Nitrogen-doped carbon nanosheets for high-performance liquid as well as solid state supercapacitor cells

In this article N-doped carbon nanosheets (NCNS), formed by carbonizing polyaniline nanosheets (PNS), are reported. PNS were pyrolyzed at different temperatures (400-600 degrees C) to get different doping levels of nitrogen in the carbon sheets. The PNS carbonized at 400 degrees C (NCNS 400) exhibited high electrochemical performance due to a high inter-planar distance of 0.45 nm and high percentage (15 wt%) of N-based functionalities. NCNS 400 shows consistently high charge storage capacity in solid (PVA/H2SO4) and aqueous (1 M H2SO4) electrolytes. The NCNS 400 supercapacitor cell showed high energy density in 1 M H2SO4 (21.6 W h kg(-1) at a power density of 293.91 W kg(-1)) and PVA/H2SO4 (9.8 W h kg(-1) at 288 W kg(-1)). Further, the low relaxation time constant (tau(o)) with low iR-drop and high capacitance retention (99.3%: H2SO4 and 99.8; PVA/H2SO4) is attributed to the improved structural properties upon nitrogen doping in the carbon sheets.