Preparation of Carbon Nanotubes/Manganese Dioxide Composite Catalyst with Fewer Oxygen-Containing Groups for Li‑O2 Batteries Using Polymerized Ionic Liquids as Sacrifice Agent

Considering the significant influence of oxygen-containing groups on the surface of carbon involved electrodes, a carbon nanotube (CNT)-based MnO2 composite catalyst was synthesized following a facile method while using polymerized ionic liquids (PIL) as sacrifice agent. Herein, the PIL (polymerized hydrophobic 1-vinyl-3-ethylimidazolium bis ((trifluoromethyl)­sulfonyl)­imide) wrapped CNTs were prepared. The composite was applied to support MnO2 by the treatment of KMnO4 solution, taking advantage of the reaction between PIL and KMnO4, which excludes or suppresses the oxidation of CNTs, and the as-synthesized material with fewer oxygen-containing groups acted as a cathode catalyst for Li-O2 batteries, directly avoiding the application of binders. The catalyst shows enhanced activity compared to that of the samples without PIL, as verified by the lower overpotential during discharging and charging (0.97 V at the current density of 100 mA g–1). Meanwhile, the performance parameters such as Coulombic efficiency and rate capability were also improved for the Li-O2 battery utilizing this catalyst. Further, the formation of confined Li2O2 particles could be responsible for the reduction of charge potential of Li-O2 batteries due to the synergy effect of the intrinsic catalytic activity of MnO2 and fewer oxygen functional groups on the catalyst surface.