How are fluorine compounds used to produce aluminum metal?

Fluorine compounds are essential to the production of aluminum metal through the Hall-Héroult process, which is the primary commercial method for aluminum smelting.1

In this process, alumina (aluminum oxide) is dissolved in a molten electrolyte bath consisting primarily of cryolite (sodium fluoroaluminate, ${\text{Na}}_3{\text{AlF}}_6$). This fluoride-based electrolyte allows the alumina to be reduced to metallic aluminum via electrolysis.21

Because some fluoride is inevitably lost during the smelting operation, aluminum fluoride is added periodically to the bath to maintain the necessary chemical composition and ensure maximum efficiency. While natural cryolite is rare, the industry relies on synthetic cryolite, which is manufactured using fluorine derived from sources such as fluorspar or hydrogen fluoride.1234