Li-ion batteries play a significant role in portable electronic devices in the running world. However, the limited energy density still needs to be improved for the growing future. Hence, we developed a photocathode nanocomposite material composed of Cadmium Selenide/Zinc Sulfide Quantum Dots with Carbon nanotube (CdSe/ZnS QD@CNT) for an efficient and tunable performance of the photoelectrochemical Li-O-2 battery system to overcome the key issue of overpotential. The QD and CNT networks can provide efficient transportation paths of the electron-hole pairs and the O-2 gas and lithium ions, respectively. The charging voltage of the photoelectrode is 2.65-4.0 V; therefore, decreased overpotential was due to efficient oxidation of Li-O-2 by photoexcited electron-hole pairs by using QDs, resulting in a long-term operational stability over 100 cycles. On the basis of the advantages, the QDs exhibit efficient potential in Li-O-2 batteries.