title: Ion-exchange mechanism of layered transition-metal oxides: case study of LiNi(0.5)Mn(0.5)O₂.
abstract: An ion-exchange process can be an effective route to synthesize new quasi-equilibrium phases with a desired crystal structure. Important layered-type battery materials, such as LiMnO2 and LiNi(0.5)Mn(0.5)O2, can be obtained through this method from a sodium-containing parent structure, and they often show electrochemical properties remarkably distinct from those of their solid-state synthesized equivalents. However, while ion exchange is generally believed to occur via a simple topotactic reaction, the detailed phase transformation mechanism during the process is not yet fully understood. For the case of layered LiNi(0.5)Mn(0.5)O2, we show through ex situ X-ray diffraction (XRD) that the ion-exchange process consists of several sequential phase transformations. By a study of the intermediate phase, it is shown that the residual sodium ions in the final structure may greatly affect the electrochemical (de)lithiation mechanism.
authors.affiliation: Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University , 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
authors.forename: Hyeokjo
authors.initials: H
authors.lastname: Gwon
authors.forename: Sung-Wook
authors.initials: SW
authors.lastname: Kim
authors.forename: Young-Uk
authors.initials: YU
authors.lastname: Park
authors.forename: Jihyun
authors.initials: J
authors.lastname: Hong
authors.forename: Gerbrand
authors.initials: G
authors.lastname: Ceder
authors.forename: Seokwoo
authors.initials: S
authors.lastname: Jeon
authors.forename: Kisuk
authors.initials: K
authors.lastname: Kang