Enhanced dielectric energy storage properties in linear/nonlinear composites with hybrid-core satellite C/SiO₂@TiO₂ nanoparticles

Polymer dielectrics for electrostatic capacitors possess well-recognized advantages, including ultrahigh power density, excellent processability, and unique self-healing capability. Nevertheless, the negative coupling relationship between dielectric permittivity and breakdown strength in dielectrics always constrains the enhancement of energy density, which cannot satisfy the ever-increasing requirements for integrated and miniaturized technologies. Here, a kind of C/SiO₂@TiO₂ triphase nanoparticle (CST NP) with a hybrid-core satellite structure is prepared and introduced into nonlinear poly(vinylidene fluoride-co-hexafluoropylene) [P(VDF-HFP)] matrix to improve permittivity and polarization. Benefited from the intensified interfacial polarization induced by CST NPs, a high permittivity of ∼18.8, which is approximately 219% that of pure P(VDF-HFP) (∼8.6), is obtained at 10 kHz. Meanwhile, a linear PEI film with high breakdown strength is stacked with the CST/P(VDF-HFP) composites, forming linear/nonlinear CST/P(VDF-HFP)-PEI bilayer composites. Eventually, a high breakdown strength of ∼503.9 kV/mm, a high energy density of ∼4.26 J/cm³, and a high efficiency of ∼91% are simultaneously achieved in the bilayer composite with merely 0.75 wt. % nanoparticles. The linear/nonlinear bilayer structure incorporated with hybrid-core satellite nanofillers offers an effective strategy to design high-performance dielectric energy storage materials.