| With the rapid development of the clean energy field,the important need for advanced electrical energy storage systems has become more urgent.Conventional energy storage devices include electrochemical batteries,dielectric capacitors,and supercapacitors,among which polymer film capacitors stand out for their high operating voltage,fast charging and discharging rates,low cost,and high reliability.Commercial biaxially oriented polypropylene(BOPP)film capacitors are the most widely used,but the relatively small relative dielectric constant of BOPP films(about2.3 at 10~3 Hz)leads to limited capacitor capacity,and the development of high energy storage density polymers has become a hot research topic in the field of dielectric energy storage.Poly(vinylidene fluoride-trifluoroethylene chlorofluoride)(PVTC),as a relaxed ferroelectric polymer,has a relatively high relative dielectric constant(about10 at 10~3 Hz),but the large residual polarization can lead to serious energy loss,limiting the synergistic improvement of energy storage density and charge and discharge efficiency.To address these problems,this paper improves the energy storage performance of PVTC-based composite films by doping with organic fillers and designing multilayer structures.The specific research contents are as follows:RBBT,a voltage stabilizer with high electron affinity and narrow energy gap,is selected as the organic filler,RBBT nanosheets are blended with PVTC by sol-gel method,and the composite films are prepared by coating and hot-pressing process.The results show that when the RBBT content is 3 wt%,the energy storage density and charge and discharge efficiency of the composite film with an applied electric field of 489.98 k V/mm reach13.43 J/cm~3 and 49.73%,respectively.The energy storage density of the hot-pressing composite film at 479.67 k V/mm electric field strength is 14.17 J/cm~3,and its charge and discharge efficiency is 55.52%.The hot-pressing process can increase theγphase content in the composite film,which is beneficial to improve the charge and discharge efficiency,but at the same time leads to a slight decrease in the breakdown field strength of the film.Three and five-layer composite films were prepared by using magnetron sputtering technology to grow a broad-band inorganic insulating layer aluminum nitride(Al N)on the surface of PVTC,and the influence law and enhancement mechanism of the thickness of Al N thin layer and multilayer structure design on the energy storage performance of PVTC were systematically studied.It is found that the Al N inorganic insulation layer grows uniformly on the PVTC surface,and the energy storage density and charge and discharge efficiency of PVTC-based composite films are enhanced the most when the thickness of Al N thin layer is 150 nm.The energy storage density and charge and discharge efficiency of the five-layer composite film are 16.62 J/cm~3 and 63.82%,respectively,when an electric field of529.88 k V/mm is applied.The Al N thin layer acts as a potential barrier layer at the interface between the metal electrode and the PVTC film layer,which significantly inhibits the electrode charge injection and reduces the conductivity loss under high electric field.The Al N intermediate layer can block the charge transport in the PVTC body layer,which reduces the leakage current density and enhances the breakdown field strength of the composite film.This paper elucidates the influence of the doping content of organic filler RBBT and hot-pressing process on the microstructure and electrical properties of PVTC,and reveals the mechanism of enhancing the insulation and energy storage performance of PVTC-based composite films based on the design of Al N inorganic functional thin layer structure,and the research results provide an important reference for the development of high energy storage density capacitor film materials. |
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