#01581984 Masatoshi SASAKI

"Pseudocapacitance of an All Solid-State Thin-Film Capacitor Device Using the Tungsten-Bronze Electrode"

Supervisor: Kazunori SATO

An all solid-state thin-film pseudocapacitor has been fabricated using the WO3 electrode and Li2O-B2O3 electrolyte. The WO3 thin-film electrode was grown over the surface of a current collecting platinum thin-film layer deposited on the quartz substrate. The WO3 thin film was prepared by the sol-gel method using tungsten pentaethoxide, W(OC2H5)5, as a starting material. Annealing of the current collecting platinum thin-film resulted in an increase of surface area and an occurrence of preferential crystal orientation, which are favorable for an enhancement of the pseudocapacitance of the present capacitor device. Cyclicvoltammograms for these devices revealed that the capacity was increased approximately 6 times by annealing the platinum thin-film. This enhancement was probably caused by an increase of the surface area of the WO3 electrodes. I have found that amorphous WO3 was effective for the intercalation of lithium ions from the lithium-ion conducting electrolyte glass. Based on the results of the scanning electron microscopic observation and the X-ray diffraction analysis, the charge-discharge performance of the WO3-based capacitor was discussed in terms of the microstructure of the electrode and the interfacial bonding between the electrode and the electrolyte.