Camphoric Carbon-Grafted Ni/NiO Nanowire Electrodes for High-Performance Energy-Storage Systems

The present study provides the first report on the preparation and utilization of camphoric carbon nanobeads grafted onto Ni/NiO nanowires for rechargeable electrodes for energy-storage applications. These functionally graded nanowires were electrophoretically deposited onto nickel foils and processed into high-surface-area electrodes. A detailed study has been performed to elucidate the effect of carbon content, different electrolytes, and their concentrations on these nanowires. BET surface area analysis revealed that these grafted nanowires could exhibit a high surface area of about 106 m²  g^-1 , compared with pristine nanowires, which exhibited a surface area of about 45 m²  g^-1 . From the analysis of relevant electrochemical parameters, an intrinsic correlation between the capacitance, internal resistance, and the surface morphology has been deduced. Relative contributions of capacitive and diffusion-controlled processes underlying these thin-film electrodes have been mathematically modeled. These thin-film electrodes exhibited specific mass capacitance values as high as (1950±80) and (1140±60) F g^-1 , as determined from cyclic voltammetry and charge discharge curves, respectively; these values were 30-50 % higher than that of a pristine nanowire electrode. Furthermore, a working model button cell employing these rechargeable electrodes is also described, which exhibited energy and power densities of 83 and 75 Wh kg^-1 , respectively. This study shows that electrodes based on such nanowire/carbon nanobead configurations can allow significant room for improvement in energy density, power density, and cyclic stability of supercapacitor/battery systems.