The Structure Design And Preparation Of Dielectric Composites With High Energy Density

Human society is becoming more and more dependent on electricity.As one of the indispensable components of energy application system,capacitors are of great importance.Dielectric is the most important part for capacitors,for its properties decide the performances of capacitors.However,due to low permittivity of polymers,the energy density of the film capacitor is difficult to get further promotion.So in this project,we discussed the polymer-based dielectric composites with high energy density,the progresses are as follows:1.A classical system of high permittivity composite:BT/PVDF was applied to discuss the effect of thermal treatment on the performance of this system,and found a significant improvement of dielectric properties as well as the voltage resistance,which led to enhanced energy storage characteristics.The highest energy density of thermal treated composite film at a low electric field(50 MV/m)was 0.69 J/cm3,which was 4.93 times higher than that of PVDF.While the charge-discharge efficiency raised from 6.36%of untreated film to 56.89%.2.The introduction of ionic liquid(IL)into polymer matrices not only remained the excellent ductility of material but also greatly improved the dielectric properties.The permittivity of 50 BP/PVDF reached 3.3 × 104,while the dielectric loss was as low as 0.65.The study showed that the improvement of dielectric properties was attributed to the "ion hopping",which improved the electrical polarization of the system.3.The incorporation of MBS into PVDF exhibited a uniform dispersion state and excellent compatibility between them,and fabricated ductile composite films successfully with high breakdown strength(535 MV/m),which resulted in a maximum energy density of 9.85 J/cm3,while the charge-discharge efficiency was as high as 62.4%.4.The addition of polyurethane(TPU)rubber with different hardness into PVDF was applied to discuss the influence of the softness of rubber on material properties.It was discovered that the smaller hardness(softer)of TPU exhited higher improvement of voltage resistance for the composite membrane.Thus,the highest breakdown strength was up to 538 MV/m,which led to a maximum energy density of 10.4 J/cm3.