Effect of particle size and morphological structure on the physical properties of NiFe2O4 for supercapacitor application

Abstract

Activated carbon (AAC), NiFe2O4, and binary nanocomposites of NiFe2O4 and AAC electrodes have been prepared for supercapacitor applications. Nickel ferrite (NiFe2O4) was prepared using four different ways: electrospinning, hydrothermal, sol–gel, and green method. The samples were characterized by XRD, FT-IR, SEM, TEM, and BET techniques. The results showed the formation of the ferrite in the cubic spinel phase with different morphological structures of nanofibers, nanotubes, nanorods, and nanospheres, as well as the formation of AAC in the flake structure. The influence of synthetic methods on electrochemical properties and their applications in storage energy was studied using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and impedance methods in a 6 M KCl electrolyte solution. The data obtained illustrated pseudo-capacitive behavior with a revisable charge/discharge property. The maximum specific capacitance for ferrite samples increased with decreasing the particle size and a capacitance value of 1130 F g−1 for the NiF2O4 nanofibers (NiFf) sample. The AAC electrode has a specific capacitance of 432 F/g. The capacitive data of an asymmetric capacitor designed from the AAC@NiFf composite electrode, the activated carbon (AAC), and a solid electrolyte composed of PVA and KOH were studied. The capacitor shows a specific capacitance of 135 F/g, a maximum energy density of 34.7 Wh/kg, a maximum power density of 5314 W/kg, and high cycling performance, with 88% capacitance retained over 10000 cycles.

Keywords

• NiFe2O4
• Activated carbon
• Composite
• Supercapacitor
• Electrospinning