CoS2 embedded graphitic structured N-doped carbon spheres interlinked by rGO as anode materials for high-performance sodium-ion batteries

Much attention has been paid to the Cobalt-based sulfides in recent years due to their high specific capacity and strong catalytic activity in the field of sodium-ion batteries (SIBs). Nevertheless, the poor cycling stability and low rate capability have hindered their practical applications. Herein, an effective strategy for the rational design of CoS2 nanoparticles embedded in the graphitic structured N-doped porous carbon spheres interlinked by the reduced graphene oxide (rGO) nanosheets (rGO-CoS2-GNCSs) is proposed. The interconnected multidimensional nanostructure constructed by CoS2 nanoparticles, graphitic structured N-doped porous carbon spheres and rGO nanosheets can provide a fast transfer pathway for electrons and electrolyte ions, which helps enhance the electric conductivity of the material and facilitate the reaction kinetics in SIBs. Moreover, benefiting from this unique microstructure, the change of the volume during sodiation/desodiation can be effectively alleviated and the stability of the architectural morphology can be enhanced. As a result, the rGO-CoS2-GNCSs used as the anode of SIBs presents an impressive electrochemical performance at a cut-off voltage of 0.4-2.9 V in the electrolyte of 1.0 M NaCF3SO3 in diglyme, delivering a high reversible capacity of 523.9 mAh g(-1) at 100 mA g(-1) after 150 cycles, an excellent rate capability of 423.3 mAh g(-1) at 2 A g(-1) and extraordinary long-term cycling stability of 465.9 mAh g(-1) at 500 mA g(-1) after 600 cycles and 412.2 mAh g(-1) at 1 A g(-1) after 400 cycles. This study puts forward a promising strategy for the rational design of anode materials for high-efficiency sodium storage by interconnecting transition metal compounds, two-dimensional materials and nanocarbon to form multidimensional nanohybrids. (C) 2019 Elsevier Ltd. All rights reserved.