Electrochemical impedance analysis of polyvinylpyrrolidone-coated sulfur/reduced graphene oxide (S/rGO) electrode

In this study, polyvinylpyrrolidone sulfur/reduced graphene oxide (S/rGO@PVP) composite for lithium-sulfur batteries was produced. Reduced graphene oxide is used to improve the conductivity of both ionic and electronic conductivity due to poor sulfur conductivity (5 x 10(-30) S cm(-1)). Graphene oxide (GO) was synthesized using modified Marcano and Hummer methods. Sulfur (S8) was prepared using the dissolution-crystallization method followed by microwave treatment to reduce the graphene oxide and sulfur impregnation into a graphene oxide reduction structure (rGO). Addition of PVP was varied at 0, 50, 67, and 75 wt% of S/rGO, with variation of microwave time at 10, 20, and 30 min. The x-ray Diffraction (XRD) pattern showed that sulfur and PVP crystals had been formed. Morphological characterization using Scanning Electron Microscopy (SEM) showed a structure of thin layers of the rGO with small layers of PVP, while Transmission Electron Microscopy (TEM) showed black dots that are characteristic of sulfur particles. TEM showed that the sulfur particles had an average size of 12.8 nm. The C-S bond in the FTIR spectrum indicates that there was an S bond in the rGO. The EIS measurement showed a tendency of adding PVP mass, which increased the value of charge transfer resistance (R-ct). On the other hand, four-point probe measurements showed that the addition of PVP mass can also decrease the conductivity. Meanwhile, microwave radiation also affects R-ct. The addition of microwave radiation time decreases the value of R-ct and increases the conductivity of the sample.