Fully liquid electrorefining: a highly efficient and selective approach for pure lithium metal recovery from low-grade alloys

Abstract

Lithium (Li) metal, a promising anode material for high-energy-density batteries, necessitates high purity that traditional refining methods struggle to achieve efficiently from low-grade metal/alloy feedstocks. Herein, we propose a fully liquid electrorefining (FLE) approach that integrates a liquid alloy anode, a molten salt electrolyte, and a liquid metal cathode in an electrolyzer. This all-liquid configuration enhances ion/atom transport kinetics and reaction selectivity while addressing issues such as anode passivation and cathode dendrite formation. At 450 °C and approximately 100 mA cm⁻², the FLE process successfully extracts Li metal with a purity exceeding 99.90% from both a multicomponent alloy (2.72% Li–96.45% Sn–0.47% Mg–0.36% Ca) and a kilogram-scale alloy (1.68% Li–98.32% Sn). Compared with conventional vacuum distillation, FLE demonstrates superior separation coefficients (β_Li/Sn = 5.01 × 10⁵, β_Li/Mg = 3.21 × 10⁴, and β_Li/Ca = 6.96 × 10³) and significantly reduced energy consumption (7.64 kWh kg⁻¹ Li). This novel approach provides a sustainable and scalable pathway for high-purity lithium production, which is critical for advancing clean energy technologies, while minimizing environmental impact.