Banana peels, a common fruit waste was adopted as a material precursor in this study to synthesize highly porous activated carbon from banana peels (ABP) which serves as an electrode material for a symmetric supercapacitor device. The activation was done using KOH pellets at different carbonization temperatures ranging from 750 degrees C to 950 degrees C. The ABP sample obtained from the 900 degrees C carbonization temperature (ABP900) exhibited unique material properties such as hierarchical porous nanoarchitecture containing micropores, and mesopores with the highest specific surface area (1362m(2) g(-1)). Electrochemical performance investigation in different neutral aqueous electrolytes showed that the best response was obtained in NaNO3 for the ABP900 electrode. The symmetric device subsequently assembled using 1 M NaNO3 operated in a potential window of 1.8 V, exhibited a specific capacitance of 165 F g(-1) with a corresponding energy density of 18.6 Wh kg(-1) at 0.5 A g(-1). A 100% capacitance retention and columbic efficiency were obtained after 10000 continuous charge-discharge cycles at 5 A g(-1). Remarkably, after subjecting the symmetric device to a voltage holding test for 60 h, the specific capacitance was observed to increase from 165 F g(-1) to 328 F g(-1) with a corresponding increased energy density to about 36.9 W h kg(-1) at 0.5 A g(-1), suggesting a 98% increase in device energy density from its initial value after voltage holding. Thus, the results reported showcase the ABP900 material as a potential nanostructured porous material useful in the design of high-performance electrodes for stable electrochemical capacitors. (C) 2018 Elsevier Ltd. All rights reserved.