Novel 3D flower-like micro/nano-structure FeS/N-doped-C composites as advanced cathodes with high lithium storage performances

Due to their merits of high capacity, abundant resources and environmental benignity, Fe monosulfides are considered as attractive electrode materials for Li-ion batteries. However, inferior cyclability and rate performances resulted from inherent low conductivity limit their applications. Herein, we present novel 3D flower-like micro/nano-structure FeS/N-doped-C composites which are directly synthesized from low-cost organosulfur compounds through facile precipitation and subsequent calcination and for the first time applied as cathodes for lithium storage. The FeS nanoparticles are coated by highly conductive N-doped-C shells. Such a confinement of coating microstructures, especially outer N-doped-C, is highly beneficial for the conversion reactions (FeS+2Li(+)+2e(-)<-> Fe + Li2S), and could strengthen conductivity and simultaneously better protect FeS from electrolyte corrosions, ensuring stable conductive frameworks. Also, such N-doped-C anchor FeS, Fe, and Li2S effectively, as confirmed by density functional theory calculations. Thus, the FeS/N-doped-C cathodes exhibit remarkable cycling stability (621 mAh g(-1) at 200th cycle at 1C, with a decay of 0.07%/cycle), and high rate performances (600 mAh g(-1) even at 10C), delivering higher energy density than commercial LiCoO2 cathodes. This work discloses a novel and paramount route to exploit transition metal sulfides for lithium storage and helps us further understand the key role of N-doping in electrochemical energy storage.