Direct synthesis of FeS/N-doped carbon composite for high-performance sodium-ion batteries

Fe-based sulfides have received tremendous attention as promising anode materials for sodium ion batteries (SIBs) owing to their advantages of abundant resources, high theoretical specific capacity, and environmental benignity. However, unsatisfactory electronic conductivity and severe volume change during the cycling process limit their applications. Here, an FeS/N-doped carbon composite (FeS/NC) is designed and prepared through an in situ chemical transformation method via pyrolyzing a mixture of Fe(NO3)(3) and urea followed by sulfidation. The individual FeS nanoparticles are coated by the in situ formed nitrogen-doped carbon and then embedded in the ultrathin carbon sheets. When evaluated as an anode material for SIBs, the composite delivered a high charge capacity of 511 mA h g(-1) after 100 cycles at 200 mA g(-1), 326 mA h g(-1) after 500 cycles at 1.0 A g(-1), and exhibited a superior rate performance of 260 mA h g(-1) at 4.0 A g(-1). This good electrochemical performance of the FeS/NC can be ascribed to the in situ carbon-coating effectively alleviating the volume change of FeS particles during the cycling process and the interconnected ultrathin carbon sheets enhancing the electronic conductivity of the ensemble.