High energy storage density dielectric capacitors, as core electronic components, are widely used in modern industries such as medical equipment and defense technology due to their high discharge power, high energy utilization efficiency, fast charging and discharging capabilities, as well as good cycle stability and operational reliability. However, the lower energy storage density limits further compression of the capacitors in terms of volume and weight, becoming the main bottleneck restricting their development towards miniaturization and lightweighting. To enhance the energy storage performance of polymer based dielectrics, the strategy of introducing high dielectric constant inorganic ceramic fillers into the polymer matrix is commonly adopted to construct polymer based composite dielectrics. However, there are significant differences in physical and chemical properties between high dielectric constant inorganic ceramic fillers and organic polymer matrices, resulting in poor interfacial compatibility and weak bonding between the two. Especially under the high filler content, nanoscale ceramic particles are prone to agglomeration, forming micropores or defects inside the composite material, which can lead to dielectric performance degradation and a decrease in breakdown strength, seriously restricting their practical application in high-frequency and high-performance passive electronic devices. Therefore, how to effectively improve the interfacial properties of inorganic fillers, enhance their dispersion uniformity in polymer matrices, and strengthen the interfacial interactions between ceramics, interfacial layers and polymers has become a key scientific issue and hot research direction in ceramic/polymer composites.
One-dimensional Ba0.6Sr0.4TiO3 nanofibers (BST NF) with uniform morphology were prepared through electrospinning technology, and surface modification was carried out with a dioctyl phosphate oxytitanate coupling agent (NDZ 101) (referred to as BST NF-NDZ). The BST NF-NDZ/polyvinylidene fluoride (PVDF) composite film was prepared by flow casting method, and the effect mechanism of modified nanofibers on the microstructure, dielectric properties, and energy storage performances of the composite films was systematically studied by combining experimental characterization and finite element simulation.
The BST NF prepared by electrospinning method had a diameter of 50-350 nm and a length of 1.5-11.5 μm, exhibiting one-dimensional nanostructure integrity. The surface modification of the titanium ester coupling agent significantly improved the dispersibility and interfacial compatibility of nanofibers in PVDF matrix. The dielectric performance test showed that as the content of BST NF-NDZ increased, the dielectric constant of the composite film gradually increased. When the filling volume fraction was 7.5%, the room temperature dielectric constant reached 24.21, exhibiting lower losses, higher breakdown strength and superior energy storage density and discharge efficiency. At a filling level of 2.5vol.% in BST NF-NDZ, the energy storage density reached 8.53 J/cm3, which was 3.05 times that of the pure PVDF film. The finite element simulation results further confirmed that NDZ-101 modification effectively regulated the local electric field distribution in the composite system, suppressed the electric field concentration effect, and thus improved the breakdown strength and overall energy storage performance. Surface modification of nanofibers with titanium ester coupling agents can effectively regulate the interface characteristics between fillers and the matrix at low filling levels, synergistically improve the dielectric constant and breakdown strength of composite films, and significantly enhance their energy storage performance. This study provides reliable experimental basis and technical support for the design and engineering application of high-performance polymer based dielectric composites.
Key words
composites films /
energy storage properties /
one-dimensional nanofibers fillers /
titanate coupling agent /
surface modification /
dielectric properties
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Funding
The Programs for Tackling Key Problems in Science and Technology of Henan Province (252102231014, 262102231004); The Innovation Training Program for College Students in Henan Province (202511517015); Key scientific research projects of colleges and universities in Henan Province (26A430004)
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