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 (Eg) and permittivity (K). Even aluminum oxide (Al2O3), which offers the best balance of Eg 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‑Eg, 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‑Eg 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.