Photo-electrooxidiation of I^- and photo-assistant rechargeable secondary Li-ion battery

The structure, micro-morphology, particle size and photo-electrochemical behavior of TiO₂ powder in I^- contained PC electrolyte were investigated by XRD, SEM and micro-cavity electrode. The results indicate that the size of used TiO₂ sample is from 100 nm to 200 nm. The results indicate that the potential of oxidation of I^- on anatase-TiO₂ is 1 V at irradiation condition, lower than that of oxidation of I^- at dark condition. Furthermore, a type of photo-assistant rechargeable Li-ion battery was composed by anatase-TiO₂/ITO semi-conductor photo-anode, poly(vinylidene fluoride)(PVDF) membrane and Li₄Ti₅O₁₂ negative electrode. The charging voltage of such battery is 0.9 V at irradiation condition lower than that of the battery at dark condition. The results of UV-Vis spectroscopy indicate that the charging product of anode half-cell is I₂. At the same time, the Li-ion insertion reaction happens on Li₄Ti₅O₁₂ negative electrode. The total photo-assistant charging reaction of battery is listed as follows: 3LiI+Li₄Ti₅O₁₂+ 3hν(3/2)I₂+Li₇Ti₅O₁₂. The results suggest that such batteries can be used as model for the development of next generation photo-assistant rechargeable Li-ion battery.