The reactivity of bare lithium metal surfaces in contact with various organic electrolytes

An in situ cutting technique has been developed to expose bare lithium metal in various organic electrolyte environments. The corrosion potential-time transients have been measured. The electrolytes investigated were LiAsF₆, LiPF₆, LiBF₄, LiClO₄, and Li(CF₃SO₂)₂N in tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2Me-THF), and propylene carbonate (PC). The transients permit the ranking of the reactivity of the electrolytes and show that the passivating reactions are completed in less than one second, even for very carefully purified electrolytes. Cyclic voltammetry and normal Raman spectroscopy (NRS) have also been used to characterize the lithium/organic electrolyte interface. For LiAsF₄/THF and 2Me-THF, NRS has given evidence for reduction of As(V) to As(III) by the bare lithium metal at open-circuit potential. The measurements have shed light on the understanding of the stability of various salts and solvents in contact with lithium