Iron-nitrogen-carbon species boosting fast conversion kinetics of Fe1-xS@C nanorods as high rate anodes for lithium ion batteries

Iron mono-sulfide anodes suffer from severe irreversible capacity loss due to their poor electronic conductivity and the formation of lithium polysulfide intermediates during cycles. Here, rod-like iron-nitrogen-carbon species integrated Fe1-xS@C composites (r-Fe-N-Fe1-xS@C) are successfully prepared via a one-step simultaneous sulfidation and nitridation of MIL-88A-Fe precursors. The low valence iron-nitrogen-carbon species may serve as polysulfide adsorbent and electrocatalysts, boosting the conversion reaction between lithium polysulfides and Fe1-xS. Its porosity with nano-sized architectures not only enhance the Fe1-xS redox kinetics, but also can mitigate volume expansion stresses. As expected, the r-Fe-N-Fe1-xS@C electrodes exhibit superior charge/discharge performances at high current density (800 mAh g(-1) at 5 A g(-1)) and remarkable long-term cycling stability. Delicately-designed low valence metallic polysulfide electrocatalysts may shed some light on the rational design of high performance sulfur-based and metal sulfide-based electrodes for lithium and/or sodium ion batteries.