Stability of RbO2 as a Discharge Product of Metal–O2 Batteries

Abstract

This study presents evidence that the discharge products of positive electrodes in metal–oxygen batteries using Rb- and Cs-based electrolytes are RbO₂ and CsO₂, paralleling the findings for Na- and K-based systems. We explored the positive electrode reaction inside alkali metal–oxygen batteries, revealing that the stability of MO₂ compounds (M = Na, K, Rb, Cs) is influenced by the alkali metal ion sizes, achieving maximum reversibility with Rb⁺ ions. Despite the high sensitivity of metal–oxygen batteries to trace amounts of moisture and CO₂ within the cell, we successfully demonstrated stable charge–discharge cycles with a nonaqueous Rb-based electrolyte.