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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High‐performance dielectric capacitors are essential components of advanced electronic and pulsed power systems for energy storage. Because of their high breakdown strength and excellent flexibility, polymer‐based capacitors are regarded as auspicious energy storage material. However, the energy storage capacity of polymer‐based capacitors is severely limited due to their low polarisation and low dielectric permittivity. The modified Stöber method was used to construct two types of CNT@SiO2 (CS) one‐dimensional core‐shell structured nanowires with different shell thicknesses. By integrating the procedures of solution mixing, melt blending, hot‐stretching orientation and hot pressing, sandwich‐structured poly (vinylidene fluoride) (PVDF)‐based composites were fabricated. The CS core‐shell nanowires dispersed in the inter‐layer serve as electron donors, leading to a high permittivity, while two PVDF outer layers provide the favourable overall breakdown strength. The insulating SiO2 shell can effectively limit the migration of carriers and keep the dielectric loss at a relatively low level in the composites. The CS/PVDF composite exhibited an enhanced discharged density (~6.1 J/cm3) and breakdown strength (~241 kV/mm) when the interlayer filled with as small as 1 wt% CS nanowires with the SiO2 shell thickness of 8 nm, which is 203% and 18.7 % higher than pure PVDF (~2.01 J/cm3 at 203 kV/mm), respectively. This research presents a practical strategy for designing and fabricating advanced polymer film capacitor energy storage devices.

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.

The addition of inorganic particles can endow polymer matrices with different new features, thereby realizing an optimization to the structural and functional properties of composite. The overall properties of composites are greatly influenced by both fillers dispersion and fillers-polymer interfacial interaction. However, to simultaneously improve these mentioned two issues is still a critical challenge in the field of polymer-based nanocomposite. Herein, a typical core-shell structured mesoporous silica-coated silica (SiO 2 @mSiO 2 ) construction was successfully synthesized by using a bi-phase method. The SiO 2 @mSiO 2 filled polyethylene (PE) nanocomposite was fabricated through a precisely controlled melt-mixing approach. Benefiting from the additional mesoporous SiO 2 shell, both the dispersion of SiO 2 @mSiO 2 and the SiO 2 @mSiO 2 -PE matrix interfacial interaction are improved. Moreover, the stress-strain behavior, temperaturedependent mechanical property, thermal stability, and electrical insulating property of SiO 2 @mSiO 2 /PE composite were studied in detail. It is found that