Dielectric capacitors are fundamental energy storage components in electronics and electric power systems due to their unique ultrahigh power density. However, their relatively low energy storage density is a long‐standing challenge which greatly limits their practical application range. Chitosan (CS) and montmorillonite (MMT) are two kinds of materials that exist abundantly on the earth with natural surface charges. The positively charged CS and negatively charged MMT can be self‐assembled into the typical sandwich‐structured CS/MMT/CS 2D structure through an electrostatic attraction. Loading these surface‐charged sandwich‐structured nanosheets into poly(vinylidene fluoride)‐based composite with a weight fraction as tiny as 0.3 wt.%, an ultrahigh energy storage density of 32.5 J cm−3 accompanied with a high efficiency of 64% are concurrently achieved with a very low cost and scalable process. Guided by finite element simulation, it is revealed that a number of electric potential wells that exist in the charged sandwich nanosheets impede the acceleration of internal charges and hinder the growth of electrical trees. The results offer a novel paradigm for exploring ultrahigh energy storage density capacitors in an economical way.

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Dielectric capacitors with an ultrahigh power density have received extensive attention due to their potential applications in advanced electronic devices. However, their inherent low energy density restricts their application for miniaturization and integration of advanced dielectric capacitors. Herein, a novel composite entirely incorporated with two-dimensional (2D) nanosheets with a topological trilayered construction is prepared by a solution casting and hot-pressing method. The 2D boron nitride nanosheets (BNNS) with a wide band gap that are oriented in a poly(vinylidene fluoride) (PVDF) matrix to form the upper and bottom outer layers would efficiently suppress the leakage current in composites, thus significantly improving the overall breakdown strength. Meanwhile, the 2D anatase-type TiO 2 nanosheets (TONS) uniformly distributed in the middle layer can enhance their interfacial compatibility and polarization with the PVDF matrix, leading to a synergistic improvement in both the breakdown strength and dielectric constant of the composite. In particular, a significantly improved dielectric constant of ∼11.42, a reduced dielectric loss of 0.03 at 100 Hz, and a maximum discharge energy density (U dis ) of 10.17 J cm −3 at an electric field of 370.1 MV m −1 can be obtained from the trilayered composite containing 3 wt % 2D TONS in the middle layer and 2 wt % 2D BNNS on the outer layer. The finding of this research offers an effective strategy for the preparation of advanced polymer-based composites with an outstanding discharge energy density performance.

In recent years, high-energy-density polymer-based capacitors have received extensive attention because of their potential applications in advanced power systems and electronic equipment. However, their development is severely hampered by the inherent features of polymers such as low polarization and low charge–discharge efficiency (η). In this study, a new strategy for core–shell Na0.5Bi0.5TiO3(NBT)@TiO2(TO) whiskers combined with sandwich-structured poly­(vinylidene fluoride) (PVDF)-based dielectric composites is proposed, in which the middle layer is the PVDF-based composites filled with different fractions of NBT@TO whiskers and the outer layers are pristine PVDF. The experimental results show that the loading of NBT@TO whiskers can simultaneously optimize electrical displacement and breakdown strength of the sandwich-structured composite due to the additional interfacial polarization and the contribution of the barrier effect between adjacent layers. Thus, a significantly improved electric displacement of ∼13.99 μC cm–2, a maximum discharge energy density (U d) of ∼15.42 J cm–3 at a low electric field of 314 MV m–1, and a high charging–discharging efficiency (η ∼ 66.12%) can be obtained from the composite with the middle layer containing 6 wt % NBT@TO whiskers. This research provides a strategy for the preparation of advanced polymer-based composites with a superior discharge energy density in the future.

Dielectric elastomer (DE) as an important electro-active polymer (EAP), is capable of providing a large elastic deformation under an external electric field. However, the excellent electro-actuated performance is usually obtained under high electric fields, which greatly limits the practical application range of DE, especially in the field of in vivo organisms. Thus, it is essential to make a reasonable structural regulation to achieve an effectively improved electro-actuation of DE materials under low driving electric fields. Herein, a typical BaTiO 3 @TiO 2 entirely-inorganic coreshell construction was prepared through the micro-emulsion method. Meanwhile, a series of polydimethylsiloxane (PDMS)-based DE composites incorporated with different fractions of BaTiO 3 @TiO 2 were synthesized by solution blending and compression molding. The BaTiO 3 @TiO 2 core-shell construction endows DE composites with an enlarged heterogeneous interface and enhanced interfacial polarization synchronously, which is also benefit to maintain the flexibility of DE materials. The buffer effect offered by TiO 2 shell is helpful to alleviate the local

