title: Superstructure in the Metastable Intermediate-Phase Li2/3 FePO4 Accelerating the Lithium Battery Cathode Reaction.
abstract: LiFePO4 is an important cathode material for lithium-ion batteries. Regardless of the biphasic reaction between the insulating end members, Lix FePO4 , x≈0 and x≈1, optimization of the nanostructured architecture has substantially improved the power density of positive LiFePO4 electrode. The charge transport that occurs in the interphase region across the biphasic boundary is the primary stage of solid-state electrochemical reactions in which the Li concentrations and the valence state of Fe deviate significantly from the equilibrium end members. Complex interactions among Li ions and charges at the Fe sites have made understanding stability and transport properties of the intermediate domains difficult. Long-range ordering at metastable intermediate eutectic composition of Li2/3 FePO4 has now been discovered and its superstructure determined, which reflected predominant polaron crystallization at the Fe sites followed by Li(+) redistribution to optimize the Li-Fe interactions.
authors.affiliation: Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan).
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Nishimura
authors.affiliation: Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8502 (Japan).
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Natsui
authors.affiliation: Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan). yamada@chemsys.t.u-tokyo.ac.jp.
authors.forename: Atsuo
authors.initials: A
authors.lastname: Yamada
keywords: LiFePO4; cathode materials; lithium-ion batteries; olivine; solid-state structures