Lamination Design Of PC/P(VDF-HFP) Dielectric Polymers And High-temperature Energy Storage Applications

High-temperature polymer-based dielectric film capacitors have very broad application prospects,which are widely used in military pulse equipment,electric vehicles,clean energy power generation and aerospace industries.At present,the dual-oriented polypropylene BOPP,which is currently commercialized,cannot meet the application requirements of high energy storage and high efficiency at high temperatures due to its low dielectric constant and poor heat resistance.Ferroelectric polymers such as PVDF and its copolymer P（VDF-HFP）have been extensively studied because of their high dielectric constant,but their energy loss increases sharply at high temperatures,the breakdown strength rapidly decreases with increasing temperature,and the charge-discharge efficiency is less than 40%at 80℃.In the field of high-temperature energy storage of polymer-based dielectric films nowadays,how to prepare polymer films with high energy storage density and high charge-discharge efficiency at high temperatures and high fields is still the focus and difficulty of current research.Therefore,through the three-layer structure design,the composite film is prepared by casting process,and the performance advantages of each component polymer are fully utilized by combining the energy storage characteristics of the insulation layer and the polarized layer,so as to obtain the electric field distribution and interface shielding effect that adjust with temperature changes,and obtain excellent energy storage density and charge-discharge efficiency by reasonably optimizing the maximum polarization value D_maxand the residual polarization value D_rem,and have good thermal stability in high temperature environment..The main content is as follows:1.Select high dielectric constant P（VDF-HFP）as the polarized phase.High glass transition temperature（about 195°C）PC has high insulation and high breakdown strength,and still maintains more than 85%charge-discharge efficiency in high temperature environment,so PC is used as high insulation layer and temperature resistant phase,and then PC/P（VDF-HFP）composite film is prepared by casting method.The energy storage performance of the intermediate layer P（VDF-HFP）with different volume fractions and the positive and reverse trilayer structures were compared to derive the optimal volume fraction and structure design.The temperature resistance of P（VDF-HFP）was significantly improved by using the composite PC with positive lamination structure.The composite film can withstand 120℃and obtain good energy storage performance.According to the difference of the dielectric constant of the inner and outer layers,the characteristics of the composite film continuously adjusting the electric field distribution with the change of temperature were obtained.2.Linear polymer PMMA still has a charge-discharge efficiency higher than 90%at room temperature and has good chemical compatibility with P（VDF-HFP）,so linear PMMA is used as the filling phase,and then PC/P（VDF-HFP）+PMMA composite film is prepared by casting method.To prepare PC/P（VDF-HFP）+PMMA composite films,use the best volume fraction and structure design in the previous chapter,take PC as the outer layer,add PMMA with different content fractions in the middle layer P（VDF-HFP）to analyze its energy storage performance,and obtain the best content ratio.By adding PMMA,the energy storage density and charge-discharge efficiency of the composite film were further improved,and the test temperature could reach 140℃.From room temperature to 120℃,the composite film shows excellent thermal stability,and the fluctuation range is only 10%.3.The PC/PMMA composite films was prepared,with PC as the outer layer,and compared with single-layer pure PC and PMMA films,double-layer structure PC/PMMA films and three-layer structure PC/PMMA/PC films at room temperature and high temperature energy storage performance.Three-layer structure is more significant for the optimization of high temperature energy storage.PMMA with poor thermal stability is applied to the high temperature field,and a high charge-discharge efficiency of 85.6%is obtained at 80℃.