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. In a collaboration with alpha-En Corporation, we have shown 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.
The rods, with lengths in excess of microns, give rise to smooth films of lithium with an iridescent blue color The cell design relies on a lithium ion conducting solid state membrane to transport Li+ ions from an aqueous mineral solution (lithium carbonate or other suitable lithium containing feedstock) to an organic conducting electrolyte in the absence of additives