Sustainable nitrogen-doped carbon electrodes for use in high-performance supercapacitors and Li-ion capacitors†
Designing energy storage systems with both high energy density and power density by using low-cost electrodes is still a formidable challenge. Therefore, we propose a successful doped porous carbon synthesis process using agricultural waste in the form of ginger straw, which can be used for fabricating high-performance supercapacitors and Li-ion capacitors. Nitrogen doping in the carbon structure improves the wettability and alters the electronic structure, playing a pivotal role in providing extra charge storage capacity. The fabricated ionic-liquid-based supercapacitors exhibit an outstanding capacitance of 122 F g−1 at 0.5 A g−1 with a superb capacitance retention ratio of 73% at 100 A g−1, excellent specific energy of 37.8 W h kg−1 at 374 W kg−1, and low capacitance loss of 13.5% after 10 000 cycles. Based on the LiPF6 electrolyte, doped carbon used as the anode shows a high capacity of 1531 mA h g−1 at 0.1 A g−1, and the fabricated Li-ion capacitor exhibits high specific energy of 214.6 W h kg−1 at 373.5 W kg−1, maintains 63.6 W h kg−1 at the high specific power of 65.4 kW kg−1, and shows promising cycling performance with 82.7% capacity retention after 10 000 cycles. This work highlights the fact that sustainably doped carbon has the potential for large-scale commercial production, and it can be promising for use as an electrode in advanced energy storage systems.