Rambutan-Like Hybrid Hollow Spheres of Carbon Confined Co3O4 Nanoparticles as Advanced Anode Materials for Sodium-Ion Batteries

Transition metal oxides, possessing high theoretical specific capacities, are promising anode materials for sodium-ion batteries. However, the sluggish sodiation/desodiation kinetics and poor structural stability restrict their electrochemical performance. To achieve high and fast Na storage capability, in this work, rambutan-like hybrid hollow spheres of carbon confined Co3O4 nanoparticles are synthesized by a facile one-pot hydrothermal treatment with postannealing. The hierarchy hollow structure with ultrafine Co3O4 nanoparticles embedded in the continuous carbon matrix enables greatly enhanced structural stability and fast electrode kinetics. When tested in sodium-ion batteries, the hollow structured composite electrode exhibits an outstandingly high reversible specific capacity of 712 mAh g(-1) at a current density of 0.1 A g(-1), and retains a capacity of 223 mAh g(-1) even at a large current density of 5 A g(-1). Besides the superior Na storage capability, good cycle performance is demonstrated for the composite electrode with 74.5% capacity retention after 500 cycles, suggesting promising application in advanced sodium-ion batteries.