Photoinduced Cu+/Cu2+ interconversion for enhancing energy conversion and storage performances of CuO based Li-ion battery

Pursuing appropriate photo-active Li-ion storage materials and understanding their basic energy storage/conversion principle are pretty crucial for the rapidly developing photoassisted Li-ion batteries (PA-LIBs). Copper oxide (CuO) is one of the most popular candidates in both LIBs and photocatalysis. While CuO based PA-LIBs have never been reported yet. Herein, one-dimensional (1D) CuO nanowire arrays in situ grown on a three-dimensional (3D) copper foam support were employed as dual-functional photoanode for both ‘solar-to-electricity’ and ‘electricity-to-chemical’ energy conversion in the PA-LIBs. It is found that light energy can be indeed stored and converted into electrical energy through the assembled CuO based PA-LIBs. Without external power source, the photo conversion efficiency of CuO based photocell reaches about 0.34%. Impressively, at a high current density of 4000 mA g−1, photoassisted discharge and charge specific capacity of CuO based PA-LIBs respectively receive 64.01% and 60.35% enhancement compared with the net electric charging and discharging process. Mechanism investigation reveals that photogenerated charges from CuO promote the interconversion between Cu2+ and Cu+ during the discharging/charging process, thus forcing the lithium storage reaction more completely and increasing the specific capacity of the PA-LIBs. This work can provide a general principle for the development of other high-efficient semiconductor-based PA-LIBs.