Characteristics of thin film supercapacitor with ruthenium oxide electrode and Ta2O5+x solid oxide thin film electrolyte

Abstract

We report findings related to a solid-state thin film supercapacitors (TFSCs) fabricated with ruthenium oxide electrodes and hydrogen doped tantalum oxide electrolyte in order to investigate a feasibility for solid oxide thin film electrolyte in all solid state micropower sources with hydrogen conducting electrolyte. The TFSCs in this study has a cell structure of RuO2/Ta2O5/RuO2/Pt. Radio frequency, off-axis r.f. sputtering deposition of a Ta2O5 thin film was performed on the bottom amorphous RuO2 electrode which was deposited by an on-axis direct current reactive sputtering, within hydrogen atmosphere to enhance the concentration of mobile proton (H+) ions. Scanning electron microscopy (SEM) measurements reveal that the RuO2/Ta2O5/RuO2 hetero-interfaces have no inter-diffusion problems. Room temperature charge-discharge measurements with constant current clearly reveal typical supercapacitor behavior. Also, owing to the fast diffusion of H+ ions within the Ta2O5 lattice without any structural deterioration, the capacitance per volume of RuO2/Ta2O5/RuO2/Pt TFSCs was maintained to be constant during above 800 cycles. This result indicated that the solid oxide thin film has possibility as the solid proton conducting electrolyte for all solid state micropower sources.