Enhanced dielectric constant and energy density in a BaTiO3/polymer-matrix composite sponge

Polymer-matrix dielectric composites are promising for use in electrostatic energy storage devices due to the ultra-fast charge–discharge speed and the long service life. Here we report a strategy for designing BaTiO3 sponge polymer composites for energy storage. BaTiO3 sponges with tunable porosities are prepared from polymethyl methacrylate micro-sphere arrays. Liquid epoxy completely fills the pores in a BaTiO3 sponge during vacuum de-foaming, forming a solid composite. The resulting composites possess a maximum dielectric constant of er~332 and er/em~85, compared to er~38 in a sample filled with BaTiO3 NPs, at 1 kHz. The composites also possess, at 100 kV cm−1, a high discharge energy density of Ud~105 × 10−3 J cm−3 and Ud/Um~51, and electric displacement of 3.2 μC cm−2, compared with those utilizing traditional strategies at low electric fields. Finite element simulation reveals the enhanced energy density is due to a high local electric displacement in composites. Polymer-matrix composites have a number of attractive properties for use as dielectrics in electrostatic energy storage devices. Here, a BaTiO3 sponge filled with epoxy achieves a high dielectric constant and energy density, attributed to large local electrical displacements.