Dielectric Properties And Energy Storage Properties Of Multilayer Core-Shell Structured Fillers/Polyetherimide Composite Dielectric

The rise of high-power applications in electronic devices and electrical systems has promoted the demand for a new generation of high-energy-density dielectric materials in the field of capacitive energy storage.Due to its ultra-high discharge power density,polymer dielectric capacitors have been widely used in high-pulse power technology,new energy vehicles,electronic equipment such as inverters and power grids,as well as power systems and other related fields.However,the relatively low discharge energy density of polymer dielectric capacitors limits their miniaturization applications in practical engineering and devices.Based on the high-speed directional spinning process,multiple groups of polyetherimide（PEI）-based composite dielectric are prepared by adjusting the structure and properties of nanofillers to improve the discharge energy density and maintain a high charge-discharge efficiency.First,high dielectric constant barium calcium zirconate titanate(Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃,abbreviated as BZCT)particles are prepared by sol-gel method.Secondly,BZCT particles are embedded in titanium Barium acid（Ba Ti O₃,abbreviated as BT）to form core-shell fibers by sol-gel method（BZCT@BT）.Thirdly,pure BT fibers,the nanofiber which BZCT particles in BZCT@BT Nanofibers with a content of 10 vol%（10%BZCT@BT）,30%BZCT@BT,and 50%BZCT@BT nanofibers were obtained by adjusting the content of BZCT particles in BT fibers,respectively.Finally,a PEI-based composite dielectric filled with BZCT@BT filler fibers（BZCT@BT/PEI）is obtained by high-speed directional spinning and hot pressing.In this process,linear dielectric PEI is used as the matrix and BZCT@BT fibers as filler for doping.When the filler content is 2 vol%,the dielectric constant of the 50%BZCT@BT/PEI（2%-50%BZCT@BT/PEI）composite dielectric is 4.85,which is 56%higher than that of pure PEI（3.1）.However,the 10%BZCT@BT/PEI（0.5%-10%BZCT@BT/PEI）composite dielectric with a filler content of 0.5 vol%has an excellent discharge energy density of 6.66 J/cm³,which is 64%higher than that of pure PEI.4.06 J/cm³,and maintain a high charge-discharge efficiency of93.29%.A layer of Si O₂ shell is coated on the basis of BZCT@BT fiber by the water bath method to further promote considerably the energy storage density of composite dielectric This can obtain a fiber with a layer of Si O₂ shell on the BZCT@BT fiber（BZCT@BT@S）.The BZCT@BT@S/PEI composite dielectric can be obtained by using PEI as the matrix and BZCT@BT@S fiber as the filler for doping.The10%BZCT@BT@S/PEI（0.5%-10%BZCT@BT@S/PEI）composite dielectric with0.5 vol%filler content has an excellent discharge energy density of 6.97 J/cm³ at a field strength of 530 k V/mm and high charge-discharge efficiency of 92.38%.In conclusion,the 0.5%-10%BZCT@BT@S/PEI composite dielectric has more excellent comprehensive energy storage performance.