Catalytic Behavior of Lithium Nitrate in Li-O2 Cells

Daniel Sharon, Daniel Hirsberg, Michal Afri, Frederick Chesneau, Ronit Lavi, Aryeh A. Frimer, Yang Kook Sun, Doron Aurbach

Research output: Contribution to journalArticlepeer-review

124 Scopus citations

Abstract

(Formula Presented) The development of a successful Li-O2 battery depends to a large extent on the discovery of electrolyte solutions that remain chemically stable through the reduction and oxidation reactions that occur during cell operations. The influence of the electrolyte anions on the behavior of Li-O2 cells was thought to be negligible. However, it has recently been suggested that specific anions can have a dramatic effect on the chemistry of a Li-O2 cell. In the present paper, we describe how LiNO3 in polyether solvents can improve both oxygen reduction (ORR) and oxygen evolution (OER) reactions. In particular, the nitrate anion can enhance the ORR by enabling a mechanism that involves solubilized species like superoxide radicals, which allows for the formation of submicronic Li2O2 particles. Such phenomena were also observed in Li-O2 cells with high donor number solvents, such as dimethyl sulfoxide dimethylformamide (DMF) and dimethylacetamide (DMA). Nevertheless, their instability toward oxygen reduction, lithium metals, and high oxidation potentials renders them less suitable than polyether solvents. In turn, using catalysts like LiI to reduce the OER overpotential might enhance parasitic reactions. We show herein that LiNO3 can serve as an electrolyte and useful redox mediator. NO2- ions are formed by the reduction of nitrate ions on the anode. Their oxidation forms NO2, which readily oxidizes to Li2O2. The latter process moves the OER overpotentials down into a potential window suitable for polyether solvent-based cells. Advanced analytical tools, including in situ electrochemical quartz microbalance (EQCM) and ESR plus XPS, HR-SEM, and impedance spectroscopy, were used for the studies reported herein.

Original languageEnglish
Pages (from-to)16590-16600
Number of pages11
JournalACS applied materials & interfaces
Volume7
Issue number30
DOIs
StatePublished - 5 Aug 2015

Bibliographical note

Publisher Copyright:
© 2015 American Chemical Society.

Keywords

  • Li-O batteries
  • carbon cathodes
  • electrocatalysis
  • oxygen evolution reactions
  • oxygen reduction reactions
  • redox mediators

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