Design of iron (Fe)-doped NiCo2O4@ rGO urchin-shaped microspheres with outstanding electrochemical performances for asymmetric supercapacitor

Abstract

Doping and compounding are two effective ways to improve material properties. The binary metals oxide NiCo2O4 is an attractive class of electrode materials for supercapacitors because of a unique composition and structure. In this report, hybrid heterostructure of Fe-doped NiCo2O4 urchin-shaped microspheres combined with reduced graphene oxide (rGO) (Fe-doped NiCo2O4@rGO) was successfully elaborated with hydrothermal and ultrasonic ways. Both XPS and HRTEM characterization showed that Fe element was successfully doped into NiCo2O4 lattice. As electrode material for supercapacitive properties, the Fe-doped NiCo2O4@rGO shows outstanding electrochemical properties with ultrahigh specific capacitance of 2772 F·g−1 at 0.5 A·g−1, ideal capacitance retention of displaying 2185 F·g−1 at 30 A·g−1 and good cycle life with 3.3% capacitance value loss during 12,000 cycles. Importantly, the analysis of the kinetic process proves the domination of the capacitive contribution over the diffusion process, during the charge storage mechanism. Interestingly, an asymmetric supercapacitor based on the Fe-doped NiCo2O4@rGO hybrid delivers superb specific energy of 93.5 Wh·kg−1 at 455 W·kg−1 specific power at 0.5 A·g−1. Therefore, the designed Fe-doped NiCo2O4@rGO could be looked as promising electrode with high practicability value for future energy storage systems.