Selective laser carving-induced patterned electrodes for high-performance binder-free and substrate-free all-carbon-based micro-supercapacitors

Activated carbon is one of the most widely used electrode materials for supercapacitors owing to its excellent porosity, large specific surface area and long cycle life. However, its utilization in electrode fabrication necessitates the incorporation of insulating binders to facilitate shaping due to its powdery nature. This may obstruct the pores and increase the internal resistance of the electrode, resulting in poor flexibility and electrochemical performance. To address this problem, an innovative and universal packaging strategy is proposed, in which composite films are prepared by double vacuum filtration, coated with gel electrolyte and then patterned by selective laser carving based on the principle of “Selective Optical Transmittance”, to achieve the fabrication of binder-free and substrate-free all-carbon-based micro-supercapacitors. The areal capacitance of obtained Activated Carbon/Super P-Reduced Graphene Oxide Micro-supercapacitors (AC/SP-rGO MSCs) without binder are three times higher than those with binder. The prepared AC/SP-rGO MSCs exhibit remarkable areal capacitance of 177.32 mF cm−2, volumetric capacitance of 52.15 F cm−3 and high energy density of 4.44 mWh cm−3. Meanwhile, they also exhibit excellent flexibility with no capacitance degradation after 5000 bending cycles. Specifically, the energy provided by four AC/SP-rGO MSCs connected in series can light up to 46 red LEDs or provide a thermo-hygrometer with a long endurance of over 45 min. This packaging method has proven to be an effective strategy for the fabrication of powdery materials into binder-free electrodes, presenting a unique idea for the fabrication of electrodes within the realm of flexible electronics.