In Situ Ambient Pressure X-Ray Photoelectron Spectroscopy Studies of Potassium-Oxygen Redox Reactions

Abstract

Rechargeable potassium−oxygen (K–O2) batteries have received much attention owing to their higher theoretical energy density (935 Wh/kg, K + O2 = KO2, E 0 = 2.48 V) compared to conventional lithium−ion batteries and their superior round-trip efficiency.1-3 In order to realize commercialization of K–O2 batteries, identifying fundamental barriers and instability that hinder the development of K–O2 batteries is required. In situ characterization methods provide valuable insight into the discharge/charge mechanisms of metal-oxygen batteries, especially the K-O2 discharge products are highly sensitive to the uncontrolled contaminations. In this work, we employed in-situ ambient pressure X-ray photoelectron spectroscopy (APXPS)4, 5 and examine in situ the chemistry of K-O2 reaction products under ultra high vacuum (UHV) and oxygen condition using APXPS. We will discuss the chemical changes of the K-O2 system during discharge and charge conditions. We show that combining in situ APXPS and electrochemical characterization techniques, the formation and disappearance of K-O2 reaction products can be directly visualized. Acknowledgement: This work was supported by a grant from the Research Grants Council (RGC) of the Hong Kong Special Administrative Region, China, T23-601/17-R. Reference: X. Ren and Y. Wu, J. Am. Chem. Soc., 135, 2923 (2013).G. Cong, W. Wang, N.-C. Lai, Z. Liang and Y.-C. Lu, Nat. Mater., 18, 390 (2019).W. Wang, N. C. Lai, Z. Liang, Y. Wang and Y. C. Lu, Angew. Chem., Int. Ed., 57, 5042 (2018).Y.-C. Lu, E. J. Crumlin, G. M. Veith, J. R. Harding, E. Mutoro, L. Baggetto, N. J. Dudney, Z. Liu and Y. Shao-Horn, Sci. Rep., 2, 715 (2012).Y.-C. Lu, E. J. Crumlin, T. J. Carney, L. Baggetto, G. M. Veith, N. J. Dudney, Z. Liu and Y. Shao-Horn, J. Phys. Chem. C, 117, 25948 (2013).