Self-Poled hBN-PVDF Nanofiber Mat-Based Low-Cost, Ultrahigh-Performance Piezoelectric Nanogenerator for Biomechanical Energy Harvesting

In this work, we demonstrate a highly efficient, flexible piezoelectric nanogenerator (PENG) using solid-state synthesized hexagonal boron nitride (hBN) nanoflakes embedded in a polyvinylidene fluoride (PVDF) matrix. The matrix was electrospun to form a piezocomposite (hBN-PVDF) free-standing nanofiber mat to power up wearable electronic devices. X-ray diffraction confirmed the hexagonal structure of boron nitride (hBN), while SEM/TEM images revealed the morphology and lattice fringes, respectively. Fourier transform infrared spectroscopy and Raman spectroscopy were used to study the increase in the piezoelectric behavior due to the increase in the polar β-phase of PVDF with the addition of hBN in the piezocomposite. hBN enhances the piezoelectric coefficient and Young's modulus of PVDF, resulting in the generation of high output voltage in the piezocomposite. The as-fabricated piezoelectric nanogenerator efficiently drives the charges generated by mechanical stress to electrodes, producing an outstanding open-circuit voltage (OCV) of ∼68 V and short-circuit current of ∼0.1 μA with a power density of 53.2 μW/cm2 across a 10 MΩ resistor, which is the highest reported performance so far among the same class of devices. Furthermore, energy is harvested from human movements like finger folding and walking. A piezopotential of ∼98 V generated during walking demonstrates a self-powered pedometer. In addition, a capacitor of 2.2 μF is charged up to ∼3 V by tapping the PENG. The robust, as-fabricated PENG showed untarnished performance even after 45 days of storage and 1500 bending cycles, thus being an ideal choice for scavenging biomechanical energy to power wide range of flexible, wearable and self-powered electronics.