Uniquely structured Sb nanoparticle-embedded carbon/reduced graphene oxide composite shell with empty voids for high performance sodium-ion storage

Nanostructure design that can effectively buffer volume changes during electrochemical reactions and compositing with carbonaceous materials are considered effective strategies in enhancing the electrochemical properties of Sb-based electrode materials for sodium-ion batteries. In this study, uniquely structured Sb nanoparticle-embedded hollow carbon/reduced graphene oxide (rGO) hybrid microspheres are prepared via facile spray pyrolysis and subsequent one-step heat treatment. Decomposition of metal tartrate chelate results in hollow microspheres with shells containing void spaces. Ultrasmall nanocrystals embedded in carbon/rGO walls are formed due to the inhibition of crystal growth by the rGO matrix surrounding them. The uniqueness of the structure and compositing with rGO matrix enable remarkable electrochemical properties when the microspheres are applied as anode material for sodium-ion batteries. The discharge capacity of the microspheres for the 2nd cycle when cycled at a current density of 0.5 A g(-1) is 433 mA h g(-1), and the capacity retention after 500 cycles, calculated from the 5th cycle, is 80%. They also exhibit excellent rate capability; a discharge capacity as high as 323 mA h g(-1) is achieved at a current density of 3.0 A g(-1).