Graphene sheet-encased silica/sulfur composite cathode for improved cyclability of lithium-sulfur batteries

Abstract

The “shuttle effect” of polysulfides is a serious issue, resulting in a decrease in the life-cycle of lithium-sulfur (Li-S) batteries. To inhibit the shuttle effect, a combination of graphene oxide and silica has been adopted in this work. Here, two different ratios of sulfur/silicon dioxide/partially reduced graphene oxide (S/SiO2/prGO - 70:20:10 and 70:10:20) composite materials were prepared via a melt diffusion method and were used as a cathode for a Li-S battery. The wrinkled sheets of partially reduced graphene oxide not only provide a conductive network for electron transport, but also ease the volume changes of active material during cycling. The 20 wt% of prGO present in the S/SiO2/prGO cathode delivers initial discharge capacity of 783 mAh g−1 at 0.2 C and remains at 491 mAh g−1 over 300 cycles, with low capacity decay rate of 0.12% per cycle. The better electrochemical performance indicates that the electrode containing 20 wt% of prGO with silica effectively suppresses the “shuttle effect” of polysulfide dissolution.