The modification of BT ceramic particles was achieved using hydrogen peroxide and vinyltriethoxysilane, resulting in the production of core–shell-structured nano-materials (VTS@BT). Upon initiation, moderately cross-linked XL-VTS@BT/PVDF composites were prepared by reacting them with modified polyvinylidene fluoride (MDPVDF). As the amount of VTS@BT increased, the dielectric constant of the composite material increased from 7.89 to 19.1, while the dielectric loss increased only slightly from 0.058 to 0.075. Furthermore, as the filling amount of VTS@BT increased, the grain size gradually increased, the nucleation rate decreased, and the addition of crosslinking agents caused a minor transformation of the β-crystalline phase to the α-crystalline phase. The moderate cross-linking improved the breakdown strength and energy storage density of the composite material, with a cross-linked structure composite material at 10wt% addition achieving an energy storage density of 10.36 J/cm3 at an electric field strength of 340MV/m, which was nearly a 57% increase in energy storage density compared to PVDF.