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Chemical vs. electrochemical extraction of lithium from the Li excess LiMn2O4 spinls a 6Li, 7Li and 1H NMR study

AuthorsSobrados, Isabel ; Tonti, Dino ; Amarilla, José Manuel ; Sanz Lázaro, Jesús; Martínez, Sandra
Issue Date11-Mar-2013
CitationInternational Battery Association Meeting (2013)
AbstractLi-Mn-O spinels are commonly used as the cathode LiM2O4 for Li-ion batteries1,2, due to a high redox potential (4V), low cost and environmental compatibility. LiMn2O4 spinels (LMS) still suffer from significant unsolved capacity fading when cycled delaying their commercial utilization. This phenomenon is related to Mn dissolution into the electrolyte in presence of HF, this acid being generated by catalytic decomposition in the presence of trace H2O. One of the most followed strategies consists in preparing lithium excess manganites. In previous works, 7Li MAS-NMR spectroscopy has been used to identify tetra and octahedral coordination of lithium in Li-excess LMS. Isotropic contact interactions of Li ions with electrons of manganese shifts Li NMR components. From this fact, Li NMR spectra can be used for analysis of different structural cationic Mn environments. This fact makes the NMR technique a useful tool to follow oxidation/reduction processes in LiMn2O43. Removal of lithium ions could be produced by acid treatments without affecting the manganese valence4; however, lithium extraction from the spinel framework is often accompanied by oxidation of Mn3+ to Mn4+. In this work, the Li+-extraction from Li-excess Li1.1Mn1.9O4 has been performed by chemical and electrochemical techniques in parallel. Samples prepared at selected pH and cut-off voltage have been investigated by XRD, chemical analyses and 7Li, 6Li and 1H MAS-NMR techniques, revealing the same LMS phases when the same Li amount is extracted. In agreement with the Hunter¿s reaction, Li is extracted in acidic environment with simultaneous partial dissolution of the starting compound and the oxidation of Mn(III) ions. However, at intermediate compositions, Li-proton exchange processes at the particle surface have been deduced by 1H NMR. The results obtained are discussed in terms of the reported Pourbaix diagram, where phases in aqueous solutions are related to pH and redox potentials.
DescriptionPóster presentado en: International Battery Association Meeting (IBA) celebrado en Barcelona del 11 al 15 de marzo de 2013
Appears in Collections:(ICMAB) Comunicaciones congresos
(ICMM) Comunicaciones congresos
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