High output flexible polyvinylidene fluoride based piezoelectric device incorporating cellulose nanofibers/BaTiO@TiO piezoelectric core-shell structure.

Flexible composite film has gained increasing attention in the fields of wearable devices and portable electronic products. In this work, a novel core-shell structure of cellulose nanofibers/BaTiO@TiO (CNF/BTO@TiO) was synthesized with the assistant of the biological macromolecule material of cellulose nanofiber (CNF), in which the CNF can improve the stability and dispersibility of BaTiO (BTO) in the aqueous phase and elevate the integrity of the core-shell structure. The core-shell structure can reduce the agglomeration of fillers in polyvinylidene fluoride (PVDF) and improve the structural defects of the composite film. Meanwhile, the core-shell structure can promote the polarization of the electric dipole and the formation of β phase in PVDF due to the generated interface spatial polarization between the shell of TiO and the core of BTO. When the content of the core-shell structure was 5 wt%, the β phase content reaches 61.89 %, and the piezoelectric coefficient of composite film reaches 84.29 pm/V. Thus the maximum output open-circuit voltage (V) and short-circuit current (I) of the piezoelectric composite film is as high as 13.10 V and 464.3 nA. In addition, its excellent pressure sensing capability allows for its application in various flexible electronic devices.