Dielectric Properties And Energy Storage Characteristics Of KNN-ST/PVDF Composite Films

With the development of electronic industry,traditional single-phase materials can not meet the needs of people.Hence,ceramic/polymer matrix composites emerge at the right moment,combining the advantages of the ceramics and polymers,the energy storage performance has been significantly improved.However,a series of challenges have arisen accordingly.High remanent polarization polarization,large energy loss and lower breakdown strength are still residual in ceramic/polymer matrix composites,these problems seriously affect the practical application of ceramic/polymer matrix composites.This paper designed and prepared potassium sodium niobate-strontium titanate ceramic materials??1-x?KNN-xST?.With the introduction of SrTiO₃,the dielectric properties and energy storage performance of KNN ceramics were greatly improved.The results show that the remanent polarization of KNN-ST ceramics decreased significantly upon doping SrTiO₃.when x=0.15,the remanent polarization of0.85KNN-0.15ST ceramics is only about 1/3 of that of pure KNN ceramics,and the maximum discharge energy storage density is 0.081 J/cm³.On this basis,this paper prepared 0.85KNN-0.15ST/PVDF composite films with different volume fractions of fillers by sol-gel method,and the influence of0.85KNN-0.15ST fillers on the microstructure,dielectric properties and energy storage characteristics of PVDF polymer matrix has been systematically studied.At100 Hz,the maximum dielectric constant of 0.85KNN-0.15ST/PVDF composite films reached 38.3,which is 2.3 times lager than that of KNN/PVDF composite film.And the remanent polarization of KNN/PVDF composite films decreased significantly,which was only 1/3 of that of KNN/PVDF composite films.This makes the energy storage performance of 0.85KNN-0.15ST/PVDF composite films significantly improved,the maximum energy storage density of 1.34 J/cm³ was obtain in 0.85KNN-0.15ST/PVDF composite films with a 12vol%loading of fillers.Finally,in order to improve the recoverable energy storage density of0.85KNN-0.15ST/PVDF composite films.0.85KNN-0.15ST ceramics were surface modified by dopamine,and DA@0.85KNN-0.15ST/PVDF composite films were prepared by sol-gel method.The modification of dopamine can effectively reduce the number of defects in polymer composites,decrease the influence of interfacial polarization on the dielectric properties of composites.Therefore,the dielectric loss of DA@0.85KNN-0.15ST/PVDF composite films is significantly reduced,and the dielectric constant of DA@0.85KNN-0.15ST/PVDF composite films is also decreased to varying degrees.The maximum energy storage density and energy storage efficiency are obtained in DA@0.85KNN-0.15ST/PVDF composite films with a 9 vol%loading of fillers simultaneously,which is 1.14 J/cm³ and 76.85%,respectively.