Superior Additive of Exfoliated RuO2 Nanosheet for Optimizing the Electrode Performance of Metal Oxide over Graphene

Abstract

An effective way to optimize the electrode performance of metal oxide was developed by employing exfoliated 2D RuO2 nanosheet as a conducting additive. The exfoliated RuO2 nanosheet was easily incorporated into the Li-MnO2 nanocomposite via a simple mixing of exfoliated RuO2 and MnO2 nanosheets, followed by the restacking with Li+ ions. The incorporation of RuO2 nanosheet was found to be quite effective in increasing the surface area of the restacked Li-MnO2 nanocomposite. The obtained heterolayered Li-MnO2-RuO2 nanocomposites delivered much greater specific capacitances than do the pristine Li-MnO2 and Li-RuO2 nanocomposites. Considering the fact that the RuO2 nanosheet has higher electrode activity than the MnO2 nanosheet, the greater specific capacitance of Li-MnO, RuO2 nanocomposite than that of Li-RuO2 strongly suggests that the incorporation of a small amount of RuO2 nanosheet into the restacked Li-MnO2 nanocomposite induces a synergistic improvement in its electrode activity. Of prime importance is that the Li-MnO2-RuO2 nanocomposites showed somewhat better electrode performances than the reduced graphene oxide (rG-O)incorporated Li-MnO2-rG-O homologues, attributable to more efficient charge transport and pore structure upon RuO2 incorporation. The hydrophilic RuO2 nanosheet is more effective in making a stronger chemical interaction with hydrophilic MnO2 and also in depressing the self-aggregation of nanosheets compared to hydrophobic rG-O nanosheet. The present study clearly demonstrates that the RuO2 nanosheet can be used as a better additive for improving the electrode performance of metal oxides compared with widely used rG-O.