Tin-doped indium oxide (ITO) thin films were deposited by radio-frequency diode sputtering at ambient temperature under a low sputtering voltage (1600 V) and a high chamber pressure (Ar and O-2, 0.2 torr). Investigations by X-ray diffraction, transmission electron microscopy, atomic force microscopy, and infrared reflectance spectroscopy showed that the ITO films were poorly crystallized, abounded with grain boundaries, and had more 'epitaxy' on oxide substrates than on silicon wafers. Cyclic voltammetry measurements indicated that the ITO films deposited on commercial ITO glass substrates showed considerable reversible charging capacity in 1 M LiClO4/propylene carbonate solution. X-ray photoelectron spectroscopy study indicated that lithium insertion took place irreversibly at the initial cycling stages. Besides, the charging/discharging process was hardly accompanied by electrochromic effect from the ITO films. Therefore, the reversible charging of the 'open-structured' ITO films is attributed mainly to the double layer effect.