Ultrahigh performance asymmetric supercapacitor devices with synergetic interaction between metal organic frameworks/graphene nano platelets and redox additive electrolyte

Abstract

One of the key challenges has been taken to design high performance hybrid energy storage devices using electrodes based on capacitive graphene nanoplatelets (GNPs) and pseudocapacitive metal organic frameworks (MOFs) with high energy storage, power density and long-life cycles. Herein, we are introducing novel hybrid capacitors based on highly porous composite electrodes of ZIF-67/GNPs and ZIF-8/GNPs and redox additive electrolyte (RAE) that is, 0.2 M [K3(Fe (CN)6)] in 1 M Na2SO4. The ZIF-67/GNPs and ZIF-8/GNPs composite electrodes were used to fabricate the asymmetric supercapacitor devices using MOFs/GNPs as a positive electrode and GNPs as the negative electrode in the presence of RAE exhibited high energy and power densities of 85.8 W h kg−1 and 60.7 W h kg−1 and 7500 W kg−1 and 7370 W kg−1, respectively at current density of 1 Ag−1. The asymmetric devices retain excellent capacitances of up to 97.7% (ZIF-67/GNPs) and 97.1% (ZIF-8/GNPs) along with remarkable columbic efficiencies near 100% after 10,000 charge discharge cycles at 2 Ag−1 in a wide voltage range of (0.0–1.5 V).