Fe3O4-seated rGO-sulfur complex as a potential cathode material for lithium-sulfur batteries

Lithium-sulfur battery has been proposed as a futuristic energy storage system owing to its positive aspects such as high theoretical specific energy density, less expensive, large availability of elemental sulfur, and better safety. Nevertheless, Li-S batteries have not come to the market for commercialization which is mainly attributed to the limitations such as the insulating nature of orthorhombic sulfur, undesirable polysulfide crossover between the electrodes, and poor interfacial properties between lithium anode and electrolytes. In order to solve these issues, several attempts have been made by researchers around the world. In the present work, in order to restrict polysulfide crossover and to promote the conductivity of elemental sulfur, Fe3O4-seated rGO-sulfur complex is prepared and used as cathode. The Li-S cell delivers a discharge capacity of 1400 mAh g(-1) at 0.1 C-rate on its first cycle and a steady discharge capacity is attained at 0.5 C-rate. In the composite cathode, every element works for a particular reason: the added rGO enhances the conductivity of cathode, while Fe3O4 confines polysulfides appreciably as evidenced by TEM and XPS analyses. The self-discharge of the cell is also reduced. The variations of electrolyte resistance (R-s), interfacial resistance (R-i), and charge transfer resistance (R-ct) for various depth of discharge (DOD) and state of charge (SOC) are systematically analyzed by electrochemical impedance spectroscopy.