High-Purity Lithium Metal Films from Aqueous Mineral Solutions

Abstract

Lithium metal is a leading candidate for next-generation electrochemical energy storage and therefore a key material for the future sustainable energy economy. Lithium has a high specific energy, low toxicity, and relatively favorable abundance. The majority of lithium production originates from salt lakes and is based on long (>12 months) periods of evaporation to concentrate the lithium salt, followed by molten electrolysis. Purity requires separation from base metals (Na, K, Ca, Mg, etc.), which is a time-consuming, energy-intensive process, with little control over the microstructure. Here, we show how a membrane-mediated electrolytic cell can be used to produce lithium thin films (5-30 μm) on copper substrates at room temperature. Purity with respect to base metals content is extremely high. The cell design allows an aqueous solution to be a continuous feedstock, advocating a quick, low-energy-consumption, one-step-to-product process. The film morphology is controlled by varying the current densities in a narrow window (1-10 mA/cm²), to produce uniform nanorods, spheres, and cubes, with significant influence over the physical and electrochemical properties.