Na-Doped C70 Fullerene/N-Doped Graphene/Fe-Based Quantum Dot Nanocomposites for Sodium-Ion Batteries with Ultrahigh Coulombic Efficiency

Na-doped C-70 fullerene (Na-C-70)/N-doped graphene (N-GN)/Febased nanocomposites (Na-C-70/N-GN/FBNCs) with the multiple morphologies are fabricated through an in situ one-step method with multifunction sodium lignosulfonate (SLS) as the structural template and the main raw material. Fe-based quantum dots (FBQDs) can be embeded in the ordered mesoporous hybrid carbon structure of Na-C-70 and N-GN through a spontaneous chelation reaction of SLS with iron ions and carbonization under relatively mild hydrothermal treatment. We investigate the influences of the molar ratio of SLS/Fe on the structure, components, and electrochemical properties of the nanocomposites. Its unique hybrid carbon structure offers metallicity and superconductivity, countless bonding sites of Na ions, and facilitates the transfer of electrons and Na ions during prolonged cycling. The nanocomposites for sodium-ion batteries anodes can achieve the highest discharge capacities of 1898 mAhg(-1) at a current density of 1000 mAg(-1), and can retain a reversible capacity of 238 mAhg(-1) after 100 cycles, which are significantly better than those of lithium-ion batteries. The discharge and charge capacities at 1 Ag-1 after 30th cycles are 356 and 119 mAhg(-1), respectively, with an ultrahigh coulombic efficiency of 299% and the highest coulombic efficiency of 463% after 220 cycles.