Significantly enhancing the low-field energy storage performance of poly(vinylidene fluoride) nanocomposites by modulating multi-interface trap energy levels

Sandwich structure and encapsulation techniques are highly effective methods for reducing leakage current density ( J ) in polymer nanocomposites. However, most studies focus on electric field homogenization, and the low-field discharge energy density ( U dis ) of current polymer nanocomposites is still limited to 5 J/cm 3 at operating conditions of 200–300 kV/mm for film capacitors in electric vehicles. To address these issues based on the multi-interface trap energy levels, we hereby design a poly(vinylidene fluoride) (PVDF) composite filled with core-shell nanoparticles of BaTiO 3 @polydopamine (BT@PDA) and sandwiched by poly(methyl methacrylate) (PMMA) layers for high low-field U dis . The coordination of deep electron traps at the PMMA/PVDF interlayer interface along with deep hole and electron traps at the PVDF/PDA interfaces can trap charges and hinder charge transport. This effectively suppresses J and significantly increases the low-field U dis , as demonstrated by interfacial energy band analysis and phase field simulations. Consequently, a high low-field U dis of 6.65 J/cm 3 at 310 kV/mm was achieved on this PMMA-BDP-PMMA nanocomposite, along with a low dielectric loss of 0.037 and a low J of 3.88 × 10 −7 A/cm 2 at 25 kV/mm and a high energy efficiency of 66 %. It represents an effective approach to improving the energy storage performance of polymer dielectrics at low fields.