Waste coffee ground derived in-situ nitrogen doped porous carbon for constructing high-performance Li-S battery cathode

Herein, an in-situ nitrogen doped porous carbon material is prepared by using waste coffee grounds, ZnCl₂ and FeCl₃ bimetallic salt activation/catalyst via a simultaneous activation carbonization method, whilst using to construct the high-performance cathode materials of lithium-sulfur batteries. The structure, morphology, chemical composition, and porous structure of the as-prepared materials are characterized using SEM, XRD, XPS, and nitrogen adsorption-desorption tests. And the discharge capacity, rate performance, cycling stability, kinetics and resistance change of the lithium-sulfur batteries are investigated by galvanostatic charge-discharge cycling, electrochemical impedance spectroscopy, and cyclic voltammetry tests. Combined with the adsorption of lithium polysulfides and component analysis of the cycled batteries, the influence of porous structure and in-situ nitrogen doping on electrochemical performance is also explored. Results show that the as-prepared porous carbon material has a specific surface area of 901.2 m²·g⁻¹ and a pore volume of 0.52 cm³·g⁻¹, whilst exhibiting 1.74% nitrogen doping. On the basis of the physicochemical synergistic adsorption of lithium polysulfides by porous structure and nitrogen doping, The corresponding porous carbon/sulfur composite cathode material exhibits a first discharge capacity of 905.6 mA·h·g⁻¹ at 0.2 C and retains 605.9 mA·h·g⁻¹ after 200 cycles. At a high rate of 1.0 C, a first discharge capacity of 613.9 mA·h g⁻¹ can be obtained, whilst a long-term cycling stability over 1000 cycles is also achieved. This strategy provides a new approach for the effective utilization of waste coffee ground.