Bifunctional Photoassisted Li-O2 Battery with Ultrahigh Rate-Cycling Performance Based on Siloxene Size Regulation.

Abstract

Directly integrating the bifunctional photoelectrode into Li-O2 batteries has been considered an effective way to reduce the overpotential and promote electric energy saving. However, more regular investigations on various bifunctional photocatalysts have still been desired for high-performance photoassisted Li-O2 batteries. Herein, a systematic exploration of various-sized siloxene photocatalysts affected by Li-O2 batteries has been introduced. Compared with the utilization of larger-sized siloxene nanosheets (SNSs), the photoassisted Li-O2 battery with a siloxene quantum dot (SQD) photoelectrode delivers a superior round-trip efficiency of 230% based on the highest discharge potential up to 3.72 V and lowest charge potential of 1.60 V and enables the maintenance of a long-term cycling life with only 13% efficiency attenuation after 200 cycles at 0.075 mA/cm2. Furthermore, this system exhibits a record-high rate-cycling performance (162% round-trip efficiency, even at 3 mA/cm2) and a high discharge capacity of 2212 mAh/g at 1 mA/cm2. These ground-breaking performances could be attributed to the synergistic effect of the photocatalytic and electrocatalytic activities of SQD photocatalysts with the ideal conduction band/valence band values, the abundant defective sites, and the stronger O2 and lower LiO2 adsorption strengths of SQD photocatalysts. These systematic research studies highlight the significance of SQD bifunctional photocatalysts and could be extended to other photocatalysts for further high-efficiency photoelectric conversion and storage.