Polarization characteristics of the high-dielectric interface in MgO/PP nanocomposite dielectrics

Power capacitor is one of the key equipment for integrating renewable energies. Using polymer nanocomposite dielectrics that inherit the excellent dielectric properties of inorganic filler and high breakdown field strength and machinability of the polymer matrix can effectively improve the energy storage performance of power capacitors. However, owing to the large difference in dielectric properties of the nanofiller and polymer matrix, the dielectric constant of nanocomposite dielectrics at high doping concentration increases at the expense of the breakdown strength, limiting the improvement of the energy storage performance. Using polypropylene (PP) as the matrix, MgO/PP nanocomposite dielectrics with different doping concentrations are prepared through the melt blending method. The experimental results show that doping with low-concentration nanofillers can improve the thermal and dielectric properties of nanocomposite dielectrics. With an increase in the doping concentration, the relative permittivity of the MgO/ PP nanocomposite dielectrics first increases and then decreases. Consequently, a two-dimensional nanocomposite dielectric structure model containing MgO nanofillers is established. Then, the distribution of electric field and electrostatic energy in the nanocomposite dielectrics and the effective relative permittivity are calculated using the multigrid finite volume iteration method. At the same time, the mechanism of nanodoping regarding the effective permittivity of the composite dielectrics is revealed. It is found that nanofillers with low doping concentration will introduce independent interface regions into the matrix, effectively facilitating the rotation of dipoles under external voltage, thereby affecting the dielectric properties of the nanocomposites. © 2023 Chinese Academy of Sciences. All rights reserved.