Epichlorohydrin functionalized graphene oxide for superior Li+ ion conduction and supercapacitor application

Abstract

Functionalization of graphene oxide (GO) by crown ether moiety to attach Li+ in the cage of five oxygens is a useful tool to achieve 2D material for Li ion battery. The attachment of crown ether occurs only through the reaction with epoxy groups of GO. In the present work, epichlorohydrin is used to increase the number of the epoxy group to enhance and precise control of the Li+ content for tuning the activation energy of Li+ migration. The Li+ containing sample is annealed at 220 °C under vaccum and after 115 °C (flash point of crown ether moiety) Li+ ions will be attached to the graphene surface through cation–π interaction due to the removal of epichlorohydrin and crown moiety. By varying the epichlorohydrin and Li+ content, the minimum activation energy of 0.24 eV much lower than the literature value (∼0.4 eV) is achieved. AC measurements on samples show that follow almost Debye-type relaxation with the exponent value nearly 1. To exploit the interaction of alkali metal ion with crown ether moiety, the supercapacitor behavior of the FGOC composite has been studied. It is seen that the specific capacitance increases significantly with the increase in crown ether moiety. We believe, this idea of using functionalized graphene oxide having strong affinity on alkali ions will be helpful to achieve better material with high storage capacity.