N-doped layered porous carbon electrodes with high mass loadings for high-performance supercapacitors

We report a porous carbon material (NPCM) with a high N content as a high-performance supercapacitor electrode material which was prepared by a simple activation-doping process using Metaplexis Japonica shell as the carbon precursor, ammonium chloride as the nitrogen source and zinc chloride as the activation agent. Its high electrical conductivity, large ion-accessible surface area and fast ion transport ability make it possible to achieve a high mass loading of NPCM per area of the electrode and a high energy and high power density supercapacitor. An electrode with a low NPCM mass loading of 1 mg cm⁻² has a gravimetric specific capacitance of 457 F g⁻¹ and an areal specific capacitance of 47.8 μF cm⁻². At a much high NPCM loading of 17.7 mg cm⁻² it has a high gravimetric capacitance of 161 F g⁻¹. Furthermore, an assembled NPCM//NPCM symmetric supercapacitor with an optimal NPCM loading of 12.3 mg cm⁻² delivered a high specific energy of 12.5 Wh kg⁻¹ at an ultrahigh power of 80 kW kg⁻¹ in 1 mol L^-1 Na₂SO₄. The achievement of such high-energy and high-power densities using NPCM will open exciting opportunities for carbon-based supercapacitors in many different applications.