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Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery
Published on: July 12, 2016
Lithium peroxide surfaces are metallic, while lithium oxide surfaces are not.
Maxwell D Radin1, Jill F Rodriguez, Feng Tian
1Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2125, USA.
Journal of the American Chemical Society
|December 14, 2011
Summary
First-principles calculations reveal that stable lithium peroxide surfaces are half-metallic and ferromagnetic, unlike insulating lithium oxide. These distinct electronic properties explain electrochemical reversibility differences in Li-oxygen batteries.
Area of Science:
- Materials Science
- Electrochemistry
- Computational Chemistry
Background:
- Lithium peroxide (Li(2)O(2)) and lithium oxide (Li(2)O) are key discharge products in Li-oxygen batteries.
- Understanding their surface properties is crucial for optimizing battery performance and cycle life.
Purpose of the Study:
- To characterize the thermodynamic stability and electronic structure of Li(2)O(2) and Li(2)O surfaces.
- To identify stable surface facets using first-principles calculations and the Wulff construction.
- To correlate surface properties with observed electrochemical behavior in Li-oxygen batteries.
Main Methods:
- Density Functional Theory (DFT) calculations were employed to investigate 40 surfaces.
- Thermodynamic stability was assessed, considering the oxygen overbinding error.
- Surface electronic structures, including magnetic properties, were analyzed.
Main Results:
- Several new, stable oxygen-rich Li(2)O(2) surfaces ({0001}, {1 ̅100}) were identified.
- Stable Li(2)O(2) surfaces exhibit half-metallic behavior and ferromagnetism due to surface oxygens.
- Stable Li(2)O surfaces are insulating and nonmagnetic, with stoichiometric surfaces being preferred.
Conclusions:
- The unique half-metallic and ferromagnetic nature of Li(2)O(2) surfaces, contrasted with insulating Li(2)O, explains differences in battery electrochemical reversibility.
- Conductive surface pathways on Li(2)O(2) may mitigate bulk electron transport limitations, potentially enhancing battery capacity.
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