Improved breakdown strength and energy storage performances of PEI-based nanocomposite with core-shell structured PI@BaTiO3 nanofillers

High dielectric constant ( ε r ) inorganic nanoparticles reinforced dielectric polymer nanocomposites have been intensively investigated for energy storage applications in current electrical and electronic systems. Although the incorporation of high- ε r inorganic nanoparticles can improve the ε r of the composites to a certain extent, it will also greatly reduce the overall breakdown strength ( E b ) of the materials, which ultimately hinders the effective improvement of the energy storage density of the composites. In this paper, an approach is developed to modify high- ε r BaTiO 3 (BTO) nanoparticles with polyimide (PI) polymer shells (PI@BTO) through an in-situ polymerization process in the polyetherimide (PEI)-based nanocomposites. The constructed PI shell improves the compatibility of the inorganic/organic interface, resulting in a uniform dispersion of nanoparticles in the PEI matrix. In particular, the spontaneous electrostatic interaction between polymer chains in the PI shell and PEI matrix enables an increased E b of the PEI/PI@BTO nanocomposite over the pure PEI, which leads to a high energy storage density ( U e ) of 6.2 J/cm 3 and a high charge-discharge efficiency (η) above 80% in the PEI nanocomposites, with an enhancement of 150% over pure PEI. In this paper, a convenient and efficient interfacial modification technique is provided for the development of flexible high energy storage density polymer/inorganic nanoparticle composites for dielectric and energy storage applications.