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