All-solid-state supercapacitors from natural lignin-based composite film by laser direct writing

Lignin as a renewable natural resource has been the focus of numerical interest in applications ranging from pitch to porous carbon material. Herein, a facile approach is reported to transform lignin into porous conductive carbon structures and interdigitated circuits for supercapacitor devices using femtosecond laser direct writing. Comparative studies revealed that the laser irradiation induced tetrahedral amorphous carbon while only graphitic carbon was obtained through pyrolysis. Meanwhile, the composite membrane was easily prepared to further optimize the capacities by mixing functional materials (MoS₂) into the lignin/polyacrylonitrile (PAN) composite polymers. A MoS₂ decorated porous carbon network material could be fabricated through focused femtosecond pulsed laser irradiation of the corresponding composite membranes. The microstructure and spectroscopic features of these laser induced hybrid carbon materials have been deeply investigated. The supercapacitor based on lignin/PAN has high areal specific capacitances of 6.7 mF cm^-2 (0.9 F cm^-3) at 10 mV s^-1. Moreover, doped microsupercapacitors with MoS₂ demonstrated enhanced areal capacitances up to 16 mF cm^-2 (2.2 F cm^-3) and at 10 mV s^-1, respectively. The relatively high areal capacitances indicate that the proposed method is potential for innovative manufacturing energy storage devices based on natural lignin.