Energy storage density of BSCZT/PVDF composites based on egg-like ceramic filler driving PVDF phase transformation

Flexible dielectrics play a crucial role in the advancement of capacitors. However, their limited energy storage density is an obstacle to both their application scope and miniaturization efforts. Inspired by an “egg effect”, this study introduces an innovative egg-like ceramic filler, namely Ba 0.34 Sr 0.51 Ca 0.15 Zr 0.1 Ti 0.9 O 3 -Y@Ba 0.34 Sr 0.51 Ca 0.15 Zr 0.1 Ti 0.9 O 3 -Mn@ZrO 2 (BSCZT-Y@BSCZT-Mn@ZrO 2 ), which is developed via a core–shell doping process. The separation of electrons and holes in the “egg yolk” (donor-rich core) and “egg white” (acceptor-rich shell) coupled with the current-limiting “eggshell” (wide bandgap oxide) in the ceramic fillers, resulting in a large effective polarization Δ P , a higher dielectric permittivity ε r , a lower tan δ , and a significant increase in the discharged energy storage density W rec of the composites. Together with the phase transition from α-PVDF to β-PVDF caused by the electrostatic interaction between fillers and PVDF, an ultra-high W rec of 33.2 J/cm 3 is achieved in the BSCZT-Y@BSCZT-Mn3@ZrO 2 /PVDF, which has the Δ P of 28.5 μC/cm 2 at 296.7 MV/m, along with ε r of 21.7 and tan δ of 0.018 at 1 kHz. Significantly, the composite film exhibits outstanding bending endurance. Even after 600 full bends, over 92 % of the capacitance retention rate can be retained. This research highlights the potential of ceramic filler structural design for flexible capacitors in low-power flexible electronics.