Au-nanocrystals-decorated δ-MnO2 as an efficient catalytic cathode for high-performance Li–O2 batteries

Abstract

A Li–O₂ battery works based on the reversible formation and decomposition of Li₂O₂, which is insulating and highly reactive. Designing a catalytic cathode capable of controlling Li₂O₂ growth recently became a challenge to overcome this barrier. In this work, we present a new design of catalytic cathode by growing porous Au/δ-MnO₂ electrocatalyst directly on a conductive substrate. We found that Au/δ-MnO₂ can catalyze the directed growth of Li₂O₂ into a thin/small form, only inside porous δ-MnO₂, and along the surface of δ-MnO₂ sheets. We proposed the catalytic mechanism of Au/δ-MnO₂, where Au plays a critical role in catalyzing the nucleation, crystallization and conformal growth of Li₂O₂ on δ-MnO₂ sheets. Li–O₂ batteries with an Au/δ-MnO₂ catalytic cathode showed excellent electrochemical performance due to this favorable Li₂O₂ growth habit. The battery yielded a high capacity of 10 600 mA h g⁻¹ with a low polarization of 0.91 V at 100 mA g⁻¹. Superior cycling stability could be achieved in both capacity-limited (500 mA h g⁻¹, 165 times at 400 mA g⁻¹) and unlimited (ca. 3000 mA h g⁻¹, 50 cycles at 800 mA g⁻¹) modes.