Flexible mica films for high-temperature energy storage

Dielectrics used for energy storage are highly desired for power electronics and pulse power applications and the polymer capacitors are the main commercial ones available. The development of flexible electronics and wearable devices require the relative materials being flexible. Besides, high temperature resistance is also desired because of the rising demand for high power devices and large electricity under elevated temperature. The polymer dielectrics for polymer capacitors are flexible but with relatively low working temperature normally less than 100 °C. Therefore, fabricating a dielectric material to satisfy the flexibility and high working temperature simultaneously is still a great challenge. Here we propose one solution by demonstrating a hand-exfoliated fluorophlogopite film with micrometer scale thickness. Among which, the mica film with a thickness of around 10 μm (Mica-10) exhibits the inorganic-like temperature stability even polymer-like flexibility. From 25 °C to 200 °C, Mica-10 has an energy density of around 11.27 J/cm³ with a variation within 2%, accompanied by a charge-discharge efficiency of around 95% at an electric field of 500 MV/m. Meanwhile, the thin thickness makes Mica-10 flexible, enabling its excellent flexibility and durability. This work revives the traditional material, mica, providing a way for high-temperature energy storage applications.