Synthesis of Co3O4@CNTs with oxygen vacancies on nickel foam for improved performance of asymmetric supercapacitor electrode

Metal oxide Co3O4 is regarded as a promising pseudocapacitance material due to its high theoretical specific capacitance and excellent reversible ability. While its poor intrinsic electronic conductivity and low activity sites limit its supercapacitor performance. Herein, oxygen vacancy-abundant Co3O4 nanowire assembly coupling with carbon nanotubes (CNTs) has been synthesized on nickel foam (Co3O4@CNTs@NF). The introduction of CNTs and oxygen vacancies provides enhanced electrical conductivity, more available active sites, and fast faradic redox reactions to the Co3O4@CNTs composite. The strong binding force between Co3O4@CNTs and nickel foam gives excellent capacitive property and remarkable cyclic durability. The Co3O4@CNTs@NF electrode exhibits a high specific capacitance of 1291 F g-1 at 5 mA/cm2 and a capacitance retention rate of 106% after 5000 cycles at 30 mA g-1. It can be used as the anode to assemble an asymmetric supercapacitor using active carbon loaded on NF (AC@NF) as the cathode. The Co3O4@CNTs@NF//AC@NF device exhibits a high energy density of 57.6 Wh/kg at 273.4 W/kg. This work provides deep insights into the development of excellent electrode materials for the next generation of supercapacitors.