Photorechargeable Lead-Free Perovskite Lithium-Ion Batteries Using Hexagonal Cs₃Bi₂I₉ Nanosheets

Materials that enable bifunctional operation in harvesting and storing energy are currently in high demand, due to their potential to efficiently use renewable solar energy. Here, we present a lead-free, all-inorganic, bismuth-based perovskite halide, which acts as a photoelectrode that can harvest energy under illumination without the assistance of an external load in a lithium-ion battery. The battery performance is shown using three different current collectors: copper, fluorine-doped tin oxide (FTO) and carbon felt (CF) to exhibit the electrode's function as a normal coin cell, as a basic photobattery with a transparent collector to elucidate its functional mechanism, and as an optimized photobattery displaying competitive metrics with other photobatteries obtaining a photo conversion efficiency of ∼0.43% for the first discharge. Upon discharging under illumination, we observed an increase in capacity from 410 to 975 mA·h·g^-1. Further exploration in anode structure and design provides a path toward more efficient photobatteries.