Improving dielectric properties and capacitive performance of P(VDF-HFP)-based dielectrics by incorporation of core-shell structured BaTiO₃@polymethacrylates

To meet the growing requirement for highly integrated electronic systems, nanocomposites comprised high dielectric constant (ε) ceramic nanofillers and large dielectric breakdown strength (E_b) polymer has been widely investigated for high energy density capacitor. However, the poor interfacial compatibility arising from the great difference of surface energies and ε values usually resulted to the sacrifice of the dielectric properties and thus the capacitive performance. In this work, a series of core-shell structured barium titanate (BaTiO₃) nanofillers were designed and prepared to address this challenge via surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate (MMA), ethyl methacrylate (EMA) and glycidyl methacrylate (GMA). BaTiO₃@PMMA (BT@M), BaTiO₃@PEMA (BT@E), BaTiO₃@PGMA (BT@G) were fabricated and incorporated into poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP), PVH), respectively. Enhanced dielectric properties, E_b, and energy storage density were observed in these nanocomposites comparing with nanocomposites of BT/PVH. It should be ascribed to the polymer shell layer alleviated the great surface energy and ε value disparity between BT filler and PVH matrix, which was responsible for the enhancement of the interfacial compatibility and homogenous distribution of electric fields. Among these three types of nanocomposites, PVH/BT@G exhibited superior dielectric properties and capacitive performance. Extraordinary advances in charge carrier suppression at elevating temperature and electric field were also witnessed in PVH/BT@G. It should be attributed to the polar PGMA layer served as the deep traps, which block the charge motion in the filler-matrix interfaces. At optimal conditions, energy density of 10.61 J cm⁻³ and efficiency of 65.7 % at 360 MV m⁻¹ was achieved. This work may provide insight into the rational design of the shell layer of the fillers for polymer nanocomposites dielectrics.