A visible light illumination assistant Li-O₂ battery based on an oxygen vacancy doped TiO₂ catalyst

TiO₂ is regarded as one of the most stable catalysts for Li-O₂ battery cathodes, however, the inert surface and weak conductivity limit its catalytic ability. In the present work, a visible light assistant electrode-process on an oxygen vacancy doped TiO₂ (TiO_2-δ) catalyst is proposed to promote its performances in Li-O₂ batteries. The TiO_2-δ is prepared by an insufficient oxidation on Ti₂O₃ through a hydrothermal process and subsequent heat-treatment, and this method guarantees the homogeneous distribution of oxygen vacancies in obtained TiO_2-δ catalysts. The TiO_2-δ possess a narrow bandgap, leading to a visible light adsorption, which leads to remarkable suppression on overpotential under illumination by xenon lamp in Li-O₂ batteries. The electrochemical measurements indicate that, the illumination can obviously enhance the catalytic currents and reduce the electrochemical reaction impedance, and these contributions are responsible for the overpotential decrease. The in-situ gas chromatography is used for inspecting the oxygen flow of a cyclic battery, and the results reveal that, the illumination results in apparent increase in oxygen consumption/evolution in discharge/charge processes. We suggest the photo-induced electrons/vacancies on catalyst surface in discharge/charge processes promote the performances and reversibility of Li-O₂ batteries.