Holey reduced graphene oxide nanosheets wrapped hollow FeS2@C spheres as a high-performance anode material for sodium-ion batteries

Abstract

Practical application of pyrite FeS2 is severely impeded by sluggish kinetics and large volumetric variation as anode material for sodium-ion batteries. To address these issues, a FeS2@carbon/holey graphene oxide (FeS2@C/HRGO) composite is prepared by self-assembling, in which the hollow FeS2@C spheres are enwrapped by HRGO nanosheets. Thanks to this unique structure, electrons and ions can rapidly migrate throughout the whole particles to construct three-dimensional ion/electron-conductive networks, and meanwhile the internal voids can efficiently accommodate the volumetric variation of FeS2 nanoparticles during cycling to maintain the electrode integrity. The as-prepared FeS2@C/HRGO anode can deliver an initial capacity of 592 mAh g−1 along with an initial coulombic efficiency of 80% at the current density of 0.1 A g−1, and retain a stable capacity of 233 mAh g−1 at the current density of 10.0 A g−1. Even at 5.0 A g−1, it still remains a capacity of 252 mAh g−1 after 1200 cycles. The results demonstrate that synergetic effort of nano-engineering and carbon encapsulation can enhance the electrochemical performance of the FeS2@C/HRGO anode significantly.