Performance Research Of Flexible Piezoelectric Energy Harvester Based On KNN/PVDF

The rapid development of society has driven the widespread application of portable,wearable,and implantable electronic devices in medical monitoring,human-computer interaction,and artificial intelligence.Mechanical energy is widely present in our living environment and even in the living body.Piezoelectric energy harvester is an electromechanical conversion device that can convert mechanical energy into electrical energy.Therefore,piezoelectric energy harvester can be used to collect sustainable mechanical energy into portable and wearable products.,Implantable electronic devices for power supply.To adapt to the complex working environment of these electronic devices,this requires the piezoelectric energy harvester to be flexible.The use of flexible composite piezoelectric materials to prepare flexible piezoelectric energy harvesters has the advantages of light weight,low cost,and simple manufacture.Therefore,this thesis builds PVDF/KNN+PVDF/PVDF(PKP)and PVDF/PVDF/PVDF/KNN+PVDF/PVDF(PKP)prepared by hot pressing method around based on potassium sodium niobate(KNN)as the piezoelectric filling material and polyvinylidene fluoride(PVDF)as the flexible substrate.Ag-KNN/PVDF(PAKP)two three-layer composite flexible films,the effect of KNN on the formation of PVDF β phase in the PKP composite film before and after polarization is studied;Ag-KNN+PVDF composite film is studied by the addition of Ag The influence of medium electric field distribution and the influence on the formation of β phase in PVDF;the influence of different KNN content on the piezoelectric output performance of PKP composite flexible piezoelectric energy harvester,and the influence of different Ag content on PAKP composite flexible piezoelectric energy harvester The piezoelectric output performance of the device is affected.The main results obtained are as follows:(1)The relative content of β-phase of PVDF in the PKP composite film prepared by hot pressing method increases first and then decreases with the increase of KNN content,and polarization can induce the formation of more β-phase,when the content of KNN is 20 wt% At the time,the maximum was 54.6%.The piezoelectric output performance test of pure PVDF and PKP composite flexible piezoelectric energy harvester with different KNN content shows that the addition of KNN can significantly improve the piezoelectric output performance of the flexible piezoelectric energy harvester,and when the KNN content of the intermediate layer is The output of the PKP(P-20%KP)composite piezoelectric energy harvester at 20 wt% is the largest,where the open-circuit voltage output is 4.47 V,the short-circuit current output is 42.14 n A,and the output power reaches when the external load resistance is 80 Ω The maximum is 92.17 n W.When the output voltage signal of the device does not attenuate during the 3000-cycle test,it proves that the device has good stability.The P-20% KP composite flexible piezoelectric energy harvester is used to collect the changes in the output voltage signal of the device under different bending angles.The results show that as the bending angle of the arm increases,the P-20% KP composite flexible energy harvester is The voltage output increases accordingly,indicating that the device has a certain angle resolution capability.At the same time,the device is used as a sensor to record the number of steps of the human body in the case of walking and jogging.The results show that the device has a good step-counting function.(2)Ag-KNN samples with different Ag content were prepared by photoreduction method.Secondly,through COMSOL multiphysics simulation,it is found that the combination of Ag and KNN during the polarization process can enhance the electric field distribution in the composite film.In PAKP composite film with Ag-KNN content of 20%,with the increase of Ag content,the relative content of β-phase of PVDF in PAKP composite film first increases and then decreases,reaching a maximum of 58.8% when the Ag content is 1 mol%.The leakage current and hysteresis loop characterization of PAKP composite films with different Ag contents were performed using a ferroelectric parameter tester.The results show that the addition of Ag can increase the leakage current of the composite film under a high electric field,and a small amount of Ag can increase The residual polarization of the composite film,when the Ag content exceeds 1 mol%,the residual polarization of the composite film begins to decrease.The piezoelectric output performance test of the PAKP composite flexible piezoelectric energy harvester with different Ag content at P-20% KP and Ag-KNN content of 20% shows that the addition of Ag can significantly improve the piezoelectricity of the flexible energy harvester Output performance,and the PAKP(P-1% AK-P)composite flexible piezoelectric energy harvester has the largest output when the Ag content in Ag-KNN is 1 mol %,where the voltage output is 6.39 V and the current output is 48.93 n A,And the output power reaches a maximum of 150.54 n W when the external load resistance is 80 Ω.When the output voltage signal of the device does not attenuate during the 3000-cycle test,it proves that the device has good stability.The P-1% AK-P composite flexible piezoelectric energy collector is used to collect the piezoelectric signals generated by the vibration of the device when the bicycle is in motion.The results show that the P-1% AK-P composite flexible piezoelectric energy harvester can charge the voltage of the 220 n F ceramic capacitor to 1.2 V in 200 seconds when the bicycle is moving slowly.In addition,the P-1% AK-P composite flexible piezoelectric energy collector is used as a sensor to measure the driving distance of the bicycle in a certain period of uniform motion,which proves that the device has a strong application prospect in measuring the driving distance of the bicycle.