A Bifunctional Photo‐Assisted Li–O2 Battery Based on a Hierarchical Heterostructured Cathode

Abstract Photo‐assisted charging is considered an effective approach to reducing the overpotential in lithium–oxygen (Li–O 2 ) batteries. However, the utilization of photoenergy during the discharge process in a Li–O 2 system has been rarely reported, and the functional mechanism of such a process remains unclear. Herein, a novel bifunctional photo‐assisted Li–O 2 system is established by employing a hierarchical TiO 2 –Fe 2 O 3 heterojunction, in which the photo‐generated electrons and holes play key roles in reducing the overpotential in the discharging and charging processes, respectively. Moreover, the morphology of the discharge product (Li 2 O 2 ) can be modified via the dense surface electrons of the cathode under illumination, resulting in promoted decomposition kinetics of Li 2 O 2 during the charging progress. Accordingly, the output and input energies of the battery can be tuned by illumination, giving an ultralow overpotential of 0.19 V between the charge and discharge plateaus with excellent cyclic stability (retaining a round‐trip efficiency of ≈86% after 100 cycles). The investigation of the bifunctional photo‐assisted process presented here provides significant insight into the mechanism of the photo‐assisted Li–O 2 battery and addresses the overpotential bottleneck in this system.