Biomass-derived nitrogen/oxygen co-doped hierarchical porous carbon with a large specific surface area for ultrafast and long-life sodium-ion batteries

Biomass derived porous carbons are economic and attractive materials for anode electrodes in sodium-ion batteries. In this work, a novel porous carbon has been prepared through activation of longan shell, which demonstrates an interconnected hierarchical porosity comprised of macro-, meso- and micro-pores as well with a high specific surface area of 2990  m2 g−1. Benefiting from the unique pore structure and oxygen and nitrogen dual doping, a well-developed ionic and electronic conductivity is achieved. Remarkably, it exhibits an excellent cycling stability with a capacity up to 345.9 mAh g−1 at a current density of 0.1 A g−1, and maintains a capacity of 304.2 mAh g−1 even at a high current density of 5 A g−1 after 1000 cycles as anodes for sodium-ion batteries. These results indicate that the fabricated porous carbon could be a promising electrode material for sodium-ion batteries. The mechanism of such high sodium-ion storage was also discussed with the scan-rate-dependent CV curves to quantify the pseudo-capacitive contribution.