Chitin-Derived Hierarchical Meso- and Microporous Carbon Enables High-Rate Sulfur Cathode of Sodium-Sulfur Batteries

Room temperature Na-S batteries are considered as a promising alternative energy storage system because of their abundant material resources and high theoretical energy density. However, the severe polysulfide shuttle effect and slow reaction kinetics hinder their practical application. Herein, a hierarchical meso- and microporous carbon with nitrogen self-doping (NSPC) is prepared using chitin as the carbon precursor and serves as a novel host to confine the sulfur (S⊂NSPC). An optimized structure of NSPC, including abundant graphite nanocrystals, large pore volume of 1.76 cm³ g^-1, and large specific surface area of 2073 m² g^-1 is obtained at the carbonization temperature of 1000 °C. These merits contribute to significantly enhanced charge transfer and ion diffusion of the as-prepared S⊂NSPC-1000 cathode, which exhibits the outstanding sodium storage performance, including high reversible capacities of 1207 mAh g^-1 at 0.1 C and 891 mAh g^-1 at 2 C and stable cycling with a low capacity decay for 400 cycles at 1 C, among other S⊂NSPC cathodes and previously reported cathodes for Na-S batteries. This cathode can also afford stable cycling at a high sulfur loading.