A Facile Preparation of S 8 /C Composite Cathode for Lithium-Sulfur Cells: Influence of Intrinsic and Extrinsic Cathode Properties on the Electrochemical Performance

Abstract

Lithium–sulfur batteries are still characterized by the low intrinsic electronic conductivity of sulfur in both its charged state (S 8 ) as well as discharged state (Li 2 S). Here, using ball milling, a well-dispersed active material within the carbon network is achieved using carbon black Super C65 and synthetic graphite KS6 as conductive agents. Calendering these electrodes increases the electronic percolation path resulting in enhanced electrochemical performances and reaction kinetics. Using high-speed and high-impact preparation methods improves the quality and performances of the S 8 /C composite electrodes when compared with electrodes prepared using a simple mixing method (magnetic stirring). The scanning electron microscopy images indicate that KS6 is able to incase S 8 particles, resulting in a homogeneous distribution of the active material that in turn enhances the accessibility of the active material by the electrolyte and electrons. Compared with the S 8 /Super C65 composite electrode, a discharge capacity of 703 mAh g −1 is delivered by the S 8 /KS6 composite electrode during the first cycle. After 30 cycles, the S 8 /KS6 composite electrode delivers 477 mAh g −1 compared to only 411 mAh g −1 for the S 8 /Super C65 composite electrode due to a continuous capacity fading.