High‐Temperature High‐Energy‐Density Dielectric Polymer Nanocomposites Utilizing Inorganic Core–Shell Nanostructured Nanofillers

Abstract

Compared to electrochemical energy devices such as batteries and supercapacitors, dielectric film capacitors have greater power densities and faster charging and discharging rates and are the essential components in power electronics. [4][5][6] Dielectric polymers possess unique features in comparison to their ceramic counterparts, including high breakdown strength, low dielectric loss, facile preparation, and graceful failure mechanism, which make them the materials of choice for scalable high-energy-density capacitors. [7][8][9][10][11] More recently, there is an urgent demand for dielectric materials capable of operating efficiently at elevated temperatures, e.g., 150 °C, in advanced electronics, electrified vehicles, and aerospace power systems. However, dielectric polymers are limited to relatively low working temperatures. [11][12][13][14][15] For example, the operation temperature of biaxially oriented polypropylene (BOPP), the industrial benchmark dielectric polymer, is well below 105 °C under the applied electric fields. [15] A variety of innovative approaches, including the incorporation of wide bandgap inorganic fillers, [16][17][18] deposition of ceramic coatings onto polymer films, [19][20][21] addition of high-electronaffinity molecular semiconductors, [22] and utilization of multilayer-structured films, [23][24][25] have been developed to improve the high-temperature capacitive performance of dielectric polymers. While these approaches are effective in hindering electrical conduction and reducing energy loss at high fields and elevated temperatures, the energy densities of the current high-temperature dielectric composites are limited (below 4 J cm −3 in most cases) owing to relatively low dielectric constant (K) values of the fillers, such as ≈3.5-4 of SiO 2 and boron nitride nanosheets (BNNSs) [16,26] and ≈7.9-10 of Al 2 O 3 . [26] On the other hand, the direct introduction of high-K inorganic fillers, such as TiO 2 with a K of 110 (ref. [27]) and BaTiO 3 with a K of ≈3000 (ref. [28]), into dielectric polymers with the goal of increasing the energy density has yielded very high energy loss and largely reduced chargedischarge efficiency (η) with increasing applied field and temperature. [29,30] For instance, at an applied field of 400 MV m −1 , the η of the polyimide composites with 1 vol% BaTiO 3 nanofibers is only 55% at 150 °C versus 92% at 25 °C. [30] Herein, we present High-energy-density polymer dielectrics capable of high temperature operation are highly demanded in advanced electronics and power systems. Here, the polyetherimide (PEI) composites filled with the core-shell structured nanoparticles composed of ZrO 2 core and Al 2 O 3 shell are described. The establishment of a gradient of the dielectric constants from ZrO 2 core and Al 2 O 3 shell to PEI matrix gives rise to much less distortion of the electric field around the nanoparticles, and consequently, high breakdown strength at varied temperatures. The wide bandgap Al 2 O 3 shell creates deep traps in the composites and thus yields ...

Microscopic Pyrolytic and Electric Decomposition Mechanism of Insulating Polyimide/Boron Nitride Nanosheet Composites based on ReaxFF

“…As a new type of polymer insulation material, polyimide (PI) has excellent characteristics, such as its high insulation strength, low dielectric constant, corrosion resistance, and low thermal expansion [ 1 , 2 ]. Therefore, PI is widely used in high-voltage electrical equipment (e.g., high-frequency transformers, variable-frequency traction motors, and solid-state transformers), the aerospace industry (e.g., fairings, missile shells, and space vehicles), microelectronics fields (e.g., substrates and packages for electronic devices), and other high-tech fields [ 3 , 4 , 5 , 6 ]. In actual operation, PI materials face ultrahigh temperatures and the accumulation of immense heat due to various factors, including the large current in high-voltage equipment and the fast and dense circuit structure in microelectronic devices.…”

High Energy Storage Density of Sandwich-Structured Na0.5Bi0.5TiO3/PVDF Nanocomposites Enhanced by Optimizing the Dimensions of Fillers

“…The challenge facing the current dielectric capacitors is their low energy storage density, especially the discharging energy density. Therefore, it is of interest to develop new dielectrics that exhibit a high discharging energy density . The energy storage density ( U ) of a dielectric is determined by the electric field ( E ) applied on the dielectric and the material’s response–electric displacement ( D ) as U = ∫ 0 D E d D .…”

“…Therefore, it is of interest to develop new dielectrics that exhibit a high discharging energy density. 3 The energy storage density (U) of a dielectric is determined by the electric field (E) applied on the dielectric and the material's response−electric displacement (D) as U = ∫ 0 D E dD. 4 For the purpose of obtaining greater U, the breakdown field strength (E b ) that the dielectric of the composite material can withstand needs to be continuously increased.…”

“…Preparation of Composite Films. 1-D NBT nanofibers (NBT-NFs, ρ = 5.7675 g/cm 3 ) and pure PVDF powders (ρ = 1.74 g/ cm 3 ) were mixed in DMF with the targeted volume ratio. The mixture was ultrasonically treated for 2 h at room temperature followed by a stirring process of 12 h at room temperature.…”

Symmetric Trilayer Dielectric Composites with High Energy Density Using a Low Loading of KNbO3 Nanosheets

“…With the rapid consumption of traditional fossil fuels, renewable energy resources have received more and more attention to de-escalate the global energy crisis. Reliable and efficient energy storage technologies become a key point of renewable sources. − Compared with electrochemical energy storage devices, dielectric capacitors are especially more suitable for application in pulsed power equipment, hybrid electric vehicle inverters, and electric weapons due to their high power density, long service life, and fast discharged speeds. − However, relatively low energy storage density of the dielectric capacitors greatly limit their wide application in the above-mentioned fields since they need high capacitance in low volume. − The value of discharge energy storage density is related to the electric displacement–electric field loop according to formula U dis = ∫ E d D , where E and D are the electric breakdown strength and electric displacement, respectively. For linear dielectrics, D = ε 0 ε r E , where ε 0 and ε r are the vacuum permittivity (=8.85 × 10 –12 F m –1 ) and relative permittivity of the dielectrics, respectively.…”