Studies of li and mn-rich Lix[MnNiCo]O2 electrodes: Electrochemical performance, structure, and the effect of the aluminum fluoride coating

Francis Amalraj, Michael Talianker, Boris Markovsky, Luba Burlaka, Nicole Leifer, Gil Goobes, Evan M. Erickson, Ortal Haik, Judith Grinblat, Ella Zinigrad, Doron Aurbach, Jordan K. Lampert, Ji Yong Shin, Martin Schulz-Dobrick, Arnd Garsuch

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Abstract

We report herein on the study of Li andMn rich Lix[MnNiCo]O 2 cathode materials with an emphasis on the effect of AlF3 coating on their electrochemical performance. The initial stoichiometry of these materials was xLi2MnO3 .(1-x)LiMnyNizCowO 2 where x is in the range 0.4-0.5 and the y:z:w ratio was as we previously reported. Their structure was considered on the basis of two-components model, namely monoclinic Li2MnO3 (C2/m) and rhombohedral LiMO2 (R-3m) (M = Mn, Ni, Co) that are structurally compatible and closely integrated phases. Based on TEM studies we concluded that the coating had a crystalline tetragonal structure t-AlF3 (P4nmm symmetry) and AlF3 nano-crystals were regularly distributed over the particles surface. Amorphous clusters of AlF3 and/or other Al-containing species, like AlFxOy, Al[FOH], etc. may also present, as it follows from solid-state NMR measurements. It was shown that electrodes comprising the AlF3-coated material exhibited higher reversible capacities of ?250 mAh/g at a C/5 rate, more stable cycling behavior, higher lithium storage capability at 60?C, and lower impedance measured during Li-deinteraclation comparing to electrodes prepared from the uncoated material. An important finding is that Lix[MnNiCo]O2 /AlF3 materials revealed much higher thermal stability both in the pristine (lithiated) and cycled (delithiated) states than their uncoated counterparts.

Original languageEnglish
Pages (from-to)A2220-A2233
JournalJournal of the Electrochemical Society
Volume160
Issue number11
DOIs
StatePublished - 1 Dec 2013

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