Linear‐Nonlinear‐Linear Sandwich‐Structured Polymer Composites With Metal‐Organic Framework (MOF) ‐Enhanced Insulating Layers and Horizontally Oriented Nanotube‐Filled Polarization Layer for High Energy Storage Performance

The design of a linear‐nonlinear‐linear (LNL) sandwich architecture is proposed for high‐performance dielectric films under extreme conditions. The architecture consists of metal‐organic framework (MOF)‐enhanced PEI insulating layers (EZ) as outer layers and P(VDF‐HFP)/TNTs composite films (PT) as the middle polarization layer. The EZ layer is constructed through the activation of Zn ²⁺ sites on ZIF‐8, coordinating with the PEI monomer (ODA) to form a multi‐site bonding network that significantly enhances breakdown strength (up to 664.50 kV mm ⁻¹ for the EZ1 composite film) and suppresses leakage current. The horizontal alignment of TNTs in the PT layer, achieved via electrospinning and hot‐pressing, improves polarization performance while maintaining high breakdown strength. The resulting ~20 μm EZ‐PT‐EZ LNL film achieves a high energy density of 13.68 J cm ⁻³ ( η = 85.5%) at 620 kV mm ⁻¹ and 25 °C, and retains a density of 8.51 J cm ⁻³ under harsh conditions (120 °C and 520 kV mm ⁻¹ ). This performance arises from the synergistic effects of the widened bandgap in the EZ layer, the reverse built‐in electric field at the L/N interface, and the hindrance of breakdown path propagation by the interlayer interface and aligned TNT fillers. This work offers a strategy for designing high‐performance polymer dielectrics.