Screen Printed Asymmetric Supercapacitors based on LiCoO2 and Graphene Oxide

Aiming at both high energy and power density, asymmetric supercapacitors with screen printed lithium cobalt oxide (LiCoO2) and graphene oxide GO as electrode materials were assembled. LiCoO2 was synthesized by a facile and inexpensive hydrothermal method, whereas GO was synthesized according to a modified Hummer's method. Both powders were coated on flexible stainless steel substrates using screen printing technology. Finally, asymmetric supercapacitors were assembled using LiCoO2 as positive and GO as negative electrode with a porous polypropylene sheet as separator and an aqueous electrolyte solution of LiClO4. The electrochemical properties of this asymmetric cell were investigated by cyclic voltammetry and galvanostatic charge/discharge experiments. The asymmetric supercapacitor LiCoO2//GO could be cycled reversibly in the wide voltage region 0-1.5 V; it shows an impressive performance with an energy density of 19.2 Whkg(-1) (based on the total mass of the active materials of the two electrodes). Importantly, this device exhibits an excellent long cycling life with 85% specific capacitance retained after 1500 cycles. A demonstration cell could effectively light up an LED.