Understanding LiOH Formation in a Li-O 2 Battery with LiI and H 2 O Additives


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Article
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Abstract

LiI-promoted LiOH formation in Li-O2 batteries with wet ether electrolytes has been investigated by Raman, nuclear magnetic resonance spectroscopy, operando pressure tests and molecular dynamics simulations. We find that LiOH formation is a synergistic effect involving both H2O and LiI additives, whereas with either alone Li2O2 forms. LiOH is generated via a nominal four-electron oxygen reduction reaction, the hydrogen coming from H2O and the oxygen from both O2 and H2O, and with fewer side reactions than typically associated with Li2O2 formation; the presence of fewer parasitic reactions is attributed to the proton donor role of water which can coordinate to O2- and the higher chemical stability of LiOH. Iodide plays a catalytic role in decomposing H2O2/HO2- thereby promoting LiOH formation, its efficacy being highly dependent on the water concentration. This iodide catalysis becomes retarded at high water contents due to the formation of large water-solvated clusters, and Li2O2 forms again.

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Keywords
LiI, Li-O-2 batteries, LiOH formation, four-electron oxygen reduction, water clusters, molecular dynamics
Journal Title
ACS Catalysis
Conference Name
Journal ISSN
2155-5435
2155-5435
Volume Title
9
Publisher
American Chemical Society (ACS)
Sponsorship
Engineering and Physical Sciences Research Council (EP/M009521/1)
European Commission Horizon 2020 (H2020) Future and Emerging Technologies (FET) (696656)
EPSRC