Eco-friendly graphene-based conductive ink for scalable production of high-performance flexible micro-supercapacitors

For achieving cost-effectiveness, the utilization of printable carbon-based conductive inks has emerged as a critical driver for the industrial advancement of flexible micro-supercapacitors (MSCs). However, the commercial application of carbon-based conductive ink is still limited by their low electrical conductivity and capacitance, attributed to the limited conductive pathways and pore structures resulting from the stacking of conductive materials. Herein, a carbon-based composite aqueous ink based on graphene, multi-walled carbon nanotubes, and conductive carbon black (GMC) is developed for scalable screen printing of MSCs. The integration of these carbon components forms a three-dimensional porous conductive network with exceptional flexibility. This network not only enhances electron transfer pathways but also increases the accessible surface area for electrolyte ions. Thanks to these advantages, the GMC-MSCs deliver high conductivity (10,843.62 S m- 1), excellent energy storage performance (an areal capacitance of 12.94 mF cm- 2 at a current density of 0.02 mA cm- 2), and stable cycling life (102.4 % capacitance retention after 10,000 cycles). Furthermore, these devices exhibit outstanding flexibility with 150 % capacity retention after 9000 bending cycles, thus paving the way for the widespread application of flexible MSCs.