Defects‐Triggered In Situ Reconstruction in Metal‐Halide Perovskites for Photo‐Rechargeable Lithium‐Ion Batteries

Photo‐rechargeable batteries (PRBs), which refer to the integrated energy conversion‐storage units, are receiving intense interest as they are able to solve the drawbacks in the traditional off‐grid supply system (e.g., intermittency of solar energy, ohmic losses by wire‐connection, and voltage mismatch). Bifunctional photoelectrodes, which are active materials with both photovoltaic and energy‐storage capabilities, are the key matrices in PRBs. Herein, a bifunctional photoelectrode with heterojunctions based on lead‐free metal‐halide perovskites (MHPs) is formed via a spontaneous two‐step reconstruction triggered by octahedral defects and arrangement. Due to the partial dissolution of octahedra (e.g., [SnI 6 ] 2 − or [Bi 2 I 9 ] 3 − ) in N ‐methyl‐2‐pyrrolidone solution during fabrication of electrodes, the Cu current collector is reactivated with the Cu + /Cu 2+ leaching, thereby enabling the in situ formation of CuO (CuI)/MHPs heterojunctions, which significantly enhances the conductivity of the photoelectrodes and effectively improves the stability. The reconstructed electrodes deliver remarkable specific capacity in both photo‐assisted (684.6 mAh g −1 at 0.6 A g −1 ) and photo‐charge (0.316 mAh cm −2 at 2 mA cm −2 ) conditions, as well as the integrated micro‐PRLIBs show all‐day applications in wearable electronics. This work provides a generalizable framework for constructing efficient photo‐rechargeable systems with high integration for wearable and portable devices, such as smart textiles and biosensors.