Study On The Piezoelectric-triboelectric Generation Performances And Mechanism Of Electrospinning PVDF-HFP Composite Fiber Film

With the increase of energy consumption and depletion of fossil resources,more and more researchers have devoted to investigating alternative energies.It has been proved that flexible piezoelectric nano generators acquire excellent mechanical properties,environment adaptabilities and high electroporation conversion efficiency,which makes them potentially applied in powering electronics and wireless sensors.Polyvinylidene fluoride(PVDF)and its copolymers are highly recommended as flexible polymer materials for their best piezoelectric properties,flexible and low costs.In the present work,polyvinylidene fluoride-hexafluoropropylene(PVDF-HFP)fiber film was prepared with electrospinning.Besides,an excellent power generating performance can be accomplished by adding inorganic piezoelectric fillers lead zirconate titanate(PZT)and barium titanate(BT).After packaging and grounding to shield the interference of external friction signals,the short-circuit current and open-circuit voltage of 20 wt% PZT/PVDF-HFP and 15wt% BT/PVDF-HFP fiber films reached 450 n A,3.4 V and 750 n A,4 V,respectively.On the other hand,thermal treatment was applied on pure PVDF-HFP,20 wt% PZT/PVDFHFP and 15 wt% BT/PVDF-HFP fiber film.The contributions of piezoelectric and friction power generation were separately discussed by regulating the fiber morphology and ? phase contents,which revealed the force-electrical converting mechanisms.It could be observed that after thermal treatment under 145?,fiber structures of electrospinning PVDF-HFP,PZT/PVDFHFP and BT/PVDF-HFP fiber films all appeared to be significantly softened,accompanied with the reduction of power generation performance.Nevertheless,at 150?,fibers were melted and adhered together,leading to the significant decrease of power generation signal while the ? phase content did not significantly decrease.Such phenomena implied that the reduction of power generation performance was mainly related to the deformation of the fibers rather than the change of the piezoelectric phase,in other words,the power generation signal of the unheated conventional sample mainly came from the friction between the fibers.Due to the polarization of the electric field during the spinning process,the upper and lower surfaces of PVDF-HFP fibers are oppositely charged.Meanwhile,the frictions exaggerated the charge in-balance on two surfaces,leading to the intensive triboelectric signals,and the friction signals between the fiber and the filler can further enhance the frictional generation performance.The PVDF-HFP,PZT/PVDF-HFP and BT/PVDF-HFP fiber films were prepared by electrospun technology,and the flexible films which acquired force-electrical converting properties were obtained.The proportion of frictional and piezoelectrical generated power were analyzed through thermal treatment.The results illustrated that the power generation performance of the PVDF-HFP at 1 Hz mainly relied on the friction between the fibers,rather than the ?-phase content,which is generally believed in previous research.Therefore,this work provided significance for the improvement of the force-to-electricity conversion performance.