Polymer-ceramic nanocomposites for high energy density applications

Next-generation capacitive energy storage requires novel materials with engineered nano-architectures to compete with conventional methods for energy storage. While current materials and processing strategies produce capacitors with enhanced dielectric permittivity, their breakdown strengths are low. The new fabrication route described in this paper provides flexible, free-standing nanocomposite films with high dielectric permittivity and high breakdown strength. Monodispersed ceramic fillers [BaTiO3, Ba1−xCaxTiO3 (X = 0.3 ± 0.05), and BaZr1−xTixO3 (X = 0.2 ± 0.05)] were synthesized via solvothermal method. Surface-exchanged nanoparticles were combined with polyvinylidene fluoride (PVDF) to fabricate stable polymer-ceramic blends. The PVDF/ceramic nanocomposites resulting from this approach have high dielectric permittivity, low loss tangent, and high electric breakdown strength. The calculated maximum energy densities for the BaTiO3, Ba1–xCaxTiO3 [X = 0.3 ± 0.05], and BaZr1–xTixO3 [X = 0.2 ± 0.05] nanocomposite films are 3.24, 4.72, and 7.74 J cm−3 respectively. This a result of the interplay between the dependencies of permittivity and breakdown strength on volume fraction. It is proposed that the interaction, enhanced by functionalized surface hydroxyl groups, between ceramic and polymer components is the main reason for the improved dielectric properties. This approach is versatile and is readily applicable to other combinations of polymer-ceramics composites so that cooperative properties can be exploited.