NiCo2O4@quinone-rich N-C core-shell nanowires as composite electrode for electric double layer capacitor

The bind-free carbon cloth-supported electrodes hold the promises for high-performance electrochemical capacitors with high specific capacitance and good cyclic stability. Considering the close connection between their performance and the amount of carbon material loaded on the electrodes, in this work, NiCo₂O₄ nanowires were firstly grown on the substrate of active carbon cloth to provide the necessary surface area in the longitudinal direction. Then, the quinone-rich nitrogen-doped carbon shell structure was formed around NiCo₂O₄ nanowires, and the obtained composite was used as electrode for electric double layer capacitor. The results showed that the composite electrode displayed an area-specific capacitance of 1794 mF·cm⁻² at the current density of 1 mA·cm⁻². The assembled symmetric electric double layer capacitor achieved a high energy density of 6.55 mW·h·cm⁻³ at a power density of 180 mW·cm⁻³. The assembled symmetric capacitor exhibited a capacitance retention of 88.96% after 10000 charge/discharge cycles at the current density of 20 mA·cm⁻². These results indicated the potentials in the preparation of the carbon electrode materials with high energy density and good cycling stability.