Lithium nitrate as regenerable SEI stabilizing agent for rechargeable Li/O₂ batteries

A major unsolved problem with rechargeable Li/O₂ batteries is the identification of electrolyte compositions that allow efficient and stable cycling of both Li metal and O₂ electrodes simultaneously. Previously, lithium nitrate (LiNO₃) was employed in a rechargeable Li/O₂ battery to stabilize the solid-electrolyte interphase on Li metal in an electrolyte based on N,N-dimethylacetamide (DMA), a solvent with favorable properties vis-à-vis the O₂ electrode. We show that LiNO₃ is regenerated following reaction with Li metal in the presence of dissolved O₂, which may account for the surprising long-term cycling previously demonstrated in DMA. According to this new concept, nitrate anions incorporated into the electrolyte react with Li metal to form soluble nitrite anions and a passivating layer of Li₂O on the Li electrode surface. The soluble nitrite anions subsequently react with dissolved O ₂ through a combined electrochemical and chemical process that results in regeneration of nitrate. Discovery of this regenerative principle provides a strategy for using other solvents that have favorable characteristics in the O₂ electrode but are highly unstable toward Li metal without the use of a ceramic Li-ion-conducting membrane.