Catalytic Behavior of Lithium Nitrate in Li-O-2 Cells

Title
Catalytic Behavior of Lithium Nitrate in Li-O-2 Cells
Author
선양국
Keywords
Li-O-2 batteries; oxygen reduction reactions; oxygen evolution reactions; electrocatalysis; redox mediators; carbon cathodes
Issue Date
2015-08
Publisher
AMER CHEMICAL SOC
Citation
ACS APPLIED MATERIALS & INTERFACES, v. 7, NO 30, Page. 16590-16600
Abstract
The development of a successful Li-O-2 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-O-2 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-O-2 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-O-2 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.
URI
http://pubs.acs.org/doi/abs/10.1021/acsami.5b04145http://hdl.handle.net/20.500.11754/26959
ISSN
1944-8244
DOI
10.1021/acsami.5b04145
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > ENERGY ENGINEERING(에너지공학과) > Articles
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