Structure Design And High-Temperature Energy Storage Performance Of Polyetherimide-Based Composite Dielectric

Polymer film capacitors are widely used in electrical engineering due to their high power density,high safety and good insulation.However,the energy storage performance of polymer dielectric film is seriously deteriorated under extreme conditions such as strong electric field or high temperature,and improving the high temperature performance of energy storage dielectric has become a research hotspot in the field.Polyetherimide（PEI）film with linear polarization property is selected as the basic energy storage unit in this thesis.The high-temperature conductivity loss is reduced through the structural design optimization of the polymer film,thereby improving the high-temperature energy storage performance.Broad band gap boron nitride nanosheets（BNNS）and magnesium oxide（MgO）were selected as inorganic functional fillers to improve the high temperature energy storage performance of PEI-based composite dielectric.PEI/BN and PEI/Mg O composite dielectric with different filler contents were prepared by solution casting method.The charge trap is introduced by using the interfacial barrier formed between the wide bandgap inorganic filler and the polymer matrix,thereby reducing the high temperature conductivity loss and improving the energy storage performance.When applied 410 MV/m electric field and 150°C,the maximum discharge energy density of 5 wt%MgO doped composite dielectric is 2.77 J/cm³,and the charge-discharge efficiency remains above 90%.The PEI/barrier layer/PEI composite dielectric with sandwich structure was constructed by introducing the inorganic barrier intermediate layer.PEI/BN/PEI and PEI/Mg O/PEI composites with wide band gap inorganic insulating layer were prepared by layer-by-layer solution casting method.By adjusting the thickness of BN or Mg O inorganic insulating layer,it is found that the inorganic insulating interlayer can hinder the charge transport in the dielectric,significantly reduce the high temperature conductivity loss and improve the energy storage performance.When applied 510 MV/m electric field and 150°C,the maximum discharge energy density of PEI/Mg O/PEI composite is 4.13 J/cm³,and the charge-discharge efficiency is higher than 90%.The inorganic barrier layer was grown on the surface of PEI film to inhibit the charge injection of metal electrode,thereby reducing the high temperature conductivity loss.A wide band gap Si O₂ barrier layer was grown on the surface of PEI film by magnetron sputtering to obtain Si O₂/PEI/Si O₂ composite dielectric with different Si O₂ film thicknesses.The growth of Si O₂ film at the electrode/dielectric interface can improve the charge injection barrier and suppress the high temperature conductivity loss.When the sputtering time is 2 hours,the thickness of Si O₂ thin film is about 125 nm,the maximum discharge energy density of Si O₂/PEI/Si O₂ composite dielectric is 2.96 J/cm³,and the charge-discharge efficiency remains above 90%.