Enhanced lithium–oxygen battery performances with Pt subnanocluster decorated N-doped single-walled carbon nanotube cathodes

Abstract

Achieving dramatic improvement in long-term cycling performance in Li–O2 batteries continues to remain a challenge, which is imperative for turning their alluring promise into reality. Developing a bifunctional cathode material capable of reducing overpotentials and enhancing the long-term cycling performances holds the key. Herein, bifunctional cathodes for Li–O2 batteries were prepared by electrodeposited Pt subnanoclusters on pristine as well as nitrogen-doped single-walled carbon nanotubes (SWCNTs) using rotating disk electrode voltammetry techniques. Diffraction, microscopic, and spectroscopic techniques were used to characterize the prepared materials, and the phase purity of the materials was confirmed. Microscopic analysis depicted a fine dispersion of ≤2 nm Pt nanoclusters on single-walled carbon nanotubes. Rotating disk electrode voltammetry measurements indicated low overpotentials as well as high catalytic ORR/OER activities with Pt nanocluster decorated SWCNTs in comparison to Pt-free SWCNTs. Among the investigated cathodes, Pt/N-SWCNTs exhibited high discharge capacities of 7685 and 5907 mAh/g at 100 and 500 mA/g, respectively, and also good capacity retention. Moreover, a stable capacity of 3000 mAh/g with 100% Coulombic efficiency at 500 mA/g was demonstrated under repeated cycling conditions. On the basis of the ex situ Raman spectroscopic studies, the high Li–O2 battery performance of the Pt/N-SWCNT cathode was attributed to the high decomposition activity of Li2O2 and negligible amount of Li2O2 accumulated on the electrode surface during cycling.