Preparation of Carbon Nanotubes/Manganese Dioxide Composite Catalyst with Fewer Oxygen-Containing Groups for Li-O₂...

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.