Microstructure Design And Energy Storage Performance Of Polyimide Based Composite Media

With the continuous development of energy storage technology,capacitors are increasingly used as energy storage devices due to their excellent energy storage capacity.Compared with batteries,electrochemical energy storage devices and other energy storage devices,dielectric capacitors have absolutely one-up charge and discharge power.Among of the dielectric material,the linear polymer has excellent breakdown strength and discharge efficiency.Polyimide（PI）is one of the most promising linear polymers with good corona resistance,mechanical properties and thermal stability,but its relatively low polarization energy storage density can’t satisfy the needs of the market.Improve the polarization of PI and keep the other electrical properties from degradation is the most effective method to solve the problem of energy storage of PI composite medium.In this paper.Calcium barium titanate zirconium nanofibers（BCZT NFs）,a kind of ceramics of perovskite structure with high dielectric,was prepared by the method of electrostatic spinning technology.By sol gel method.We coating the of silica（Si O₂）with insulation performance on the surface of BCZT NFs,obtained core-shell structure nanofiber（Si O₂@BCZT）.chose 1 vol.%,3 vol.%,5 vol.%and 7 vol.%four kinds of volume fraction to modified PI.Compared with the pure PI in dielectric constant,dielectric loss,breakdown strength and energy storage performance to choose the optimal components as polarization layer.At the same time,the silane coupling agent（KH550）was used for surface modification of the filling phase.The dielectric properties and energy storage properties of the composite films before and after modification were compared.It was found that after modified by silane coupling agent,the compatibility between the filling phase and the matrix was significantly improved.The polarization strength,breakdown strength and energy storage performance are all improved with different degrees,and the dielectric loss decreases when filling with low volume fraction.In order to further improve the breakdown strength of composite film.Boron nitride（BN）with larger band gap width was exfoliated by the method of wet ball mill,at the same time,hydroxy was grafted on the surface.After modified by silane coupling agent,chose 1 vol.%,3 vol.%and 5 vol.%three kinds of volume fraction to modified the PI.Chose the composite film with most excellent dielectric properties as the insulating layer together with the polarization layer to build sandwich structure on the macro level.Because the introduction of insulation layer hindered the development of electrical branches in composite films,its breakdown strength was greatly improved.Meanwhile,its maximum discharge energy density and discharge efficiency reached 3.37 J/cm³ and 84.89%,respectively.Providing an effective method for optimizing the energy storage performance of PI-based composite media.