Non-aqueous lithium-oxygen (Li-O₂) batteries are considered as the potential energy storage system for electric vehicles due to its comparable energy density (11682 W h kg^-1) with gasoline (13000 W h kg^-1) [1]. However, the development of Li-O₂ batteries is still at its early stage and suffers from some critical issues, such as short cycle life, poor electrolyte and electrode stabilities, and low energy efficiency [2], most of which are related to the high charge overpotential during the oxygen evolution reaction (OER). One widely applied approach to decrease the high charge overpotential is using catalyst, such as carbon-based materials, noble metals, metal oxides and so on. Even with this effort, however, it is still difficult to lower the charge voltage as much as possible (e.g. 3.5 V) to ensure the stabilities of electrolyte and electrode materials when Li₂O₂ is the discharge product [3]. Recently, an alternative strategy that achieves an ultra-low charge ovepotential and excellent stability has been reported, which is to form solid-state LiOH rather than Li₂O₂in the discharge process [4, 5]. However, the mechanism of crystalline LiOH decomposition on catalysts is still unknown, and the possible catalysts that can promote the decomposition of solid-state LiOH are also limited.

In this regard, a first-principles study was used to investigate the OER process in non-aqueous Li-O₂batteries via LiOH formation and decomposition. We developed an interfacial model to study the decomposition mechanism of LiOH on different surfaces of ruthenium, and the charge overpotentials among different surfaces were compared. Moreover, the decomposition path of crystalline LiOH and the rate determining step (RDS) were investigated. Our results demonstrate the activity of ruthenium towards the decomposition of crystalline LiOH, and different surfaces can lead to the different decomposition paths.

Further analysis of the decomposition mechanism of crystalline LiOH will be presented at the meeting. Our investigations give new insight into the future catalyst design in non-aqueous Li-O₂batteries.

References                                                         

[1] G. Girishkumar, B. McCloskey, A. Luntz, S. Swanson and W. Wilcke, The Journal of Physical Chemistry Letters, vol. 1, pp. 2193-2203, 2010.

[2] J. Christensen, P. Albertus, R. S. Sanchez-Carrera, T. Lohmann, B. Kozinsky, R. Liedtke, J. Ahmed and A. Kojic, J. Electrochem. Soc., vol. 159, pp. R1-R30, 2011.                                

[3] M. M. Ottakam Thotiyl, S. A. Freunberger, Z. Peng and P. G. Bruce, J. Am. Chem. Soc., vol. 135, pp. 494-500, 2012.                                                              

[4] F. Li, S. Wu, T. Zhang, P. He, A. Yamada and H. Zhou, Nature Communications, vol. 6, 2015.                                                         

[5] T. Liu, M. Leskes, W. Yu, A. J. Moore, L. Zhou, P. M. Bayley, G. Kim and C. P. Grey, Science, vol. 350, pp. 530-533, Oct 30, 2015.