2–2 Type PVDF-Based Composites Interlayered by Epitaxial (111)-Oriented BTO Films for High Energy Storage Density

Quick charge/discharge polymer-based composites filled with inorganic nanosheets have attracted extensive attention and provided a more efficient way to achieve high energy storage density (U) because of the alleviated agglomeration of fillers and the formation of conduction barriers. However, conductive paths have a chance to extend along out-of-plane directions by circumventing the micrometer-sized nanosheets. Here, large-sized (111)-oriented BaTiO₃ (BTO) films with outstanding epitaxiality and ferroelectricity are embedded in poly(vinylidene fluoride) (PVDF) using optimal transfer and hot-pressing processes. The 2D–2D (2–2) type BTO/PVDF composites interlayered by 2-layer BTO (about 0.2 µm thick of each layer) exhibit the highest U of 20.7 J cm^-3 at 690 MV m^-1, which is 222.6% that of pure PVDF. Phase-field simulations reveal that high-resistance PVDF films as outer layers can prevent the charges injection from electrodes and high-dielectric BTO films as inner layers can effectively suppress the mobile charges across interfaces between layers, leading to a remarkable improvement of breakdown strength. This work puts forward a scalable approach to enhance the U of inorganic/organic composites for advanced energy storage materials and applications.