Zn-based coordination polymer derived N-doped defective carbon for high energy density supercapacitor using aqueous, dual redox additive and ionic liquid electrolytes

Abstract

Porous carbons are excellent supercapacitor materials due to their high-power density, rapid charge-discharge rates and extended cycling stability. However, the restricted energy density poses a bottleneck for their practical applications. The ideal approach to enhance the energy density is by utilizing redox additives and ionic liquid electrolytes. Herein, the defect-rich nitrogen-doped porous carbons (N-PCs) are synthesized at 700, 850 and 1000 °C using Zn-BTC BPY coordination polymers as the sacrificial template for high energy density supercapacitor application. The defect density increases while the percentage of N-doping decreases with the increase in carbonization temperature. In three-electrode system, N-PC-1000 carbon delivered a high capacitance of 151 F g-1 at 1 A g-1, whereas N-PC-700 and N-PC-850 carbons delivered capacitance of 129 and 87 F g-1, respectively, with more than 98% capacitance retention. Additionally, the N-PC-1000||N-PC-1000 symmetric coin cell device delivered high energy densities of 14.2 and 16.9 Wh kg-1 in organic (KOH + HQ) and inorganic-organic dual redox additive (KOH + KI + HQ) electrolytes, respectively. Further, the assembled symmetric device demonstrated maximum energy and power densities of 31.3 Wh kg-1 and 15,881 W kg-1, respectively in [EMIM][ESO4] ionic liquid electrolytes, while retaining 99 % capacitance over 6000 GCD cycles. Overall, this study presents the idea of using coordination polymer-based porous carbons for developing next generation energy storage devices.