Photo-rechargeable Li-Ion Batteries with Lead-Free Double-Perovskite Halide Cs₂NaBiI₆

High Resolution Image Download MS PowerPoint Slide Perovskite halides are promising materials for bifunctional devices that can achieve both photovoltaic energy generation and energy storage. Here, a lead-free all-inorganic double-perovskite halide, 3D Cs 2 NaBiI 6, has been investigated as both electrode and photoelectrode active layer in a Li-ion battery. This nontoxic, environmentally friendly material shows impressive lithium storage capacity performance, as compared to previous perovskite photoelectrodes, such as Cs 3 Bi 2 I 9. Li-ion batteries using this material, in a standard coin cell configuration, achieved a champion first charge specific capacity of 450 mAhg –1 and 150 mAhg –1 after 90 cycles, with devices functioning well beyond 500 cycles. Furthermore, bifunctional performance with energy harvesting and energy storage properties was achieved by fabricating photobatteries (PHBATs) in a modified coin cell. PHBATs using Cs 2 NaBiI 6 represent the first double perovskite to be used in this application and achieved a “first charge” light conversion efficiency (LCE) of 0.27%, higher than most photoelectrode materials reported to date and with better stability than previously studied bismuth perovskites.