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Cation deficiency associated with the chemical exfoliation of lithium cobalt oxide
Author(s) -
Pachuta Kevin G.,
Pentzer Emily B.,
Sehirlioglu Alp
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16382
Subject(s) - exfoliation joint , cobalt , inorganic chemistry , materials science , x ray photoelectron spectroscopy , oxide , intercalation (chemistry) , lithium (medication) , chemical engineering , dissolution , transition metal , graphene , chemistry , catalysis , nanotechnology , organic chemistry , medicine , endocrinology , engineering , metallurgy
Compositional changes associated with the chemical exfoliation of lithium cobalt oxide, a layered transition metal oxide, are discussed. Starting from a layered bulk structure, lithium cobalt oxide can undergo chemical exfoliation through a two‐step method: treatment with a protic acid, then treatment with tetramethylammonium hydroxide (this intercalates the layered structure and yields exfoliated nanosheets). This work provides an in‐depth analysis of compositional and structural changes occurring to the powder upon the first step to exfoliation, treatment with acid, revealing variations in vacancies and valence changes depending on the conditions used. Through coupled analysis of X‐ray photoelectron spectroscopy, X‐ray diffraction, UV‐Vis absorption spectroscopy, and inductively coupled plasma‐optical emission spectroscopy data, we illustrate that both lithium and cobalt ions are diffusing out the structure along with the dissolution of full unit cells. As such, nanosheets accessed from the bulk by this exfoliation process should not be considered simply as divisions of the original unit cell. This work provides fundamental insights on the stability of LiCoO 2 and the exfoliation of layered transition metal oxides, beyond the access of individual nanosheets, and is vital to determining structure‐property relationships of chemically exfoliated nanosheets (eg, changes in valency which dictate catalytic activity, magnetic susceptibility, etc).