Molten salts approach of metal-organic framework-derived nitrogen-doped porous carbon as sulfur host for lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries have attracted significant attention as next-generation energy storage systems owing to their high theoretical specific capacity (1675 mAh g−1) and energy density (2567 Wh kg−1). However, the low electrical conductivity of S and the dissolution of polysulfides in organic electrolytes pose significant challenges for their industrial applications. Herein, we report a facile, scalable, and solvent-free synthetic method based on metal–organic-framework (MOF) for synthesizing N-doped carbon-based materials with hierarchical porous structures and large specific surface areas (2297 m2 g−1) as efficient cathode hosts for Li-S batteries. The cathode materials were synthesized via solvent-free mixing, followed by the direct carbonization of adenine and tetracarboxylic acid with zinc acetate using the molten salt method. Zinc salt was employed as a template for mesopores as well as binding sites for other organic materials. The irregular surface morphology and N-doping of the resulting porous carbons act as physical barriers to confine polysulfides within the carbon matrix. The S-loaded cathode was stable and exhibited a discharge capacity of 555 mAh g−1 over 290 cycles at a current density of 0.5C, corresponding to the capacity retention of 63%. The facile modified MOF synthetic strategy, assisted by molten salt processing, holds promise for the synthesis of noble cathode materials for high-performance Li-S batteries.