Rational design of graphene oxide wrapped porous microspheres as high-performance sulfur cathode in lithium-sulfur batteries

Abstract

The application of lithium-sulfur batteries (LSBs) encounters many problems including polysulfides shuttling, low sulfur conductivity and poor stability. To address these issues, a porous microsphere-based sulfur cathode, consists of Mg2+ etched ZIF-67 and carbon nanotubes encapsulated with graphene oxide (Mg ZIF-67/CNT@GO), was fabricated. The introduction of CNTs endows the composite with good electrical conductivity, and at the same time the loss of polysulfides is mitigated through its unique porous structure. Moreover, the Mg2+ etched ZIF-67 also provides a large area of active interface, which promotes its trapping with polysulfides and catalytic performance towards polysulfides conversion. Accordingly, the sulfur cathode with Mg ZIF-67/CNT@GO composite delivers good electrochemical performance. The battery exhibits a high capacity retention rate of 87.4% and an areal capacity of 3.35 mAh cm-‍2 under 3.0 mg cm-2 sulfur loading at 0.2 C. In addition, the pouch cell cycled at 0.1 C retains its high capacity of 640.8 mAh g-l after 50 cycles. This work provides a promising sulfur cathode design approach for the implementation of LSBs.