A solar-driven nitrate molten salt lithium-oxygen battery based on built-in bifunctional cathode

Lithium-oxygen (Li-O₂) batteries using molten nitrate electrolyte (typically LiNO₃-KNO₃ eutectic) are considered to have extremely high theoretical energy density due to its unique reaction path achieving complete utilization of O₂. However, suffering from high temperature application environment and limited cathode catalytic ability, further development of the battery has been hindered. In this study, we successfully designed a bifunctional cathode, which could not only drive batteries by photothermal effect, but also effectively catalyze the mediate reaction in electrolyte. Helped by the newly adopted TiO₂ nanorod substrate and Ru catalyst with plasmon effect, a high absorption (>93 %) to full spectrum of sunlight is realized, making the assembled battery easier to reach operating temperature. Furthermore, three-dimensional nanostructure brings more catalytic active site and significantly reduced the overpotential. This is the first light-driven molten nitrate Li-O₂ battery, exhibiting excellent performance in terms of capacity (>10 mAh), stability (>500 cycles), energy efficiency (>90 %), and other aspects. Our work provides effective strategies for enhancing the kinetics of the mediate reaction in nitrate molten salt Li-O₂ batteries, and takes a significant step towards their practical application.