title: Chemical vs. electrochemical extraction of lithium from the Li-excess Li(1.10)Mn(1.90)O4 spinel followed by NMR and DRX techniques.
abstract: Lithium extraction from the Li-excess Li1.10Mn1.90O4 spinel has been performed by chemical and electrochemical methods in aqueous and in organic media, respectively. De-lithiated samples have been investigated by XRD, SEM, TG, (7)Li and (1)H MAS-NMR techniques. The comparative study has allowed demonstrating that the intermediate de-intercalated samples prepared during the chemical extraction by acid titration are similar to those prepared by the electrochemical way in a non-aqueous electrolyte. LiMn2O4 based spinel with a tailored de-lithiation degree can be prepared as a single phase by controlling the pH used in chemical extraction. (7)Li MAS-NMR spectroscopy has been used to follow the influence of the manganese oxidation state on tetra and octahedral Li-signals detected in Li-extracted samples. The oxidation of Mn(III) ions goes parallel to the partial dissolution of the spinel, following Hunter's mechanism. Based on this mechanism, a generalized chemical reaction has been proposed to explain the formation of intermediate Li(+) de-intercalated samples during acid treatment in aqueous media. By the (1)H MAS NMR study, no evidence of Li-H topotactic exchange in the bulk of the acid treated material was found.
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, c/ Sor Juana Inés de la Cruz, no. 3, Cantoblanco, 28049 Madrid, Spain. isobrado@icmm.csic.es.
authors.forename: S
authors.initials: S
authors.lastname: Martinez
authors.forename: I
authors.initials: I
authors.lastname: Sobrados
authors.forename: D
authors.initials: D
authors.lastname: Tonti
authors.forename: J M
authors.initials: JM
authors.lastname: Amarilla
authors.forename: J
authors.initials: J
authors.lastname: Sanz