Structure-designed synthesis of FeS2@C yolk-shell nanoboxes as a high-performance anode for sodium-ion batteries

Pyrite (FeS2) is an attractive anode material for sodium-ion batteries (SIBs) with a high theoretical capacity of 894 mAh g(-1). However, its practical application is greatly hindered by the rapid capacity fading caused by the large volume expansion upon sodiation. Tuning the morphology and structure at nanoscale and applying a higher cut-off voltage are essential to address this issue. Here, a facile etching method coupled with a novel sulfidation-in-nanobox strategy is developed to synthesize unique FeS2@C yolk-shell nanoboxes. The as-obtained FeS2@C nanoboxes reveal excellent sodium storage performance. The remarkable electrochemical properties are attributed to the elaborate yolk-shell nanoarchitecture. In particular, it delivers a high specific capacity of 511 mAh g(-1) at 100 mA g(-1) after 100 cycles. Furthermore, a high specific capacity of 403 mAh g(-1) even at 5 A g(-1) is delivered. Most impressively, a stable capacity of 330 mAh g(-1) can still be retained at 2 A g(-1) even after 800 cycles.