Search

Abstract: In this study, the excellent energy storage performance is achieved by constructing opposite double‐heterojunction ferroelectricity–insulator–ferroelectricity configuration. The PbZr0.52Ti0.48O3 films and Al2O3 films are chosen as the ferroelectricity and insulator, respectively. The microstructures, polarization behaviors, breakdown strength, leakage current density, and energy storage performance are investigated systematically of the constructed PbZr0.52Ti0.48O3/Al2O3/PbZr0.52Ti0.48O3 opposite double‐heterojunction. The ultrahigh electric field breakdown strength (≈5711 kV cm−1) is obtained, which is beneficial to achieve high energy storage density. Meanwhile, the high linearity of hysteresis loops with low energy dissipation is obtained at a proper annealing temperature, which is induced by partially crystallized and is in favor of achieving high energy storage efficiency η. The PbZr0.52Ti0.48O3/Al2O3/PbZr0.52Ti0.48O3 annealed at 550 °C exhibits excellent energy storage performance with a storage density of 63.7 J cm−3 and efficiency of 81.3%, which is ascribed to the synergetic effect of electric breakdown strength (EBDS = 5711 kV cm−1) and the polarization (Pm–Pr = 23.74 µC cm−2). The proposed method in this study opens a new door to improve the energy storage performance of inorganic ferroelectric capacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy density of 19.3 J cm−3 and efficiency of 61 % are achieved at 549.2 kV mm−1. • Lamellar-structured BiFeO 3 @TiO 2 fillers possess BFO/TO/BFO triple-layered structure. • Breakdown strength is significantly enhanced by BiFeO 3 @TiO 2 fillers. • Opposite double heterojunction electric field forms between BiFeO 3 and TiO 2 layers. • Opposite double heterojunction electric field offsets most applied electric field. Polymer-based dielectric capacitors are well recognized for high energy density and efficiency. However, the energy density is restricted by the deterioration of breakdown strength with excessive addition of inorganic fillers. Herein, an innovative design of the lamellar-structured BiFeO 3 @TiO 2 (BFO@TO) fillers is proposed and a small amount of BFO@TO is added into P(VDF-HFP)/PMMA blended polymer to fabricate BFO@TO-P(VDF-HFP)/PMMA composites, which delivers an outstanding energy density of 19.3 J cm−3 at 549.2 kV mm−1. The filler possesses a BFO/TO/BFO triple-layered structure. Due to the different Fermi level, electrons are injected from TO into BFO to form electron accumulation layer and construct the heterojunction electric fields between TO and BFO layers. Heterojunction electric fields at two interfaces produced by the triple-layered structure are opposite. The opposite double heterojunction can withstand larger external electric field and improve the breakdown strength. Besides, BFO, as a narrow bandgap semiconductor, is easier for electrons and holes to separate, which further widens the width of the built-in electric field and reduces the dielectric breakdown. Electric field distribution simulations intuitively confirm the enhancement of the breakdown strength. The results provide an effective strategy to address the critical issue of improving the breakdown strength for high energy storage capability. [ABSTRACT FROM AUTHOR]

Incorporating inorganic ceramic fillers in organic polymer matrix has been demonstrated as the major and effective strategy for excellent energy storage performance. Nevertheless, the excessive addition leads to the deterioration of breakdown strength and energy density, thus impedes the practical application. Herein, a completely new idea of preparing high-entropy oxide (Eu 0.2 Bi 0·2 Y 0·2 La 0·2 Cr 0.2) 2 O 3 (EBYLCO) nanofiber fillers is proposed and the EBYLCO-P(VDF-HFP)/PMMA nanocomposites are fabricated with an ultralow filling content. The enhanced entropy in the lattices results in the local polymorphic distortion and effectively increases the degree of the structural disorder. The random stress field and random electric field are remarkably enhanced. The pinning effect produced by the local polymorphic distortion restricts the movements of long polymer chains, which builds a stronger cross-linked network structure, reduces the loss under the strong electric field and further promotes the breakdown strength of the nanocomposites. Besides, the charge-shielding layers between polymer and nanofillers block the injection and transmission of space charges, which also contributes to high breakdown strength. Combining the enhanced breakdown strength of 509.4 kV mm−1 with the significantly increased polarization, the nanocomposite releases a maximum energy density of 15.13 J cm−3 and energy efficiency of 71%. This work is expected to provide a novel design paradigm for the nanofillers and further improves the energy storage capability for the dielectric capacitors. [Display omitted] • Energy density of 15.13 J cm−3 and efficiency of 71% are achieved at 509.4 kV mm−1. • A completely new high-entropy oxide nanofiber is synthesized. • Pinning effect restricts the movements of long polymer chains. • Breakdown strength is enhanced due to the pinning effect. • Charge-shielding layer blocks the injection and transmission of space charges. [ABSTRACT FROM AUTHOR]

Polymer-based dielectrics are widely utilized due to the high power density, fast discharging-charging speed and broad operating temperature range. However, suffering from the inherent low energy density, the practical application is restricted. Herein, a novel structure design of lamellar-structured MgO and BiFeO 3 /MgO (BFO/MgO) fillers is proposed and a series of PVDF-based composites are fabricated. The breakdown strength is significantly improved due to the large heterojunction electric field produced by BFO and MgO. Meanwhile, the large polarization contributes to a high energy storage performance. A high energy density of 9.93 J cm−3 at 409.6 kV mm−1 with energy efficiency of 66% is achieved in 0.9 wt% BFO/MgO-PVDF/PMMA composites. Compared with previous literatures, high energy density is obtained in a relatively low electric field in this work at such trace filling content, which is quite suitable for the long-term electric field application. This work establishes a facile and effective approach for developing the flexible dielectric capacitors with high energy storage capability. [Display omitted] • Energy density of 9.93 J cm−3 and efficiency of 66% are achieved at 409.6 kV mm−1. • Lamellar-structured BiFeO 3 @MgO fillers possess BFO/MgO/BFO multilayered structure. • Heterojunction electric field forms between BiFeO 3 and MgO layers. • Heterojunction electric field counterbalances most of the applied electric field. • Breakdown strength is significantly improved by BiFeO 3 @ MgO fillers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy density of 22.7 J cm−3 and efficiency of 72% are obtained at 759 kV mm−1. • Al 2 O 3 @BiFeO 3 nanofillers with different thickness of BiFeO 3 shell are prepared. • Breakdown strength is enhanced by core shell structured Al 2 O 3 @BiFeO 3 nanofillers. • A large heterojunction electric field helps to improve the breakdown strength. • Regulation of electron depletion layer for high breakdown strength. Polymer-based dielectrics trigger great interests in advanced electric systems due to their high breakdown strength and power density. However, a major drawback is that excessive addition of high- ε r ceramic nanofillers may deteriorate their breakdown strength and further reduce energy density. Herein, a general strategy is provided to dramatically enhance the breakdown strength by introducing a small amount of core–shell structured Al 2 O 3 @BiFeO 3 nanofibers into PVDF/PMMA polymer matrix. The thickness of BiFeO 3 shell is regulated by controlling its molar concentration. A significantly enhanced breakdown strength (759 kV mm−1) and an ultrahigh energy density (22.7 J cm−3) with an energy efficiency of 72% are observed. The greatly improved breakdown strength is ascribed to the regulation of electron depletion layer. When the width of heterojunction region gradually approaches to the scale of electron depletion layer, more annihilation of electrons happens and thus contributes to the enhancement of the breakdown strength. The results suggest that our designed structure can help to address the issue of both enhancing the breakdown strength and energy density for diverse nanocomposites over a broad application. [ABSTRACT FROM AUTHOR]