High-temperature dielectric polymer nanocomposites with interposed montmorillonite nanosheets

Over the past decades, energy densities have always been considered as the key factors for realizing compact and highly efficient dielectric polymer capacitors. However, high-energy-density polymer dielectrics are limited by insurmountable drawbacks of high energy loss and low charge-discharge efficiency, which are far behind the industrial requirement for application under high temperature/voltage working conditions. Herein, a versatile method to suppress the energy loss of polymer dielectrics is presented, whereby two-dimensional montmorillonite nanosheets are interposed at the interfaces of a sandwich-structured barium titanate/polyamideimide film. The anisotropic electrical conductivity of the nanosheets provides paths to relationally regulate the charges transport along the in-plane direction while suppressing the through-plane conduction. As a result, nearly 50% of the energy loss can be eliminated with an applied electric field of 400 MV m⁻¹ at 150 °C, thus leading to a ~100% enhancement of energy density (3.6 J cm⁻¹), accompanied with a high charge-discharge efficiency of 70%, which outperforms all commercial high-temperature polymers. This work uncovers an effective and scalable pathway to enable high-density dielectric energy storage applicable to a wide range of polymer dielectrics at harsh operating conditions while promoting mechanism understanding of interfaces for interfacial engineering of high-performance dielectrics.