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Not AvailableThe demand for energy storage devices with high energy density, power density, and higher efficiencies has motivated researchers to explore novel materials and designs beyond current limitations. Polymer-based dielectric capacitors are flexible, lightweight, self-healable, and compatible with a variety of nanofillers. Despite a plethora of studies on polymer nanocomposites with 2D nanofillers, the role of multilayered 2D nanofillers in polymer nanocomposites in the context of energy storage properties has yet to be determined. In this work, mechanically exfoliated 2D mica nanofillers were incorporated with poly(vinylidene fluoride) (PVDF) polymer to fabricate PVDF-mica-PVDF (PMP) multilayered heterostructure capacitors. A single exfoliated layer of mica with an average thickness of the flakes of 20 nm interfaced within layers of PVDF to form PMP and using two layers of mica to form PVDF/mica/PVDF/mica/PVDF (PMPMP) heterostructure capacitors. Average enhancements of 100% and 170% were measured for the dielectric constants of PMP (εav ∼ 22.9) and PMPMP (εav ∼ 30.8), respectively compared to that of the pristine PVDF (εav ∼ 11.4) films measured using the same setup. The highest discharged energy density of PMP and PMPMP nanocomposite films reached 27.5 J/cm3 (E = 670 MV/m) and 44 J/cm3 (E = 570 MV/m), compared to 11.2 J/cm3 (E = 396 MV/m) for the pristine PVDF capacitor. This work develops a detailed understanding of the use of multilayered 2D nanofillers to develop high-capacitance and high energy density polymeric dielectric capacitors and opens avenues for developing orientation-controlled 2D nanofiller-based capacitors for use in industrial applications. 

High‐energy‐density storage devices play a major role in modern electronics from traditional lithium‐ion batteries to supercapacitors for a variety of applications from rechargeable devices to advanced military equipment. Despite the mass adoption of polymer capacitors, their application is limited by their low energy densities and low‐temperature tolerance. Polymer nanocomposites based on 2D nanomaterials have superior capacitive energy densities, higher thermal stabilities, and higher mechanical strength as compared to the pristine polymers and nanocomposites based on 0D or 1D nanomaterials, thus making them ideal for high‐energy‐density dielectric energy storage applications. Here, the recent advances in 2D‐nanomaterial‐based nanocomposites and their implications for energy storage applications are reviewed. Nanocomposites based on conducting 2D nanofillers such as graphene, reduced graphene oxide, MXenes, semiconducting 2D nanofillers including transition metal dichalcogenides such as MoS₂, dielectric 2D nanofillers including hBN, Mica, Al₂O₃, TiO₂, Ca₂Nb₃O₁₀and MMT, and their effects on permittivity, dielectric strength, capacitive energy density, efficiency, thermal stability, and the mechanical strength, are discussed. Also, the theory and machine‐learning‐guided design of polymer 2D nanomaterial composites is learnt and the challenges and opportunities for developing ultrahigh‐capacitive‐energy‐density devices based on these nanofiller polymer composites are presented.