| In order to meet the increasing demand of new energy storage devices in modern electronic and power systems,it is urgent to develop advanced energy storage materials.Among many dielectric materials,polymer based dielectric materials have the advantages of low dielectric loss,high breakdown strength,light weight and high power density.Its excellent insulation and mechanical properties are one of the most promising energy materials in military and civil fields.However,the energy storage density of polymer based dielectrics is restricted by the low dielectric constant,which seriously limits the wide application of capacitor devices made of polymer based dielectrics in the field of energy storage.In recent years,researchers have made remarkable efforts to improve the energy density of polymers.Studies have shown that the introduction of high-potassium inorganic nano fillers into the polymer matrix to form polymer nanocomposites can effectively enhance the material's mesopoint response.However,increasing the dielectric constant is usually at the cost of greatly reducing the breakdown strength,which is not ideal for improving the energy density.In recent years,dielectric films with optimized polymer-based layered structures are considered to be an emerging method to solve the existing contradiction between high dielectric constant and high breakdown strength in single-layer dielectric films.According to research reports,through systematically By adjusting the interlayer interface,composite ratio and chemical structure,the dielectric loss,electric field distribution,breakdown strength,and capacitive energy storage of polymer films have been significantly improved and improved.Therefore,this paper takes low-loss and high-dielectric materials as the main research object,and focuses on the interlayer structure of polymer films,and the following research work is carried out:(1)In order to obtain an ideal energy storage material and solve the contradiction between loss and dielectric,this paper selects high-dielectric and low-loss materials to composite,and combines the advantages of both to prepare energy storage thin film materials.Starting from bulk composite and multi-layer composite(also called inter-layer composite),select high-dielectric PVDF,low-loss PMMA and PEI as the research materials,and adopt bulk composite and interlayer composite methods respectively.Produce composite materials with different volume fractions.The study found that PMMA and PVDF can be mixed in a high proportion due to the similar structure.The phase separation of PMMA/PVDF composite is not obvious.Only in the high electric field and high frequency environment,the phase separation will limit the energy storage performance of the film to a certain extent.The interlayer recombination still shows excellent performance under high electric field and high frequency.Due to the large difference in structure of the PEI/PVDF combination,the bulk composite system exhibits serious phase separation,and the film is broken down in a low electric field environment and cannot be used in the field of energy storage.However,a dielectric film prepared by a multi-layer composite method Shows excellent energy storage performance.Through the comparison of the two composite methods of the three materials,it is found that the multilayer composite has obvious advantages in energy storage.(2)PP is an excellent non-polar low-loss dielectric material.It is very suitable as a low-loss substrate to prepare multilayer composite dielectric films.However,due to its special structure,it is incompatible with most organic solvents and is difficult to pass through casting Method to prepare polymer films.However,PP can be prepared by melt extrusion and biaxial stretching to obtain BOPP(hereinafter referred to as PP)film,and the prepared film has excellent energy storage properties.Melt-extruded film is difficult and unsuitable for miscibility with other polymer materials in solution,so PP can be used as a carrier tape,and a high-dielectric material can be directly cast on its surface to prepare a multilayer dielectric film.The surface energy of PP film is low,and it cannot fit perfectly with most high-dielectric materials.In response to this situation,we adopt chemical and plasma methods to modify the surface of PP to improve its surface energy.The study found that the electrical properties of the treated PP film have been improved,reducing the probability of local discharge polarization,increasing the intrinsic breakdown field strength,and at the same time,its surface energy is greatly improved,and the bonding performance with high-dielectric materials It has also been significantly improved,which broadens the thinking and space for the selection of dielectric materials.(3)In this paper,the low-loss and high-breakdown material PP is selected as the base film,and the high-dielectric material P(VDF-TrFE-CFE)is used as the composite layer film,and a variety of P(VDF-TrFE-CFE)/PP composite media with different thickness ratios are prepared.membrane.Through the collocation between the two materials,the interlayer composite dielectric film combines the high dielectric properties of P(VDFTrFE-CFE)and the low loss of PP,with high charge and discharge efficiency,low dielectric loss,Higher relative permittivity and higher insulation resistivity.The study found that with the increase in the volume composite ratio of the P(VDF-TrFE-CFE)composite layer,the performance of the dielectric film has undergone significant changes.The obvious performance is the relative dielectric constant and maximum polarization of the double-layer composite dielectric film.The strength has been improved,but the dielectric loss and leakage current of the composite film have also increased,but it can be controlled at a lower level.At the same time,the loss is controlled within 1.4%,which improves energy storage compared with PP.By 156%,the energy storage density of the dielectric is effectively increased,and the charge and discharge efficiency is still controlled at a relatively high level. |
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