Structure-designed fabrication of all-printed flexible in-plane solid-state supercapacitors for wearable electronics

The current development of wearable electronics has raised the requirement for developing matchable supercapacitors. Currently, most researches have been focused on the electrode materials, but few studies have been carried out on the structure of supercapacitors. Herein, we report an efficient fully-printing fabrication approach to construct flexible in-plane solid-state supercapacitors. Utilization of the screen printing technique, a series of factors which affect the performance of planar supercapacitors have been studied to construct smart planar supercapacitors, including dimensions, finger interspaces, functional layers of active materials and asymmetric structure, which is firstly systematically investigated for efficiently increasing the performance of planar supercapacitors. More interestingly, the planar supercapacitors can be fabricated as various patterns with artistic design on various flexible substrates, demonstrating that the screen printing process is facile and easy scalable for practical production. The optimized symmetric supercapacitors exhibit good mechanical flexibility, outstanding areal capacitance of 35.3 mF cm−2 and superior cycling performance. Compare with the symmetric supercapacitors, higher energy density of asymmetric supercapacitors can be achieved (from 0.00177 mWh cm−2 to 0.00687 mWh cm−2). We envision that this strategy of constructing fully-printed flexible planar supercapacitors with structural design paves the way for the improvement of flexible energy storage devices.