Toward Transformative Ambient Rare Earth Metal Electrorefining: A Perspective on Electrolyte Design and Circular Processing

Abstract

Ambient electrochemical production of rare earth metals (REMs) in organic electrolytes has emerged as a promising alternative to conventional high-temperature and chemically intensive processes. Over the past two decades, a limited number of research groups have demonstrated the feasibility of REM electrodeposition under room temperature conditions. However, practical implementation remains limited by challenges in metal stability, selectivity, electrolyte performance, and scalability. This perspective critically assesses reported ambient REM electrochemical systems, including ionic liquid, solvent-based, ligand-coordinated, and mediated strategies. Particular attention is given to efforts toward coupling REM production with rare earth element recovery, including direct and indirect electrorefining of spent NdFeB magnets. While conceptually promising, these approaches reveal key limitations, such as complex hydrometallurgical processing, limited anodic dissolution and loss of REM selectivity. Another central focus is the insufficient validation of electrodeposition product quality and performance, as reported characterization techniques often provide inconclusive evidence regarding purity and metallic REM formation. Future progress requires integrated advances in coordination chemistry, interfacial electrochemistry, electrolyte and electrode design, alongside process engineering and technoeconomic assessment. Within this framework, a conceptual M2REM (Magnet-To-Rare Earth Metal) is illustrated as an example of integrated electrorefining platform for the direct and ambient transformation of spent magnets into REMs, paving the way for energy-efficient and circular rare earth metal processing.