KOH activated carbon derived from biomass-banana fibers as an efficient negative electrode in high performance asymmetric supercapacitor

Here we demonstrate the fabrication, electrochemical performance and application of an asymmetric supercapacitor (AS) device constructed with β–Ni(OH)₂/MWCNTs as positive electrode and KOH activated honeycomb-like porous carbon (K-PC) derived from banana fibers as negative electrode. Initially, the electrochemical performance of hydrothermally synthesized β–Ni(OH)₂/MWCNTs nanocomposite and K-PC was studied in a three-electrode system using 1 M KOH. These materials exhibited a specific capacitance (Cs) of 1327 F/g and 324 F/g respectively at a scan rate of 10 mV/s. Further, the AS device i.e., β–Ni(OH)₂/MWCNTs// K-PC in 1 M KOH solution, demonstrated a Cs of 156 F/g at scan rate of 10 mV/s in a broad cell voltage of 0–2.2 V. The device demonstrated a good rate capability by maintaining a Cs of 59 F/g even at high current density (25 A/g). The device also offered high energy density of 63 Wh/kg with maximum power density of 5.2 kW/kg. The AS device exhibited excellent cycle life with 100% capacitance retention at 5000th cycle at a high current density of 25 A/g. Two AS devices connected in series were employed for powering a pair of LEDs of different colors and also a mini fan.