NaCl-assisted synthesis of porous carbons with ultra-high electrical conductivity for high-performance supercapacitors

A facile and green strategy is proposed for preparing porous carbons (Ma-NaCl-X) from ammonium lignosulfonate under the assistance of sodium chloride. Ma-NaCl-900 prepared at 900 °C shows a remarkably higher degree of order and electrical conductivity value than its counterpart obtained at 800 °C thanks to the catalytic effect of molten NaCl. When carbonization temperature reaches 1000 °C, the catalysis and activation effects of NaCl are responsible for the sharp increases in specific surface area, micropore volume and sp2 carbon content of the resultant Ma-NaCl-1000 compared with Ma-NaCl-900. Due to the ultrahigh electrical conductivity of 2535 S m−1 and considerable surface area of 1212 m2 g−1 for Ma-NaCl-1000, the corresponding symmetrical supercapacitor can deliver a high energy density of 51.0 Wh kg−1 at 510 W kg−1 in EMIMBF4 electrolyte, retaining an impressive value of 16.8 Wh kg−1 at an ultrahigh power density of 16.8 kW kg−1. Moreover, Ma-NaCl-700 with suitable heteroatom content (12.8 at.%) exhibits a high specific capacitance of 215 F g−1 at 0.25 A g−1 with excellent rate capability (156 F g−1 at 50 A g−1) in aqueous symmetric supercapacitor.