Ultrathin Titanate Nanosheets/Graphene Films Derived from Confined Transformation for Excellent Na/K Ion Storage.

Confined transformation of assembled two-dimensional MXene (titanium carbide) and reduced graphene oxide (rGO) nanosheets was employed to prepare the free-standing films of the integrated ultrathin sodium titanate (NTO)/potassium titanate (KTO) nanosheets sandwiched between graphene layers. The ultrathin Ti-based nanosheets reduce the diffusion distance while rGO layers enhance conductivity. Incorporation of graphene into the titanate films produced efficient binder-free anodes for ion storage. The resulting flexible NTO/rGO and KTO/rGO electrodes exhibited excellent rate performances and long cycling stability characterized by reversible capacities of 72 mA h g-1 at 5 A g-1 after 10000 cycles and 75 mA h g-1 after 700 cycles at 2 A g-1 for sodium and potassium ion batteries, respectively. These results demonstrate the superiority of the unique sandwich-type electrodes.