Polyvinylidene fluoride/barium titanate composites with separation structure for improved energy storage density at a low field strength

Abstract

Polymer-based dielectric composites exhibit substantial potential for utilization in electrostatic energy storage. Through structural design, controlling the spatial distribution of functional fillers within a polymer matrix can effectively enhance the dielectric constant (ε′) and polarization of composites. In this study, the innovative application of a 3D separation structure, prepared through water vapor induced phase separation combined with hot-pressing technique, achieves a significant enhancement of polarization performance at relatively low electric fields in polyvinylidene fluoride/barium titanate (PVDF/BT) dielectric composites. The continuous distribution of BT in PVDF matrix effectively enhances the local electric field and helps to achieve consistent polarization direction and remarkable dipole moment enhancement. Consequently, the ε′, maximum electrical displacement (D_max), and discharge energy density (U_d) of PVDF/BT are effectively enhanced. The addition of 10 vol% BT results in PVDF/BT composites exhibiting a ε′ exceeding 20 (10³ Hz) and a D_max of 9 μC/cm² (180 MV/m). The U_d of PVDF/BT with 10 vol% BT added is 5.08 J/cm³ (at 180 MV/m), representing a 52.1 % growth in comparison to pure PVDF (3.34 J/cm³, 180 MV/m), and exceeding 2.5 times that of biaxially oriented polypropylene (2 J/cm³, >600 MV/m).