Integrating conductivity and active sites: Fe/Fe3C@GNC as an trapping-catalyst interlayer and dendrite-free lithium host for the lithium–sulfur cell with outstanding rate performance

Abstract

Lithium–sulfur batteries have attracted wide attention due to its extremely high theoretical energy density, but suffer from severe intermediate shuttle and sluggish reaction kinetics on the cathode along with rigorous dendrite growth on the anode. Herein, a highly graphitic N-doped carbon matrix implanted by dual-role Fe and Fe₃C nanoparticles (Fe/Fe₃C@GNC) is designed to simultaneously tackle challenges existing in both cathode and anode. On the cathode, a Fe/Fe₃C@GNC interlayer guaranteed excellent rate capability even at 55 °C (442 mA h g⁻¹ in 10C) featuring rapid Li⁺ diffusivity, low barrier of Li₂S decomposition, and improved electron/ion conductivity. On the anode, a thin layer of Fe/Fe₃C@GNC with lithiophilic surface as an ideal Li host effectively suppressed the Li dendrite growth and regulated Li plating/stripping, thus leading to outstanding cycling stability even at a high current density of 5 mA cm⁻². On this basis, a brand-new Li–S full cell was constructed by simultaneously employing Fe/Fe₃C@GNC as an interlayer sandwiched between the cathode and separator, as well as a lithium metal anode host. As a result, the as-prepared full cell demonstrates boosted performance of 598 mA h g⁻¹ at 2C.