Integrated carbon nanospheres arrays as anode materials for boosted sodium ion storage

Developing cost-effective advanced carbon anode is critical for innovation of sodium ion batteries. Herein, we develop a powerful combined method for rational synthesis of free-standing binder-free carbon nanospheres arrays via chemical bath plus hydrothermal process. Impressively, carbon spheres with diameters of 150–250 nm are randomly interconnected with each other forming highly porous arrays. Positive advantages including large porosity, high surface and strong mechanical stability are combined in the carbon nanospheres arrays. The obtained carbon nanospheres arrays are tested as anode material for sodium ion batteries (SIBs) and deliver a high reversible capacity of 102 mAh g⁻¹ and keep a capacity retention of 95% after 100 cycles at a current density of 0.25 A g⁻¹ and good rate performance (65 mAh g⁻¹ at a high current density of 2 A g⁻¹). The good electrochemical performance is attributed to the stable porous nanosphere structure with fast ion/electron transfer characteristics.