Study On Energy Storage Performance Of P(VDF-TrFE-CFE)-based Composite Dielectric

The development of high-performance electronic devices in the direction of integration puts forward higher requirements for the energy storage performance of dielectric capacitors.As one of the most common dielectric capacitor,polymer capacitor has the characteristics of high power density,low cost and easy processing,but its small dielectric constant may lead to low energy storage density,which greatly limits the polymer capacitors to be applied much more widely,so how to improve the energy storage density of polymers has become a research hotspot.In this paper,poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene)(PVTC)ferroelectric polymer is selected as the research object,it has nonlinear polarization properties.Although PVTC exhibits a higher polarity at low electric fields,the hysteresis effect will induce a large residual polarization and energy loss,so it is difficult to obtain high energy storage density and charge/discharge efficiency.In order to solve the problems of low energy storage density and improve the energy storage performance of PVTC,this paper proposes to regulate the structure of inorganic filler and to design the multi-layer interfaces.The main research content is given as follows:In the aspect of the structure regulation for the inorganic filler,we focus on the problem of weak interfacial compatibility between the inorganic filler and the organic polymer matrix,the solution method is used to blend the zirconium(Zr-O)solution with the polymer PVTC,and the organic/inorganic hybrids are obtained.The influence of zirconium content on the electrical properties of hybrid films is investigated and analyzed systematically.When the zirconium content is 10 wt.%,the energy storage density of 9.9 J/cm~3and charge/discharge efficiency of 53%are obtained in 10%Zr-O/PVTC hybrid films under an electric field of 400 k V/mm.The study shows that the introduction of the Zr-O inorganic filler by solution blending can ensure its uniform dispersion in the polymer matrix,and the composites can also obtain a synergistic increase in polarization strength and breakdown strength.In the aspect of the interfacial structure design,we focus on the problem of large residual polarization of the PVTC itself,the polyimide(PI)film with linear polarization acts as insulation layer,which combines with the PVTC ferroelectric layer to construct heterogeneous-structured PI/PVTC bilayer films.The influence of PI volume fraction on the polarization characteristics of the bilayer films is investigated and analyzed systematically.When the volume fraction of PI is 50 vol%,the energy storage density of 9.6 J/cm~3and charge/discharge efficiency of 58%are obtained in 50%PI/PVTC bilayer films under the electric field of 400 k V/mm.The study found that the dielectric difference between the PI film layer and the PVTC film layer is used to control the electric field distribution of the bilayer films,thereby improving the polarization behavior and breakdown characteristics of the bilayer films,and ultimately increasing the energy storage density and charge/discharge efficiency of the bilayer films.Both the methods of inorganic doping and multi-layer structure design can improve the energy storage performance of polymer composites.However,the electric charge injection at the electrode/dielectric interface would increase the conduction loss and reduce the energy loss under high electric field strength.Therefore,an inorganic oxides insulation layer(INL)was grown on the surface of polymer films by using the magnetron sputtering technology,such as SiO₂with excellent insulation and Ba Zr_0.2Ti_0.8O₃(BZT)with high dielectric constant.The influence law and mechanism of deposition time of INL on the breakdown strenght and energy storage performance of multi-layer composites are systematically investigated and analyzed.The results show that when the multi-layer films are composed of 2h SiO₂INL as surfacial layer and 1h BZT INL as intermediate layer,the SiO₂-2h/PVTC/BZT-1h/PVTC/SiO₂-2h multi-layer films are obtained.The energy storage density of 11.8 J/cm~3and charge/discharge efficiency of 59%are achieved under an electric field of 390 k V/mm.The study found that SiO₂INL grown on the surface of the polymer film act as an interfacial barrier layer between the electrode and the composites,restricting the electric charge injection and reducing the conduction loss under high electric field.At the same time,the BZT INL with high dielectric constant acts as an interlayer and improves the polarization strength of composites.The results demonstrate that INL with an appropriate thickness can effectively increase the energy storage density and charge/discharge efficiency of the multi-layer films.The influence law of different structural design and regulation method on the polarization strength and breakdown characteristics of ferroelectric polymer composite are studied,the mechanism to improve the macroscopic energy storage performance of the composite dielectrics is clarified.This study lays the research foundation for promoting the application of ferroelectric plymer-based composites in the field of dielectric energy storage.