Effect of the size-selective silver clusters on lithium peroxide morphology in lithium-oxygen batteries

Lithium-oxygen batteries have the potential needed for long-range electric vehicles, but the charge and discharge chemistries are complex and not well understood. The active sites on cathode surfaces and their role in electrochemical reactions in aprotic lithium-oxygen cells are difficult to ascertain because the exact nature of the sites is unknown. Here we report the deposition of subnanometre silver clusters of exact size and number of atoms on passivated carbon to study the discharge process in lithium-oxygen cells. The results reveal dramatically different morphologies of the electrochemically grown lithium peroxide dependent on the size of the clusters. This dependence is found to be due to the influence of the cluster size on the formation mechanism, which also affects the charge process. The results of this study suggest that precise control of subnanometre surface structure on cathodes can be used as a means to improve the performance of lithium-oxygen cells.This work was supported by the US Department of Energy (DOE) under Contract DE-AC02-06CH11357 from the Vehicle Technologies Office, DOE, Office of Energy Efficiency and Renewable Energy (EERE) and Division of Materials Science, Basic Energy Sciences, Department of Energy, Office of Science. J.L. was supported by the DOE, Office of EERE Postdoctoral Research Award under the EERE Vehicles Technology Program administered by the Oak Ridge Institute for Science and Education for the DOE. We acknowledge the financial support from the Human Resources Development of the Korea Institute of Energy Technology Evaluation and Planning grant funded by the Ministry of Knowledge Economy (No. 20124010203310) of the Korean government and by the National Research Foundation (NRF) of Korea grant funded by the Korea government (MEST) (No. 2009-0092780). We also acknowledge grants of computer time through INCITE awards for BlueGene/Q computer at Argonne National Laboratory and allocations on the CNM Carbon Cluster at Argonne National Laboratory, the ALCF Fusion Cluster at Argonne National Laboratory, and the EMSL Chinook Cluster at Pacific Northwest National Laboratory. Use of the Advanced Photon Source and the Electron Microscopy Center for Materials Research was supported by the US DOE, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. The authors would also like to thank Dr Jeffrey W. Elam of Energy systems division at Argonne National Laboratory for his help on preparing Al<INF>2</INF>O<INF>3</INF>-coated carbon via ALD method