Improved energy storage density and breakdown strength of “3 + 2” layered flexible composite with charged interlayer double hydroxide nanosheets

Abstract Polymer dielectric capacitors have emerged as attractive energy storage solutions for pulsed power applications, attributed to their exceptional breakdown strength and superior processability. Nevertheless, the energy storage performance of polymers is limited by low polarization, making it crucial to develop rational strategies to enhance their energy storage density (U_e). In this article, Mg‐Al layered double hydroxide nanosheets (MALNS) were in‐plane oriented within a polyvinylidene fluoride (PVDF) matrix through spray‐coating, double‐folding, and hot‐pressing methods, forming the typical “3 + 2” layered composite, consisting of two oriented MALNS layers sandwiched between three PVDF matrix layers. Orientation regulation of positively charged MALNS can enhance their effective area of capturing free charges, which restrains the formation of breakdown paths. Furthermore, two polymethylmethacrylate (PMMA) ultrathin layers were coated onto the surfaces of the layered composites to reduce the defects at the dielectric‐electrode interface. Consequently, the PMMA‐covered layered composite filled with 1 mg oriented MALNS in PVDF achieves a high U_e of up to 11.9 J/cm³ under an electric field of 443.2 MV/m, which is 264% and 133% higher than that of pure PVDF (4.5 J/cm³ and 333.5 MV/m). This research presents a robust and effective strategy for the design and fabrication of high U_e energy storage devices. Highlights The in‐plane orientation of MALNS is achieved via the spray‐coating process. The overall polarization and E_b of the V_x composites have been enhanced. The M₅₀₀₀V₁M₅₀₀₀ composite exhibits a high U_e of 11.9 J/cm³ and a η of 59.9%. The “3 + 2” orientation structure enhances the capture area for free charges. The multi‐layer structure interface suppresses the migration of space charges.