Nanostructured porous RuO2/MnO2 as a highly efficient catalyst for high-rate Li–O2 batteries

Abstract

Despite the recent advancements in Li–O₂ (or Li–air) batteries, great challenges still remain to realize high-rate, long-term cycling. In this work, a binder-free, nanostructured RuO₂/MnO₂ catalytic cathode was designed to realize the operation of Li–O₂ batteries at high rates. At a current density as high as 3200 mA g⁻¹ (or ∼1.3 mA cm⁻²), the RuO₂/MnO₂ catalyzed Li–O₂ batteries with LiI can sustain stable cycling of 170 and 800 times at limited capacities of 1000 and 500 mA h g⁻¹, respectively, with low charge cutoff potentials of ∼4.0 and <3.8 V, respectively. The underlying mechanism of the high catalytic performance of MnO₂/RuO₂ was also clarified in this work. It was found that with the catalytic effect of RuO₂, Li₂O₂ can crystallize into a thin-sheet form and realize a conformal growth on sheet-like δ-MnO₂ at a current density up to 3200 mA g⁻¹, constructing a sheet-on-sheet structure. This crystallization behavior of Li₂O₂ not only defers the electrode passivation upon discharge but also renders easy decomposition of Li₂O₂ upon charge, leading to low polarizations and reduced side reactions. This work provides a unique design of catalytic cathodes capable of controlling Li₂O₂ growth and sheds light on the design of high-rate, long-life Li–O₂ batteries with potential applications in electric vehicles.