Structure adapting of bulk FeS2 micron particles and the corresponding anode for high performance sodium-ion batteries

The practical application of Pyrite iron disulfide (FeS2) as anode material of sodium-ion battery is limited by its low electronic conductivity, large volume changes during charge/discharge. To overcome these challenges, a novel structure design single-walled carbon nanotubes (SWCNTs) composited polyaniline (PANI)-wrapped FeS2 (FeS2-PANI-SWCNTs) electrodes are successfully achieved in this work. PANI can protect the FeS2 particles from collapse and offer a protective layer to relive the polysulfides shuttling effect, and also promote the electron and Na+ diffusion during the chemical conversion process. Under the dual protection of PANI and SWCNTs, the FeS2-PANI-SWCNTs film electrode demonstrates a good structural integrity, which accounts for the excellent rate capability and long cycling performance. In addition, the PANI coating and SWCNT network in the fabricated electrode can synergistically anchor polysulfides and therefore strongly suppress shuttle effect during the charge–discharge processes, resulting in less capacity loss. The anode with a loading 3.2 mg cm−2 of FeS2 coated with PANI exhibits the initial coulombic efficiency of 81.5% and delivers a specific capacity of 625.8 mAh g−1 after 100 cycles at 200 mA g−1. High flexible and binder-free FeS2-PANI-SWCNTs film anode demonstrates a reversible capacity of 537 mAh g−1 after 550 cycles at 1 A g−1. This research may offer an efficient method to improve electrochemical performance of the metal sulfides in sodium-ion batteries.