Printing of graphene supercapacitors with enhanced capacitances induced by a leavening agent

摘要

The excellent electrical and mechanical properties of graphene make it a promising electrode material for energy storage devices such as supercapacitors. However, graphene flakes tend to restack upon processing which lowers the inner electrode surface area that contacts the electrolyte. We report on a straightforward and scalable approach where we add a chemical leavening agent to suppress the restacking of printed and reduced graphene oxide (rGO) flakes, resulting in a significant enhancement of the electrode capacitance. Upon mild heating, the leavening agent releases gasses that rise the gaps between rGO flakes and, hence, increase the surface area that is accessible for the electrolyte. We also optimize ink and micro-dispensing process that is utilized to print such risen rGO electrodes. The supercapacitor characterization indicates that the capacitance enhancement strongly depends on the size of the GO flakes; sizes on the order of magnitude of microns are most suitable. The printed and risen rGO electrodes feature typical electrical double layer capacitance behavior along with a good cycling stability having an 82% capacitance retention after 5000 charge-discharge cycles at a current density of 1.0 A/g.