Three-dimensional sandwich-type graphene@microporous carbon architecture for lithium–sulfur batteries

Abstract

The commercial applications of lithium–sulfur batteries are hindered by several issues including the poor electronic/ionic conductivity of sulfur and discharge products, the dissolution of lithium polysulfides in organic electrolytes, and the volume change during charge/discharge processes. In this study, a three-dimensional (3-D) sandwich-type graphene@microporous carbon (G@MC) architecture with large pore volume (2.65 cm³ g⁻¹) and ultrahigh surface area (3374 m² g⁻¹) was designed to encapsulate sulfur and polysulfides in the hierarchical microporous structure. The G@MC materials with a lot of sp² hybrid carbon atoms can provide 3-D electron transfer pathways for sulfur and discharge products. Furthermore, the G@MC materials with the novel hierarchical structure can absorb a lot of polysulfides and restrain the polysulfide diffusion, and provide adequate nanospace for sulfur expansion ensuring the structural integrity during the cycling. Thus, the optimized G@MC–S nanocomposite with high sulfur loading (75.4 wt%) retains a discharge capacity of 541.3 mA h g⁻¹ after 500 cycles at 0.5C. This design strategy is simple and broadly applicable, providing new opportunities for materials design that can be extended to various electrode materials.