All-printed solid-state supercapacitors with versatile shapes and superior flexibility for wearable energy storage

Abstract

A supercapacitor, as a new green energy source, has attracted considerable attention because of its intrinsic high safety, fast charge/discharge rate and long cycle life. Meanwhile, the traditional energy devices present large limitations with respect to their structure and performance, which cannot meet the demand of shape diversity in the wearable electronic field. Herein, all-printed solid-state flexible supercapacitors with versatile shapes were fabricated as power sources by the screen printing method. The flexible supercapacitors were prepared by using cobalt hexacyanoferrate (CoHCF) nanocubes as electrode materials. They not only presented a variety of shapes, such as squares, school emblems of the Wuhan University, flowers and carps, but also showed excellent areal capacitance of 12.5 mF cm⁻². There was no significant capacitance loss of these flexible supercapacitors even on bending to 180°, showing excellent mechanical flexibility. In addition, the highest energy density and power density of these printed flexible solid-state supercapacitors were 0.0011 mW h cm⁻² and 0.44 mW cm⁻², respectively. The capacitance was retained at 90% of the initial value after 8000 cycles. This efficient printed electronic technology is expected to provide an economical and practical method for the future construction of flexible energy storage devices with versatile patterns for wearable electronics.