Study On Preparation And Energy Storage Properties Of Ferroelectric Polymer-Based Dielectric Composites With Laminated Structure

With the rapid development of electronic industry,higher requirements are put forward for the storage density of dielectric capacitors.The two important parameters related to the energy storage density of dielectric capacitors are the dielectric constant and breakdown strength.In order to achieve an enhancement of the energy storage density,it is necessary to increase the dielectric constant and breakdown strength of the dielectric at the same time.The combination of inorganic materials with high dielectric constant and organic polymers with high breakdown strength is one of the ways to make composites have high energy storage density.In recent years,contructing multilayer structure has been proved to be one of the effective ways to improve the energy density of composites.Currently,the intermediate layer of multilayer structural composite often acts as a high insulating layer or a high dielectric layer.The intermediate layer of typical multilayer structure composite usually blends the filler with the polymer directly.Fillers are easy to aggregate in the matrix,which leads to the decrease of the breakdown strength,thus limiting the optimization of energy storage density of the composite.Therefore,we designed a non-traditional sandwich structured composites in which the middle layer is the polarization layer and the two sides are the insulation layer and the middle layer is the insulation layer and the upper and lower layers are the polarization layer.Here,high dielectric constant 2D nanosheets are oriented perpendicular to the direction of electric field to block the development of electrical branches in the dielectric,so as to realize the synchronous increase of breakdown strength and dielectric constant.Therefore,we conducted the following research.（1）“Preparation of two-dimensional sheet GO@Si O₂of semiconductor@insulator”and“Performance study of PVDF/GO@Si O₂/PVDF composites”.We prepared GO@Si O₂nanosheets using the St（?）ber method.PVDF/GO@Si O₂/PVDF composites were prepared by solution pouring method and spraying process.When the GO@Si O₂spray volume was 1.37wt%accounting for the composites,the breakdown strength reached 253 MV/m.Discharged energy density of 5.19 J/cm³were obtained,which increased by 161%compared with pure PVDF.（2）“Preparation of titanium dioxide（Ti O₂）nanosheets of semiconductor two-dimensional sheet materials”and“Performance study of PVDF/Ti O₂/PVDF composites”.We prepared Ti O₂nanosheets by hydrothermal method.PVDF/Ti O₂/PVDF sandwich structured composites were prepared by solution casting method and hot pressing process.The study found that,when the packing load was 0.65 wt%accounting for the composites,the breakdown strength reached 332.99 MV/m,and the corresponding discharged energy density reached 4.41 J/cm³increased by 114%compared with the discharged energy density of pure PVDF.（3）“Preparation of barium titanate（Ba Ti O₃）nanowires”and“Performance study of PVDF-Ba Ti O₃/Ti O₂/PVDF-Ba Ti O₃composites”.We prepared Ba Ti O₃nanowires by two-step hydrothermal method,PVDF-Ba Ti O₃composite film by solution casting method,and then prepared PVDF-Ba Ti O₃/Ti O₂/PVDF-Ba Ti O₃composites by spraying method and hot pressing method.The study found that when the Ba Ti O₃nanowire load was 1 wt%accounting for the composites,the breakdown field strength reached 296.27 MV/m.Discharged energy density of 5.24 J/cm³was achieved,which was increased by 154%compared with pure PVDF.In summary,by designing a non-traditional sandwich structured composites in which the middle layer is the polarization layer and the two sides are the insulation layer and the middle layer is the insulation layer and the upper and lower layers are the polarization layer.synchronous enhancement of dielectric constant and breakdown strength can be achieved,thereby achieving an increase in energy storage density.It is significant to improve the application of dielectric capacitor in electrical power system.