Effect of BaTiO₃ nanowire distribution on the dielectric and energy storage performance of double-layer PVDF-based composites

A series of novel double-layer PVDF-based composites filled with different concentration of BaTiO₃ nanowire were fabricated employing hot-pressing process. The effects of various BT-NWs concentrations in isolated layers on the dielectric properties, energy storage density of the composites were investigated. The experimental dielectric constants of double-layer composites are lower than expected. The breakdown strength (E_b) of double-layer composites was obtained in the experiment, and predicted via capacitance series formula (CSF) and finite element analysis (FEA). Results show that the data predicted by FEA are closer to the experimental values. Compared with dielectric constant, the enhancement of E_b induced by double-layer structure is more significant for the energy storage performance of composites. A design route including E_b measurement of single-layer composites, E_b prediction of double-layer composites via FEA, selection of single-layer material and composites fabrication is proposed to prepare the multi-layer composites with excellent dielectric properties and energy storage.