Research On Structure Design And Energy Storage Performance Of Polyetherimide-based Composite Dielectric

Linear polymer dielectrics are widely used in electrical and electronic engineering because of their ultra-high power density and superior reliability.However,the possibility of obtaining excellent energy storage performance is limited by the low relative permittivity,small energy density,and severe degradation of the insulation characteristics under high temperature and strong electric fields.In this thesis,high temperature resistant linear polymer polyetherimide（PEI）is used as the basic energy storage unit,through a series of performance optimization and structural design,the dielectric and breakdown characteristics of the polymer dielectric are improved over a wide temperature range,resulting in superior energy storage performance.In response to the problems of low relative permittivity and low energy density for linear dielectrics such as PEI,this thesis introduces titanium hydroxide Ti（OH）₄,an inorganic functional material with high relative permittivity,and prepares Ti（OH）₄/PEI/Ti（OH）₄ composite dielectric containing a surface functional layer by in situ growth method.The synergistic optimization of the polarization strength and dielectric properties of the composite media was achieved by using the high dielectric surface inorganic functional layer and its interfacial polarization effect formed with the polymer matrix.When an electric field of 600 MV/m is applied and 150℃,the maximum charging energy density of the composite medium is 7.20 J/cm³,which is1.38 times that of PEI under the same conditions.In order to solve the problems of increasing conductivity loss and degradation of insulation performance caused by internal carrier transport for PEI and its composite media at high temperature,this thesis introduces a wide band gap potential barrier layer and then constructs a PEI/Ti（OH）₄/PEI/Ti（OH）₄/PEI five-layer composite media with inorganic interlayer,and further explore its optimal preparation process.The higher relative permittivity and band gap width of Ti（OH）₄ compared with PEI are fully utilized,which makes the composite medium have a wider interfacial barrier height under high temperature and strong electric field,thus hindering the long-range transport of carriers inside the composite medium and inhibiting the formation of breakdown paths.At the same time,the current density and high-temperature conductivity losses are effectively reduced,achieving significant optimization of insulation performance and energy storage performance for composite media in a wide temperature range.Among them,PTPTP-15 obtains the best comprehensive energy storage performance with moderate inorganic interlayer thickness.Its ability to withstand electric field strengths of up to 750 MV/m at room temperature and to obtain a discharge energy density of 7.62 J/cm³.At 150℃,it still maintains an electric field strength of 670 MV/m and a discharge energy density of 5.32 J/cm³ at this time.This thesis carries out a series of performance optimization and structural design of PEI,elucidating the mechanism of enhancement of polarization strength and breakdown characteristics of composite media by high dielectric,wide bandgap surface functional layer and inorganic interlayer over a wide temperature range.It provides a theoretical and experimental basis for promoting the application of wide-temperature region energy-storage polymer-based insulation media.