Preparation And Properties Of Inorganic Nanoparticles Modified Energy Storage Films Of Polyvinylidene Fluoride

With the coming of the electrical generation,high-performance energy storage devices for advanced electronics,electric vehicles,power systems and other fields are needed urgently to meet the growing desire.Polymer-based nano composites which possess a lot of advantages,such as low cost,ease of processing and reusability,have attracted the attention of a growing number of researchers.In the last decade,some significant results have been achieved in improving the dielectric constant,energy density and other key parameters of polymer matrix composites.However,a number of issues,for instance,how to achieve uniform and effective dispersion of nanofillers in polymer matrix materials,how to reduce the high dielectric losses associated with highly filled fillers and how to improve the breakdown properties of polymer nanocomposites and so on,hindered the further development of nanocomposite applications.Based on previous research,in this paper poly(vinylidene fluoride)(PVDF)was utilized as the polymer matrix material to improve the dielectric properties as well as the energy storage properties of polymer-based nanocomposites by adding nano barium titanate and nano organic montmorillonite,respectively.The main experiments and related results are as follows.(1)To ensure the dispersion of barium titanate(Ba Ti O₃)nanoparticles with a high filler content in the PVDF substrate and the interaction of the filler with the interface.two types of shell structures with different degrees of hardness and softness were coated on the surface of Ba Ti O₃using the RAFT reagent prepared by the laboratory respectively.The two different barium titanate fillers were blended with PVDF by solution method.The results of scanning electron microscopy showed that PMMA and P(MMA-BA)are able to ensure the dispersion of Ba Ti O₃nanoparticles in the PVDF matrix even at high filler content due to their good compatibility with PVDF,and the two polymer-based nanocomposites exhibit different dielectric losses due to the different shell layer structures encapsulated on the surface of Ba Ti O₃.This significantly affects the energy storage characteristics and enhances the charging and discharging efficiency.The P(MMA-BA)@BT/PVDF nanocomposite with a filler content of 30wt%exhibited a dielectric loss of only 0.018 at 1 k Hz,which was lower than that of the PVDF polymer matrix and PMMA@BT/PVDF nanocomposite at the same frequency.And at a field strength of 150 MV/m,an energy efficiency of 80%was achieved.(2)Energy storage films with good optical transmission and breakdown resistance were prepared by combining a small amount of lamellar organic montmorillonite(OMMT)with PVDF substrate by a simple but effective solution casting method.Scanning electron microscopy results showed that small amounts of organic montmorillonite can be well dispersed in the substrate.XRD and FT-IR results showed that the incorporation of OMMT effectively converts the crystalline structure of the PVDF matrix,making it more favourable for use in dielectric energy storage films.The polymer-based nano-energy storage films exhibited an optical transmittance of approximately 90%at 800 nm.More importantly,the presence of OMMT,a unique lamellar structure,can effectively hinder the growth of electrical trees within the polymer composite,thereby enhancing the overall breakdown strength of the composite.For example,at 0.6wt%filler content,the PVDF/OMMT nanocomposite exhibited a breakdown strength of 460 MV/m and a discharge energy density of 7.26 J/cm³,as well as an energy efficiency of 69%.