3D-engineered WO 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 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 microspheres exhibited a high sodiation capacity of 431 mA h g at 100 mA g and an excellent rate performance of 60 mA h g at 500 mA g 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 could be recovered at a current density of 50 mA g, suggesting excellent sodium storage reversibility.