High-performance flexible lead-free nanocomposite piezoelectric nanogenerator for biomechanical energy harvesting and storage

•Lead-free piezoelectric nanocomposite with high piezoelectricity.•Utilization of highly crystallized β-phase PVDF-TrFE matrix.•Harvesting biomechanical energy and storing the generated electricity into a microbattery.

Environmentally friendly and flexible piezoelectric nanogenerators (PENGs) have attracted considerable interest for use in autonomous micro-/nano-systems, wearable electronics, and implantable biomedical devices. Herein, a flexible, lead-free, solution-processable and efficient PENG is demonstrated, based on a highly piezoelectric nanocomposite thin film of barium titanate nanoparticles (BT NPs) embedded into a highly crystalline polyvinylidene fluoride–trifluoroethylene (P(VDF–TrFE)) polymer for charge storage. The nanocomposite PENG (nc-PENG) with high loading of BT NPs up to 40 wt% in the nanocomposite can produce output voltage as high as 9.8 V and output power density of 13.5 µW/cm2 under cyclic bending, comparable to the output of conventional inorganic polycrystalline lead zirconate titanate PENGs. The high performance of these nc-PENGs is primarily attributed to the very high effective piezoelectricity of the highly crystalline P(VDF-TrFE), strengthened by the BT NPs. The nc-PENG was also demonstrated to harvest biomechanical energy from simple body movements and store the generated electricity during mechanical and biomechanical motions in a rechargeable microbattery.

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