Structural Design And Performance Of Polymer Composites With High Energy Storage Density Via Incorporating Two-dimensional(2D) Nanosheets

With the rapid development of microelectronics,power,and energy systems,polymer film capacitors are not only important electronic components,but also have become the important energy storage devices in the fields of electric vehicles,smart grid frequency modulation,pulse power systems,and advanced electromagnetic weapons.Compared to batteries and supercapacitors,polymer film capacitors feature high power density,fast charge and discharge rates,low cost,and light weight.Hence,the film capacitors have received more and more concerns,however,they still suffer from some challenges:1)low energy density,falling short of the growing demands for energy storage.2)poor heat resistance,leading to a sharp decline in charge and discharge efficiency and energy storage density as the operating temperature increase.Therefore,research on high-temperature-resistant polymer film materials with high energy storage density has become an important subject in the field of energy storage.In this dissertation,based on the heat resistant polyimides?PI?,the influence rules of 2D nanosheets of hydrotalcite on the energy storage performance of Ba Ti O3/PI and graphene/PI nanocomposites were discussed in detail.The specific results are as follows:1. PI/LDH nanocomposites.With 2D nanosheets of hydrotalcite as the polyimides filler,it was found that the dielectric constant and dielectric loss of the PI/LDH composites increased with the increase of 2D nanosheets in polyimide matrix,while the breakdown strength increased first and then decreased.When the constant of LDH was 1%,the breakdown strength and dielectric constant of the composite film increased compared with the pure PI film,so the energy density of the composite film with the content of LDH was 1%increased.This showed that the 2D nanosheet of hydrotalcite can improve the energy storage performance by enhancing the breakdown strength and dielectric constant of the composites.2. PI/Ba Ti O₃/LDH composites.The breakdown strength and energy storage density of the PI/Ba Ti O₃/LDH composites were improved by adding LDH nanosheets to PI/Ba Ti O₃composites.When 20%Ba Ti O₃ and 1%LDH were added together to polyimide,the breakdown strength and energy storage density were increased by 12.4%and 14.6%,respectively,compared with only 20%Ba Ti O₃ in PI matrix.This may be due to the improvement of the dispersibility of Ba Ti O₃ in the ternary composites after the addition of LDH nanosheets,thus improving the breakdown strength of the PI/Ba Ti O₃/LDH composites.3. PI/GO@LD composites.LDH nanosheets and graphene oxide could form into the electrostatic self-assembly by a certain proportion,with which PI/GO@LD composites were constructed.It was found that the breakdown strength and energy storage density of the PI/GO@LD composites were obviously improved compared with that of the PI/GO composites.With the same 1%GO,the breakdown strength and energy storage of the PI/GO@LD composites with GO@LDH self-assembly as filler reached 196 k V/mm and 1.09J/cm³,respectively,which were increased by 113%and 206%,respectively,compared to the PI/GO composites with only 1%GO added.