In situ synthesis of iron sulfide embedded porous carbon hollow spheres for sodium ion batteries

Iron sulfide embedded porous carbon hollow spheres (FeS_x@CS) have been successfully synthesized through a facile and environment friendly in situ synthetic method. Using this method, a porous carbon matrix and uniformly dispersed iron sulfide nanoparticles were formed simultaneously and assembled into hollow spheres. The as-synthesized FeS_x@CS material showed high reversible capacity, outstanding cycle performance, and excellent rate capability when it was applied as an anode material for sodium ion batteries. It delivered a remarkable charge capacity of 656.75 mA h g^-1 in the first cycle and a capacity retention of 97% after 100 cycles. When the current density was increased from 50 mA g^-1 to 1000 and 2000 mA g^-1, high capacity retention of 76.3% and 62.5% was achieved, respectively.