In response to the demand for miniaturization and lightweighting in the electronics industry, achieving enhanced energy density of dielectrics is crucial. Constructing nanocomposites consist of ceramic fillers and polymer matrix is an effective strategy in this regard. To address the adverse coupling between polarization and breakdown strength of the nanocomposites, a series of BaTiO3@SiO2 nanofillers with customizable SiO2 shell coverage degrees (90 degrees, 180 degrees, and 360 degrees) is designed and synthesized by surface-confined winding assembly of SiO2 on the surface of BaTiO3. When a half area of BaTiO3 core is coated by SiO2 layer, it is defined as 180 degrees. A larger coverage degree implies better reduction of leakage current injection, and more effective suppression of local electric field concentration. However, it also leads to a more pronounced reduction in the polarization. 180 degrees BaTiO3@SiO2 demonstrates the most effective mitigation of the adverse coupling between polarization and breakdown strength in nanocomposites. The 180 degrees BaTiO3@SiO2/Poly(vinylidene fluoride) (PVDF) nanocomposite achieves high breakdown strength while maintaining relatively higher polarization intensity, for example, the energy density reaches 20.64 J cm(-3) at 650 MV m(-1), which is 2.62 times of pure PVDF. This work reveals the growth mechanism of customizable SiO2 shell coverage degrees on BaTiO3 surfaces, providing an effective strategy for high-performance dielectrics

High-energy density dielectrics for electrostatic capacitors are in urgent demand for advanced electronics and electrical power systems. Poly(vinylidene fluoride) (PVDF) based nanocomposites have attracted remarkable attention by intrinsic high polarization, flexibility, low density, and outstanding processability. However, it is still challenging to achieve significant improvement in energy density due to the common contradictions between electric polarization and breakdown strength. Here, we proposed a novel facile strategy that simultaneously achieves the construction of in-plane oriented BaTiO3 nanowires and crystallization modulation of PVDF matrix via an in-situ uniaxial stretch process. The polar phase transition and enhanced Young’s modulus facilitate the synergetic improvement of electric polarization and voltage endurance capability for PVDF matrix. Additionally, the aligned distribution of nanowires could reduce the contact probability of nanowire tips, thus alleviating electric field concentration and hindering the conductive path. Finally, a record high energy density of 38.3 J/cm3 and 40.9 J/cm3 are achieved for single layer and optimized sandwich-structured nanocomposite, respectively. This work provides a unique structural design and universal method for dielectric nanocomposites with ultrahigh energy density, which presents a promising prospect of practical application for modern energy storage systems.

The development of dielectric capacitors with high energy density and energy efficiency is of great significance in the modern electronic components market. To reduce the high energy loss of Bi0.5Na0.5TiO3, 0.55Bi0.5Na0.5TiO3 -0.45(Sr0.7Bi0.2)TiO3 (BNT-BST) nanofibers with a high aspect ratio are synthesized via electrospinning. To achieve a high energy density, the design of a symmetric trilayer nanocomposite consisting of a BNT-BST/polyvinylidene difluoride (PVDF) layer with a high dielectric constant sandwiched between two layers of pure PVDF is herein described. The trilayer structure can effectively alleviate the electric field concentration effect, resulting in a considerably enhanced breakdown strength and improved discharge energy density. The maximum discharge energy density of 17.37 J/cm3 at 580 kV/mm could be achieved in the symmetric trilayer nanocomposite with a BNT-BST/PVDF middle layer, which is 90.5% greater than that achieved using pure PVDF (9.21 J/cm3 at 450 kV/mm). This study presents a new case for developing dielectric capacitors with high energy density.

Polymer dielectrics are crucial for use in electrostatic capacitors, owing to their high voltage resistance, high energy storage density, and ultrahigh reliability. Furthermore, high-temperature-resistant polymer dielectrics are applied in various emerging fields. Herein, poly(ether imide) (PEI)-based polymer dielectrics prepared by adding a low loading of dimethylimidazolium cobalt (ZIF-67) with a narrow bandgaps are investigated. The results show that the composites exhibit considerably increased Young's modulus, suppressed conductivity loss, and improved breakdown strength compared with pure PEI. Consequently, a stable energy storage performance is realized for ZIF-67/PEI composites. Particularly, at 150 °C, 1 wt % ZIF-67/PEI composite affords an excellent energy storage density of 4.59 J/cm3 with a discharge energy efficiency of 80.6%, exhibiting a considerable increase compared with the values obtained for PEI (2.58 J/cm3 with a discharge energy efficiency of 68.8%). The results of this study reveal a feasible pathway to design polymer dielectrics with the potential for use in capacitive applications in harsh environments.

Thelow discharge energy density and operation temperature of dielectricslimit the integration application of capacitors under extreme environmentconditions. In order to reduce the dielectric loss of Bi0.5Na0.5TiO3, 0.55Bi(0.5)Na(0.5)TiO(3)-0.45(Bi0.2Sr0.7)TiO3 (BNT-BST) nanofibers with optimized diameter were synthesized andutilized to improve the high-temperature capacitive energy storageof polyetherimide (PEI) nanocomposites. Benefiting from the introductionof nanofibers, the leakage current is significantly reduced and chargemigration is limited, contributing to the enhancement of the energystorage properties. For example, the leakage current density of the3 wt % BNT-BST/PEI nanocomposite is suppressed from 0.136 & mu;A/cm(2) of PEI to 0.056 & mu;A/cm(2) at 250 kV/mm. Thenanocomposite with 3 wt % BNT-BST achieves an excellent dischargeenergy density of 10.37 J/cm(3) at 560 kV/mm, which is 65.4%higher than that of PEI. When the environment temperature is up to100 & DEG;C, the discharge energy density of the nanocomposite maintainsa high level of 4.76 J/cm(3). Furthermore, the nanocompositedisplays outstanding cycling stability and fast charge-dischargeperformance. For instance, after 10(6) charge-dischargecycles at 150 kV/mm, the discharge energy density and efficiency remainat 99 and 95% of the initial values, respectively. This work providesa feasible idea for achieving high-energy density nanocomposites underhigh environment temperature.

The scheme of the CQD structure and its interaction with the polymer matrix; the comparison between the 0.1 wt% CQD nanocomposite and pristine polymer.

In the past decade, poly(vinylidenefluoride) (PVDF)-based polymers have attracted increasing attention in energy storage applications due to the advantages of high breakdown strength, flexibility, processability, and low cost. Compared with the PVDF homopolymer and binary copolymer, terpolymer poly(vinylidenefluoride-trifluoroethylene-chlorotritivity due to a strong polar group and its relaxor characteristic. However, its breakdown strength is limited due to the premature saturated polarization and low Young's modulus. In this work, a facile drawing strategy has been employed to overcome this problem. With the increase in the stretching ratio from 0 to 10, the crystalline grain size is declined from 8.9 to 6.7 nm with the increase in crystallinity, all of which are favorable to improving the breakdown strength and energy storage density, and alpha/gamma-phase tends to transform to beta-phase as well. It turns out that the optimal property could be obtained with the stretching ratio of 6, where the breakdown strength could reach 620 kV/mm and a discharge energy density could reach up to 18.3 J/cm3. The optimized performance is significantly larger than that of the original terpolymer P(VDF-TrFE-CTFE) with breakdown strength and energy density of 280 kV/mm and 6.9 J/cm3, respectively. This work demonstrates that the uniaxial drawing is an effective strategy to improve the performance of P(VDF-TrFE-CTFE).