Boosted pseudocapacitance contribution in lithium ion storage performance of Fe3O4/Fe7S8 anode by nanoscale heterostructuring

The hexagonal sheet shaped Fe3O4/Fe7S8 heterojunction with lateral size of 1.5 μm has been controllably synthesized by gas sulfuration process. The most fascinating performance of this Fe3O4/Fe7S8 heterojunction structure is that the capacity attenuation is rather small of only 18%, from 818 mAh·g−1 to 670 mAh·g−1, when the current density increases ten-fold from 0.2 A·g−1 to 2.0 A·g−1. This high capacity retention upon current density shifting, is attributed to pseudocapacitance contribution, which is related to the two-dimensional hexagonal structure, faster electron/ion transfer and synergistic effect for the stepwise lithiation of Fe3O4 and Fe7S8 at different voltage in Fe3O4/Fe7S8 heterojunction. This rational design on heterojunction structure sheds light on further constructing novel anode material for secondary ion batteries.