Modulation PI film performances to fit flexible substrate of transparent supercapacitors

Background With the increased demand for energy storage devices, transparency, flexibility, and miniaturization are gradually becoming the future development direction of energy storage devices, among which supercapacitors have unexceptionable application potential. However, due to the limitation of substrate material, the flexibility, transparency, thermal properties, and mechanical properties of supercapacitors cannot be perfectly unified. Methods Herein, we fabricated a series of transparent Polyimide (PI) films by combining para-amide-linked diamine (AB-TFMB) with different ratios of Pyromellitic dianhydride (PMDA) and 4,4′-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA). A series of characterizations were conducted regarding the thermal stability, mechanical properties, dielectricity, optical properties, transmittance, moisture absorption, and solubility of the PI films. The transparent PI film was used as a flexible substrate and assembled into a transparent supercapacitor. Significant findings The results showed that the comprehensive performance of PI films could be effectively regulated by changing the monomer types and contents. Also, the assembled transparent supercapacitor exhibited good capacitance characteristics, and the capacitance retention rate after bending at different angles and repeating bending 10,000 times can reach 100 % and 99.45 %, respectively. These promising results demonstrate that turning PI monomers is a favorable method for preparing transparent supercapacitors, which is conducive to the development of transparent flexible supercapacitors in the future.