No abstract

In this work, electron beam irradiation technology was used to increase the dielectric and energy storage performance of polypropylene (PP) films. Electron beam irradiation makes no difference on the crystal morphology but decreased the crystallinity and crystal size of PP. Besides, irradiation improved the thermal stability and polarity of PP. The irradiated PP films behaved much higher dielectric constant than pure PP films. Actually, the dielectric constant of the irradiated PP with 30 kGy was 3.98, while the dielectric constant of pristine PP was only 2.8. Furthermore, the irradiated PP films still kept low dielectric loss and AC conductivity. Weibull distribution test results proved electron beam irradiation improved the breakdown strength of PP films. The discharged energy storage of PP films increased from 1.3 J/cm3 of pristine PP film to 3.6 J/cm3 of irradiated PP with 30 kGy film. Moreover, the PP film irradiated with 30 kGy displayed an excellent charge–discharge efficiency of more than 95%. This research provides an easy and practical approach to investigate dielectric PP material for energy storage.

A novel copolymer (MG) which is methacrylate (MMA) and glycidyl methacrylate (GMA) is synthesized and the dielectric films are applied to dielectric and energy storage aspects.

Linear dielectric polymers are potential candidates for electrostatic capacitors due to their high breakdown strength, high efficiency, and low dielectric loss. In this work, a novel poly (vinylidene fluoride) (PVDF) tailored linear PMMA-co-GMA (MG) copolymer-based all-organic dielectric film with high breakdown strength and discharge energy density was prepared by the solution blending method. Compared with the PMMA homopolymer, the MG copolymer behaved with a higher energy density (5.6 J/cm3) since the GMA component bestowed higher polarity and yielded deep traps for the copolymer. On the other hand, the introduction of PVDF into MG further improved the dielectric constant and overcame the brittleness of MG films. When the concentration of PVDF was 30 wt %, the MG/PVDF film exhibited a high discharged energy density of 10.8 J/cm3 at 600 MV/m with a 78.7% discharge efficiency, which was 2.5 times that of pure PVDF (4.3 J/cm3 at 320 MV/m) and 1.9 times that of pure MG (5.6 J/cm3 at 460 MV/m). The improvement in energy storage performance might be ascribed to the excellent thermodynamic miscibility and hydrogen bond interaction between the linear MG copolymer and the ferroelectric PVDF. This research provides a new and feasible strategy for designing all-organic dielectric films with high energy density for energy storage applications.

Dielectric nanocomposites have attracted much attention due to their wide applications in electronics and electrical industry. Recently, incorporating core-shell nanoparticles into polymer matrix to improve the dielectric properties of nanocomposites has been widely reported. Tailoring the interfacial region between the polymer and the nanoparticles plays a crucial role in achieving the desired dielectric and energy storage properties of nanocomposites. However, the effect of shell structure in the interface region on the dielectric and energy storage properties is rarely studied. Based on this, core-shell BaTiO 3 nanoparticles with two different shell polymers, a "hardsoft" copolymer of methyl methacrylate and butyl acrylate (P[MMA-BA]) and a "hard" homopolymer of methyl methacrylate (PMMA), were prepared in this paper. The effect of core-shell BaTiO 3 nanoparticles with different shell structures on the dielectric and energy storage properties of poly(vinylidene fluoride) (PVDF) was investigated in depth. Due to the formation of a tight interfacial region between P(MMA-BA)@BT and PVDF matrix, P(MMA-BA) @BT/PVDF nanocomposites not only have low dielectric loss but also higher energy efficiency than PMMA@BT/PVDF nanocomposites. This study suggests a potential strategy that fabricating a "hard-soft" copolymer shell on BaTiO 3 surface can obtain desirable energy storage efficiency than the single "hard" shell structure in dielectric nanocomposites.