title: Lithium dynamics in LiMn2O4 probed directly by two-dimensional (7)Li NMR.
abstract: LiMn2O4 has been studied using magic-angle-spinning nuclear magnetic resonance (MAS NMR). 1D MAS NMR shows three Li resonances assigned to different crystallographic sites. At low temperatures an extra peak appears, indicating charge ordering of Mn3+ and Mn4+. Direct observation of the lithium dynamics was possible using rotor-synchronized 2D exchange NMR. A millisecond time scale exchange of lithium starts around 285 K between the 8a and the 16c site. At 380 K lithium even starts to hop between more than two sites. The activation energies and Li jump rates are derived and are in agreement with those determined macroscopically.
authors.affiliation: Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands.
authors.forename: V W
authors.initials: VW
authors.lastname: Verhoeven
authors.forename: I M
authors.initials: IM
authors.lastname: de Schepper
authors.forename: G
authors.initials: G
authors.lastname: Nachtegaal
authors.forename: A P
authors.initials: AP
authors.lastname: Kentgens
authors.forename: E M
authors.initials: EM
authors.lastname: Kelder
authors.forename: J
authors.initials: J
authors.lastname: Schoonman
authors.forename: F M
authors.initials: FM
authors.lastname: Mulder