Electrospun BaTiO3-doped trilayer composite film for enhanced energy storage performance and retained high breakdown strength properties

Polymer dielectrics suffer from inherently low dielectric constants, thereby limiting the energy density and hindering the miniaturization of high–voltage power equipment. Improving both the dielectric constant and the breakdown strength of materials is necessary to enhance the energy density. However, conventional approaches involving high–dielectric–constant inorganic fillers are often accompanied by a significant decrease in breakdown strength, constraining the optimized energy storage performance. This work utilized electrospinning to introduce a thin inorganic–doped inner layer, composed of polyvinylpyrrolidone (PVP)–wrapped BaTiO 3 nanoparticle fibers, and employed polymethyl methacrylate (PMMA) as the outer layer material. Combined with a hot–pressing process, a trilayer composite film was fabricated. Experimental results demonstrate that the fabricated trilayer composite films, featuring a thin inorganic–doped layer, exhibit breakdown strengths exceeding 500 kV/mm while maintaining high charge–discharge efficiencies (over 70 %). In particular, the film with a 5 wt % BaTiO 3 inner layer (denoted as PM–5 % B/P-PM) achieved a discharge energy density of 10.4 J/cm 3 at 548 kV/mm, with a charge–discharge efficiency surpassing 80 %. This structural design mitigated the significant reduction in breakdown strength often caused by excessively high inorganic filler contents. Meanwhile, combining electrospinning with hot–pressing was effective in controlling the dispersion of BaTiO 3 particles and enhancing the interfacial polarization effect, demonstrating simultaneous improvements in the energy density and insulation performance.