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

Practical application of pyrite FeS 2 is severely impeded by sluggish kinetics and large volumetric variation as anode material for sodium-ion batteries. To address these issues, a FeS 2 @carbon/holey graphene oxide (FeS 2 @C/HRGO) composite is prepared by self-assembling, in which the hollow FeS 2 @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 FeS 2 nanoparticles during cycling to maintain the electrode integrity. The as-prepared FeS 2 @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 FeS 2 @C/HRGO anode significantly. • 3D ion/electron conductive networks are formed in the FeS 2 @C/HRGO particles. • Volume change of the FeS 2 nanoparticles is efficiently accommodated. • Electrochemical performance of the FeS 2 anode is improved dramatically.