Due to their feature of the conversion from electrical to mechanical energy under an applied electric field, dielectric elastomers (DEs) have been widely adopted in smart devices. However, the significant electro-actuated property of DEs is always obtained under a giant driving electric field, which raises a potential safety hazard and limits their practical application range. Moreover, the traditional strategy of regulating the flexibility of DEs via physical swelling effect would result in an undesired plasticizer leakage and an irreversible reduction in both electromechanical stability and lifetime. Herein, a typical heterogeneous multi-layered polydimethylsiloxane (PDMS)-based DE composite was prepared by solution blending and the layer-by-layer casting method. Through synchronously introducing the high-permittivity BaTiO3 and the plasticizer dimethyl silicone oil in the middle layer, both the dielectric and mechanical property of the composite are effectively regulated. Not only the interlayered mechanical mismatch is eliminated but also the problem of plasticizer leakage is optimized through this reasonable structural design. The maximum electro-actuated strain obtained in the sandwiched DE composite was as large as 24.25% under 60 V/ μm, which is 338.52% higher than that of pristine PDMS. Furthermore, the composite exhibits the largest driving strain (58.31%) near its breakdown electric field of 77.82 V/ μm. Therefore, this study provides a promising route for the preparation of advanced DE composite with an improved low-field electro-actuated property.

With the rapid development of modern electronic and power systems, the low energy storage density is a critical weakness that greatly restricts the functional performance and application range of dielectric capacitors. Generally, the overall dielectric constant and breakdown strength are two key parameters that determine the energy storage density of a dielectric material. However, there is a significant negative coupling effect between these two parameters. Herein, a multilayer-structured composite showing an excellent energy storage performance was designed and fabricated by combining the continuous processes of spraycoating, melt mixing-extruding, in-situ dragging, alignment of oriented fibers, and hot-pressing procedures. This fabrication process has great potential in scaled production in industries. In this multilayered construction, the upper and lower layers are the PVDF thin layer deposited with in-plane oriented BN nanosheets (BNNSs), which provides a high breakdown strength for the composite. The intermediate layer is a PVDF-based composite uniformly dispersed with in-plane oriented TiO 2 nanowires (TONWs), which enhance the interfacial and dipole polarizations in composites. The synergetic contribution of good dispersion and orientation perpendicular to the electric field minimizes the occurrence probability of ohmic contact and tunneling effects between TONWs, which limits the transport of charges in the intermediate polarized layer, increases the dielectric constant, and avoids the premature breakdown of composites. Under the extremely low filler loadings (BNNSs and TONWs are 0.11 and 1 wt % in the outer and middle layers, respectively), both the significantly enhanced excellent discharge energy density of 6.67 J/cm 3 and breakdown strength of 376 MV/m were achieved from the BNNS/TONW/PVDF sandwich composite, which were 340 and 156% greater than those of the pure PVDF matrix (1.96 J/cm 3 and 240 MV/m) respectively. This work provides an effective and feasible strategy for the enhancement of both energy storage density and scaled-production potential of polymer-based composite dielectrics.

In order to meet the ever‐increasing demands of complex engineering applications, it is necessary to design the polymer‐based composites with the synergistic improvements in strength and toughness. Herein, the novel carbon nanotubes (CNT)‐bismaleimide (BMI) hybrid construction (CBH) was prepared through mechanical blending and pulverizing. The as‐prepared CBH with a stable structure and well‐regulated morphological construction was employed as a special functional filler to endow the epoxy‐based composites with a significantly enhanced overall mechanical property. Due to CBH can provide a multiscaled interfacial interaction with matrix, the composite loaded with 1 wt% CBH exhibited the synchronously improved both tensile modulus (1.31 GPa) and toughness (1.89 MJ m−3), which are 27.18% and 209.83% higher than those of pure epoxy, respectively. Moreover, good interfacial compatibility between CBH and matrix allows the composite loaded with 1 wt% CBH to exhibit the thermal conductivity of 0.18 W m−1 K−1, which was 28.57% higher than pure epoxy (0.14 W m−1 K−1). Be different from many other CNTs‐loaded counterparts, the aligned‐CNTs loaded composite showed a well‐maintained insulating feature. The novel carbon nanotubes‐polymer hybrid construction expands the application range of epoxy‐based insulating composites by optimizing their mechanical and thermal properties.