The strategy improves breakdown strength and polarization in dielectric nanocomposites

Electrostatic capacitors are an important component in high-power pulsed equipment, power transmission and transformation engineering, new energy vehicles, and 5G communications. Their ability for ultrafast charging-discharging and ultrahigh power density is critical to their performance.

Nevertheless, their relatively low capacitance and power density limit their rapid development towards the lightweight, flexible, integrated trend in electrical and electronic devices. Overcoming energy density perturbations for dielectrics has become a research focus that urgently needs attention.

Dielectric strength and permittivity, or polarization, are two important parameters for high energy density in dielectrics. One of the most common strategies is the incorporation of various ceramic nanoparticles such as BaTiO.₃SrTiO₃, among others, in a high-insulation polymer matrix to exploit their respective advantages. However, achieving a significant increase in permittivity requires a higher loading of nanoparticles, which increases electrical conductivity and thus compromises fracture toughness.

In one study Published In the magazine Advanced powder productsA team of researchers from Central South University in Changsha, China proposed a new facile strategy to realize the joint enhancement of breakdown strength and electric polarization for dielectrics.

„Our strategy allows us to achieve simultaneous on-board construction of BaTiO.₃ Crystallization modulation of nanowire fillers and polyvinylidene fluoride (PVDF) matrix in an in-situ uniaxial stretching process,” explains Du Zhang, senior and corresponding author of the study.

Compared to zero-dimensional nanoparticles, one-dimensional nanowires with high aspect ratios have high polarizability and a large dipole moment in the longitudinal direction, making them more effective in improving the permittivity of the composite at low loading conditions while maintaining electric field tolerance.

The research demonstrated that high-strain stress induced an ultrahigh polar β phase and enhanced Young’s modulus, which contributed to a simultaneous increase in both the electrical displacement and fracture strength of the polymer matrix. Notably, the finite element simulation results revealed an oriented distribution of nanowires, reducing the contact probability of nanowire tips, thus mitigating the electric field concentration and preventing the breakdown path.

“The newly designed stretched PVDF-based nanocomposite is capable of operating with a high voltage withstand capacity of 843.0 kV/mm and simultaneously provides an energy density of 40.9 J/cm.³. „This is the best capacitive performance ever achieved in polymer dielectrics,” says Zhang.