Oxygen‐Deficient Birnessite‐MnO2 for High‐Performing Rechargeable Aqueous Zinc‐Ion Batteries

Abstract The development and commercialisation of Zinc‐Ion Batteries (ZIBs) faces a daunting challenge caused by the limited selection of cathode materials. Among all the available choices, Manganese‐Based Oxides show the most promising potential due to the various benefits such as, low costs, natural abundance of Manganese, environmental benignity and its multiple valence states. Most notably, Manganese Dioxide (MnO 2 ) as a cathode material for ZIBs has always been a popular area of research as it can exist in various phases with tunnelled and layered structures for the (de‐)intercalation of Zn 2+ ions. However, despite many works reported on enhancing the electrochemical performances of MnO 2 , most of the proposed methodologies of improving the performance is based on Zn 2+ ion insertion kinetics and these methods has been pushed to saturation. Herein, we propose an alternative direction of creating oxygen deficiency via defect engineering to enhance the surface‐capacitive electrochemical performance of MnO 2 . In this work, the Zn//Oxygen‐deficient Birnessite‐MnO 2 achieved a specific capacity of 378 mAh g −1 which is one of the highest among other existing Zn//Birnessite‐MnO 2 battery systems. Thus, this work is expected to shine light on the potential of defect engineering as a strategy to enhance electrochemical performances of MnO 2 .