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 epsilon(r)similar to 332 and epsilon(r)/epsilon(m)similar to 85, compared to epsilon(r)similar to 38 in a sample filled with BaTiO3 NPs, at 1kHz. The composites also possess, at 100kVcm(-1), a high discharge energy density of U-d similar to 105 x 10(-3)Jcm(-3) and U-d/U-m similar to 51, and electric displacement of 3.2 mu C 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.