High-performance hybrid capacitors based on the FeNi3/NiFe2O4 composite powders synthesized by combustion method

Abstract

A facile combustion method was applied to prepare the FeNi3/NiFe2O4 composite powders by using metal nitrates as oxidants and glycine as fuel. The effects of fuel contents and combustion conditions on structural, microstructural, physical, and electrochemical properties were studied by various characterization techniques such as X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry, cyclic voltammetry, and galvanostatic charge/discharge. With the increase of fuel contents, the crystallinity and amount of FeNi3 phase increased up to 56 wt. % which was accompanied by the enhancement of magnetic properties as a function of combustion conditions. The microstructural evolution from porous to bulky was related to the formation of intermetallic FeNi3 phase. The powders prepared at the highest fuel contents showed the highest specific capacitance of 552 F g−1 at a current density of 0.5 A g−1. The rather high capacity retention of 71% was attributed to the high conductivity because of the presence of the FeNi3 phase. Moreover, the asymmetric capacitor of FeNi3/NiFe2O4//AC had a stable potential window of 0–1.4 V with a high energy density of 24.4 Wh kg−1 at a power density of 754 W kg−1.