Cobalt Nanorods as Transition Metal Electrode Materials for Asymmetric Supercapacitor Applications
Sarkis Sarkis, Xintang Huang
Abstract
A porous cobalt nanorods (Co-NRs) structure is successfully synthesized via annealing of Co(OH)2 nanorods at 350 °C with the presence of ethanol glycol (EG). The Co-NRs@Ni foam electrode displayed an ultrahigh specific capacitance of 3142.8 F g–1 at a current density of 1 mA cm–2; high-rate capability behavior can be proved by 87% of initial capacitance maintenance at 20 mA cm–2 and an excellent cycling life with a retention of 124.5% after 20,000 galvanostatic charge–discharge (GCD) cycles. The excellent electrochemical behavior of the Co-NRs@Ni foam electrode can be ascribed to the hierarchical porous nanorod structure, which can offer high electrical conductivity, enhance the electrolyte ions diffusion pathways, and abound electrochemical active sites. Its asymmetric supercapacitor device Co-NRs∥AC showed a specific energy density of 143.94 Wh kg–1, with a power density of 791.5 W kg–1 at a current density of 1 A g–1. Furthermore, an excellent cycling life behavior by retaining 95.88% of its initial capacitance throughout 20,000 GCD cycles was achieved. The exceptional electrochemical behavior of the Co-NRs@Ni foam electrode displays its great potential in applications as a promising electrode material candidate for energy conversion and storage equipment.