Construction of Functional Carbon Nanoarchitectonics for Mitigating Shuttle and Boosting Conversion of Polysulfides in Lithium–Sulfur Batteries

Abstract

Low-cost and high-quality functional porous carbon materials are highly considered as sulfur hosts for high-performance Li–S batteries. Herein, a functional porous carbon material is constructed using waste coffee shells and bimetallic salt activation/catalyst via facile mechanical agitation and high-temperature pyrolysis. An in situ nitrogen doping is easily achieved due to the inherent nitrogen-rich composition of coffee shells. After detailedly regulating the concentration of bimetallic salts, the optimal carbon material exhibits good nanoarchitectonics with ultrahigh specific surface area (2270 m² g⁻¹) and large pore volume (2.1 cm³ g⁻¹). This is contributing to accelerating the electrolyte infiltration and intimate contact with active sulfur encapsulated into the pore architecture, while improving the redox conversion of polysulfides. Moreover, the polysulfides shuttle is effectively mitigated by the synergistic adsorption of porous structure and nitrogen doping. When used as sulfur host, the optimal cathode exhibits the initial discharge capacity of 928 mAh g⁻¹ and retains 625 mAh g⁻¹ after 200 cycles at 0.2 C. Even at 1.0 C, the first capacity of 721 mAh g⁻¹ is still procured and the capacity decay per cycle for 1000 cycles is 0.03%.