Nanoscale phase separation achieved through trace PVDF/PEI blending enhances mechanical and energy storage performance at high temperatures

Due to the development of advanced electronic systems, there is an urgent need for polymer dielectric film capacitors with high breakdown strength (E_b) and high discharge energy density (U_d) at elevated temperatures. Herein, an all-organic blend polymer composite is fabricated by blending polyetherimide (PEI) and a trace amount of Poly(vinylidene fluoride) (PVDF), achieving nanoscale phase separation and forming interfaces between PEI and PVDF grain. The real permittivity (ε_r) and E_b of blend composites are simultaneously enhanced after PVDF introduction. It is worth noting that increasing the temperature does not reduce the E_b of the PEI/xPVDF blend composite. Our Study shows that optimizing the plasticity and storage modulus of PEI/xPVDF significantly contributes to maintaining E_b at elevated temperatures. Additionally, high temperatures enhance the entanglement of molecular chains at the PVDF-PEI interface, further supporting the preservation of E_b. Finally, a high E_b of 540 MV/m, a high U_d of 5.92 J/cm³ are achieved for the PEI/0.5PVDF blend at 150 °C. This work presents a new approach to enhance the E_b of dielectric polymers by optimizing mechanical properties at high temperature, which providing a different strategy for enhancing the energy storage performance.