Rechargeable potassium−oxygen (K–O₂) batteries have received much attention owing to their higher theoretical energy density (935 Wh/kg, K + O₂ = KO_2, E⁰ = 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:

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