Revealing the illumination effect on the discharge products in high-performance Li-O2 batteries with heterostructured photocatalysts

Aprotic lithium-oxygen batteries (LOBs) have been recognized as novel energy storage devices for their outstanding specific energy density, while the large discharge/charge overpotential is a tough barrier to be overcome. Here, hetero-structured MoS2/ZnIn2S4 nanosheets have been prepared to capture visible light and the generated charge carriers are utilized for promoting both the oxygen reduction reaction and the oxygen evolution reaction. With the light illumination in the discharge process, the abundant photo-inspired electrons serve as the reaction sites to promote the reduction of O-2 into LiO2 which is finally deposited as Li2O2. On the contrary, the generated holes in the valence band can contribute to the low oxidization potential of Li2O2 during the charge process. It delivers a low charge potential of 3.29 V, with an excellent resulting energy efficiency of 96.7%, much superior to that of 69.2% in the dark condition. It is noted that the involvement of photoelectrons has influenced the growth of Li2O2 films on the MoS2/ZnIn2S4 nanosheets through the surface-adsorption pathway. The insights from the theoretical calculation confirm that the photoelectrons favor the absorption of LiO2 and the formation of the Li2O2 film through the surface route. Therefore, this paper provides a deeper understanding of the mechanism of photo-inspired charge carriers in LOBs and will enable further exploration of photo-involved energy storage systems.

Automated summary

This study demonstrates the use of hetero-structured MoS2/ZnIn2S4 nanosheets to capture visible light and utilize the generated charge carriers for promoting the oxygen reduction and evolution reactions in lithium-oxygen batteries. The involvement of photoelectrons is found to significantly impact the growth and formation of Li2O2 films in the battery.