Micro-perforation strategy for stable, large-area conversion of polyimide into highly robust expanded graphitic carbons

Carbon-based nanomaterials have received attention owing to their exceptional properties, including high electrical conductivity, chemical stability, and large surface area, rendering them ideal for multifarious energy and electrochemical applications. However, their production typically requires high-temperature and time-consuming processes under controlled atmospheres, hindering their large-scale commercialization. This study proposes a facile and efficient method to rapidly (in milliseconds) and stably produce mechanically robust, porous graphitic carbon sheets with large surface areas from polyimide (PI) films by combining flashlight irradiation with a micro-perforation strategy. Conventional laser-based carbonization strategies rely on localized scanning, whereas the flashlight approach enables efficient large-area processing. To address limitations related to unstable carbonization, micro-perforations were introduced into the PI films using micro-needles to ensure uniform heat distribution, facilitate gas release, and alleviate drastic volume changes. This strategy effectively prevented delamination, wrinkling, and cracking, enabling stable carbonization with a high yield. The graphitic carbon sheets derived from the micro-perforated PI films exhibited superior electrical conductivity, mechanical robustness, and structural uniformity compared to those obtained from the non-perforated PI films. For practical validation, the carbonized sheets were employed as electrodes in supercapacitors. The perforated-PI-derived electrodes exhibited superior performance, delivering an areal capacitance, energy density, and power density of 96.1 mF cm⁻², 10.8 μWh cm⁻², and 157.3 μW cm⁻², respectively. These values surpassed those of their non-perforated counterparts and conventional laser-carbonized electrodes. This study demonstrates a promising pathway for the scalable production of high-quality graphitic carbon sheets to meet the demands of next-generation electrochemical energy storage applications.