High‐Entropy‐Nanofibers Enhanced Polymer Nanocomposites for High‐Performance Energy Storage

Abstract

Polymer composite dielectrics capable of high energy density, high efficiency, and high‐temperature stability are in high demand for application in various electronic vehicles and power systems. A major challenge, however, is the reasonable design of high‐performance nanofillers that are beneficial to the polarization and breakdown strength simultaneously. Here, high‐entropy‐induced ceramic nanofibers with a stable Bi2Ti2O7‐type pyrochlore phase are developed as effective nanofillers to enhance the energy storage performance of polyetherimide (PEI) composites. Benefiting from the linear pyrochlore phase, refined grain size, and increased amorphous fraction of the high‐entropy nanofillers, the resultant PEI composites exhibit significantly improved energy storage performance over a wide temperature range of 25–150 °C. Notably, a high energy density of 6.46 J cm−3 under an electric field of 590 MV m−1 is achieved at 150 °C, which outperforms most of the reported PEI composites. This study provides a guideline for the development of dielectric fillers with tunable dielectric properties and microstructures, thus promoting the development of high‐performance polymer composites.

Enhanced High-Temperature Capacitive Energy Storage by 0.55Bi0.5Na0.5TiO3-0.45(Bi0.2Sr0.7)TiO3 Nanofibers in Polyetherimide Nanocomposites

“…This is mainly because BNT-BST nanofibers tend to be distributed along the in-plane during solution casting, and this arrangement makes BNT-BST nanofibers perpendicular to the electric field. When the vanguard of the breakdown phase encounters BNT-BST nanofibers, it usually chooses to penetrate nanofibers. ,, Therefore, the BNT-BST nanofibers block the propagation of electrical trees and suppress leakage current, and nanocomposites with an appropriate amount of BNT-BST nanofibers can withstand high breakdown fields . However, as the loading of BNT-BST nanofibers further increases, the introduction of defects increases, leading to local electric field distortion and a significant decrease in E b …”

“…23,43,51 Therefore, the BNT-BST nanofibers block the propagation of electrical trees and suppress leakage current, and nanocomposites with an appropriate amount of BNT-BST nanofibers can withstand high breakdown fields. 36 However, as the loading of BNT-BST nanofibers further increases, the introduction of defects increases, leading to local electric field distortion and a significant decrease in E b . 23 Figure 7c shows the electric displacement−electric field (P−E) loops of samples.…”

“…Impressively, nanocomposites exhibit good dielectric temperature stability, with the addition of a small amount of nanofibers having little effect on the dielectric loss of the nanocomposites, maintaining low and stable values of <0.02. The Weibull distribution of PEI and nanocomposites was tested and calculated based on the equation P(E) = 1 − exp(−(E/E b ) β ); 7,11,36 the E values can be obtained by applying increasing electric field to each sample using a ferroelectric analyzer until breakdown, and at least 9 data points need to be tested for the same sample. The E b represents the characteristic breakdown strength.…”

“…Polymer-based dielectric materials have high losses under high electric fields or high temperatures, and the losses will sharply increase with the applied temperature and electric field, which will lead to a decrease in U dis and efficiency. − The commonly used biaxially oriented polypropylene film in commercial applications has a U dis of 2–3 J/cm 3 and can withstand operating temperatures of less than 85 °C. − Polyetherimide (PEI) is a thermoplastic engineering resin with high glass transition temperature, excellent breakdown field strength, mechanical properties, and high temperature stability. − Lin et al prepared high-entropy-induced ceramic nanofibers as a filler by electrospinning to enhance the energy storage performance of PEI. Due to the refined grain size, linear pyrochlore phase, and increased amorphous fraction of nanofillers, composites exhibit significantly enhanced U dis over the temperature range of 25–150 °C …”

“…Due to the refined grain size, linear pyrochlore phase, and increased amorphous fraction of nanofillers, composites exhibit significantly enhanced U dis over the temperature range of 25−150 °C. 36 Herein, the influence of viscosity parameters of electrospinning solution on the diameter distribution of BNT-BST nanofibers has been systematically studied. The BNT-BST nanofibers with the optimal diameter were introduced into the PEI.…”