Chemical Exfoliation of Metal Oxide Nanosheets for High-Performance Ion Conducting Membranes

Two-dimensional (2D)-material-based membranes show great potential for investigating mass and charge transport inside multiple nanoconfined capillaries. The weak interaction between the surface charges and ions in the hydrophilic nanofluidic channels makes it favorable for fast ion transport. In this work, we report the general synthesis of negatively charged metal oxide nanosheets through ion intercalation. Thereof, the Ti0.88O20.48– nanosheet dispersion was used to fabricate self-assembled membranes, which exhibit Li ion conductivity of 0.21 and 0.62 S cm–1 at ambient temperature and 90 °C, respectively. The high Li ion conductivity is due to the well-ordered 2D water networks, low ion transport barrier, and abundant ion provider centers. The implementation of the CoO2– membrane demonstrates the versatility of the role of surface-charged metal oxides for ion transport. Such high-performance membrane highlights new possibilities for discovering unusual nanofluidic phenomena in the nanosized channels enabled by controlled assembly of 2D nanomaterials.