Facile synthesis and very stable cycling of polyvinylidene dichloride derived carbon: Sulfur composite cathode

Activated microporous carbon with narrow pores up to 1 nm, high surface area of about 1000 m2 /g and pore volume of 0.43 cc/g was synthesized by facile one-step carbonization of polyvinylidene dichloride (PVDC) resin at high temperature without any additional activation process and was used for the preparation of sulfur-carbon (S/C) composite electrodes with sulfur content of 40 wt% in the composite S/C powder and 32 wt% in the composite electrode. The electrodes thus obtained, demonstrate a very stable cycling performance with more than 2000 charge-discharge cycles delivering about 600 mAh/g at a current rate of 1.04 A/g with Coulombic efficiency close to 100% at 30? C. Stable and highly reversible behavior was also obtained at 45? C for hundreds of cycles. Quasi-solid state type of behavior with single reduction plateau was observed for these Li-S cells using organic carbonates based electrolyte solutions. The formation of solid electrolyte interphase (SEI) on the surface of the cycled S/C electrodes was demonstrated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). For the composite sulfur electrodes prepared with PVDC-derived carbon the shuttle phenomena are fully avoided due to appropriate encapsulation, surface protection and quasi-solid state operation mechanism.