 6 , and Na 2 LiAlF 6 within the electrolyte system. This study systematically measured the initial crystallization temperatures of the Na 3 AlF 6 -K 3 AlF 6 -Li 3 AlF 6 -AlF 3 -KF-Al 2 O 3 electrolyte system. It significantly advances the progress of the aluminum electrolysis industry toward green and low-carbon development, opening new technical pathways for achieving energy conservation and emission reduction targets in aluminum electrolysis production processes. Graphical