Layer‐Controlled Perovskite 2D Nanosheet Interlayer for the Energy Storage Performance of Nanocomposites

Polymer‐based nanocomposites are desirable materials for next‐generation dielectric capacitors. 2D dielectric nanosheets have received significant attention as a filler. However, randomly spreading the 2D filler causes residual stresses and agglomerated defect sites in the polymer matrix, which leads to the growth of an electric tree, resulting in a more premature breakdown than expected. Therefore, realizing a well‐aligned 2D nanosheet layer with a small amount is a key challenge; it can inhibit the growth of conduction paths without degrading the performance of the material. Here, an ultrathin Sr1.8Bi0.2Nb3O10 (SBNO) nanosheet filler is added as a layer into poly(vinylidene fluoride) (PVDF) films via the Langmuir–Blodgett method. The structural properties, breakdown strength, and energy storage capacity of a PVDF and multilayer PVDF/SBNO/PVDF composites as a function of the thickness‐controlled SBNO layer are examined. The seven‐layered (only 14 nm) SBNO nanosheets thin film can sufficiently prevent the electrical path in the PVDF/SBNO/PVDF composite and shows a high energy density of 12.8 J cm−3 at 508 MV m−1, which is significantly higher than that of the bare PVDF film (9.2 J cm−3 at 439 MV m−1). At present, this composite has the highest energy density among the polymer‐based nanocomposites under the filler of thin thickness. Energy storage performance of nanocomposites is improved through the use of parallel 2D nanosheets fabricated via Langmuir–Blodgett deposition. Specially, the introduction of seven‐layered Sr1.8Bi0.2Nb3O10 nanosheets with ultrathin thickness (14 nm) effectively inhibits electrical treeing and improves energy storage performance.