Strong polar nonaqueous solvent-assisted microwave fabrication of N and P co-doped microporous carbon for high-performance supercapacitor

Abstract Porous carbons are considered as ideal electrode materials to match the performance and cost requirements of commercial supercapacitor. However the energy waste in the conversion of raw materials to porous carbons by traditional heating method is enormous. Herein we report a strong polar nonaqueous solvent-assisted microwave method for cost-efficient preparation of N and P co-doped microporous carbon. Compared with traditional heating method, the reported material fabricated by microwave irradiation exhibits much higher specific surface area (2204 m2 g−1) and higher large micropore (1 nm ≤ d ≤ 2 nm) proportion, more pseudo-capacitance contribution and stronger conductivity also are procured through microwave irradiation. The specific capacitance reaches up to 317 F g−1 in 6 M KOH solution, which is about 1.36 times higher than that of the control sample fabricated by traditional heating method. The symmetrical supercapacitor device based on the reported material exhibits excellent rate and cycle performance, whose capacitance retention arrives 88% even under high current density of 20 A g−1, and more than 95% of initial capacitance is retained after 10,000 cycles. Meanwhile, when ionic liquid (EMIMBF4) is employed as electrolyte, the energy density of the supercapacitor device reaches up to 48.6 Wh kg−1 at a power density of 468.8 W kg−1.