12. Polymer Nanocomposites Dielectrics for Energy Applications

Dielectric capacitors have been the major enabler for many applications in advanced electronic and electrical power systems due to their capability of ultrafast charging–discharging and ultrahigh power density. The low energy density of polymer dielectrics used in these capacitors could not meet the ever increasing demands for compact, reliable, and efficient electrical power systems. Polymer nanocomposites, in which high dielectric constant (k) nanofillers are incorporated in polymer matrix, have been actively pursued. In this chapter, we begin with two theoretical considerations for concomitantly increasing the dielectric permittivity and breakdown strength of nanocomposites, i.e., the critical interfacial polarization and distribution of local electric field. In the framework of these considerations, recent progresses based on two approaches, e.g., core–shell structured polymer nanocomposites and dielectric anisotropy, toward polymer nanocomposites of high energy density are reviewed. Novel composite design paradigm, such as nanocomposites with hierarchical interfaces and topological-structure modulated nanocomposites, for concomitant enhancement of dielectric permittivity and breakdown strength is also reviewed. In addition to energy density, thermal stability of nanocomposites is another critical parameter that dominates the reliability of nanocomposites at high temperatures. The advantages and promises of nanocomposite approach in raising the energy storage performance at temperatures are also considered.