Dielectric properties of a linear polymer-matrix composite filled with aligned Ag@BaTiO3 flakes

Composites with linear dielectric properties possess advantages in energy storage fields for the high charge-discharge efficiency with low energy loss. However, energy density of them is limited due to low permittivity. Here, a linear dielectric polydimethylsiloxane (PDMS) composite filled with parallel aligned core-shell Ag@BaTiO3 (BT) 2D flakes is prepared by directional shearing, which possesses high permittivity and excellent energy storage properties. Compared with traditional polymer/core-shell hybrid filler composites, this work presents modified filler composition, different filler dimension and enhanced energy storage performances. Conformably-coated Ag@BT flakes are prepared through simultaneous hydrolysis on polyvinylpyrrolidone-functionalized Ag flakes, forming a smooth ∼100 nm thick coating layer. The aligned PDMS/40 vol% Ag@BT flake composite exhibits a very high permittivity of 347 and a low dielectric loss< 0.03 at 100 Hz from 20 to 150 °C. The comp°site exhibits an enhanced breakdown strength of 26 kV cm−1 owing to BT coverage-shell blocking and parallel filler arrangement, compared with that of percolative composites filled with metal particles without shell-coverage. The composite exhibits linear dielectric characteristics with high discharged energy density of 6.18 × 10−3 J cm−3 and superhigh charge-discharge efficiency> 95% at 20 kV cm−1. This study demonstrates Ag@BT flake based linear-polymer composites for energy related applications.