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

Abstract

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.