Binary Hierarchical Porous Graphene/Pyrolytic Carbon Nanocomposite Matrix Loaded with Sulfur as a High-Performance Li–S Battery Cathode

A N,O-codoped hierarchical porous nanocomposite consisting of binary reduced graphene oxide and pyrolytic carbon (rGO/PC) from chitosan is fabricated. The optimized rGO/PC possesses micropores with size distribution concentrated around 1.1 nm and plenty of meso/macropores. The Brunauer–Emmett–Teller specific surface area is 480.8 m2 g–1, and it possesses impressively large pore volume of 2.14 cm3 g–1. On the basis of the synergistic effects of the following main factors: (i) the confined space effect in the hierarchical porous binary carbonaceous matrix; (ii) the anchor effects by strong chemical bonds with codoped N and O atoms; and (iii) the good flexibility and conductivity of rGO, the rGO/PC/S holding 75 wt % S exhibits high performance as Li–S battery cathode. Specific capacity of 1625 mA h g–1 can be delivered at 0.1 C (1 C = 1675 mA g–1), whereas 848 mA h g–1 can be maintained after 300 cycles at 1 C. Even at high rate of 5 C, 412 mA h g–1 can be restrained after 1000 cycles.