Research progress in mechanisms and processes for producing metallic magnesium by molten-salt electrolysis of MgO

Metallic magnesium and its alloys are important lightweight materials for new-energy vehicles, aerospace and emerging low-altitude applications. Their growing use has intensified the need for low-carbon production technologies with broad feedstock adaptability. Molten-salt electrolysis of MgO can directly utilize diverse magnesium-bearing oxide resources and offers the potential for large-scale, continuous and clean magnesium production. However, the solubility of MgO in fluoride melts is typically below 1 wt.%, resulting in an insufficient O 2− supply, concentration polarization, anode effects and reduced current efficiency, which collectively constitute the principal barrier to process development. Focusing on MgO molten-salt electrolysis, this review connects four interdependent aspects: MgO dissolution, molten-salt regulation, electrode/electrolyte interfacial reactions and mass transfer, and electrolysis process routes. MgF 2 -LiF-based melts, multicomponent fluoride systems and additive-regulation strategies are critically assessed to elucidate how electrolyte composition governs MgO solubility, melt properties and electrochemical behavior. Direct electrolysis, solid-cathode electrolysis, liquid-metal-cathode electrolysis and MgO chlorination-electrolysis are further compared in terms of ion transport, interfacial reactions, Mg formation, current efficiency and product purity. By correlating dissolution mechanisms and electrolyte structure with interfacial transport and process performance, this review identifies low-solubility-induced mass-transfer limitations as the central challenge and demonstrates that coordinated optimization of the electrolyte, electrode interfaces and process configuration is essential for efficient, low-carbon and scalable magnesium production.