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 MnO 2 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 MnO 2 by the treatment of KMnO 4 solution, taking advantage of the reaction between PIL and KMnO 4, 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-O 2 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-O 2 battery utilizing this catalyst. Further, the formation of confined Li 2 O 2 particles could be responsible for the reduction of charge potential of Li-O 2 batteries due to the synergy effect of the intrinsic catalytic activity of MnO 2 and fewer oxygen functional groups on the catalyst surface.