Lignin-Derived Nitrogen-Doped Porous Carbon as a High-Rate Anode Material for Sodium Ion Batteries

Nitrogen-doped carbon anode materials have been prepared by a hard-template (SiO2 nanoparticles) method, in which alkali lignin-derived azo polymer (AL-azo-NO2) was used as a low-cost carbon precursor. The as-prepared N-doped carbon materials show a honeycomb-like morphology with uniform nanopores. These materials are able to reversibly insert Na+ ions and show promising cycling performance. In particular, the porous carbon material with larger surface area and pore volume delivers a higher initial capacity of 205 mAh g[?]1 in the voltage range of 0.01-2 V at 50 mA g[?]1, compared to the material with lower surface area and pore volume (only 155 mAh g[?]1). The former also exhibits much better rate capability than the latter. Even at a high current density of 1 A g[?]1, it shows a high specific capacity of 101 mAh g[?]1 after 1100 cycles, which retains 92% of its initial capacity. Electrochemical impedance spectroscopy (EIS) results prove that the enhanced electrochemical performance is attributed to the improved Na+-ions kinetics in this material. This work presents an alternative approach for the synthesis of high-rate carbonaceous anode materials for sodium ion batteries from low cost and sustainable feedstock.