328 / 2018-10-03 12:35:34

Advances in Energy Storage Dielectric Polymer Composites

dielectric,polymer,energy storage,composite

It has been for several decades that the biaxially oriented polypropylene (BOPP) is used as dielectric layer in the film capacitors due to an extremely high breakdown strength of BOPP. However, the low dielectric permittivity of BOPP makes it a very low energy storage density, which results in a large volume and weight of the film capacitors in order to meet the engineering application. Very recently, many works are devoted to develop the advanced dielectric polymer materials with high energy storage density by preparing new polymers or fabricating the polymer composites. In this work, we will introduce some key progress to study on dielectric polymer composites with high energy storage density. In order to arrive the high energy storage density, the dielectric films with both high dielectric permittivity and high breakdown strength should be realized by employing new material design idea. In common, the improvement of dielectric permittivity can be realized easily in the polymer nanocomposites when the inorganic nanoparticles with high dielectric permittivity or high electric conductivity are dispersed into the polymer matrix. Comparison to pure polymer matrix, in this case, the breakdown strength of polymer nanocomposites decreases remarkably.
In this presentation, we propose to disperse a flexible rubber phase into thermoplastic polymer matrix to improve the breakdown strength of the composites by restraining and repairing the defects in the amorphous region of the thermoplastic polymer through the rubber phase segment. Although the dielectric constant of the composites is slightly decreased, the energy storage density of the composites is obtained effectively. In order to keep the dielectric constant of the composites unchanged or slightly improved, a small amount of high dielectric BaTiO3 nanoparticles were coated with rubber, and the coated functional nanoparticles were compounded with the polymer matrix. In this case, the dielectric constant and electrical strength of the composites were improved at the same time. Finally, the energy storage density of the three-phase composites was obtained. Figure 1 shows the basis idea in this work.