Highly-efficient MnO₂/carbon array-type catalytic cathode enabling confined Li₂O₂ growth for long-life Li–O₂ batteries

Li–O₂ batteries recently have attracted intensive research interest because of the rather high energy density. The electrochemical performance of Li–O₂ batteries, however, is largely limited by the insulating and reactive Li₂O₂, which necessitates a renovation on the design of catalytic cathodes. In this work, we propose a unique MnO₂/carbon submicron tube (MnO₂/CST) array-type catalytic cathode capable of controlling Li₂O₂ growth spatially and structurally. The high catalytic activity of ultrathin MnO₂ nanosheets enables conformal growth of thin-layered Li₂O₂ on the MnO₂ sheets, which relieves or defers electrode deactivation upon discharge and renders easy catalytic decomposition of Li₂O₂ upon charge. In situ transmission electron microscopy characterization confirms the presence of Li₂O₂ on discharged MnO₂/CST and reveals the phase transition and morphology changes upon charge. The array-type architecture of the catalytic cathode facilitates barrier-free transportation of oxygen gas and Li ions. The absence of polymer binder and the reduced carbon exposure to Li₂O₂ (or LiO₂) exclude or minimize the parasitic reactions related to binder and carbon. As a result, Li–O₂ cells with MnO₂/CST catalytic cathode exhibit superior cycling stability and low polarization. At 800 mA g^–1, the cell can sustain a stable cycling of over 300 cycles at a limited capacity of 1000 mAh g^–1.