3D-engineered WO 3 microspheres assembled by 2D nanosheets with superior sodium storage capacity.

Because of the inadequate sodium storage capacity of graphite, the exploration of high-performance SIB anodes is a crucial step forward. Herein, we report the hydrothermally synthesized self-assembled interconnected nanosheets of WO 3 microspheres possessing admirable sodium storage in terms of cycling stability and acceptable rate capability. Benefitting from the interconnected nature of the nanosheets with a hollow interior, the WO 3 microspheres exhibited a high sodiation capacity of 431 mA h g -1 at 100 mA g -1 and an excellent rate performance of 60 mA h g -1 at 500 mA g -1 with an impressive coulombic efficiency of around 99%. Importantly, even after continuous cycling with increasing current densities, a specific capacity as high as 220 mA h g -1 could be recovered at a current density of 50 mA g -1 , suggesting excellent sodium storage reversibility.