Pea-Pod-like Carbon Microspheres Encapsulated by Graphene-like Carbon Nitride for Enhanced Thermal Conductivity in Polyimide Films

Owing to superior comprehensive performance, polyimide film (PI) has been extensively used as flexible substrate to support and fix electronic components. However, the current PI film has inferior thermal conductivity, especially in the vertical direction, causing failure of electronic devices in overheating conditions. Herein, an electrically insulating pea-pod-like filler with high thermal conductivity in both horizontal and vertical directions was prepared by encapsulating interconnected carbon microsphere (CM) with graphene-like carbon nitride (g-C3N4). The resultant thermal conductivity of PI film in horizontal and vertical directions has been improved by 11 (1.98 W m–1 K–1) and 2.4 (0.43 W m–1 K–1) times at 30 wt % CM@g-C3N4 loading, respectively. Furthermore, benefiting from satisfactory light absorption of CM@g-C3N4, the PI/CM@g-C3N4 film displays rapid heating capability under illumination. Meanwhile, the PI/CM@g-C3N4 film keeps intrinsic electrical insulation, thermal and dimensional stabilities. This work provides an effective method to solve the bottleneck of the current PI film in inadequate thermal conductivity.