Deposition of carbon electrodes for supercapacitors using atmospheric plasma torch

Abstract

The power and energy-storage capabilities of supercapacitors are closely linked to the physical and chemical characteristics of the carbon electrodes. In the present work, the surfaces of activated carbon electrodes were treated in low pressure oxygen and argon plasma for selected times of 15, 30, 60, 120, 180 and 300 s. The plasma source was a DC glow discharge in argon and oxygen gases generated by magnetron sputter deposition technique with Ni cathode. The working gas pressure was 1.3 Pa - 1.8 Pa and the distance between anode of magnetron and substrate - 30 mm. The dissipated power in plasma was equal to 250 W. The negative - 100 V bias voltage was supplied to the carbon electrode. The conducted studies of carbon surface topography showed that plasma treatment initiated microscopic roughening of the surface of activated carbon which was pronounced for short time ( less than 30 s) plasma interaction. This was attributed to an increased of carbon surface area caused by argon-oxygen plasma etching. For discharge times greater than 10 min, combined effects of plasma chemical etching of carbon by oxygen atoms, physical sputtering by argon ions and deposition of nickel oxide deposit appeared to have a smoothing effect and led to a reduction of the measured surface area. Capacitance of electric double layer capacitors (EDLCs) with activated carbon electrodes after 1 min plasma surface treatment was increased by 70% compared to EDLCs cells with the original activated carbon electrodes without plasma treatment and nickel oxide deposition. The results have shown that the modification by plasma treatment of activated carbon electrodes is a suitable technique for EDLCs used in high current applications.