A functional carbon decorated separator for the confinement and redox conversion of lithium polysulfides in high sulfur-loading lithium sulfur batteries

Abstract

Severe shuttle effect and sluggish conversion of lithium polysulfides (LiPSs) generally reduce the actual energy density of lithium sulfur batteries. In this work, a waste honeycomb derived functional porous carbon is synchronously used to design sulfur cathode and modify separator for the lithium sulfur batteries. The as-prepared carbon material shows the in-situ N-doping and abundant hierarchically porous structure with high specific surface area (1711.8 m2/g) and large pore volume (0.949 m3/g). This endows the porous carbon/sulfur cathode with favorable electron transport channels and synergistic physicochemical adsorption of the LiPSs. The functional carbon modified separator not only can further block and capture the soluble LiPSs, but also accelerate the redox conversion of the LiPSs adhered to the separator surface. Besides, the functional carbon modified separator acts as an upper current collector to reactivate the ‘‘dead sulfur”. Benefiting from the above structure merits, the resulted sulfur cathode with a practical sulfur content of 73wt % (2.3 mg/cm2 in areal sulfur loading) combined with the modified separator delivers the high discharge capacity of 954 mAh/g at 0.2 C. Also, a long-term cycling up to 800 cycles can be achieved at a high current rate of 1 C.