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

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.