Significantly Enhanced Breakdown Strength and Energy Density in Nanocomposites by Synergic Modulation of Structural Design and Low-Loading Nanofibers

Abstract

Polymer-based dielectric nanocomposites have attracted great attention due to the advantages of high-power density and stability. However, due to the limited breakdown strength (E b) of the dielectrics, the unsatisfactory energy density becomes the bottleneck that restricts their applications. Here, newly designed sandwich-structured nanocomposites are proposed, which includes the introduction of low-loading 0.4BiFeO3–0.6SrTiO3 (BFSTO) nanofibers into the poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix as the polarization layer (B-layer) to offer high permittivity and the selection of poly(methylmethacrylate) (PMMA)/P(VDF-HFP) all-organic blend film as the insulation layer (P-layer) to improve E b of the nanocomposites. The optimized sandwich-structured PBP nanocomposite exhibits significant enhancement in E b (668.6 MV/m), generating a discharged energy density of 17.2 J/cm3. The dielectric and Kelvin probe force microscope results corroborate that the outer P-layer has a low surface charge density, which can markedly impede the charge injection from the electrode/dielectric interface and thereby suppress the leakage current inside the nanocomposite. Furthermore, both the finite element simulations and capacitive series models demonstrate that the homogenized distribution of electric field in the PBP sandwich-structured nanocomposite favors the improvement of energy storage performance. This work not only provides insightful guidance into the in-depth understanding of the dielectric breakdown mechanism in sandwich-structured nanocomposites but also offers a novel paradigm for the development of polymer-based nanocomposites with high E b and discharged energy density.

Improved high‐temperature energy storage density at low‐electric field in BOPP/PVDF multilayer films

“…According to the voltage‐sharing model, PVDF layer with larger dielectric constant shares a lower electric field, conversely, a higher electric field locates in BOPP layer. Besides, BOPP layer as outer can reduce charge injection especially at high temperatures due to its excellent insulation compared to PVDF 25,33 . Although combining BOPP and PVDF can alter the electrical properties efficiently, the inverse relationship between dielectric constant and breakdown strength is still unsolved, as given in Figure 2c.…”

“…Since electric field redistribution happens in BOPP and PVDF layers which may suppress the early‐excited conduction in PVDF layer 32,34–36 . Additionally, due to the BOPP layer as outer layer can inhibit electrode charge injection and the interface between BOPP and PVDF layers can block charge migration, resulting in a decreased leakage current 33,37 …”

“…Besides, BOPP layer as outer can reduce charge injection especially at high temperatures due to its excellent insulation compared to PVDF. 25,33 Although combining BOPP and PVDF can alter the electrical properties efficiently, the inverse relationship between dielectric constant and breakdown strength is still unsolved, as given in Figure 2c. In addition, the leakage current density of the BPB sandwich films is provided in Figures 2d and S3c.…”

Single‐Crystalline BaZr0.2Ti0.8O3 Membranes Enabled High Energy Density in PEI‐Based Composites for High‐Temperature Electrostatic Capacitors

“…[8,27,28] Remarkably high dielectric constant of 46 was obtained in PI-based composites added with 50 vol% PbTiO 3 nanofibers, which was improved nearly an order of magnitude. [29] In general, good energy storage performances can be achieved by adding fillers with optimal concentration, [30,31] large-aspect-ratio microstructural morphology, and homogeneous dispersion. But the improvement of U e is still restricted for the relatively low E b of added high-dielectric fillers as well as the higher local electric field and conductive paths generated around the fillers.…”

Enhanced High-Temperature Capacitive Energy Storage by 0.55Bi0.5Na0.5TiO3-0.45(Bi0.2Sr0.7)TiO3 Nanofibers in Polyetherimide Nanocomposites

“…Nanofibers with a high aspect ratio can not only improve the mechanical strength of nanocomposites but also further enhance the energy storage properties of the polymer. − Electrospinning is an efficient way to prepare nanofibers. , For example, Hu et al. employed electrospun BaTiO 3 nanofibers to effectively reduce the leakage current and improve the thermal conductivity of BaTiO 3 /PI nanocomposites.…”