Molecular-Level Design of Pyrrhotite Electrocatalyst Decorated Hierarchical Porous Carbon Spheres as Nanoreactors for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are a class of new-generation rechargeable high-energy-density batteries. However, the persisting issue of lithium polysulfides (LiPs) dissolution and the shuttling effect that impedes the efficiency of LSBs are challenging to resolve. Herein a general synthesis of highly dispersed pyrrhotite Fe1-xS nanoparticles embedded in hierarchically porous nitrogen-doped carbon spheres (Fe1-xS-NC) is proposed. Fe1-xS-NC has a high specific surface area (627 m(2) g(-1)), large pore volume (0.41 cm(3) g(-1)), and enhanced adsorption and electrocatalytic transition toward LiPs. Furthermore, in situ generated large mesoporous pores within carbon spheres can accommodate high sulfur loading of up to 75%, and sustain volume variations during charge/discharge cycles as well as improve ionic/mass transfer. The exceptional adsorption properties of Fe1-xS-NC for LiPs are predicted theoretically and confirmed experimentally. Subsequently, the electrocatalytic activity of Fe1-xS-NC is thoroughly verified. The results confirm Fe1-xS-NC is a highly efficient nanoreactor for sulfur loading. Consequently, the Fe1-xS-NC nanoreactor performs extremely well as a cathodic material for LSBs, exhibiting a high initial capacity of 1070 mAh g(-1) with nearly no capacity loss after 200 cycles at 0.5 C. Furthermore, the resulting LSBs display remarkably enhanced rate capability and cyclability even at a high sulfur loading of 8.14 mg cm(-2).