Superb high-temperature energy storage performances obtained in all-organic sandwich-structured dielectric capacitors

Abstract

As power electronics technology continues to advance, there is an increasing demand for capacitors of operating at high temperatures. However, among the pure polymers studied, polyvinylidene fluoride (PVDF) exhibits a high dielectric constant (ε_r) but poor thermal stability, limiting its use in extreme conditions. Polyetherimide (PEI) offers excellent thermal stability at 150 °C, but its low dielectric constant restricts its applications. To overcome this issue, a sandwich-structured film, consisting of PEI as the outer layers and PVDF as the central layer, is prepared in this study. This sandwich structure effectively combines the high ε_r of PVDF with the high operating temperature of PEI. Moreover, the interfaces between adjacent layers effectively impede charge carrier movement and enhance the breakdown strength. As a result, a remarkable discharge energy density (U_d) of 11.99 J cm⁻³ is realized at room temperature under an enhanced breakdown strength (E_b) of 540 MV m⁻¹. More importantly, it demonstrates excellent capacitive performances at 150 °C with an impressive U_d of 6.20 J cm⁻³ and an efficiency (η) of up to 71 %. All these results demonstrate that the sandwich-structured film design incorporating PVDF and PEI offers a feasible approach for fabricating high-temperature capacitors.