Biomass-derived hierarchical porous carbons: boosting the energy density of supercapacitors via an ionothermal approach

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 5; no. 25; pp. 139 - 1318
• Main Authors: Liu, Yuchuan, Huang, Baobing, Lin, Xiaoxiao, Xie, Zailai
• Format: Journal Article
• Language: English
• Published: 2017
• Subjects: Alternative energy sources; Aqueous electrolytes; Biomass; Capacitance; Carbon; Electrodes; Energy density; Supercapacitors
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c7ta03639f

High mass energy density coupled with high power density is highly desired for electrical double-layer capacitors. Usually the capacitive performance is improved by optimizing the pore size and volume distribution. Herein, the authors report an efficient approach to optimize the porous structure through a facile ionothermal carbonization method. A series of hierarchical porous carbons with unique sub-micrometer sized morphology, high surface area and abundant mesopores ( e.g. S BET = 2532 m 2 g −1 and V meso = 1.077 cm 3 g −1 ) have been synthesized, using Jujun grass as a nitrogen-containing precursor. The ionic liquid acts not only as a reaction medium for the conversion of biomass to carbon but also as a porogenic agent for inducing mesoporosity. The results indicate that the ionothermal method can balance the micro- and mesoporosity of the optimized porous carbon, making it one of the competent alternatives to the state-of-the-art electrodes for ultra-high energy density supercapacitors. The optimized ionothermal carbon (ITC-JG-900) shows an impressively high specific capacitance of 336 F g −1 at 1 A g −1 in 6 M KOH, and even retained a capacitance of 222 F g −1 at 10 A g −1 , which is 66% of the initial capacitance. The maximum energy density of ITC-JG-900 as a supercapacitor is found to be over 72.7 W h kg −1 when the power density is 1204 W kg −1 , which is higher than those of most of the equivalent benchmarks tested in aqueous electrolytes. High mass energy density coupled with high power density is highly desired for electrical double-layer capacitors.