Phase Stability of Li-Mn-O Oxides as Cathode Materials for Li-ion Batteries: Insights from ab initio Calculations

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Phase Stability of Li-Mn-O Oxides as Cathode Materials for Li-ion Batteries: Insights from ab initio Calculations

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Title: Phase Stability of Li-Mn-O Oxides as Cathode Materials for Li-ion Batteries: Insights from ab initio Calculations
Author(s):
Longo, R. C.;
Kong, F. T.;
KC, Santosh;
Park, M. S.;
Yoon, J.;
Yeon, D-H;
Park, J-H;
Doo, S-G;
Cho, Kyeongjae
Item Type: article
Keywords: Phase diagrams
Lithium Manganese Dioxide (LiMnO₂)
Li2MnO3
Spinel phases
Description: Includes supplementary material.
Abstract: In this work, we present a density-functional theory (DFT) investigation of the phase stability, electrochemical stability and phase transformation mechanisms of the layered and over-lithiated Mn oxides. This study includes the thermodynamic stability of Li and oxygen vacancies, to examine the electrochemical activation mechanisms of these cathode materials. The DFT calculations provide phase diagrams of the Li-Mn-O system in both physical and chemical potential spaces, including the crystals containing vacancies as independent phases. The results show the ranges of electrochemical activity for both layered LiMnO₂ and over-lithiated Li₂MnO₃. By using a thermodynamic model analysis, we found that the required temperature for oxygen evolution and Li vacancy formation is too high to be compatible with any practical synthesis temperature. Using solid-state transition calculations, we have identified the key steps in the phase transition mechanism of the layered LiMnO₂ into the spinel phase. The calculated effects of pH on the Li-Mn-O phase stability elucidated the mechanism of Mn² formation from the spinel phase under acidic conditions.;
Publisher: Royal Society of Chemistry
ISSN: 1463-9084
Persistent Link: http://dx.doi.org/10.1039/C4CP00937A
http://hdl.handle.net/10735.1/4015

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