Intercalative and non-intercalative photo-recharge using all-solid-state cells for solar energy conversion and storage

Abstract

Photo-rechargeable systems, which can efficiently convert and store solar energy into chemical energy within single devices, are essential to harness sunlight effectively. Photo-(de)intercalation plays a pivotal role in the functionality of photo-rechargeable systems. Nevertheless, the photo-(de)intercalation process has not been conclusively confirmed owing to potential interference from side reactions, such as the decomposition of liquid electrolytes and the elution of electrode materials. In this study, we successfully demonstrated photo-responsive Li⁺-deintercalation using an all-solid-state thin-film battery composed of epitaxially grown anatase TiO₂ doped with Nb (a-TiO₂:Nb) as the cathode, in combination with operando X-ray diffractometry. Under light irradiation, Li⁺-deintercalation occurred and was subsequently reversibly intercalated into a-TiO₂:Nb during discharge. Furthermore, it was observed that a portion of the charge capacity under light irradiation resulted from non-intercalative (non-redox-reactive) electron transfer, akin to supercapacitors. These findings suggest that both intercalative and non-intercalative photo-charging mechanisms can be applied to secondary batteries and supercapacitors, respectively. Therefore, photo-rechargeable all-solid-state cells, encompassing both secondary batteries and supercapacitors, hold significant promise for advancing solar energy conversion and storage.