On the incompatibility of lithium–O2 battery technology with CO2

Abstract

When solubilized in a hexacarboxamide cryptand anion receptor, the peroxide dianion reacts rapidly with CO₂ in polar aprotic organic media to produce hydroperoxycarbonate (HOOCO₂⁻) and peroxydicarbonate (⁻O₂COOCO₂⁻). Peroxydicarbonate is subject to thermal fragmentation into two equivalents of the highly reactive carbonate radical anion, which promotes hydrogen atom abstraction reactions responsible for the oxidative degradation of organic solvents. The activation and conversion of the peroxide dianion by CO₂ is general. Exposure of solid lithium peroxide (Li₂O₂) to CO₂ in polar aprotic organic media results in aggressive oxidation. These findings indicate that CO₂ must not be introduced in conditions relevant to typical lithium–O₂ cell configurations, as production of HOOCO₂⁻ and ⁻O₂COOCO₂⁻ during lithium–O₂ cell cycling will lead to cell degradation via oxidation of organic electrolytes and other vulnerable cell components.