Piezoelectric Nanogenerators Based on Electrospun PVDF-Coated Mats Composed of Multilayer Polymer-Coated BaTiO₃ Nanowires

With the surge in demand for green energy, nanocomposites composed of piezoelectric polymers and nano-piezoelectric ceramics show great prospects in preparing excellent performance piezoelectric nanogenerators (PENGs). However, the agglomeration of the piezoelectric enhancement phase and the low degree of polarization significantly impair the piezoelectric properties of the nanofibers; thus, the output performance of PENGs is severely limited. In this work, barium titanate nanowires piezoelectric ceramics were synthesized by the hydrothermal method. By surface-initiated polymerization, the hyperbranched barium titanate nanowire was surface-grafted with poly(methyl methacrylate) (PMMA). The high dielectric constant and low dielectric loss of hyperbranched polymers lead to higher β-phase content in electrospun nanofilms and suppress current leakage. The PMMA coating results in the uniform dispersion of BaTiO3 nanowires in poly(vinylidene fluoride) (PVDF), thereby enhancing the piezoelectric performance of the fiber nanocomposite PENG. The open circuit voltage and short circuit current of the PENG composed of PVDF and core-double shell PMMA-coated hyperbranched BaTiO3 (BTO@HBP@PMMA) nanowires can reach 3.4 V and 0.32 μA, and the peak output power is 5.25 μW, which is significantly improved compared to that of the unmodified PENG. Furthermore, the flexible PENG has high durability and can continuously generate stable piezoelectric signals for 6000 cycles without decay. The prepared PENG can also efficiently harvest the energy generated by human daily activities. In general, this study provides a new microstructure design for the fabrication of high performance PENGs.