Issue 18, 2024

Nature of Li2O2 and its relationship to the mechanisms of discharge/charge reactions of lithium–oxygen batteries

Abstract

Lithium–air batteries (LABs) are considered one of the most promising energy storage devices because of their large theoretical energy density. However, low cyclability caused by battery degradation prevents its practical use. Thus, to realize practical LABs, it is essential to improve cyclability significantly by understanding how the degradation processes proceed. Here, we used online mass spectrometry for real-time monitoring of gaseous products generated during charging of lithiumoxygen batteries (LOBs), which was operated with pure oxygen not air, with 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) tetraethylene glycol dimethyl ether (TEGDME) electrolyte solution. Linear voltage sweep (LVS) and voltage step modes were employed for charge instead of constant current charge so that the energetics of the product formation during the charge process can be understood more quantitatively. The presence of two distinctly different types of Li2O2, one being decomposed in a wide range of relatively low cell voltages (2.8–4.16 V) (l-Li2O2) and the other being decomposed at higher cell voltages than ca. 4.16 V (h-Li2O2), was confirmed by both LVS and step experiments. H2O generation started when the O2 generation rate reached a first maximum and CO2 generation took place accompanied by the decomposition of h-Li2O2. Based on the above results and the effects of discharge time and the use of isotope oxygen during discharge on product distribution during charge, the generation mechanism of O2, H2O, and CO2 during charging is discussed in relation to the reactions during discharge.

Graphical abstract: Nature of Li2O2 and its relationship to the mechanisms of discharge/charge reactions of lithium–oxygen batteries

Article information

Article type
Paper
Submitted
30 1 2024
Accepted
18 3 2024
First published
19 3 2024
This article is Open Access
Creative Commons BY-NC license

Phys. Chem. Chem. Phys., 2024,26, 13655-13666

Nature of Li2O2 and its relationship to the mechanisms of discharge/charge reactions of lithium–oxygen batteries

Y. Gao, H. Asahina, S. Matsuda, H. Noguchi and K. Uosaki, Phys. Chem. Chem. Phys., 2024, 26, 13655 DOI: 10.1039/D4CP00428K

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