Enabling superior high-temperature capacitive performance in polymer dielectrics by multifunctional alternating nanolaminate coating

Abstract

Achieving high energy-storage performance in polymer capacitors at elevated temperatures remains a critical challenge for next-generation power electronics, due to conduction loss caused by charge injection at electrode/polymer interfaces. Conventional inorganic barrier layers are constrained by an intrinsic trade-off between bandgap (E_g) and permittivity (K). Even aluminum oxide (Al₂O₃), which offers the best balance of E_g and K, reaches a material-limited ceiling in charge-blocking performance. Herein, we propose a counterintuitive interfacial design that overcomes this limitation by strategically embedding narrower-E_g, high-K zirconium oxide (ZrO₂) nanolayers within an Al₂O₃ barrier framework. An ultrathin (∼36 nm) alternating Al₂O₃/ZrO₂ nanolaminate was uniformly deposited on both surfaces of the polymer film via atomic layer deposition. Combined experimental and phase-field simulation results reveal that the wide-E_g Al₂O₃ outer layers provide a high injection barrier, while the embedded ZrO₂ interlayers (∼3 nm), with higher permittivity, introduce deep-level charge traps and enable lateral electric-field redistribution. This architecture integrates charge-blocking, charge-trapping, and electric field-modulating functions, which collectively suppress charge injection and deflect electrical-tree propagation, thereby outperforming conventional single-layer coatings. As a result, the nanolaminate-coated polycarbonate achieves a record discharge energy density of 8.50 J cm⁻³ with an ultrahigh efficiency of 96.4% at 150 °C, surpassing all previously reported polymer-based dielectrics. Moreover, this strategy demonstrates broad applicability across various polymer substrates, with coated films retaining excellent mechanical flexibility and uniform capacitive performance, indicating compatibility with roll-to-roll manufacturing. This work provides a feasible and scalable route for developing polymer dielectrics with superior high-temperature capacitive performance.