Highly porous nitrogen-doped seaweed carbon for high-performance lithium–sulfur batteries

Due to its natural abundance, low cost and environmental sustainability, carbon derived from biomass has been widely utilized for energy storage and conversion. Herein, we report a facile strategy to synthesize a hierarchically porous carbon via the pyrolysis of seaweed biomass under inert atmosphere and apply it as a cathode material in lithium–sulfur (Li-S) batteries for the first time. Systematic materials characterization suggests that the seaweed carbon (SWC) is doped with N and displays micro-, meso- and macroporous structures and possesses a high total pore volume of 1.48 cm3 g−1 and a high surface area of 1510.71 m2 g−1, which is beneficial for encapsulating a large amount of sulfur. The as-obtained SWC-S composite, containing 65.7 wt% sulfur content, delivered a high initial discharge capacity of 1221.2 mAh g−1 and retained a capacity of 826.4 mAh g−1 after 70 cycles at 0.2 C. Additionally, the SWC-S composite produced a reversible capacity of 540.6 mAh g−1 after 300 cycles at high rate of 1 C. Compared to the pure sulfur cathode, the SWC-S cathode displays excellent rate capabilities, low polarization and good reaction kinetics, highlighting that this biomass-derived porous carbon is suitable for assembling high-performance Li-S batteries.