Polyimide-Based Composite Films with Largely Enhanced Energy Storage Performances toward High-Temperature Electrostatic Capacitor Applications

Abstract

The next generation of high-energy-density electrostatic capacitors operable under elevated temperatures is urgently demanded to cope with the development of advanced high-power electronic systems. However, the inherent characteristics of the existing polymer dielectrics, such as poor heat dissipation, narrow band gaps, and high conduction loss, limit their energy density at high temperatures and result in a major hindrance to their applications under harsh conditions. Herein, a class of sandwich-structured dielectric polymer nanocomposites based on high-permittivity barium titanate nanoparticles (BT NPs) and heat-resistant hexagonal boron nitride nanosheets (BNNSs) are reported. In contrast to the traditional single-layer designs, the sandwich-structured configuration could elegantly combine the complementary functionalities of multicomponents in a synergistic fashion. Accordingly, functionalized with BT NPs in the outer layers offering superior permittivity and BNNSs in the central layer impeding the charge injection from electrodes, the properly designed sandwichstructured polymer composite films achieve a superior discharge energy density (U d ) of 11.5 J cm −3 accompanied by an efficiency (η) of 86.2% at room temperature, which is a 570% enhancement of neat polyimide (PI ∼2.00 J cm −3 ) and 960% over biaxially oriented polypropylene (∼1.2 J cm −3 ). Particularly, the composite films exhibit high-temperature performances with U d ∼ 4.072 J cm −3 and η ∼ 83.3% at 150 °C. The remarkable U d and η obtained in this work proved the feasibility of the layered polymer nanocomposite film in high-temperature electrostatic capacitors.

Enhanced High-Temperature Capacitive Performance of a Bilayer-Structured Composite Film Employing a Charge Blocking Layer

“…Figure a illustrates the comparison of U e and η of PI/BNNS film with reported PI dielectric materials, including intrinsic PI, , PI nanocomposites, − all-organic PI composites, ,, multilayer-structured PI composites, , and PI composites containing inorganic layer. ,,− The blue, gray, yellow, purple, and green boxes are used to classify the above materials on the right of Figure a. It is found that the PI/BNNS film achieves the maximum U e when η is greater than 90%, which is far superior to the reported PI-based dielectric materials at different temperatures.…”

“…The area of the PI/BNNS-2 film decreases slightly with the increase in temperature, revealing high temperature stability of capacitive performance. Figure 6a illustrates the comparison of U e and η of PI/ BNNS film with reported PI dielectric materials, including intrinsic PI, 14,39 PI nanocomposites, 40−44 all-organic PI composites, 15,45,46 multilayer-structured PI composites, 47,48 and PI composites containing inorganic layer. 28,29,49−52 The blue, gray, yellow, purple, and green boxes are used to classify the above materials on the right of Figure 6a.…”

Thermally activated dynamic bonding network for enhancing high-temperature energy storage performance of PEI-based dielectrics

“…22 Among them, PEI has been widely acknowledged to be the appropriate linear dielectric for preparing the high-temperature dielectric capacitors owing to its excellent thermal stability and high glass transition temperature. 5,13,23 However, according to the Schottky injection formula, the injections and movements of charge carriers become active with increased temperature, which inevitably intensify material deformation. 17 Meanwhile, the conjugated segments in PEI endow the carriers with high conduction at high electric field, resulting in drastically increased conduction loss with the coupling effect of high-temperature.…”

Polyimide Nanocomposites Filled with SiO2 Nanoparticles of Different Sizes for High-Temperature Energy Storage

“…Broadband nanofillers such as SiO 2 , Al 2 O 3 , TiO 2 , BNNs, CaF 2 , and MgO have been shown to enhance the electrical properties of polymers at high temperatures when compounded with polymers. − Wang et al investigated the electrical properties of MgO/PI nanocomposites with different morphologies and demonstrated that the high specific surface area of MgO nanosheets could enhance the electrical properties of the composites to a greater extent. The two-dimensional morphology better impedes carrier migration at high temperatures and significantly reduces the composite leakage current, resulting in superior electrical performance and energy storage density .…”