Natural Okra Shells Derived Nitrogen-Doped Porous Carbon to Regulate Polysulfides for High-Performance Lithium–Sulfur Batteries

Low conductivity of elemental sulfur, the “shuttle effect” of polysulfides, and structural change hamper lithium–sulfur batteries that have poor electrochemical performance. Herein, a facile and scalable approach to fabricate porous carbon is derived from common okra wastes, okra shells, as a matrix for sulfur active materials. Especially, the material calcined under NH₃ (N-doped biomass-derived porous carbon [N-OSC]) with a high specific surface area of 2702 m² g⁻¹ and large pore volume (0.17 cm³ g⁻¹) provides necessary physical adsorption, resulting in the 69.71 wt% loading of sulfur and excellent trapping capacity for polysulfides during the redox process. Furthermore, N element can act as catalytic active sites to facilitate redox conversion from polysulfides to Li₂S. Benefiting from the aforementioned advantages, the cell of the N-OSC/S electrode manifests superior electrochemical performance. The initial capacity is found up to be 1387 mA h g⁻¹ at a current density of 0.1 C and 750 mA h g⁻¹ after 200 cycles at 0.5 C rate (where 1 C = 1672 mA h g⁻¹). For durability evaluations, the capacity is maintained at 416 mA h g⁻¹ at 2 C after 1000 cycles with a mere decay of 0.05% per cycle.