Hierarchically Organized Ultrathin NiO Nanofibers/Highly Defective-rGO Heteronanocomposite: An Advanced Electrode Material for Asymmetric Supercapacitors

Herein, defective-rGO (D-rGO) is endorsed as a unique conducting matrix for defect-induced interfacial growth of ultrathin dangling-NiO nanofibers. The physicochemical analyses corroborate added defect density on the graphene surface, defect-induced growth of NiO, and excellent hydrophilicity of NiO/D-rGO heteronanocomposite. Thorough electrochemical analyses of NiO/D-rGO heteronanocomposite show high specific capacitance of 1992 F g(-1), ultralow equivalent series resistance (ESR) of 1.7 omega, and approximate to 92.5% retention of charge storage after 5000 galvanostatic charge-discharge (GCD) cycles. The advanced NiO/D-rGO || Bi2O3 asymmetric supercapacitor (ASC) device delivers high areal/mass specific capacitance and exhibits outstanding rate capacitance under extreme current density conditions. The ASC device retains a significant 89.5% of areal capacitance after 5000 GCD cycles under high rate conditions. The ASC device also delivers a high energy density of approximate to 43.7 Wh kg(-1) at a power density of approximate to 4799 W kg(-1) and retains approximate to 46% of the energy density at a very high power density of approximate to 18 518 W kg(-1). The excellent performance of the ASC device is ascribed to defect-induced improved bonding between D-rGO and NiO, microstructural stability of NiO/D-rGO, D-rGO prompted conductivity, and "ion-buffering-reservoir" -alike behavior of the fiber assembly. The present approach is significant in developing new-age supercapacitors for high rate applications.