Simultaneously enhanced energy storage and thermal conductive properties of polyimide dielectric films via facile sandwich structure design

Abstract High dielectric constant (ε_r), large breakdown strength (E_b) and improved thermal conductivity (λ) of polymer dielectric materials are critical in increasing the overall energy storage density and enhancing the electrical stability for advanced electronic devices. In this study, sandwich PI composite films (B‐G‐B) with simultaneously improved ε_r and E_b were designed by alternately casting boron nitride nanosheets/polyimide (BNNS/PI, B) and graphene oxide/polyimide (GO/PI, G) precursor solutions. Results showed that GO contributed greatly to the ε_r due to the enhanced interfacial polarization, while wide bandgap BNNS effectively enhanced the E_b of composites via introducing large deep traps. The ε_r, E_b, and λ of sandwich B‐G‐B (1‐0.1‐1) film are 4.7 (@1 kHz), 537 kV/mm, and 0.21 W/mK, being 127%, 128%, and 114% times higher than that of neat PI, respectively. Consequently, a distinct improvement in energy storage density of 6.41 J/cm³ (2.63 J/cm³ of pure PI) was achieved. Heat transfer simulation demonstrates a significant decrease in heat transfer time, which implies a reduced thermal accumulation, showing potential applications in embedded capacitors. Highlights Wide bandgap BNNS introduces more deep traps in the outer layer. GO further promotes interfacial polarization in the inner layer. Sandwich structure design balanced the ε_r and E_b simultaneously. Synergistic enhancements in U_e and η were achieved. Effectively promotes thermal transfer and reduces heat accumulation.