Amorphous iron phosphate/carbonized polyaniline nanorods composite as cathode material in sodium-ion batteries

As-prepared polyaniline (PANI) nanorods have been used to synthesize an iron phosphate/polyaniline (FePO4/PANI) composition through the microemulsion technique. After sintering at 460 °C under a nitrogen protective atmosphere, the PANI carbonized, yielding the amorphous iron phosphate/carbonized polyaniline nanorods (FePO4/CPNRs) composite, which acts as the cathode material in sodium-ion batteries (SIBs). The electrochemical performance of FePO4/CPNRs composite shows an initial discharge specific capacity of 140.2 mAh g−1, with the discharge specific capacity being maintained at 134.4 mAh g−1 after the 120th cycle, up to 87.9 % of the theoretical capacity (154.1 mAh g−1 for NaFePO4), as well as an excellent rate capability in sodium-ion batteries. Compared with pure FePO4, the electrochemical performance has been greatly improved. On the one hand, using the CPNRs as conductive medium significantly improves electronic transport. On the other hand, the FePO4 sphere of nanoscale particles, which has a large specific surface area, can promote an active material/electrolyte interface reaction and improve the speed of sodiation and desodiation during the charge and discharge process. The amorphous FePO4/CPNRs composite shows outstanding electrochemical performance as competitive cathode material in SIBs.