Charge Rate‐Dependent Decomposition Mechanism of Toroidal Li2O2 in Li‐O2 Batteries. Issue 10 (24th July 2021)

• Record Type: Journal Article
• Authors: Shen, Zhen‐Zhen; Zhou, Chi; Wen, Rui; Wan, Li‐Jun
• Is Part Of: Chinese journal of chemistry. Volume 39:Issue 10(2021)
• Page Start: 2668
• Page End: 2672
• Publication Date: 2021-07-24
• Subjects: Li‐O2 Batteries -- Scanning probe microscopy -- Toroidal Li2O2 -- Oxidation -- Structure‐activity relationships; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/cjoc.202100222
• Languages: English
• ISSNs: 1001-604X

Abstract

Main observation and conclusion: Using in situ atomic force microscopy, we visualized the oxidation dynamic process of toroidal lithium peroxide (Li2 O2 ) in a working Li‐O2 battery and clarified the correlation between the decomposition behavior and the charging rate. It was found that at a low charge rate, the decomposition could occur at the Li2 O2 /electrolyte interface, providing strong evidence that a tiny current is allowed to pass through the bulk phase of toroidal Li2 O2 . Further, the evolution of the periphery thickness, diameter and center thickness of the toroid as a function of charge capacity was quantitatively analyzed. In the early stage of charging, the diameter of the toroid radially shrinks and the shrinking rate slows down in the later stage. Besides, the periphery thickness of the toroid decreases at a faster and uniform rate, while the center thickness decreases obviously in the later stage of charging. Increasing the charging rate promotes the decomposition occurring at the Li2 O2 /electrode interface, causing direct desorption of the Li2 O2 from the electrode and irreversible capacity degradation. Abstract : In situ atomic force microscopy was performed to clarify the correlation between the decomposition behavior of toroidal lithium peroxide (Li2 O2 ) and the charging rate in a working Li‐O2 battery. In situ views reveal that at a low charge rate, the decomposition of toroidal Li2 O2 could occur at Li2 O2 /electrolyte interface, indicating that a tiny current is allowed to pass through the bulk phase of toroidal Li2 O2 . Since the limited traverse ability of electrons and ions through bulk Li2 O2, increasing the charging rate will promote the decomposition of Li2 O2 at the Li2 O2 /HOPG interface. And it causes the desorption of Li2 O2 from the electrode, thus resulting in irreversible capacity degradation.