Lignin-derived nitrogen-doped porous ultrathin layered carbon as a high-rate anode material for sodium-ion batteries

Nitrogen-doped porous ultrathin layered carbon (LC) was prepared via annealing alkaline lignin with melamine and urea. As the anode material of sodium-ion batteries, the as-prepared LC shows high reversible capacity, outstanding rate performance and excellent cycling performance. In particular, the ultrathin graphitic carbon with large surface area and pore volume provide abundant sodium storage active sites, delivering a higher initial capacity of 320.5 mAh g−1 in the voltage range of 0.01–3 V at a current density of 0.1 C (1C = 30 mA g−1). Besides, the structure defects resulted from the doping of N also benefits to its high capacity. Capacitive and diffusion contribution calculation and EIS analysis proved the improved the Na+-ion storage kinetics due to LC's unique porous ultrathin structure, resulting in outstanding rate performance. LC delivers a high capacity of 138.7 mAh g−1 at 5 C. Besides, LC's porous ultrathin structure also guarantees its stable cycling performance. Even at a high current density of 5 C, there's no obvious capacity decay after 4000 cycles. 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.