氧化铝包覆SrTiO_(3)纳米纤维/聚偏氟乙烯复合材料的制备与介电储能性能

Dielectric Energy Storage Performance of Alumina Coated SrTiO_(3) Nanofiber/Polyvinylidene Fluoride Composites

目的通过开发出工作场强更高、储能效率更高的电介质储能材料,从而提高电力设备的性能、减小电力设备体积。方法采用静电纺丝工艺结合溶胶凝胶工艺制备具有一维核壳结构的SrTiO_(3)@Al_(2)O_(3)纳米纤维填料,并结合流延成型工艺制备出聚偏氟乙烯(PVDF)电介质复合材料。系统地研究了SrTiO_(3)纳米纤维填料表面包覆Al_(2)O_(3)对PVDF电介质复合材料界面极化、介电性能、储能性能的影响。结果制备的一维纳米填料具有良好的核壳结构,其中芯层为SrTiO_(3),壳层为Al_(2)O_(3),Al_(2)O_(3)包覆厚度为6 nm。低填充量下,一维核壳结构SrTiO_(3)@Al_(2)O_(3)纳米纤维填料均匀地分散在PVDF基体中。在相同的体积分数填料填充下,SrTiO_(3)@Al_(2)O_(3)纳米纤维/PVDF复合材料表现出更低的介电损耗和漏电流、更强的耐击穿场强、以及更高的储能密度和放电效率。SrTiO_(3)@Al_(2)O_(3)纳米纤维/PVDF电介质复合材料的最大储能密度达到8.9 J/cm^(3)。结论Al_(2)O_(3)包覆层可以阻止SrTiO_(3)纳米纤维填料在复合材料中的接触,减小Maxwell-Wagner-Sillars界面极化,降低漏电流,进而提高复合材料薄膜的击穿强度和储能性能。

Polymer-matrix dielectric composites have greatly potential in high power density film energy-storage capacitors due to their advantages such as light weight,high power density,fast charge and discharge rate,wide working voltage,which are widely used in new energy vehicles,smart grids and many other fields.At present,dielectric capacitors show low energy storage density and low discharge efficiency under high working voltage conditions,which hinder the development of energy storage devices and systems towards miniaturization and high capacity.It is of great significance to develop dielectric energy storage materials with higher working field strength and higher energy storage efficiency to improve the performance of power equipment.The composite method can greatly improve the dielectric properties and energy storage properties of polymer materials.However,the introduction of inorganic ceramic fillers leads to the accumulation of space charges at the interface of the composites,resulting in strong interface polarization,as well as high dielectric loss and low discharge efficiency of the composites.The work aims to introduce core-shell structured fillers to reduce the interface polarization.The SrTiO_(3)@Al_(2)O_(3) nanofiber with a one-dimensional core-shell structure was prepared by electrospinning combined with sol-gel process.The filler was functionalized with 3-aminopropyl triethoxysilane to improve the compatibility between nanofiber filler and PVDF matrix.The PVDF composites were prepared by casting.The effects of Al_(2)O_(3) coated on the surface of SrTiO_(3) nanofiber fillers on the interface polarization,dielectric properties and energy storage performance of PVDF dielectric composites were systematically studied.The test results showed that the prepared powder was one-dimensional nanofiller with a good core-shell structure.The core layer was SrTiO_(3) and the shell layer was Al_(2)O_(3).The Al_(2)O_(3) layer was evenly coated on the nanofiber surface with an average coating thickness of 6 nm.At low filling levels,the one-dimensional core-shell nanofiber filler was evenly dispersed in the PVDF.Under the same volume fraction of filler,SrTiO_(3)@Al_(2)O_(3)nanofiber/PVDF composite exhibited lower dielectric loss and leakage current,as well as higher breakdown strength.At the same time,SrTiO_(3)@Al_(2)O_(3)nanofiber/PVDF dielectric composites had higher energy storage density than that of SrTiO_(3)nanofiber/PVDF composites.The energy storage density of SrTiO_(3)@Al_(2)O_(3)nanofiber/PVDF composite was 8.9 J/cm^(3).While,the energy storage density of SrTiO_(3)nanofiber/PVDF composite was 6.8 J/cm^(3).For the 2.5 vol.%of SrTiO_(3)@Al_(2)O_(3)nanofiber dielectric composite,it exhibited an efficiency of 84.2%at 1000 kV/cm and was higher than 64.9%at 3950 kV/cm.The discharge efficiency of pure PVDF was significantly reduced from 75.4%at 1000 kV/cm to 42.4%at 4000 kV/cm.This was because the Al_(2)O_(3)coating layer prevented the contact of the SrTiO_(3)nanofiber filler in the composites,which could reduce the interface polarization,significantly reduce the leakage current,and improve the breakdown strength of the composite.This work may supply effective ways to raise discharged energy density of polymer composites in high electric fields.