Polymer film capacitors are essential energy storage components in advanced electrical and electronic systems. Recently, many industrials require capacitors operating at the temperature as high as 200 ℃, while polymer dielectric materials suffer from significantly increased conduction loss under elevated temperatures. To address this issue, we deposited ultrathin wide-bandgap HfO₂ films onto both sides of Poly(ether imide) (PEI) substrate using atomic layer deposition (ALD) and investigated the leakage current, breakdown strength and energy storage performance of HfO₂/PEI/HfO₂ composites at 200 °C. Experiment results show that a dense and uniform layer of amorphous HfO₂ forms on the surface of PEI. The resultant composites exhibit reduced leakage current, enhanced breakdown strength, enhanced charge-discharge efficiency and discharged energy density compared with neat PEI. Moreover, thicker HfO₂ coating layers are more effective in suppressing the conduction loss at elevated temperatures.

polymer dielectrics,capacitors,high temperature,electrical energy storage,hafnium oxide

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