ELECTROCHEMICAL CAPACITORS USING HYDROUS RUTHENIUM OXIDE AND HYDROGENINSERTED RUTHENIUM OXIDE

Electrochemical capacitors made with hydrous ruthenium oxide (RuO2;xH( 2)O) and hydrogen inserted hydrous ruthenium oxide (H6RuO2.xH(2)O) ele ctrode materials were investigated. The electrochemical behavior of Ru O2.xH(2)O in the potential range of -0.2 to 1.3 V vs. saturated calome l electrode (SCE) was characterized using a cyclic voltammetry techniq ue. It was found that, electrochemically, amorphous RuO2.xH(2)O electr odes behave quite differently from crystalline RuO2. The potentials of both the positive and the negative electrodes of the capacitors were monitored relative to SCE. For capacitors made with RuO2.xH(2)O electr ode material, gas evolution and an increase of cell resistance were ob served in the first few charge/discharge cycles. This was due to the f act that the potentials of the starting materials were close to the ox idation limit of the potential window. Hydrogen inserted hydrous ruthe nium oxide with potentials near the center of the potential window wer e prepared using both electrochemical and chemical methods. It was dem onstrated that capacitors made of hydrogen inserted ruthenium oxide el ectrodes exhibited high efficiency, high energy, and high power throug h a cycle life over 60,000 times.