Nitrogen-Doped Porous Carbon Framework Supports Ultrafine FeS₂ Nanoparticles as Advanced Performance Anode Materials for Sodium-Ion Batteries

FeS2 as a sodium-ion battery anode material has attracted great attention on account of its high theoretical capacity, abundance, low cost, and other advantages. However, the poor electrical conductivity of FeS2 and the huge volume expansion in the sodium-ion insertion/extraction process are the key factors affecting its electrochemical performance. Herein, NaCl was used as a template to successfully synthesize a composite material of a nitrogen-doped porous carbon framework loaded with ultrafine FeS2 nanoparticles (FeS2/NPCF). The three-dimensional porous carbon framework improves the conductivity of the material as well as effectively suppresses the volume expansion of the material during the charge and discharge process, thus improving the cycle performance of the composite material. In the three-dimensional porous carbon framework with a larger specific surface area, ultrafine FeS2 particles can lessen the diffusion distance and enhance the Na+ diffusion rate. The ultrafine FeS2 nanoparticles loaded on the nitrogen-doped highly conductive porous carbon framework reduce the e-transport resistance and limit the volume change of FeS2 during the cycle, which improves the structure’s stability. These advantages make FeS2/NPCF an ideal anode electrode material of a sodium-ion battery that shows excellent sodium storage performance. A reversible capacity of 552 mAh g–1 is maintained with a capacity retention of 87% at 0.5A g–1 after 100 cycles. Remarkably, even at 5A g–1, the FeS2/NPCF electrode still delivers a discharge capacity of 430 mAh g–1after 500 cycles. FeS2/NPCF, with its excellent electrochemical performance, is considered a potential anode material for sodium-ion batteries.