The Preparation And Electrical Properties Study Of MoS₂ Based Flexible Ferroelectric Polymer Composites

Dielectric materials with excellent dielectric property and energy storage capability have been received more and more attention because of their wide range of applications in the electronic and electrical industry and military field,such as electrostatic capacitors,weapons,and field-effect transistors,which play an important role in promoting the development of advanced technology and national economy.Polymeric materials are good candidates as dielectrics because of their flexibility and ease of processing.Nowadays,apart from the synthesis of intrinsic high-?polymers,hybrid strategies to fabricate polymer based composites have been widely used to achieve high-?materials.For example,one is the addition of high-?ceramics?e.g.,BaTiO₃,TiO₂,SrTiO₃?into a polymer matrix,the other is incorporating conductive fillers such as graphene nanosheets and carbon nanotubes into a polymer matrix to form percolating systems.The above composites combine the advantages of both polymer and filler,realizing high dielectric constant.However,at the same time these composites also exhibit the disadvantages of difficulties of processing,low breakdown strength and decreased energy density,etc.In this paper,we successfully prepared flexible MoS₂ based polymer composites through synthesis of MoS₂ nanosheet superstructures and core-shell structured filler,researching the influence of semiconductive MoS₂ on electrical properties of polymer based composites.Firstly,in experimental process two kinds of MoS₂ nanosheet superstructures?i.e.,hydrangea-like flowers and nanosheet clusters?were synthesized by hydrothermal methods according to controllable morphology of MoS₂ superstructure.Ferroelectric polymer composites were prepared by introducing the MoS₂ superstructures into PVDF.The as-obtained composites exhibit high dielectric constant and high energy density.Recently,molybdenum disulfide?MoS₂?nanosheets received a lot of attention because of their semiconducting nature,appreciable band gap,and electric field tunable dielectric constant.These features make MoS₂nanosheets exhibit high potential to tune the dielectric properties of polymer composites.In this experimental process,nanosheet superstructures rather than individual nanosheets were used as filler because of their facile large-scale production and excellent repeatability of the products.It was shown for the first time that the MoS₂ superstructures based composites can exhibit significantly enhanced dielectric properties.Furthermore,when the loading of MoS₂ nanosheet superstructure in the composites is relatively high,both types of composites exhibit percolation-like electrical characteristics,resulting in low breakdown strength.Thus,the influence of MoS₂ nanosheet superstructure on the energy storage density was studied when the loading of MoS₂ is low in this paper.Interestingly,the composites exhibit significantly improved electrical energy storage capability when the loading of MoS₂superstructures was low.This may open a new route to fabricate flexible polymer composites for high-dielectric and electrical energy storage applications.Secondly,we mainly researched on the dielectric property and energy storage capability of polymer based composites with core-shell structured filler.In the experimental process organics and inorganics doped core-shell structured filler F-TiO₂@MoS₂@MRF was synthesized.Then the as-synthesized new material was used to fabricate P?VDF-HFP?based composites with excellent dielectric property and high energy storage density.On one hand,in the composite system,the core of MoS₂@MRF was treated as electrode material and the shell of fluorinated-TiO₂?F-TiO₂?was treated as dielectric material for microcapacitors in the composites.At the same time,F-TiO₂ exhibits two-dimensional nanosheet structure and large surface area can effectively block the space charge carrier,suppressing the leakage current in the composites.On the other hand,the core-shell structured filler and polymer matrix realize stepped distribution of dielectric constant of the composites,effectively tuning the dielectric constant of composite system,which could contribute to withstanding higher applied electric field and high energy storage density.It's worth noting that in this experimental process the problem that compatibility between filler and polymer matrix would influence properties of composites to a great extent was concerned.Therefore we prepared outermost TiO₂ nanosheets with abundant fluorine on the surface,improving the interface compatibility in the system and enhancing the dielectric performance of the composites.This work provides a new route to fabricate core-shell structured filler to realize the excellent dielectric and electrical energy storage capability of the composites.