Highly-flexible piezoelectric nanogenerators with silver nanowires and barium titanate embedded composite films for mechanical energy harvesting

Piezoelectric nanogenerators (PNGs) is one of the promising technologies to convert mechanical energies into electricity for driving various mobile/portable electronic devices. Generally, the electrical output performance of PNGs is enhanced by electrical poling or annealing treatment, which involves high voltage and temperature techniques. Herein, we successfully demonstrated a flexible PNG designed by the barium titanate embedded polyvinylidene difluoride (i.e., BaTiO3/PVDF) composite film and attained a significant output performance with avoiding electrical poling process. These barium titanate micro stone-like architectures (BTO-MSs) were synthesized by a facile, eco-friendly, and cost-effective solid-state reaction. In addition, the output performance of PNG is further improved by dispersing the silver nanowires (Ag-NWs) as a conducting supplement filler along with the BTO-MSs into the PVDF matrix. Resultantly, the PNG with Ag-NWs/BTO/PVDF composite film exhibited a high open-circuit voltage (VOC) of ∼ 14 V and short-circuit current (ISC) of ∼ 0.96 μA compared to the PNG with only BTO/PVDF (VOC/ISC ∼ 11 V/0.78 μA) upon the application of a low pushing force of 3 N, cyclic pushing-releasing frequency of 5 Hz. Additionally, the effect of external load resistance, pushing force, and frequency on the electrical output performance of PNGs was investigated, including its mechanical stability and durability. Finally, an optimized PNG was employed to efficiently harvest/detect the mechanical energy from automotive vehicle motion and human body movements.