High-temperature energy storage performance of PEI/PVDF blends enhanced by Al₂O₃ inorganic layer depositing

In polymer dielectric energy storage, even polymers with high glass transition temperatures suffer significant degradation in energy storage performance as temperature increases, primarily due to a sharp rise in electrical conduction loss. In this study, we employ atomic layer deposition to coat the surface of a PEI/PVDF blend film with an Al₂O₃ inorganic layer to enhance its energy storage performance at high temperatures. The influence of the inorganic layer's thickness on high-temperature energy storage performance is thoroughly analyzed. Experimental results and finite element simulations demonstrate that an ultra-thin Al₂O₃ inorganic layer with the thickness of 50 nm effectively reduces leakage current density and mitigates space charge accumulation within the PEI/PVDF blends, thereby improving the high-temperature energy storage performance of the blends. Notably, under an applied electric field of 500 MV/m at 150 °C, the PEI/PVDF blend film with 50 nm Al₂O₃ layer achieved a discharge energy density of 5.45 J/cm³ and a charge-discharge efficiency of 97.75 %.