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 lignosulfo-nate under the assistance of sodium chloride. Ma-NaCl-900 prepared at 900 degrees C shows a remarkably higher degree of order and electrical conductivity value than its counterpart obtained at 800 degrees C thanks to the catalytic effect of molten NaCl. When carbonization temperature reaches 1000 degrees 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.