High capacity Li storage in sulfur and nitrogen dual-doped graphene networks

Three-dimensional (3D) networks composing of S and N dual-doped graphene (SNG) were synthesized by a chemical vapor deposition approach using MgSO4-containing whiskers as templates and S source and NH3 as N source. Energy dispersive spectrometer mapping and X-ray photoelectron spectroscopy coupled with Raman analysis have revealed that S and N atoms with concentrations of 5.2 and 1.8 atom%, respectively, have been substitutionally incorporated into the graphene networks via covalent bonds. The SNG, as an anode material for lithium ion batteries (LIBs), exhibits extremely high capacity (3525 mAh/g at the current density of 50 mA/g) and superior rate capability (870 mAh/g at 1000 mA/g) with excellent cycling stability (remaining a reversible capacity of 400 mAh/g at 10 A/g after 2500 cycles). The enhanced conductivity, the 3D porous network with many disorders and the intrinsically high Li storage capacity of S and N-doped carbon segments have led to the excellent electrode performance of the SNG networks. The effects of binder content and calendaring pressure on the electrode performance have been investigated. The full LIB with SNG as anode and LiCoO2 as cathode can afford a high reversible capability (164 mAh/g at 0.2 C) and good cycling stability.