High-performance supercapacitor electrode at commercial-level mass loading from N-enriched activated carbon derived from soybean dregs

N-enriched activated carbons (ACs) are prepared via a facile triple-doping technique route. The self-doping from the precursor of soybean dregs and additional introduction from egg white guarantee a high-level of N contents in the Hydrothermal carbonization (HTC) products (biochar). With a KOH-activation, relatively high surface area and easy-accessible ion channels are constructed. A post-doping from the subsequent ammonia-activation compensates the loss of the N contents during the KOH-activation. Relatively high surface area of 1518 m2/g and N atomic fraction of 4.311 % are achieved. Taking advantage of the compaction density of 0.68 g/cm3, electrodes with commercial-level mass loading of ∼10 mg/cm2 are fabricated with a moderate thickness of ∼0.15 mm. With symmetric supercapacitors (SCs) of commercial-level electrodes, high values are achieved of 357.1 F/g in gravimetric capacitance and 235.7 F/cm3 in volumetric capacitance at 0.5 A/g are achieved in 1 mol/L H2SO4. With 1 mol/L Et4NBF4 in acetonitrile (AN) as electrolyte, the gravimetric capacitance is 246.2 F/g and volumetric capacitance is 162.5 F/cm3. Moreover, a high energy density of 44.27 Wh/kg delivered at a high power of 2656 W/kg, good rate capability and excellent long-term cycling stability make the N-enriched ACs a competitive candidate for practical applications.