Nitrogen-doped biomass-derived carbon by mechanochemical synthesis for lithium-sulfur batteries

Nitrogen-doped carbons were synthesized by a solvent-free mechanochemically-induced one-pot synthesis, by using renewable biomass waste. In particular, we used three solid materials: sawdust as a carbon source, urea and/or melamine as a nitrogen source and potassium carbonate as an activation agent. The resulting nitrogen-doped porous carbons offer a very high specific surface area of up to 3000 m2 g- and a large pore volume up to 2 cm3 g-1. Also, a high nitrogen content of 4 wt.% (urea only) up to 12 wt.% (melamine only) was generated, depending on the used nitrogen and carbon source. The mechanochemical reaction and the impact of different wood components on the porosity and surface functionalities are investigated by nitrogen-physisorption and high-resolution X-ray photoelectron spectroscopy (XPS). These N-doped carbons are highly suitable as cathode material for Li-S batteries showing high initial discharge capacities up to 1300 mAh g-1sulfur (95% CE) and capacity retention (> 75%) within the first 50 cycles at low electrolyte volume.