Thin Film Coatings on Multiwalled Carbon Nanotubes for Lithium-Oxygen Battery Cathodes: Eliminating the Carbon Surface

Energy storage is one of the biggest challenges in our way before switching to sustainable energy resources. Batteries can be a viable solution to this challenge if “better” batteries with higher energy density, improved stability and cheap price can be realized. Lithium-oxygen batteries have become popular recently as they can theoretically offer much higher energy densities compared the widely used Li-ion or Ni-Mh batteries. However, realizing Li-O₂ batteries is no easy task, because of the electrolyte decomposition, cathode degradation and anode related problems which were intensively studied in recent years.^1,2 These aforementioned problems come together to complicate the electrochemistry taking place inside the cell, consecutively over-potential, low cycling life and poor current rate responses are observed.

In this study thin film coatings of TiO₂ are fabricated using atomic layer deposition technique (ALD) on multiwalled carbon nanotubes (MWCNT) and these composites were used as cathode for Li-O₂ battery. (Fig.1) Such a structure eliminates the direct interaction of carbon surface with electrolyte molecules and prevents the degradation of carbon cathode without sacrificing the high energy density carbon provides. TiO₂ was chosen as the coating material, since in a recent study by Thotiyl et. al. a thin surface film of TiO₂ was shown to increase the oxygen reduction and evolution reactions activity of the TiC cathodes.³ The electrochemical properties of the prepared composites and the comprehensive analysis of their effect on degradation mechanisms will be discussed in this presentation.

References

1. Thotiyl, M. M. O., Freunberger, S. A., Peng, Z., Bruce, P. G., J. Am. Chem. Soc. 2013, 135, 494.
2. McCloskey, B. D., Speidel, A., Scheffler, R., Miller, D. C., Viswanathan, V., Hummelshøj, J. S., Nørskov, J. K., Luntz, A. C., J. Phys. Chem. Lett., 2012, 3, 997.
3. Thotiyl, M. M. O., Freunberger, S. A., Peng Z., Chen, Y., Liu, Z., Bruce, P. G., Nat. Mater. 2013, 12, 1050.