High-energy-density ferroelectric polymer nanocomposites utilizing the Coulomb-blockade effect

Ferroelectric polymers have been regarded as promising dielectric materials for high volumetric energy density dielectric capacitors due to their high dielectric constant and facile processability. However, ferroelectric dielectric polymers suffer from high intrinsic loss, resulting in low charge-discharge efficiency and insufficient breakdown strength. Here, a sandwich-structured ferroelectric polymer nanocomposite with high energy density is fabricated by sandwiching an array of ultra-small metal particles grown in-situ between two layers of ferroelectric polymers. Due to the unique Coulomb-blockade effect of the ultra-small metal particles, the nanocomposites with suitable distribution density of metal particles exhibit significantly suppressed leakage current density and superior breakdown strength. Compared with Au and Ag, the Pt particle with the highest work function is more effective in improving the capacitive performance of the polymer. In addition, it is revealed that within the theoretical particle size range where the Coulomb-blockade takes effect, the nanocomposite with larger metal particles exhibits better capacitive performance. The optimal composition with an extremely low fraction (0.07 vol%) of 10-nm-size Pt nanoparticles shows a remarkable discharge energy density of 28.6 J/cm3 and a charge-discharge efficiency of 76%. This method effectively suppresses the energy loss of ferroelectric polymers, and bypasses the dispersion issues in the traditional polymer nanocomposites, providing a new paradigm for fabricating high-energy-density and high-efficiency polymer dielectrics.