Design Of Microstructure And Study Of Energy Storage Properties Of PMMA/P(VDF-TrFE-CFE) Based Composite Dielectric

With the rapid development of the global economy and technology,the demand for advanced energy storage technologies and equipment is also growing rapidly.Compared with batteries,supercapacitors,etc.,polymer-based dielectric capacitors have the advantages of fast charge and discharge speed,light weight,good expandability,high cycle number,etc.,and play an important and unique role in modern electronic power systems.Increasing the energy storage characteristics of polymer-based dielectrics is of great significance for the development of aerospace,military and other industries.Among them,the polarization behavior of the polymer and the breakdown electric field are the key factors determining its energy storage performance.It is an important means to optimize the energy storage performance of the dielectric by designing the microstructure of the dielectric to regulate the polarization and breakdown characteristics of the dielectric.Relevant researches have important research significance.Aiming at the problem that the traditional single polymer-based dielectric can not balance the dielectric and breakdown properties,this paper proposes to combine the polymer with high insulation properties and dielectric properties to prepare a composite dielectric with heterostructure and microscopic combination.The interface structure design comprehensively controls the polarization behavior and breakdown characteristics of the dielectric to improve the energy storage characteristics of the dielectric.In this paper,two polymers（polymethyl methacrylate（PMMA）and ternary ferroelectric polymer（P（VDF-TrFE-CFE）））with good compatibility and different dielectric and breakdown properties were selected as storage units.The basic unit can be prepared,and the composite dielectric is prepared and its basic electrical properties are studied.The results of single-layer dielectrics show that PMMA has good insulating properties.However,the dielectric constant of P（VDF-TrFE-CFE）is2.4 times that of PMMA.Next,it is proposed to further improve the polarization characteristics of the P（VDF-TrFE-CFE）layer by doping high dielectric inorganic barium titanate nanofibers（SrTiO₃ NFs）.Studies have shown that the doping of SrTiO₃ nanofibers increases the dielectric constant of SrTiO₃ NFs/P（VDF-TrFE-CFE）composite dielectric by 10%,and the storage density is 8 J/cm³,which is as twice as the density of the original P（VDF-TrFE-CFE）.In order to improve the energy storage performance of composite dielectric,based on the systematic analysis of the polarization behavior and energy storage performance of the above two polymers,the electrical characteristics of PMMA and P（VDF-TrFE-CFE）dielectric are fully utilized.The macrostructure and inorganic phase content of the multilayer composite dielectric are controlled to optimize the microscopic interface state and polarization characteristics of the dielectric,and improve the energy storage performance of the composite dielectric.The results show that the relative dielectric constantε_r of PMMA-SrTiO₃ NFs/P（VDF-TrFE-CFE）composite dielectric is based on the dielectric PMMA（ε_r=4.7,10 Hz）and 3vol%SrTiO₃ NFs/P（VDF-TrFE-CFE）based on the capacitor series model.Composite dielectric（ε_r=12.34,10 Hz）,and increases first and then decreases as the number of laminated interfaces increases.The research proves that the storage density and energy storage efficiency of PMMA-SrTiO₃ NFs/P（VDF-TrFE-CFE）composite dielectric are improved compared with energy storage units.In order to reduce the influence of the breakdown performance caused by the inorganic filling phase and further improve the energy storage performance of the composite dielectric,a full organic composite dielectric with different layers is constructed.It is found that for all-organic composite dielectric,the dielectric constant of PMMA/P（VDF-TrFE-CFE）composite dielectric increases first and then decreases with the increase of the number of laminated interfaces.The electrical constant reaches a maximum of 8.3,which is 1.3 times that of the three-layer composite dielectric;the breakdown field strength also increases first and then decreases.When the number of layers is 9,the breakdown field strength is about 390kV/mm,the storage density is 16 J/cm³.The above studies demonstrate the role of interface design in optimizing the polarization behavior and breakdown characteristics of composite dielectric.