Some factors influencing power and energy capabilities of RuO2 supercapacitors.

Ruthenium oxide electrodes prepared by different routes were studied and the results discussed in terms of the possibility of using these electrodes in high power/high energy supercapacitors. The supercapacitor electrodes were prepared by mixing RuO(2) particles with a binder (Nafion(®) or polyvinilydenfluoride) in various ratios. The results show that charging/discharging reaction of RuO(2) consists of at least two redox reactions taking place simultaneously at different rates. The contribution of each reaction in the overall process depends on the hydration of RuO(2) as well as on the type of binder and binder/RuO(2) ratio. From both energy and power capability of supercapacitors the best electrode composition would be hydrous RuO(2) with ~20% Nafion(®) as a binder. Asymmetric supercapacitors assembled with RuO(2) and activated carbon as a counter electrode gave 26 and 12 W h kg(-1) at average specific power of 5 W g(-1) for RuO(2)/Nafion(®) and RuO(2)/polyvinylidene fluoride, respectively.