All-Printed Paper-Based Micro-supercapacitors Using Water-Based Additive-Free Oxidized Single-Walled Carbon Nanotube Pastes

Printing technologies that integrate wearable components onto flexible and stretchable substrates are crucial for the development of miniaturized wearable electronics. In this study, we developed all-printed paper-based flexible micro-supercapacitors based on water-based additive-free oxidized single-walled carbon nanotube pastes. The use of a modified Brodie’s method with mild oxidants and minimum usage of strong acids enabled the production of highly conductive and printable oxidized single-walled carbon nanotube pastes. Pseudo-plastic pastes were obtained because of the numerous hydrogen bonds between the oxidized single-walled carbon nanotubes. By photothermal treatment with intense pulsed light irradiation, a microporous structure was developed in the interdigitated energy storage electrodes to facilitate the infiltration of electrolytes. The paper-based flexible micro-supercapacitor exhibited a high energy density of 0.51 μW h cm–2 at a power density of 0.59 mW cm–2 and a superior capacity retention of 85% after 10,000 bending cycles with a bending radius of 3 mm. The all-printed flexible micro-supercapacitor array with a total capacitance of 0.1 mF charged to 4.0 V successfully powered a commercial digital clock for approximately 40 s. The micro-supercapacitor array operated properly under both tensile and compressive strains. These results demonstrate that the water-based additive-free oxidized single-walled carbon nanotube pastes are promising printable materials for the construction of flexible micro-supercapacitors.