Progress and perspective on two-dimensional unilamellar metal oxide nanosheets and tailored nanostructures from them for electrochemical energy storage

Research on molecularly thin two-dimensional (2D) nanosheets has experienced significant progress since the discovery of graphene. Due to the high tunability of the structure, composition, and functionality, a great number of recent studies have focused on 2D ultrathin metal oxides, which have shown promising perspectives in many fields, including electrochemical energy storage. In this review, we focus on recent advances in 2D genuine unilamellar metal oxide nanosheets delaminated from their layered parent precursors and overview nanostructured materials based on these nanosheets for electrochemical energy storage applications. In particular, new, molecular-scale integrated superlattice structures fabricated by facile solution-based strategies using 2D unilamellar metal oxide nanosheets as building blocks are highlighted as emerging electrode materials to provide ultimately enhanced performance. Finally, current opportunities and future challenges for research into 2D unilamellar metal oxide nanosheets are proposed and outlined.