Halide double perovskite-based efficient mechanical energy harvester and storage devices for self-charging power unit

With the rapid development of portable/wearable electronic devices, the demand for highly efficient and sustainable self-powered systems to support their off-grid operation has risen considerably. Recently, metal halide perovskites (MHPs) have been suggested as promising materials for energy harvesting and storage devices because of their excellent optoelectronic, ferro/piezoelectric, and ion migration properties. However, the high toxicity and poor physicochemical stability of MHPs hamper their practical application. Herein, for the first time, the potential of methylammonium tin halide (MA₂SnX₆; X = Cl, Br, and I) double perovskite thin films for high-efficiency self-charging power units (SPUs) is elucidated by virtue of their high stability in air. To this end, the integration of an MA₂SnCl₆-based piezoelectric nanogenerator (PENG) with a lithium metal battery (LMB), which also uses an MA₂SnCl₆-based thin film as the cathode, is demonstrated. The MA₂SnCl₆-based PENG exhibited a high output power density of 7.33 μW cm⁻² and an excellent mechanical durability. Furthermore, MA₂SnCl₆ as a cathode in LMB recorded the highest specific capacity of 589.98 mAh g⁻¹. A 1 nm-thick Al₂O₃ coating on the MA₂SnCl₆ surface improved the capacity retention from 16.9 % to 75.1 % for 100 cycles, indicating its stable performance. The MA₂SnCl₆-based LMB is charged by the MA₂SnCl₆-based PENG and utilized as an SPU for operating various small-scale electronics (humidity meter, calculator, and LED). This work not only demonstrates the feasibility of MHPs toward high-capacity batteries and energy harvesters but also provides insights into the general design principles of MHP-based devices.