A Micromolding Method for Transparent and Flexible Thin‐Film Supercapacitors and Hybrid Supercapacitors

Abstract

Thin-film supercapacitors are promising candidates for energy storage in wearable electronics due to their mechanical flexibility, high power density, long cycling life, and fast-charging capability. In addition to all of these features, device transparency would open up completely new opportunities in wearable devices, virtual reality or in heads-up displays for vehicle navigation. Here a method is introduced for micromolding Ag/porous carbon and Ag/NixFeyOz@reduced graphene oxide (rGO) into grid-like patterns on polyethylene terephthalate foils to produce transparent thin-film supercapacitors and hybrid supercapacitors. The supercapacitor delivers a high areal capacitance of 226.8 µF cm−2 at a current density of 3 µA cm−2 and with a transparency of 70.6%. The cycling stability is preserved even after 1000 cycles under intense bending. A hybrid supercapacitor is additionally fabricated by integrating two electrodes of Ag/porous carbon and Ag/NixFeyOz@rGO. It offers an areal capacitance of 282.1 µF cm−2 at a current density of 3 µA cm−2, a transparency of 73.3% and the areal capacitance only decreases slightly under bending. This work indicates that micromolding of nano- and micro-sized powders represents a powerful method for preparing regular electrode patterns, which are fundamental for the development of transparent energy storage devices. © 2020 Wiley-VCH GmbH