Hybrid\nCore–Shell TiCN@SiO<sub>2</sub> Nanoparticles\nin Percolation-Based Polyvinylidene Fluoride Dielectrics for Improved\nHigh-Voltage Capacitive Energy Storage

Solid-state\npolymer dielectrics offer an exceptional dielectric\nbreakdown, but require an enhanced energy density to be competitive\nwith alternative electrolyte-based energy storage technologies. Therefore,\nthis research introduces conductive titanium carbonitride (TiCN) nanoparticles\nin a polyvinylidene fluoride (PVDF) matrix to obtain flexible percolation-based\nnanodielectrics by ultrasonication-based suspension processing and\nhot pressing. Well-dispersed TiCN nanoparticles in PVDF were obtained\nfor a wide range of filler volume fractions, and an exceptional peak\nin the dielectric constant equal to 1130 (0.1 Hz) and 29 (10 kHz)\nwas observed near the percolation threshold (9.2 vol %). The enhanced\ndielectric constant was ascribed to massive interfacial polarization\noccurring, resulting from Maxwell–Wagner–Sillars (MWS)\npolarization and a nanocapacitor mechanism that are dominant at low\nand high frequencies, respectively. An improvement by 30% in the energy\ndensity (0.042 Wh kg<sup>–1</sup>) compared with the neat PVDF\nmatrix was achieved for the PVDF/TiCN nanodielectrics. The first successful\nuniform deposition of a nanometer-thin (3 nm) silica (SiO<sub>2</sub>) shell via the Stöber process on TiCN nanoparticles significantly\nsuppressed the dielectric losses near percolation for the PVDF/TiCN@SiO<sub>2</sub> nanodielectrics by more than 1 order of magnitude while offering\ndielectric constants of 34 (0.1 Hz) and 10 (10 kHz). This study demonstrates\nthe potential of hybrid (core–shell) percolation-based dielectrics\nfor an improved capacitive dielectric performance by an integrated\ndielectric characterization approach that simultaneously optimizes\nthe dielectric constant, loss tangent, breakdown strength, and energy\ndensity.